nuts & volts 25-09 - sep 2004
TRANSCRIPT
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4Circle #154 on the Reader Service Card.
Cover.qxd 8/13/2004 9:43 AM Page 108
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CoverInside.qxd 8/10/2004 4:35 PM Page 2
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Circle #72 on the Reader Service Card. 3SEPTEMBER 2004
Page 3.qxd 8/11/2004 9:03 AM Page 3
Vol. 25 No. 9
SEPTEMBER 20044
p. 78
p. 22
p. 50
p. 46
FEATURES COLUMNS
DEPARTMENTS
PROJECTS65 TETSUJIN 2004
The cutting edge event sponsoredby our sister publication, SERVOMagazine.
66 THE DIGITAL CONSUMER TECHNOLOGY HANDBOOKBook review.by Ed Driscoll, Jr.
68 A NEW LIFE FOR LORAN —PART 2Completing the conversion tosolid-state amplifiers.by Clifford Appel
73 HAM RADIO FOR DUMMIES Another book review.by Karl Lunt
46 SPIN A MOTOR WITH YOUR COFFEE MUGUse that excess heat!by Dr. Ralph Lorenz
50 THE ELECTRONIC SNIFFERAn electronic nose for detectingchemicals.by Ron Newton
54 THE ENIGMA MACHINE,PART 4De-bunking Kirlian photography.by Gerard Fonte
61 FLOATING LIGHT SHOW A fun summer project to jazz upyour swimming pool.by Michael Simpson
8 TECHKNOWLEDGEY 2004Magnetic refrigeration; piratedsoftware; and more.
14 JUST FOR STARTERSLearn all about diodes.
18 MICRO MEMORIESShakey, an early robot.
22 LET’S GET TECHNICALDigital data compression.
30 Q&AAll about lightning; more 555timer circuits; classic carvoltage conversion; and more.
78 PERSONAL ROBOTICSHexapod hoedown!
83 IN THE TRENCHESFor design engineers facing realworld problems.This month:specifications.
89 STAMP APPLICATIONSAn active coffee stabilizationsystem.
94 NEAR SPACEDetecting cosmic rays.
105 Advertiser’s Index75 Classified Display Ads12 Electro-Net44 Electronics Showcase38 New Product News28 Newsbytes42 NV Bookstore6 Publisher’s Info6 Reader Feedback102 Tech Forum
Nuts & Volts (ISSN 1528-9885/CDN Pub Agree#40702530) is published monthly for $24.95 per year byT & L Publications, Inc., 430 Princeland Court, Corona, CA 92879. PERIODICALS POSTAGE PAID ATCORONA, CA AND AT ADDITIONAL MAILING OFFICES. POSTMASTER: Send address changes toNuts & Volts, 430 Princeland Court, Corona, CA 92879-1300 or Station A, P.O. Box 54,Windsor ON N9A 6J5; [email protected]
SEPTEMBER 2004
TOC.qxd 8/13/2004 10:04 AM Page 4
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5SEPTEMBER 2004
Full Page.qxd 8/12/2004 1:49 PM Page 5
Dear Nuts & Volts:I was taken back to my college
days at the University of Colorado bythe article “A New Life for LORAN”(August 2004). I took power lab fromProf. Easton and electronic lab fromProf. Wicks in the same semester.There was a friendly exchange ofbarbs between the two; in particular,Prof. Easton accused the circuits labof dealing in “sneak currents,”milliamps vs. real currents of dozensor even hundreds of amps in thepower lab. The last day of class, Prof.Wicks distributed data sheets for theF1086 tube, pointing out that the12.6 volt AC filaments ran 200 amps,asking us to “Tell Prof. Easton thatthis is not a sneak current!” when wewent to the final power lab class.Thanks for the memory.
Jerry Berry, BSEE '59via Internet
Dear Nuts & Volts:Having been a Loran A instructor
during World War II, and havingconducted the first airline evaluation ofLoran C in the 1950s, I was surprisedto learn from Clifford Appel's article inyour August issue that Loran C is stillalive and pulsing. However, he fails tomention what agencies might use ittoday. Considering that GPS seems tohave become the method ofpreference for geographic positionfixing in the 21st century, I would havethought that Loran C would have gonethe way of Decca/Dectra, Omega, andthe other navigational systems of the20th century.
Also, I was very interested inMichael Banks' article about Hugo
Gernsback. This is the first completeaccount I have ever seen of his lifeand accomplishments. Those of uswho got our start in radio in the1930s well remember waiting inanticipation each month for the latestissue of his Shortwave Craft (if I havethe name right?).
Paul Rafford Jr. NY4Lvia Internet
Dear Nuts & Volts:While thumbing through your
August 2004 issue, I came to the article“Just for Starters” by Mark Balch andwas happy to see a section titled Ohm'sLaw. One of my minor hobbies isanalyzing explanations of “Ohm's Lawfor beginners” to see how close to thetruth the author came. (What does thattell you about my life!?)
People who work with objects thatconduct electricity are often interestedin knowing the current I that flowswhen a voltage E is applied, and theratio of E/I of these quantities. Thisratio turns up so often that it is handyto have a name and symbol for it, andin fact it has been given the name“resistance” and the symbol R. Thus,the expression R=E/I is not any kindof law, but simply a definition ofresistance. Ohm's Law, on the otherhand, is more significant than this. Itis an experimentally determined lawof nature, not just a definition.
So what is Ohm's Law? If we applyvoltage E1 and measure current I1,and then apply a different voltage E2and measure current I2, Ohm's Lawstates that E1/I1 will be equal to E2/I2.Since we have made a definition for theratio E/I, and since the test voltages
were arbitrary, another way tosay this is R=constant. In otherwords, Ohm's Law states thatthe resistance of a conductorstays the same for any appliedvoltage. Since we all know thisisn't true (visualize thecharacteristic curve of a silicondiode), why is Ohm's Lawimportant? The answer, ofcourse, is because lots ofimportant devices do obey theLaw for a wide range of voltagesand currents. The diode just isn'tone of them. Even for the diode, we can use the definitionto calculate an effectiveresistance for a given voltage orcurrent. But when we do this,
AUGUST 2004
Reader Feedback
by J. Shuman
6
NU
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&VO
LTS
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Published Monthly By T & L Publications, Inc.
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All advertising is subject to publisher's approval.Weare not responsible for mistakes, misprints, ortypographical errors. Nuts & Volts Magazine assumesno responsibility for the availability or condition ofadvertised items or for the honesty of theadvertiser. The publisher makes no claims for thelegality of any item advertised in Nuts & Volts.This isthe sole responsibility of the advertiser.Advertisersand their agencies agree to indemnify and protectthe publisher from any and all claims, action, orexpense arising from advertising placed in Nuts &Volts. Please send all subscription orders,correspondence, UPS, overnight mail, and artworkto: 430 Princeland Court, Corona, CA 92879.(Continued on Page 45)
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SEPTEMBER 2004
TechKnowledgey2004AdvancedTechnologiesLords of the Flies
RRecently, some researchers atCornell and Binghamton
Universities (www.cornell.edu andwww.binghamton.edu) have beenspending a lot of time with flies. No,this is not a reflection of their person-al hygiene, but an embodiment of agrant from the National Institute onDeafness and Other CommunicationDisorders (NIDCD, www.nidcd.nih.gov) that has underwritten astudy of Ormia ochracea, which is apeculiar cousin of your commonhousefly. Most flies primarily eatplants and animals that are alreadydead or decaying, but Ormia is a par-asitoid; it lives off of living animals.
When a female Ormia hears thechirp of a male field cricket, she fliesto within a few inches of it, sneaks upon its back, and deposits larvae thateventually burrow down into thecricket. In a few days, the larvae
emerge from the unfortunate, deadcricket and fly away, much as rela-tives flee from your home afterdevouring a huge holiday meal andfinishing off all of the good Scotch.
Perhaps the most remarkablething about this process is that, eventhough Ormia is endowed with thestandard array of sensory equipment(compound eyes, antennae, andultrasensitive legs), it locates thecricket by directional hearing in thesame way that humans use stereoprocessing to determine which near-by car is blaring the offensive musicat 140 dB. However, the fly’seardrums — located beneath its head— are only 0.5 mm apart, which, theoretically, is too close to allow“bilateral interaural intensity differ-ences” to be detected at the cricket’schirp frequency of about 5 kHz(which translates into a wavelengthof approximately 69 mm).
The secret lies in the fact that thefly’s eardrums are connected by asmall bridge. The official explanationis that, when a sound is detected in theright ear, the right eardrum vibrates,causing the left eardrum to vibrate outof sync, and vice versa. This back-and-forth vibration of the eardrums createsa difference in pressure between thetwo ears, which the fly’s ganglia andbrain quickly compute. Within 50nanoseconds (1,000 times fasterthan you can do it), Ormia’s brainsends a signal to its muscles and thefly turns toward its target. When arecording of a cricket’s chirp is playedfor the subject fly, it responds quicklyand accurately (much more so than afemale cricket, which was what themale was actually hoping to attract).
By now, you are probably won-dering what this has to do with elec-
tronics. The connection is that thefly’s audio equipment has inspired anovel design for hearing aids that,within a few years, could performbetter and cost much less than exist-ing designs. As stated by NIDCDDirector James Battey, Jr., “The bio-logical lessons provided by Ormia’sabilities in hyperacute time codingand localization of sound promise toproduce strategies for improved nano-or micro-scale directional micro-phones in hearing aids. Applicationsof these new principles may improvelife for individuals with hearing losswho depend upon hearing aids.”
Improvement in MagneticRefrigeration
TThe concept of magnetic refriger-ation has existed since the
1920s and one scientist (CanadianWilliam Francis Giauque) even won a1949 Nobel Prize for related work. Amagnetic refrigerator could poten-tially offer better energy efficiency,lower operating costs, the elimina-tion of environmentally hostilecoolants, and nearly silent operation.Nevertheless, the concept has neverbeen translated into practical, com-mercial products and we all still livewith the century-old technology ofvapor-compression cooling systems.
The situation could change, how-ever, as a result of developments atthe National Institute of Standards andTechnology (NIST, www.nist.gov).An NIST team has discovered that, byadding a small amount (about 1%) ofiron to a gadolinium-germaniumalloy, its cooling capacity can beincreased by 15 to 30%, resulting in,“a much-improved magnetic refriger-ant for near-room-temperature appli-
Events, Advances, and NewsFrom the Electronics World
The hyperacute directional hearing ofOrmia ochracea results from its uniqueears, which are part of the prothorax
behind its large head, as shown.Photo by R. Hoy and G. Haldeman/CornellUniversity. Copyright Cornell University,
reproduced with permission.
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cations.” The iron nearly eliminatescostly hysteresis effects that other-wise appear during the on-and-offcycling of the applied magnetic fieldthat drives the refrigeration device.
In operation, when exposed to amagnetic field, the gadolinium alloyand other materials heat up as theirspinning electrons align with the field,thereby magnetizing the materialsand raising their temperatures. Whenthe external field is removed, thematerials demagnetize (the electronsrevert to a disordered magnetic spinstate), and their temperature drops.The two stage process forms themagnetic refrigeration cycle.
Magnetic refrigeration is alreadya potential contender for specializedapplications, such as cooling sensorsin spacecraft and the liquification ofgases. With additional development,it could be extended to householdrefrigerators and freezers, dehumidi-fiers, and air conditioners — whichnow account for about 25% of residential power use.
Computers andNetworkingHP Introduces NewWorkstations
CContinuing with now-typical evolu-tionary — rather than revolution-
ary — developments in the microcom-puter industry, Hewlett-Packard(www.hp.com) has introduced threenew machines. The HP Workstationxw4200 is the entry level machineaimed at engineers, artists, designers,scientists, and other users who haveintense application demands, requirelarge, complex models or data sets,and have multitasking requirementsor extensive graphic needs.
The xw4200 features Intel’s 925XExpress chipset and Pentium 4processors with Hyper-Threadingtechnology and speeds up to 3.6 GHzwith an 800 MHz front-side bus. Thenew chipset drives the PCI-Expressgraphics and input/output interface,DDR-2 memory architecture, integrat-ed Serial ATA RAID controller, and —when available — support for future
Intel EM64T processors.Also introduced were the xw6200
and xw8200 models. All supportWindows® XP Professional and Red HatEnterprise Linux WS 3.0 operating sys-tems. The xw4200, xw6200, andxw8200 are priced at $849.00,$1,399.00, and $1,799.00, respectively.
624 MHz Pocket PC
DDell has introduced three newAxim handheld computers that
include Intel’s PXA270 processors,Windows Mobile® 2003 Second Editionsoftware for Pocket PC, and Bluetooth®
wireless technology. Two of the threeconfigurations feature a combinationof Bluetooth and WiFi® 802.11b wire-less. Bluetooth allows personal areanetworking with computer systems andBluetooth-enabled devices such asmobile phones, GPS receivers, key-boards, and other handheld comput-ers. Integrated WiFi enables users to
Dell’s Axim handhelds employ Intel’sPXA270 processor and are available
with wireless technology.
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connect wirelessly to the Internet atrestaurants and coffee houses, collegecampuses, sports venues, hotels, air-ports, and other locations.
Prices start at $199.00 for a non-wireless 312 MHz configuration,$249.00 (after a $30.00 rebate) if youinclude combination wireless capabili-ty, and $349.00 for the 624 MHzmodel. All three configurations includea built-in secure digital I/O slot, a 3.5inch transflective TFT color displaywith 240 x 320 (QVGA) resolution, aheadphone jack and improvedrecorder capability, plus a scroll dial.
The $199.00 and $249.00 con-figurations come with a travel synccable, while the $349.00 configura-tion comes with a sync/recharge cradle with an extra battery chargeslot that accommodates either thespare standard battery (950 mAh) orthe optional high capacity (1,800mAh) battery ($99.00). Details areavailable at www.dell.com
Circuits and DevicesHigh-End MiniDisc Player
IIf your bank account has beenlooking too plush lately, Sony
Electronics has a solution in theform of its QUALIA 017 MiniDiscplayer. According to Sony,“Individually crafted from a solid brassblock and perched on a beautifullydesign charging station, the QUALIA017 is truly an objets d’art.” It’s not allgood looks and snob appeal, though.The construction is said to provide amore rigid case, which reduces thekind of wear and tear experienced by
all portable audio devices.Included with the player is a set
of high quality, low profile ear budheadphones that feature extendedbass capability. It has been reportedthat the headphones can reproducefrequencies up to 100 kHz, which willcome in handy if your dog likes touse it. It also comes with a carryingcase that employs a magnetic lockand it is available in chrome, silver-plated, or gold-plated finishes. As ofthis writing, the device was availableonly by special order, with a baseprice of $1,900.00.
For an interesting twist on mar-keting techniques, visit www.qualia.sony.us/qualia_main.html whereyou can view/download a fourminute promotional movie thatwraps tranquilizer music around amontage of nature scenery and tellsyou absolutely nothing about theproduct line. It’s impressive and kindof relaxing, really, but I suspect thatmost of us will still opt for a $29.95player from Wal-Mart.
Industry and theProfessionPirated SoftwareFlourishing
AAccording to a study conductedby the research firm
International Data Corporation (IDC— www.idc.com) and recentlyreleased by the Business SoftwareAlliance (BSA — www.bsa.org),36% of all software installed on com-puters in 2003 was pirated, repre-senting a loss of nearly $29 billion tothe software industry. This year’sBSA global piracy study incorporat-ed major software market segments,including operating systems, con-sumer software, and local marketsoftware, as well as business soft-ware applications.
The study found that, while $80billion in software was installed oncomputers worldwide last year, only$51 billion was legally purchased.For its analysis, IDC drew upon worldwide data for software and hardwareshipments, conducted more than
5,600 interviews in 15 countries, andused its in-country analysts aroundthe globe to evaluate local marketconditions. IDC identified the piracyrate and dollar losses by utilizing proprietary IDC models for PC, soft-ware, and license shipments by allindustry vendors in 86 countries.
Geographically, the piracy ratesbreak down as follows: EasternEurope, 71%; Western Europe, 36%;Latin America, 63%; Middle Easternand African nations, 56%, and NorthAmerica, 23%. Summing it up, BSAPresident and CEO Robert Holleymancommented, “The fight for strong intel-lectual property protection and respectfor copyrighted works spans the globeand there is much work to be done.”
New Computer ProjectAnnounced
CCOLSA Corporation (www.colsa.com) and Apple Computer
Corporation (www.apple.com)have jointly announced the develop-ment of one of the largest and mostpowerful computers in the world.COLSA has contracted with Apple todeliver the components for a super-cluster computer system with morethan 3,000 processors to its cus-tomer, the US Army’s Aviation andMissile Research, Development, andEngineering Center (AMRDEC —www.redstone.army.mil/amrdec).
The system will consist of 1,566dual-processor, rack-mountableXserve G5 units, which employApple’s 2.0 GHz G5 CPU. COLSA willbuild, install, test, and operate thesystem. The supercluster will beemployed to model the complexaero-thermodynamics of hypersonicflight, including applications relatedto missile interceptors and scramjetengine performance. It will offerpeak performance of 25 TFLOPs.
At a cost of about $5 million, itcompares favorably with Japan’sEarth Simulator computer, whichoffers 40 TFLOPS performance, but costs $350 million. The machineis expected to be operational late this fall. NV
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Lower costs, higher output—it’s easy to measure the value of eBay.My company counts on me to get great deals on test equipment. That’s why
I count on eBay. Oscilloscopes, lenses, transformers, signal generators…
all the gear I want is there for less. So far, I’ve bought $40,000 worth of
new and used equipment for just $20,000. With a well-equipped lab, we’re
troubleshooting more efficiently and getting products to market faster.”
“
www.ebaybusiness.com
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Stan Searing – eBay User ID: searing (595)Application Engineering Manager, Pixim, Inc., a 50-person manufacturer of imaging platforms
in Mountain View, CA.
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Materials that can conductcurrent (silver, gold, alu-minum, copper, etc.) con-
tain large numbers of loosely heldelectrons. Their resistance to the flowof current is measured in just a fewmillionths of an ohm per centimeter.Insulators — such as glass, rubber,and plastic — have very few looselyheld electrons and their resistance tothe flow of current is measured in afew million ohms per centimeter.
Semiconductors
As the term implies, semi-conductors are not as conductive asmetal, nor are they as non-conductiveas insulators. The most commonlyused materials in semiconductors aregermanium and silicon. Germanium,in its pure form, is rated at 60 ohmsper centimeter, while silicon is ratedat 60,000 ohms per centimeter.
What enables semiconductors tochange their state of conductivity isthe addition of controlled amounts ofimpurities. Arsenic and antimonyadded to the mix will produce what isknown as an n-type material becauseof the negative charge from the excessof free electrons. A p-type junction canbe produced with the careful addition
of aluminum, gallium, or indium.
P-N Junction
When a p-type junction is made,the electrical equivalent of “holes” oran absence of electrons is set up. Ann junction has an excess of electrons.Combining p and n materials andapplying negative current results in adiffusing of electrons across the junc-tion is known as diffusion current.
As you can see in Figure 1, asurplus of electrons from the n material penetrate the space-chargeregion, flow across the junction, andmove through the holes to the positive lead. This is known as forward biasing and results in signalbeing transferred through the diode.
When the current is reversed, thefree electrons are drawn to the positive terminal and the holes areattracted to the negative terminal.This is known as reverse biasing andresults in no passage of currentthrough the diode. The more reversebiasing is applied to it, the moreresistance the diode presents.
Biasing
Like bipolar transistors, diodesdo not respond tosignals until a
threshold voltage is achieved. Thebiasing level can vary from onediode to another, but most diodeswill trigger at about 0.7 volts. Reversebiasing does not have a thresholdand a diode starts responding at thefirst sign of a signal. Since diodes aremostly given the duty of switchingnon-sinusoidal signals, biasing — forthe most part — is not a factor.
Doping
Doping is the name given to theprocess of adding impurities thatenable the diode to respond to cur-rent. Different doping procedures canproduce different types of diodes.
For example, over-doping can pro-duce something called a tunnel diode.
Tunnel Diodes
A tunnel diode has a high concen-tration of impurities in both the p andthe n sections of the device. Thespace-charge region is so narrow inthis diode that an electrical charge canpass through the device by tunneling,a quantum-mechanical action thatproduces a negative-resistance regionthat has the potential of achievingamplification. In circuits where signalintensity is compromised for one rea-son or another, the tunnel diode can
Just For StartersBasics For Beginners
A Tutorial on Diodes
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Figure 1. Combined P and N junctions
Figure 2. Zener diode operation
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help achieve a critical thresholdpoint. Oscillators, pulse genera-tors, and RF energy generationare the areas where the tunneldiode is most applicable.
Zener Diode
Voltage regulation is animportant function in modernelectronics and the zener diode isdesigned to do just that. It achieves thisin the reverse bias mode. You can see inthe diagram (Figure 2) that the zener iswired across a power supply outputwith the anode lead connected toground and the cathode lead connectedto the supply output.
Like regular diodes, zener devicesresist the flow of voltage when reversebiased. The zener, however, is designedto resist the flow of voltage only to agiven breakdown point. Anything overthe breakdown point will be passed toground. Acting as a reference source,the zener diode is capable of providingvery accurate, constant current loads.Popular cutoff points are 5, 9, and 12volts to accommodate most power supply requirements.
Varactor
One of the most unusual devicesis the varactor or variable-reactance
diode. The varactor acts as a voltagesensitive capacitor in series with aresistance. Its use is basically confined to microwave equipment.
Diode Types
As you can see in the illustration,diodes come in a wide variety ofshapes and sizes. The size of a diodewill most likely relate to its powerhandling capacity. Leads are identi-fied as anode and cathode and —on most diodes — polarity is identi-fied by a line on the cathode side,as shown in the diode type illustra-tion (Figure 3).
Your local supplier should havemost types in stock. Low level glassdiodes, such as the 1N914, areinexpensive (about 10 for $1.00)and widely available. Harder to finddiodes can be ordered from suppli-er catalogs or from the advertisers
in Nuts & Volts.
SCRs
An SCR (Silicone ControlledRectifier) is like a diode with an extralead. The device will not pass currentuntil a pulse is applied to the third lead,which is called a gate. Many switchingfunctions that were formerly controlled
SEPTEMBER 2004 15
Figure 3. Diode types
Figure 4. SCR operation
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by heavy, slow, expensive mechanical relays can be execut-ed by an SCR. Loading problems are another disadvantageof relays that disqualifies them from low current circuits,especially since they need a constant DC input to stay on.
Only a brief pulse is necessary toturn on an SCR — and it stays on.
There are two ways to turn it off.The first is by applying a negativepulse to the gate and the second isby disengaging the output load. Thissecond method is popular as a resetin alarm circuits (see Figure 4).
One thing that is necessarywhen working with SCRs is a constant output load. Most welldesigned circuits will provide asteady load to maintain the on con-dition of the SCR. Experimentationwill determine whether or not the circuit will sustain an on condition inan SCR controlled situation.
LEDsLight Emitting Diodes (LEDs)
have been around for quite a while now and almost all elec-tronic devices have one or more. The LED is made byadding metals — such as aluminum, gallium, and indium— to arsenic antimony and phosphors. By changing theratio of elements, it is possible to vary the color, theamount of infrared radiation, and the brightness greatlyfrom one LED to another.
Wherever you need a visual indication of electricalactivity, the LED is the answer. Seven segment displaysenable light emitting diodes to indicate letters and numbers and are used in clocks and calculators. Arrays —consisting of several LEDs in a single case — are used toindicate sound levels in recording devices. New productsare being developed all the time and amazing devices arefinding their ways to the shelves of your suppliers.
Diodes as Isolators
No circuit demonstrates the ability of diodes to pass
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Figure 5. Diode isolated voltage sequencer
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Figure 6. Bar graph sound level indicator
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and isolate analog signals better thana sequencer. The sequencer in Figure5 is a 4017 decade counter and it pro-duces a high output (equal to thepower supply) at only one of its 10outputs. The other nine outputs arelow and all of the outputs are connect-ed to potentiometers.
When a pulse is fed to pin 14, thecounter advances to the next stage.Since only one diode at a time ishigh, it passes whatever voltage is setby its potentiometer to the outputbus. This voltage reverse biases allother diodes, so they become highlyresistive and isolate the nine low stateoutputs.
No interaction between stageswill occur because only the voltage atthe active stage will be passed to thebus. The result is a manuallyadjustable staircase wave shape. Thiscircuit is ideally suited to operate volt-age controlled oscillators and otherelectronic music circuits.
Integrated Circuits
Diode elements are etched intoICs to direct signals, prevent falsetriggering, and stabilize — as well asprotect — the circuit. Tunnel diodedoping techniques are beingresearched to increase the efficiencyof the new breed of integrated circuits.
Bar Graph SoundLevel Indicator
Figure 6 shows how to use diodesin series to set a “trip point.” Twenty-two diodes and six LEDs — along withthree resistors and a capacitor —comprise this simple sound level indi-cator. The input accepts a high levelaudio signal through D1. As a lowlevel signal rises in amplitude, itmeets the biasing threshold of diodeD2 and LED D23 lights. When thesignal increases beyond the biasingrequirement of D3 and D4, LED D24will light. This process continuesdown the line to LED D28, as long asthe signal level increases.
The new extra bright LEDs work
best in this circuit, but, if they are too bright, increase the value of resistor R1.
Because audio levels from musiccan be transient, signals may occurtoo quickly to be observed.
Capacitor C1 will help hold thesignal long enough for it to be seen. If the capacitor does not hold the signal long enough, try a
larger value.
Conclusion
Diodes can help you achieve yourcircuit goals, whether you want totrigger an alarm, regulate a powersupply, or light up a project withLEDs. The diode will point you in theright direction. NV
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Micro Memories
Readers of Nuts & Volts andespecially SERVO — our sister publication — know
first hand the remarkable strides thatrobotics has made in the last 10years or so.
Yet, as one developer told me,robotics in the first decade of the21st century are still very much akinto where personal computers were inthe mid-1970s. Just as it tookdecades of experimentation andresearch to get to the first microcom-puter, it has taken robots an equallylong gestation period to get to thehobbyist level.
In the 1960s, it required enor-mous sums of capital just toresearch robots. There were essentially two groups doing
research into robotics: one corporateand the other using governmentmoney. Dr. Joseph Engelberger wasdeveloping the first robots for automobile assembly lines — tech-nology eagerly purchased byGeneral Motors and, later, by otherautomobile manufacturers.
Meanwhile, Stanford ResearchInstitute (later known as SRI) — located in Menlo Park, CA — wasworking with ARPA, the AdvancedResearch Projects Agency, the central research and developmentorganization for the US govern-ment’s Department of Defense.(Later, it became officially known asDARPA. The added D stands forDefense. In the late 1960s, it alsogave the world Arpanet, the direct
forerunner to today’sInternet.)
The result was arobot eventually knowninformally — but lovingly— as “Shakey” becauseof its herky-jerkymotions. It became amilestone in roboticstechnology. As Dr.Richard J. Waldinger ofSRI told me, its buildershad several objectivesfor their robot. First, “itwas combining whollydifferent elements in arti-ficial intelligence into asingle thing. It did havesome English under-standing, so you couldtype commands intoShakey in English and itwould type back inEnglish. And then therewas vision because itcould recognize objects
— it had a TV camera so that it couldsee things and there was work ongetting it to tell where the edge of theroom was. It could recognize blocks.It could find ramps and other thingslike that.”
Beyond that, one of the goals ofthe Shakey program was to build arobot that could be given instruc-tions that were less than step-by-stepand still have it figure out how toaccomplish its tasks. As Waldingersays, its instructions wouldn’t say“go here and then go there;” rather,they would say “move this box to thislocation.”
Shakey had no hands, but, asWaldinger says, “it could push boxeswith its ‘stomach.’ It was like a bulldozer; it could push boxes alongand the tasks that it could do had todo with moving a box from one placeto another and, sometimes, therewere things that it had to move out ofthe way in order to get through adoorway.
In some cases, there were uncer-tainties; it would think that a box wasin place and then someone wouldsecretly move it and it would have toadjust to contingencies that mighthave interrupted its plans. , it was thefirst time that a whole bunch of different things were integrated intoone system.”
The Birth of Shakey
The robot was initially createdbecause Dr. Charles A. Rosen — wholed SRI’s applied physics lab — had aremarkable idea in 1963. As his colleague, Dr. Nils J. Nilsson, wrotein a 1984 paper, “What would it belike, he wondered, to build a largelearning machine whose inputs
Shakey — A 1960s Predecessor toToday’s Advanced Robotics
SEPTEMBER 2004
Shakey quietly resides in a Plexiglas case at theComputer History Museum in Mountain View, CA.
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would come from television camerasand other sensors and whose outputswould drive effector motors to carrythe machine purposefully through itsenvironment?”
Rosen wrote a memo outlininghis plans for such a robot or“automaton,” as he called it. Then,as Nilsson describes it, “During1964, we spent a lot of time plan-ning a robot research project anddiscussing the idea with possiblesponsors. As interest in computerscience and artificial intelligencegrew, we were ready to concede thatour robot ought to be equipped withheuristic computer programs, aswell as pattern-recognizing learningmachines.”
Their proposal eventually wonfunding from ARPA, which sent an informal request to SRI to bid on a research program to developautomatons.
Meet Shakey
Shakey wasn’t designed to be anaesthetic knockout — in fact, it wasrather ungainly looking. It was several feet tall with a sort of headcontaining a TV camera and rangefinder, but that head was attached toa square body containing onboardlogic and electronics, a camera
control unit, a rubberized “bumpdetector” for when it came in contact with a wall or other object,and — underneath it all — driveand caster wheels.
Of course, as Dr. Waldingernotes, “There were no personalcomputers in those days and computers back then were biggerand heavier than you’d want tocarry around.”
So, Shakey’s brains, “were in alarger computer and I think theychanged computers from time totime as newer computers camealong. I think there was maybe anSDS940 and that might have beenreplaced by a DEC10. It may havehad some things onboard, but notvery much.” Shakey was connect-ed to them first by cable, “andthen, eventually, I think there was aradio link.”
Like many prototypes,Waldinger remembers Shakey asbeing “a very unreliable piece ofequipment. First of all, it was veryslow and, when it was moving some-thing, it was not very long beforesomething would go wrong.
For example, a lot of things donein the movies were pieced together —it didn’t do things all at once; it did alittle bit and then it broke and thensomebody had to fix it.”
SRI made a series of films ofShakey in action. Waldinger notesthat, “in the first movie, there was aclock on the wall and you could seeby looking at the clock how longthings were taking. Actually, sometimes the clock would seem tomove backward, because somethinghad been done late one day and thenwas picked up the next day or maybe
SEPTEMBER 2004 19
Shakey's head combined a television camera anda rangefinder. Unlike a human, his actual brainsresided in computers that connected to Shakey
via cables, and later, a wireless connection.
Circle #129 on the Reader Service Card.
Jr. Micro Memories
RLMicroMemories.qxd 8/10/2004 1:45 PM Page 19
a couple of days later. So, in subsequent movies, they removedthe clock from the wall.”
Because Shakey’s visual recognition system was far from perfect, it had problems recognizingwhere the wall ended and where thefloor began, so, eventually, SRI painted the baseboard in the roomwhere Shakey ran a darker color to
make it obvious where the endof the wall was. If Shakeycouldn’t see where the end ofthe room was, it was difficultto orient it.
Six Degrees of ShakeySeparation
All technology has tobegin somewhere and there’sa direct link between Shakeyand the mobile robots oftoday. There may be otherlinks as well: Waldingerremembers a presentationgiven to a group of high-rank-ing Army officials. One ofthem asked the men at SRI,“Could you attach a 36-inchblade to that thing?” Theresponse was basically, “Idon’t see why not!” That mayhave been the birth of RobotWars, 30 years before its time.
Shakey has anotheramusing link to today’s technology. After DARPA terminatedfunding on Shakey in 1972, the robotsat in SRI’s lobby for several yearsbefore eventually ending up in theComputer History Museum inMountain View, CA (see the July2001 issue of Nuts & Volts).
Nils Nilsson told me that, whileShakey was on display at SRI, various
school groups wouldpass by Shakey, includ-ing one with a juniorhigh school studentnamed Bill Gates.Gates later told anassociate at Microsoft,“I remember that — Iwas a junior highschool student. I wentto SRI and saw Shakeythe Robot and it got meall excited about computers.”
For a robot thathad trouble seeingwhere it was going,Shakey’s legacy defi-nitely went far. NV
A mid-1960s photo from the Stanford ResearchInstitute diagrams the key features of Shakey.
SEPTEMBER 2004
Shakey used loops of wires as "bump sensors," to alert himto when he was about to hit a wall or other obstacle.
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Micro Memories
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Re-Map Your Fuel Curve After Upgrading Injectors!KC-5385 $46.00. Due late September ‘04A huge revolution in Do It Yourself automotivemodifications has occurred. This project allows youto re-map your air/fuel ratio throughout theentire load range. One use for this is upgradingyour fuel injectors, then re-mapping the fuel supply to eliminate the need for new engine orfuel management systems. It offers incrediblemapping resolution, and features rival many commercially availableunits costing hundreds of dollars more! Kit supplied with PCB,machined case, and all electronic components. Programmed via DigitalHand Controller (KC-5386 shown below).
Keep an Eye on Your Car’s Fuel Mixture and PerformanceKC-5374 $16.00It is quite common for thefuel mixture to becomevery lean in turbochargedand supercharged motorsunder high load conditions.This not only decreases potential power, but can also causeengine problems. This kit displays the fuel mixture on aseries of LEDs, with an integrated buzzer that sounds whenthe mixture is critically low. Kit supplied with PCB and all electronic components. Requires engine to be fitted with an EGO (Exhaust Gas Oxygen) sensor.
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A Cheap Nitrous Fuel Mixture ControllerKC-5382 $14.50. Due late September ‘04Nitrous oxide systems can be expensive to set up, butnow you can do it for much less. This project pulses afuel injector at a preset rate, adding a fixed amount ofnitrous fuel when you activate it. It will save you a bundle on dedicated fuel solenoids and jets. It can alsobe used to control electronic waterpumps, cooling fans, andmore. Kit supplied withPCB and all electroniccomponents. *Pleasecheck local laws regardingthe use of Nitrous Oxidesystems in your vehicle.
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LCD Digital Hand ControllerKC-5386 $34.50. Due late September ‘04Not only can you re-map your injectors withthe kit above, it also suits other projects weoffer such as electronic boost controllers,additional injector controllers, and more! You can program the kit then remove it, orleave it connected for real time display. Kit supplied with PCB, silkscreened and machined case, LCD, and all electronic components.
Circle #81 on the Reader Service Card.
Full Page.qxd 8/11/2004 9:38 AM Page 21
Let’s Get Technical
Data compression has beenaround for a long time. Ifyou’ve heard the expres-
sion, “A picture is worth a thousandwords,” then you are familiar with thebasic principle of data compression:replacing one set of symbols withanother, smaller set. A high resolu-tion photograph of an object is a better description than a mere thousand words can evoke.
Today — with practically every-thing represented by 1s and 0s insome form or another — there is agreat need for digital data compression. Why? The answer istime and space. Oh, the Universe ispretty old and really big, but we stillwant to transmit data from oneplace to another quickly and wewant to use as little storage spaceas possible.
If you are downloading a file, youwant the download to take place asfast as possible. The time required todownload the file depends — amongother things — on the Internet con-nection speed and the size of the file.A file size of 2.5 MB will require moretime to download than a 245 KB file.
What if, however, there was a
way to convert the 2.5 MB file into a245 KB file? Then, the transfer wouldtake place quickly and the requiredstorage space would be significantlyreduced. Even better, after the file isdownloaded, the compressed datacan be expanded back into the original 2.5 MB.
First, let us think about logicalcompression. This has to do with theway we represent the data beingstored before compression. Onemethod may be better than another,in terms of its built-in logical compression. For example, supposea programmer has written code towrite sensor data to an output file.The programmer used a simple loopof code to write 16-bit ASCII stringsof “0” characters and “1” characters,such as:
1001001111101010
which requires 16 bytes of file space.If the programmer was to spend
a little more time in the output loop,then the 16-bit string could be converted into a four-character hexadecimal string, such as:
93EA
saving 12 bytes offile storage space,compressing the out-put file by 75%, andgiving us 4:1 com-pression. The pricewe paid was to spendmore time on theprocessing. With thefast computers avail-
able today, we can afford the processing time and make use ofvery complex techniques to obtaingood compression rates.
As we just saw, logical compression leads to physical compression. A good example of alogically-compressed code is MorseCode. This code was invented bySamuel Morse in 1844 for use withtelegraphs. Letters, digits, andpunctuation symbols are defined bydots and dashes in the code. Figure1 shows the Morse Code for the letters A to Z.
Notice that the most frequently-used letter — E — is represented by asingle dot. Other popular letters,such as A and I, require only twosymbols (dot-dash and dot-dot,respectively). Letters not frequentlyused, such as X, Q, and Z, containfour symbols each in their codes.Samuel Morse built data compres-sion into his code by designing it sothat frequently used letters requiredthe fewest symbols and, thus, weretransmitted more quickly than thesymbols for less frequently used letters.
You can experiment with digitaldata compression yourself by working through the following stepsto design your own binary version ofthe Morse Code. In the exampledescribed in these steps, a tone generator and speaker are controlledby a single bit. When the bit is high,the speaker emits a tone. When thebit is low, the speaker is quiet.
1. Assign binary patterns to dots anddashes. Since a dash is longer than a
Getting More for Less —A First Look at Digital Data Compression
Figure 1. A portion of the Morse Code alphabet.
Electronic Theories and Applications From A to Z
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SEPTEMBER 2004
Let’s Get Technical by James Antonakos
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dot (Its tone lasts longer whenplayed), let us use one bit for a dotand two bits for a dash. So, a dot willbe a 1 and a dash will be a 11.
2. Assign binary patterns to the symbol, letter, and word spacing. Thesymbol spacing is the quiet timeneeded between one dot/dash and another.
For example, in the code for letter A, we have a dot followed by a dash. If we let the symbol spacing be a single bit (equal to 0), we can represent the letter A by thebinary pattern 1011. The letter spacing is the quiet timeneeded between the letters that make up a word or abbreviation. This spacing needs to be longer than thesymbol spacing.
Let us use two 0s for the letter spacing. Now the lettersOK will encode as 11011011001101011. Last, the quiet time between words must be longer than the quiet time between letters. For this, let us use three 0s. Then, the words HI JIM will encode as1010101001010001011011011001010011011000.
3. Count the number of bits required to encode a messagein the chosen format. For our example, the binary stringencoding HI JIM contains 40 bits.
4. Repeat steps 1 through 3, making one or more changesto the binary patterns assigned. Encode the same message as before.
5. Compare the number of bits required for each encoding. If one method is better than another, can youdetermine why?
You may also change the hardware requirements andsee what effect they have on the format and compressionof the encoded binary string.
Another logical type of compression is performedwhile encoding an MP3 audio file. MP3 files get their namefrom the MPEG Audio Layer 3 specification. MPEG(Moving Picture Experts Group) audio and video are popular encoding methods for creating high quality, low-bitrate multimedia files.
There are three audio layers defined in the MPEGstandard. Table 1 lists some of their features. As indicated, Layer 2 is superior to Layer 1, and Layer 3 issuperior to Layer 2. Layer 3 requires the most processingpower to implement the decompression algorithm; Layer1 requires the least. Layer 3 encoding did not becomepopular until the speed of the PC was able to support itscalculations. Before the MP3 audio file, the WindowsWAV file provided digitized audio for the PC. The WAV filesimply stores the sampled audio data without compression.
The Compression column refers to how well the audio
information compresses compared to a CD quality,uncompressed bit stream of 1,411,200 bits/second (two16-bit channels, sampled 44,100 times each second). Asindicated in the table, the more processing power you canthrow at the compression algorithm, the better your datawill compress (to a certain limit).
All three MPEG layers use the same basic techniques for encoding audio and compressing thedata. These techniques — called perceptual audio coding and psycho-acoustic compression — utilizeknowledge of how humans hear and process sounds toeliminate information that is duplicated or masked outby other sounds.
By eliminating the redundant or unnecessary information, the MP3 file requires less storage space thanan uncompressed WAV file for the same audio information. For example, a 30 second WAV file requiring
23SEPTEMBER 2004
os Let’s Get Technical
MPEG Audio Layer Encoder Complexity Compression Typical Bit Rate
1 Low Low (4:1) 384 Kbps
2 Medium Medium (8:1) 192 Kbps
3 High High (12:1) 112 Kbps
Table 1. MPEG audio layer differences.
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Serial link passes through base unit without retransmission distortion or delay.
Captures full duplex data with precise time tagging and line states.
Measures transmit and receive line voltages.
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Data can be easily exported to third application.
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Smartronix
Circle #152 on the Reader Service Card.
RLLetsGetTechnical.qxd 8/10/2004 11:47 AM Page 23
330 KB of storage wasconverted into a 220 KBMP3 file. The MP3 filesounds as good as — ifnot better than — theoriginal WAV file, withthe absence of 110 KB ofsound information.
Even sampling theanalog sound informa-tion can be approachedfrom different direc-tions. Using an analog-to-digital converter, youmay sample the converter 8,000 timesper second, reading aneight-bit sample each time. Thus, aone second audio waveform wouldrequire 64,000 bits of storage.
Now, suppose you change thesampling hardware to one that usesa delta modulation method, wherethe sample can only increase ordecrease by a small value eachtime. (This is the delta.) Then, eachsample only requires one bit ofstorage.
Now, one second of audio onlyrequires 8,000 bits of information.If the delta modulation methoddoes not have significant slopeoverload losses (signal level chang-ing faster than one delta betweensamples), it provides a nice, built-incompression over the eight-bit A/Dmethod.
Once the MP3 compressor hasthrown away the WAV file’s redundant and unnecessary signalinformation, there is no way to get itback. In this case, it does not matter,since the MP3 format has high quality.
What if we need to have every bitof the original data back when it is
uncompressed? If we compress aprogram file and then uncompressit, every byte in the file has to becorrect or the program will not function correctly when the program is executed.
In this case, we need a com-pression algorithm that is “lossless.” The technique used toconvert the WAV file to an MP3 fileis a “lossy” compression technique,since some of the original data isthrown away.
Okay, so the MP3 audio file isone place where lossy compressionmay be used to advantage, butwhere else can we get away with it?We cannot do so in program files,for sure, or even files that containimportant information, such asdatabases, but what about imagefiles?
Browsing the Internet is a wide-spread activity, awash with images ofmany shapes and sizes. Webbrowsers that display graphicalimages accept two different types ofimage files: GIF images and JPG (orJPEG) images. GIF stands for
Graphics InterchangeFormat. JPEG stands forJoint Photographic ExpertsGroup. GIF files were creat-ed by CompuServe as amethod of exchanginggraphical information. Thefeatures of a .GIF file areas follows:
• Maximum of 256simultaneous colors
• Lossless compressionusing LZW (Lempel-Ziv-Welch) algorithm
• Support for animation andtransparency built-in
• Interlaced and non-interlacedformats
The quality of the GIF image waskept low so that its file size could bemanaged. People with dial-upmodems for their Internet connection do not want to wait forever for an image to load.
When the GIF image data isdecompressed for display purposes,an exact copy of the original data isreproduced, due to the lossless compression used on the originalimage data.
Compare the properties avail-able in GIF encoding with those of JPG:
• 24-bit color (16,777,216 simul-taneous colors with eight bits eachfor red, green, and blue)
• Lossy compression using theDCT (Discrete Cosine Transform) algorithm on eight-by-eight blocksof pixels
• No animation or transparency available
• Non-interlaced format only
JPG files are preferred over GIFfiles for their photographic-qualitycolor. In addition, the lossy JPG
SEPTEMBER 200424
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Property GIF Image JPG Image
Bits / Pixel 8 24
Colors Used 256 20,089
Max Colors 256 16,777,216
File Size 24,557 bytes 10,097 bytes
Table 2. Comparison of the same image saved as a GIF and a JPG.
Let’s Get Technical
Figure 2. Sample image containing 24,320 pixels.
RLLetsGetTechnical.qxd 8/10/2004 11:47 AM Page 24
compression provides better compression, in general, than thelossless compression used in GIFfiles, with little noticeable effect onimage quality. Some images lookvery poor when saved and viewed asGIF files due to the lack of colorsavailable.
For others, the lossy format ofthe JPG is unacceptable. This is especially true for medical images,where the actual shade or color of apixel is important. In the lossy-compressed JPG image, eight-by-eight blocks of pixels have their values adjusted slightly, so the original content of some pixelsare lost.
Consider the image shown inFigure 2. The image contains 190 ×128 or 24,320 pixels. Without compression, a total of 24,320 byteswould be needed to store all the eight-bit pixel values for an image of 256colors and 72,960 bytes would berequired for an image with 24-bit pixelvalues.
Examine Table 2, which showsthe results of saving the image in GIFand JPG formats. Both formatsrequire fewer than the 24,320 byte,uncompressed, eight-bit color filesize. The JPG compression is clearlysuperior to the GIF compression;however, the JPG image file requiresless than half the space of the GIFimage file and only one seventh of
the estimated 72,960 bytes for anuncompressed, 24-bit color file.Viewing each image side by side alsoillustrates why JPEG is the better format for high quality images. TheJPG image contains almost 80 times the number of colors as theGIF image.
So, we have seen that there arelossy and lossless compression
techniques and that there are applications for both methods.
Next time, we will examine somespecific compression techniques,including run-length coding, Huffmancoding, the LZW algorithm, andsequence coding (all lossless), as wellas the Discrete Cosine Transform(which is used within the JPG’s lossycompression algorithm). NV
James Antonakos is a Professor inthe Departments of ElectricalEngineering Technology and ComputerStudies at Broome CommunityCollege. He has over 28 years of experience designing digital and analogcircuitry and developing software.He is also the author of numeroustextbooks on microprocessors, pro-gramming, and microcomputer systems. You may reach him at [email protected] or visit hiswebsite at www.sunybroome.edu/~antonakos_j
About the Author
Let’s Get Technical
25SEPTEMBER 2004
RLLetsGetTechnical.qxd 8/10/2004 11:47 AM Page 25
MMiinnii--KKiittss......TThhee BBuuiillddiinngg BBlloocckkss!!TTiicckkllee--SSttiicckkThe kit has a pulsing 80 volttickle output and a mischie-vous blinking LED. And whocan resist a blinking light! Greatfun for your desk, “Hey, I told you not to touch!”Runs on 3-6 VDCTS4 Tickle Stick Kit $12.95
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Need professional quality features but can't justify the cost of a commer-cial FM exciter? The FM25B is the answer! A cut above the rest, theFM25B features a PIC microprocessor for easy frequency programming with-out the need for look-up tables or complicated formulas! The transmit fre-quency is easily set using DIP switches; no need for tuning coils or "tweak-ing" to work with today's 'digital' receivers. Frequency drift is a thing of thepast with PLL control making your signal rock solid all the time - just likecommercial stations. Kit comes complete with case set, whip antenna, 120 VAC power adapter, 1/8" Stereo toRCA patch cable, and easy assembly instructions - you'll be on the air in just an evening!
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The FM10A has plenty of power and our manual goes into great detailoutlining all the aspects of antennas, transmitting range and the FCC rulesand regulations. Runs on internal 9V battery, external power from 5 to 15VDC, or an optional 120 VAC adapter is also available. Includes matching case!
FM10C Tunable FM Stereo Transmitter Kit $44.95FMAC 110VAC Power Supply for FM10A $9.95
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Run your own radio station! The AM25 operates anywhere within the stan-dard AM broadcast band, and is easily set to any clear channel in your area. Itis widely used by schools - standard output is 100 mW, with range up to ¼ mile,but is jumper settable for higher output where regulations allow. Broadcast frequen-cy is easily set with dip-switches and is stable without drifting. The transmitter acceptsline level input from CD players, tape decks, etc. Includes matching case & knob set and AC power supply!
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This nifty kit includes a pre-made high voltage iongenerator potted for your protection, and probablythe best one available for the price.
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Includes ion power supply, 7 ion wind tubes, and mounting hardware for the ionwind generator. Runs on 12 VDC.
Negative ions with a blast of fresh air! Generates 7.5kV DC negative at 400µA Steady state DC voltage, not pulsed!
IG7 Ion Generator Kit $64.95AC125 110VAC Power Supply $9.95
PPllaassmmaa GGeenneerraattoorr
PG13 Plasma Generator Kit $64.95PS21 12VAC Output 110VAC Power Supply $19.95
LLaasseerr LLiigghhtt SShhooww
You've probably seen a laser show at con-certs or on TV. They’re pretty impressive tosay the least! Knowing that you can’t afford aprofessional laser display we challenged our engi-neers to design one that’s neat and easy to build, yet inexpensive. Well, the resultis the new LLS1 Laser Light Show! This thing is sweet! It utilizes two smallmotors and a small standard laser pointer as the basics. Then, we gave it variablepattern and speed controls to customize the pattern!
Not enough, you say? How about a line level audio input to modulate the patternwith your CD’s or music? You bet! Everything is included, even the small laserpointer. And to make the kit absolutely safe, we even used plastic mirrors insteadof glass that could break! Runs on 6-12 VDC or our standard 12VDC AC Adapter(not included). If you’re looking for a fun and neat little laser kit, the LLS1 is foryou!
LLS1 Laser Light Show Kit $44.95AC125 110VAC Power Supply $9.95
EElleeccttrroonniicc LLeeaarrnniinngg LLaabbss
Whether you want to learn the basics of electricity, the theory of electronics, oradvanced digital technology, our lab kits are for you! Starting with our PL130, wegive you 130 different electronic projects, together with a comprehensive 162page learning manual. A great start for the kids...young and old!
Step up to our PL300, which gives you 300 separate electronic projects along with165 page learning and theory manual. The PL300 walks you through the learningphase of digital electronics.
If you’re looking for the ultimate lab kit, check out our PL500. Includes a whop-ping 500 separate projects, a 152 page starter course manual, a 78 pageadvanced course manual, and a 140 page programming course manual! ThePL500 covers everything from the basics to digital programming! Learn aboutelectronics and digital technology the fun way and build some neat projects!
Learn and build! 130, 300, & 500 In One! Super comprehensive training manuals!
PL130 130 In One Learning Lab Kit $39.95PL300 300 In One Advanced Learning Lab Kit $64.95PL500 500 In One Super Learning Lab Kit $159.95
WhereElectronicsIs Always
FUN!Prices, availability, and specifications are subject to change. Visit www.ramseykits.com for thelatest pricing, specials, terms and conditions. Fall Super Sale expires 10-10-2004Copyright 2004 Ramsey Electronics, Inc.
MORE than just friendly on-line ordering!Clearance Specials, Ramsey Museum, User Forums, Dealer Information, FAQ’s, FCCInfo, Kit Building Guides, Downloads, Live Weather, Live Webcams, and much more!
5500WW SStteerreeooFFMM TTrraannssmmiitttteerr
The PX50 is the latest ultra reliable LPFMtransmitter from Ramsey. It provide 50watts of continous duty RF power outputwith full automatic station monitoring.
The PX50 constantly monitors all of the critical circuits within the transmitter andmakes subtle adjustments to various circuit parameters depending upon frequen-cy, temperature, power, audio level, and deviation - in short, it’s like having a sta-tion engineer constantly monitoring and adjusting on-the-fly! Automatic VSWRprotection automatically reduces power output until the VSWR problem is cleared.Likewise, if the power amplifier temperature exceeds 70° C, the transmitter willreduce power output until it cools down below 60° C. You can set automaticPower Reduction On Error (VSWR & Temperature errors) to 85%, 75%, 50%, 25%or full disable of the set power. Full power is restored when the error is cleared.
You can also set the Power Restoration Timer for the error testing time to matchyour specific site environment. If the error is cleared within this time, the trans-mitter is restored to full power for unattended operation! Your station stays onthe air, and needless trips to your tower site are eliminated!
Connection is a breeze anywhere in the world. Give it anything from 85-264VACor 120-370VDC and you’re all set. Don’t have AC? Simply give it 12-14VDC froma battery source. Connect your stereo audio source and you’re on the air! Digitalinputs are also provided for RDS and SCA applications!
There has been a lot of confusion, and a lot of concern, regarding equipmentrequirements for licensed LPFM transmitters. The PX50 is FCC CERTIFIED forPARTS 2, 73, & 74 (ID: PF3PX50). No more worries about your station beingforced off the air due to non-compliance!
If you’re looking for ultimate reliability in a LPFM stereo transmitter withoutspending a fortune, the PX50 is your answer! It not only gets you on-the airquickly, but KEEPS you on-the-air! And that’s what it’s all about.
Generate 2” sparks to a handheld screwdriver!
Light fluorescent tubes without wires! Up to 25kV @ 20 KHz!
PX50 50W FM Stereo Transmitter, FCC Certified $1995.00
www.ramseykits.com800-446-2295
This new kit was conceived by one of ourengineers that likes to play with things thatcan generate large, loud sparks and otherfrightening devices.
During the process of looking for parts for one of his latestexperiments, he discovered how difficult it was to find a fly back transformer thatmet his requirements. This kit creates very impressive displays, drawing largesparks, and performing lots of high voltage experiments. It can also be used forpowering other experiments, let your imagination be your guide!
The high voltage at the terminal won't electrocute you, so it's relatively safe, but itcan burn you! So use caution when the power is on!!! Can also be run from 6-16VDC so the output voltage can be directly adjusted. Advanced experimentersonly! Not for the faint of heart!
50W RF output Automatic monitoring Automatic VSWR protection Automatic temerature protection Automatic battery backup FCC CERTIFIED under parts 2, 73, 74
PL130PL300
PL500
Audio input modulates pattern! Adjustable pattern and speed! Projects neat motorized patterns! Uses safe plastic mirrors
$37.95
$57.95
$57.95
$39.95
X
X
X
X
FALL SUPER SALE!Expires 10/10/04
FALL SUPER SALE!Expires 10/10/04
FALL SUPER SALE!Expires 10/10/04
FALL SUPER SALE!Expires 10/10/04
$34.95$59.95
XX
FALL SUPER SALE!Expires 10/10/04
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Game Fair Or Job Fair?
If you’re in San Francisco around October 6th, 2004, youmight want to take a peek at the goings on at the Bill
Graham Civic Auditorium. That’s where the World CyberGames 2004 Grand Final is being held. Representativesfrom 60 countries will be logging on with their computers,“where cultural barriers are stripped away andinternational exchange and harmony are promoted.” Ofcourse, this is the sort of harmony found on the receivingend of a megawatt pulse rifle aimed from an armoredpersonnel capsule on a high-arc jump.
The WCG 2004 is a video game competition, wherethe best in the world will attempt to out-drive, out-gun, andout-think their hardware accelerated, texture mapped, andcaffeine amped opponents. Official games for both PC andXbox machines include Counter-Strike: Condition Zero,Unreal Tournament 2004, Project Gotham Racing 2, andHalo. And, in case you think this is just a small event of anunder-represented subculture, consider the numbers fromthe 2003 event: 600,000 competed at the internationalqualifying events and earned over $1.8 million in prizemoney from sponsors like Samsung and nVidia.
If I was looking for youngpeople with fast reflexes, acutesituation planning skills, and amastery of computer inputdevices for the next generation ofremotely piloted vehicles, thiswould be a goldmine. But if you’rejust a gamer looking to frag somenewbies, you can register online:www.worldcybergames.com
Power On A Roll
Just get your hands onone of these SolarRoll™
14 flexible solar panelsand you’ll see what Imean. Produced byBrunton of Riverton, WY,these lightweight andwaterproof panels can berolled up unto a 3” dia.tube for easy storage between uses, empowering theaverage gadgeteer to step outside and get some rays. Themodel 14 produces 14 watts of power — 15.1 volts at 900mA — and includes adapter cables for several differentdevices, like satellite phones, digital cameras, and thatbeanie cap with electric propeller. For larger devices likelaptops or basic battery charging, two or more panels canbe linked together to increase power output. Though it isn’texactly cheap at $370.00, it is readily available. For moreinfo, visit www.brunton.com
O Marks The Spot
Integration is the future ofconsumer electronics, and the
cell phone is ground zero for amyriad of ongoing research.Enter the SpotCode platform,from developers High EnergyMagic out of Cambridge in theUK. Looking like a bar code justremoved from a spin art
machine, ablack and white glyph called a BangoSpot may become the “real worldhyperlink.” The Bango Spot isdesigned to be read by specialsoftware that processes the real-timeimage from your camera phone. Theresult of that processing —information on orientation, position,and size — is combined with thedecoded numeric identifier and bothare transmitted via Bluetooth to acomputer in the area, allowing thephone to become a universal pointingdevice, personal display, andkeyboard. Commercial applicationsabound, where consumer interestcould be indicated. Not to mention,walking up to a soda machine andbuying a Dr. Pepper. (This earns 9.5out of 10 on Editor Dan’s Clever-o-Meter!) Visit the developers atwww.highenergymagic.com
SEPTEMBER 2004
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Electronics Q&ALightning Physics
QQ.. During a lightning strike, is theearth considered positive or
negative?Gene Bozekvia Internet
AA.. Positive. In an electrical storm,the storm cloud is charged like a
giant capacitor. The upper portion ofthe cloud is positive and the lowerportion is negative.
Like all capacitors, an electricfield gradient exists between theupper positive and lower negativeregions. The strength or intensity ofthe electric field is directly related tothe amount of charge build-up in thecloud. The charge is created by colliding water droplets.
As the collisions continue and thecharges at the top and bottom of thecloud increase, the electric fieldbecomes more intense — so intense,in fact, that the electrons at theearth’s surface are repelled deeperinto the earth by the strong negativecharge at the lower portion of thecloud. This repulsion of electrons
causes the earth’s surface to acquirea strong, positive charge.
The strong electric field alsocauses the air around the cloud tobreak down and become ionized (aplasma). A point is reached (usuallywhen the gradient exceeds tens ofthousands of volts per inch) wherethe ionized air begins to act like aconductor. At this point, the groundsends out feelers to the cloud,searching for a path of least resistance. Once that path is established, the cloud-to-earthcapacitor discharges in a bright flashof lightning (Figure 1).
Because there’s an enormousamount of current in a lightningstrike, there’s also an enormousamount of heat. (In fact, a bolt oflightning is hotter than the surface ofthe sun.) The air around the strikebecomes super heated — so hot thatthe air immediate to the strike actual-ly explodes. The explosion creates asound wave that we call thunder.Some say that lightning strikes likethis in the early days of the Earth ledto the creation of life.
Cloud to ground strikes are notthe only form of light-ning, though. There arealso ground to cloud(usually originating froma tall structure) andcloud to cloud strikes.These strikes are furtherdefined into normal light-ning (discussed above),sheet lightning, heatlightning, ball lightning,red sprite, blue jet, andothers that are lesserdefined. For more infor-mation on lightning,check out http://science.howstuffworks.com/lightning.htm
Figure 1
In this column, I answer questions about all aspects of electronics, including computer hardware,software, circuits, electronictheory, troubleshooting, andanything else of interest tothe hobbyist.
Feel free to participatewith your questions, as well as comments and suggestions.
You can reach me at:[email protected]
What's Up:Have questions about
lightning? I have answers.
Two unique 555 timer
applications, a low-power
headphone amplifier, and
a classic car voltage
conversion. Plus the
usual website suspects
and lots of feedback
from our readers.
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Mapping Lightning
QQ.. The local TV weather programssometimes plot the various
lightning occurrences as they happen— usually for a three hour periodaround the state. I’ve wondered howthe lightning strikes are sensed andplotted. Maybe this is done visuallyfrom satellite images? Does that workfor lightning below the cloud deck?Are there sensing stations that give abearing to the lightning strike for stations to triangulate on — eitherradio or visual sensors? I’m just acurious ham operator.
Wally WillhardBountiful, UT
AA.. Satellites are more often used tofollow lightning strikes around the
world and haven’t advanced to thepoint where they can accurately maplocal areas like Bountiful, UT (butwe’re getting there). For that, a network of ground sensors is used.There are two types of sensors commonly used — magnetic directionfinders and VHF interferometery.
The National Lightning DetectionNetwork (NLDN), which is operatedby Global Atmospherics, Inc., (GAI)in Tucson, AZ (a wholly-owned sub-sidiary of Vaisala) is a network ofmore than 130 magnetic directionfinders that covers the entire US —more than twice the coverage of existing weather radar networks.
Each direction finder determinesthe location of a lightning dischargeusing triangulation and is capable ofdetecting cloud-to-ground lightningflashes at distances of up to 250miles and more. Processed informa-tion is transmitted to the NetworkControl Center (NCC) where it’s displayed in the form of a grid mapshowing lightning across the US(www.lightningstorm.com/tux/jsp/gpg/lex1/mapdisplay_free.jsp).
Recently, NASA has improvedthe resolution of the system byadding acoustical measurements tothe mix. Although the flash andresulting thunder occur at essentially
the same time, light travels at186,000 miles per second, whereassound travels at the relative snail paceof one-fifth of a mile in the same time.Thus, the flash — if not obscured byclouds — is seen before the thunder isheard. By counting the secondsbetween the flash and the thunderand dividing by 5, an estimate of thedistance to the strike (in miles) canbe made.
In the NASA lightning sensor, alow frequency receiver detects thelightning strike. The leading edge ofthe electric-field pulse is used to starta timer and the leading edge of the
thunder pulse is used to stop thetimer. A microcontroller in eachreceiver transmits the time measuredto a processing station, where thetimes are converted to distances thatare used to compute the location ofthe lightning strike (see Figure 2) towithin 12 inches. However, the NASAsensors have to be located within a 30 mile radius of the strike to be accurate — which is no big deal, giventhat these receivers cost far less to make and install than the GAIdirection finders.
You can build a simple, electric-field receiver using the schematic in
Figure 2
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Figure 3. The receiver is tuned to 300kHz; the sensitivity is adjusted by thelength of the antenna in the range of1 to 3 feet. The longer the antenna,the more sensitive the receiver. Thereceiver outputs a pulse to the 555monostable timer when a lightningstrike is detected, which causes thepiezo buzzer to beep.
A 5 volt Pulse Out signal is alsoavailable to start a timer, which youcan stop manually when you hearthe thunder (or build your own sonicthunder detector). That will give youthe distance to the strike. To triangu-late, you’ll need two or morereceivers and a software program(like Excel) to do the math.
Outbuilding Timer
QQ.. When I want something frommy shed, I flip on the light, get
what I need, and leave. Of course,
more often than not, I forget to shutoff the light. Since the shed has nowindows, I never notice that the lightis on until my next trip to the shed.What I’d like is a timer that wouldautomatically turn the light off after,let’s say, 15 minutes.
The switch should work normal-ly if you flip it off before the timeexpires; otherwise, the timer wouldtake control and turn off the light.Ideally, all the components would fitin a standard electrical utility box,along with the switch. An adjustabletime delay would be nice. Any ideason how I might build such a device?
Dick Balohvia Internet
AA.. My first suggestion is to installa motion detector wall switch,
like the one made by Eagle that’savailable at most hardware stores($19.95). As long as you are in the
shed and moving around, the lightremains on. Of course, it has itsdrawbacks. If you working in an areathat has you shielded from the sensor, you could find yourself in thedark. So, I can see why you mightwant to build your own timer circuitwith a predictable off time. For this, asingle 555 IC and an optoisolator(Figure 4) will do the trick and the circuit will easily fit into the utility box.
This circuit requires that youremove the wall switch from the ACwiring and use it to switch the 9 voltpower source instead. This can be a9 volt battery, but I’d use a wall-wartbecause the circuit won’t work if thebattery goes dead. Turning “on” thelight applies voltage to the 555 chip.The 0.1 µF cap on pin 2 forces thetrigger input low during power-upand starts the timing period.
The time is adjustable between 2and 20 minutes using the 1M pot. Ifyou turn off power to the chip beforethe time expires, the optoisolator’sLED goes out and the light turns off.If you forget and leave the switch on,the 555 timer will turn off theoptoisolator LED and do the job foryou. When building the circuit, besure to keep the AC mains as faraway as possible from the wall switchand 555 circuitry.
Low Voltage 555Timer
QQ.. I’d like a 555 timer to actuate arelay (5 VDC @ 150 mA) for 1
SEPTEMBER 2004
Q&A
Lightning Detector
2
6
73
51
48
555
OutPulse
0.1
+-
BuzzerPiezo
1 - 3 ft
ANT
10pF
1uH
10uH
.0011M
10k
270k
270k
.0012N3904
33k100k
.010.1
+5V Figure 3
Wall Switch Timer
3555
8 4
1 5
762
LED
SwitchWall
1M
0.1
+
1000uF
NeutralAC
HotAC
200V6A
.01
+9V
MOC30206
4
1
2
Lamp
180470100k47k
Low-Power Timer
26
7
3
51
48
555
+
100uF
+
1000uF
+
330uF
Relay3VDC
.01
+3V
47
15k
160k
Figure 4 Figure 5
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second and recycle this event every 13 seconds; therefore,this relay would be engaged for one second for every 13seconds. However, the entire circuit — relay included — hasto operate from 3 volts at 30 mA. (I’d be happier if it wouldoperate even at a lower voltage, such as 1.5 volts.) Myproblem is that I can’t “amplify” the voltage somehow forthe relay to be actuated just for 1 second.
Davevia Internet
AA.. You can’t operate the relay you selected from yourpower supply. The relay you specify has a coil resist-
ance of 33 ohms (R = 5/0.15 = 33 ohms), which meansit takes 90 mA to hold the relay in at 3 volts (I = 3/33 =90 mA). The answer is to use a 3 volt relay and run it atreduced current, as described in the June 2004 column(“About Relays”). All Electronics (888-826-5432;www.allelectronics.com) sells a 3 volt relay (#RLY-623) that should work. It has a coil resistance of 45ohms and draws 67 mA at 3 volts. In the reduced currentmode, it draws about 33 mA, which should be within thecapabilities of your power supply. Find the circuit atFigure 5.
The 555 chip has to be a ZSCT1555 from Zetex. Digi-Key (800-344-4539; www.digikey.com) has them instock at $3.47 each. Unlike the 555 — which has a mini-mum operating voltage of 4.5 volts — the ZSCT1555 oper-ates over a range of 0.9 to 6 volts. The timing resistors andcapacitor are adjusted to your specs, but can be changedto satisfy any duty cycle. When the output goes low, the330 µF cap charges through the relay coil and engages therelay. After the capacitor is charged, the current flowsthrough the 47 Ω resistor to reduce the relay load. The1,000 µF cap provides the surge current needed to pull inthe relay.
Seeking Clock Chip
QQ.. I have a kit clock that I built in the early 90s that runson the MM5314N clock IC from National
Semiconductor. I was wondering if you can help me locatea few more of these ICs, in case the one in the clock dies?
Benjamin Rappevia Internet
AA.. I have one of those kits, too, so I know your concern.Unfortunately, the MM5314N is almost impossible to
find in the US — and for good reason. An eight-bit MCU likethe 16F628 can do everything it used to — and more — forless money. Your best bet for a supplier is to look overseas.The following sites claim to have the MM5314N in stock forsmall quantity purchases.
www.scottele.com
www.computerville.it/tuscania/ik0mmy/ic.htm
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www.dicomse.com.ar/
In case you want to do a work-around using present-day MCU/logicchips, here is a pinout of theMM5314N:
http://users.otenet.gr/~athsam/Data_Base/MM5314N_clock_alarm.htm
Cassette To PC
QQ.. I have a collection of vinylrecords and cassette tapes that I
would like to copy over to my PC.However, my system is an older,bookshelf stereo with no line-in orline-out jacks. It does have a 1/4 inchheadphone jack, though, which Iplan to use.
If possible, I would like to listento the music while copying. Howmuch power is needed by the line-ininput of the sound card and howmuch is needed by the headphones?Do I need a circuit to reduce theheadphone signal?
Dean HansenNew Lisbon,WI
AA.. I’ve been monitoring a CD-ROM chat room for a while now
and have learned a lot about thetransfer of record/tape to a PC’s harddisk. One thing I learned is that youcan use the headphone jack to
directly feed the sound card lineinput as long as you have a compat-ible patch cable (1/4” to 3.5 mmstereo, in your case) and adjust theplayback system’s volume control toprovide a solid signal without distor-tion. No special electronics arerequired.
All you have to do is tap into thisline for monitoring — but it has to bedone without pulling down the linewith low impedance earphones.What I suggest is a low power head-phone amplifier — like the LM4808 —to isolate the headphones from thesound card. The chip is availablefrom Digi-Key. A typical circuit isshown in Figure 6.
I’ve adjusted the values for 4.5volt operation — three AA cell batteries, which you can replace witha 5 volt wall-wart. Also, note that I’musing R1 for the volume control.Adjust it to your needs; the lower theresistance, the louder the sound. Ofcourse, you have to supply all thecable breakouts and end connectors.RadioShack should have what youneed.
Project Needs PICBurner
QQ.. In the April 2004 issue, there isa project entitled “Hand-held
Messenger” that seems very interest-ing to me.However, when Itry to downloadthe file that con-tains the codefor the micro
(the hex file) from the Nuts & Voltswebsite, my computer can’t open it.Do I need a special program or software to view this file? I surewould like to see the code, as I aminterested in building the project.
Brianvia Internet
AA.. When programming a micro-controller (or a CPU, for that
matter), you first create a sourcecode file. This file contains all theinstructions in computer-ese (proba-bly assembly or Basic) that you can modify — or just read. However,the microcontroller can’t read computer-ese. It has to work withbinary numbers.
So, the source code is convertedinto hex format, which the chipunderstands. This is done usinganother program, called an assem-bler or compiler. Once converted tohex, all you can see (using WordPad)are long ASCII strings of 0 through 9,and A through F. At this point, youcan’t change the program withoutgoing back to the source code, mak-ing the changes, and generating anew hex file. (Don’t write — I know!)
Just having the hex code isn’tenough. To get the hex file into themicrocontroller, you need a burner.This is a piece of hardware that thecontroller chip plugs into and con-nects to the serial, parallel, or USBport of your computer. When yourun the burner software, the hex fileis transferred to the microcontroller’smemory. You’re now set. PIC pro-grammers are plentiful and include
SEPTEMBER 2004
LM4808
LEFT RIGHT
FromStereo
To PCSound Card
Audio Line Monitor
+
1uF
Headphones
+
100uF
+100uF
+
2.2uF
+
2.2uF
+4.5V
R110
3.9k
3.9k100k
100k
3.9k
3.9k
Car Battery Downverter
GNDSw
BstFB
VinLM2678
4
23
1
6
+12.6V
1.0k 4.22k
+6.3V
.01
12uH
50WQ03FN
+
100uF
+
470uF
Figure 6
Figure 7
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the popular EPIC frommicroEngineering Labs (shop aroundfor the best price). Kits and DIY plansfor PIC burners are also plentiful.
Be aware, though, that not allPICs are created equal and the HEXcode for the “Hand-held Messenger”won’t work with just any PIC micro-processor. Make sure you get a burn-er that supports the PIC16C84 calledfor in the project. Here’s a short list ofsuppliers:
Dontronicswww.dontronics.com/
diyk96.html
EPIC Pluswww.jameco.com
NOPPPwww.covingtoninnovations.com/
noppp
PICALL, available fromAmazon Electronicswww.picallw.com
Classic CarConversion
QQ.. A friend of mind has an oldFord that he restored to excellent
condition. Against my advice, he con-verted the car to 12 volts. The originalradio works fine on the 6 volts it wasdesigned for. I can change the six parallel filaments to three sets of twoseries filaments (7A7s, 7B6, 7B8,7C5, and 7Y4). I was wondering, if Ihit the power transformer with short,12 volt pulses, would it work as if itwas seeing 6 volt vibrator pulses? Iwant to take this route before designing and building a 60 wattswitching power supply.
Merlin Bakervia Internet
AA.. When I converted my ‘55 Fordto 12 volts, I used a 1 ohm, 50
watt resistor in series with the hotlead of the 6 volt radio. If you remem-ber the cars of that era, the resistorserved double duty by dropping thevoltage from 12 to 6 — and heating
up the cabin’s drafty interior. (Carheaters in those days left a lot to be desired.)
If you’d rather not waste thepower, you can build a simple, step-down converter using an LM2678switching regulator (Figure 7). Thecircuit was created using NationalSemiconductor’s Webench onlinedesign software (www.national.com/appinfo/power/webench/).The only critical component is theinductor, which must be rated at 12µH at 5.5 amps, like the PM2120-120K from JW Miller (Digi-Key#M6184-ND).
ProtectingProjection Lamps
QQ.. Can you provide a circuit toslowly power-up projection
lamps in video and movie projectors? These high wattagelamps are expensive and short lived;I would bet a slow turn on wouldextend the life of the lamps by limit-ing inrush currents.
Mikevia Internet
AA.. I assume you are talking abouttungsten filament lamps and not
the halogen or metal halide versions.The answer is an NTC thermistor.This thermistor starts out with a highresistance that decreases as it heatsup from current flow. You can buythem from Digi-Key for under $3.00.The trick is to match the thermistor to
the lamp using a rather intricate formula.
To spare you the calculations,I’ve assembled a table for a few ofthe most popular lamps. If you don’tfind your lamp listed, cross it to thevoltage and wattage columns to findthe inrush thermistor that’s right foryou. The thermistor should be inserted between the fan and thebulb so that it doesn’t limit the fan’scooling air.
Thanks ... ForNothing!
QQ.. Some time ago, I requested ascramble/descramble diagram
for my 2.4 GHz wireless video cam-era, but you’ve entirely ignored myrequest.
Then, I really wanted an USBtrans-receiver with an USB modulefrom www.linxtechnologies.comThey are actually a Nuts & Voltsadvertiser. So much for helping themincrease their sales by featuring a dia-gram with their USB module! Arethey aware of your help in not helpingthem sell such modules — especiallywhen they indirectly sign your paycheck?! Once again, you ignored myrequest. Maybe other readers like mewould have been interested in building such a project. Have youthought of that?
Then, I requested a self-poweredtimer for an auto ceramic heater (Ieven sent you a JPEG photo of theheater) to heat up inside a coil and
LampType
LampVolts
LampWatts
LampAmps
GE ThermistorModel Number
ColdOhms
HotOhms
CLS 120 300 2.5 CL-80 47 0.6
CZA 120 500 4.2 CL-50 7 0.13
CZX 120 500 4.2 CL-50 7 0.13
DDB 120 750 3.6 CL-30 2.5 0.09
ELH 120 300 2.5 CL-80 47 0.6
EXR 82 300 3.7 CL-70 16 0.3
EHJ 24 250 10.4 CL-11 0.7 0.03
Inrush Thermistor Selection Guide
Q&A
SEPTEMBER 2004 35
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then run inside a fan, based on a self-timer. Yet again, you ignored myrequest!
Now, I have this audio frequen-cy amplifier (Please, don’t ask mewhat it’s for!) with all the parts for it,but I’ve forgotten which part goeswhere. Can you please help me findthe accurate values for caps andresistors from the parts list given.My JPEG image doesn’t containviruses!
D. Zillbermannvia Internet
AA.. I never ignored your requestsand even responded to at least
one via Email. The problem is thatyour questions either require morepage space than this column affordsor that they are too ambiguous orapplication specific. As for the LinxTechnologies question, did you evercheck their website? It has youranswers.
If other readers feel like Mr.Zillbermann — in that I’m ignoringyou — please realize that I receivemore questions per month than I canpossibly publish. I have to selectthose questions that appeal to thegreater audience. If your question hasto be bumped, I do my best to Email
you the answer or flip it over to theTech Forum. Be aware, though, Ican’t answer a question that takes allof my time or uses up my month’sallotment of ink. For that, we havefeature articles. So, don’t expect meto build your science project or writeyour thesis.
Hopefully, I will soon have a Nuts& Volts “Q & A” web page for thosespill-over questions that didn’t makethe cut for the magazine, but needanswering. Stay tuned.
MAILBAG
Dear TJ,I have been rummaging through
my back copies of Nuts & Volts,looking for a schematic that youmight have been a part of. In doingso, I noted a Mailbag entry in theOctober 2003 issue from JosephWilson suggesting that a particularHeath site did not exist.
Being old enough to have builtthese kits, I looked for the site andfound it at www.circuitarchive.fsnet.co.uk/heath.htm (It may takea few tries to access the site; it isavailable intermittently.) The URL inthe magazine left out FSNET.
Plus, in surfing around, I hit upon
this site for Heath Robot owners (Ihave a Hero Jr.): http://hero.dsavage.net
Richard OberBaton Rouge, LA
Also try http://ww_heco.home.mindspring.com/ It keepsbetter track of the moving Heathwebsites than I can.
— TJ
Dear TJ,Regarding the February 2004
issue, the concept of a 42 volt system(actually 36 volts) is not really new.Back in the 1920s and 1930s, 36 voltlighting systems were used in manyrailway passenger cars and in ruralAmerica where there were, as yet, nocommercial power lines. The lampswere designed to operate at 32 voltsand looked like ordinary householdlamps with the standard Edison screwbase and fitted ordinary 110 volt-typesockets. This concept was wonderfulfor its time.
While it’s true that a higher voltage system in an automobile willallow smaller and lighter wiring to beused, there is a potential problem.The wire used on a 36 volt systemmay need only 1/3 the cross-section-al area of the equivalent 12 volt system, but — in Canada and thenorthern US — this thinner wire canbe susceptible to disruptive corrosioncaused by road salt used in the winterto clear the roads.
The problem with corrosion usually is not along the length of thewire, which is insulated, but at thepoint the wire terminates, where thecopper is exposed. Unless the automakers take much greater care indesign and installation to protectthese smaller wires than they current-ly do, there will be a rash of variouskinds of automotive electrical systemfailures long before their time.
Ernie MooreNepean, Ontario
Dear TJ,Your discussion of battery
arrangements in the April 2004 issue
Q&A
SEPTEMBER 2004
Electronics and Electrical V8.2
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brings back a memory from the 50s.There were many small sized com-munities in which telephone servicewas provided by manual switch-boards operated by independent telephone companies. I wasemployed by a telecom manufacturerto convert these communities to dialoperation.
At one site, our customer (thelocal phone company) had arrangedfor Bell Systems to provide someinter-connecting arrangements toother exchanges. The installation oftheir equipment was to be concur-rent with ours. At one point, I wasasked where they could pick off 24volts for their vacuum tube equip-ment. Our power source consisted of23 lead-acid cells — 48 volts total. Atthe direction of the TELCO engineer,I tapped the battery midway and created a distribution point on our panel.
I quickly found I could either boil
the water out of half the battery or letthe other half go flat. Perhaps theengineer should have known better; Icertainly never suspected.Fortunately, the 24 volt load wasquite steady. So, I mounted a numberof sockets on a piece of crating lum-ber and screwed in 100 watt lightbulbs until the loads were balanced —problem solved.
I went on to another assignment,but had an occasion to revisit the siteduring an evening hour somemonths later, only to find an eerieglow of 115 volt bulbs still runningoff the 24 volt bank. It was not thekind of jury-rig I expected to remainindefinitely.
John S.YoungScottsdale,AZ
Q&A
SEPTEMBER 2004 37
National Semiconductor has offered its popular Webench online simulator for powersupply design for several years (see “ClassicCar Conversion” above).The company has
now broadened the scope of its online toolswith “Amplifiers Made Simple.” Use it to
design your next op-amp application.www.national.com/appinfo/amps/
Need to kill some time? Try this fun puzzle.www.johnrausch.com/SlidingBlock
Puzzles/nooff.htm
The Universe began not with a bang, butwith a low moan — building to a roar thatgave way to a deafening hiss. Hear it here.
www.newscientist.com/news/news.jsp?id=ns99995092
Tired of waiting for Adobe’s Acrobat Readerto load? The “Adobe Reader SpeedUp” is a
small utility that fixes that.www.tnk-bootblock.co.uk/
prods/misc/index.php
Cool Websites!
Circle #123 on the Reader Service Card.
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DIGITAL POWER CONTROLLERSPEEDS PRODUCTDEVELOPMENT
TThe versatile power, control, and data interfaces of theMultiDriver™ Board save valuable time by providing
an integrated system for digital controller development.Typical applications include power, thermal, motion, light-ing, and flow control for industrial and educational pur-poses. The switching power stage accepts 12 V to 48 Vsupplies and provides a 6 A half-bridge or 3 A full-bridgeoutput current. Protection features include current limitand thermal shutdown, as well as filters and clamping ona split ground plane. FlexController™ SOC allows quickverification of control algorithms through the PC with freeFTview™ software.
The 28-pin DIP controller socket also accepts PICmicrochips and provides an In-Circuit-Debugger connec-tion. Data communication is through the FlexBus™ isolat-ed multi-drop serial bus that eliminates line drops andground noise from measurements, provides protectionfrom power transients, and enables operation at voltagesnot possible with other systems. The data bus is port-powered, four-device addressable, and compatible withcommon USB to serial converters for maximum flexibility.
Flextek’s product manual provides application noteswith schematics and code examples. The board is 2.3 x3.0 x 0.9 inches with convenient screw terminal connec-tors. The MultiDriver Board FCMD010 is available nowfrom Flextek Electronics for $79.50.
For more information, contact:
FLEXTEKWeb: www.flex-tek.com
Circle #54 on the Reader Service Card.
POLOLU USB-TO-SERIALADAPTER
PPololu introducestheir new USB-to-
serial adapter for con-necting microcon-troller-based projects
to personal computers. The diminutive unit measures under1.0” x 0.7” including its connector, making it perfect forprojects where space is a premium. For quick prototyping,the simple layout of the ground, transmit, and receive linesallows for easy mounting that takes up as little as fourbreadboard rows.
The USB adapter’s drivers make it look like a standardserial port to the operating system.
Therefore, the adapter can be used with existingsoftware — such as servo controller interface programs —that are designed for traditional serial ports. Unlike mostUSB-to-serial adapters that require an additional RS-232-to-TTL converter, the Pololu USB adapter uses 3.3 V signallevels that can be connected directly to microcontrollersrunning at up to 5 V.
The adapter is compatible with USB 2.0 standards andallows baud rates of up to 921.6 kbps. Support is initiallyavailable for Windows 98 through XP; Mac and Linuxsupport will follow shortly.
With the trend toward removing serial ports fromnew computers, the Pololu USB-to-serial adapter providesone of the most economical, small, and simple solutionsto the common problem of interfacing small projects toPCs. The price for one unit is $23.00 with free shipping inthe US.
For more information, contact:
POLOLU CORPORATION6000 S. Eastern Ave., Suite 5-E
Las Vegas, NV 89119Tel: 1-877-7-POLOLU or (702) 262-6648
Fax: (702) 262-6894Email: [email protected]
Website: www.pololu.comCircle #33 on the Reader Service Card.
ezVID SERIAL VIDEO MODULE
TThe ezVID serialvideo module is a
simple video card foruse with microcontrollers,Stamp modules, and similardevices. The module makesuse of an onboard micro-controller and video signalgenerating chip to allow
simple color video generation withonly two I/O lines.
The easy-to-use ezVID commands allow placement ofany built-in or user defined character anywhere on thescreen in any one of 14 colors; it also allows the user todefine up to 256 custom characters, change thebackground color to any one of 14 colors, clear the entirescreen to any one of 14 colors, or reset the system for a
New Product News
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clean start. The pixel resolution of the screen is 188 by 254.The ezVID comes in a simple to use 2” x 2” SIP
module that has four mounting holes for secureplacement in your project. A four-pin header is providedfor easy connection to your project in order to supplypower and access the TTL level asynchronous serial datalines. It also comes with a standard RCA style jack for thevideo output.
The ezVID sells for $59.95 and is available through theMultilabs website. It is only available in NTSC.
For more information, contact:
MULTILABSLake Forest, CA
Email: [email protected]: www.multilabs.net
Circle #61 on the Reader Service Card.
GPRS/GSM APPLICATION KIT
ZZ-World has now released theGPRS/GSM Application Kit.
The kit will allow machines theability to notify a user when theyneed servic-ing, havetheir settingsc h a n g e dfrom any-
where in the world, upload datawirelessly, send commands fromone machine to another, and sendvehicle location/conditions viaEmail. The GPRS/GSM ApplicationKit is designed to integrate embed-ded controls with wirelessGPRS/GSM communication appli-cations.
Z-World’s GPRS/GSM ApplicationKit provides all the necessary tools tosample and develop applications thatcombine a Rabbit-based controldevice with a GSM/GPRS modem,manufactured by Enfora, Inc. Thelibraries and sample programs allowa device connected to the cellularnetwork to send SMS (text) mes-sages to a RabbitCore module (RCM)that can interpret messages as com-mands and, in turn, execute controlfunctions. The RCM can alsosend/receive GPRS Email wirelesslyto/from any PC, GSM device, or cellphone. The LCD/keypad moduleincluded in the GPRS/GSM
Application Kit incorporates a menu system that providesfor an easy interface to read or send text messages andEmail.
Kit applications include, but are not limited to:wireless automation and control, alarm and notificationsystems, remote monitoring, data and event logging,machine communication, FTP (File Transfer Protocol)uploading, Telnet, Email, and text messaging comm-unications.
The GPRS/GSM Application Kit includes Z-World’sDynamic CTM integrated development software withroyalty-free TCP/IP stack and PPP module, along with aquad band wireless modem and all supporting embeddedsystem hardware.
GPRS/GSM Application Kits are available to shipimmediately with a price of $649.00.
For more information, contact:
Z-WORLD2900 Spafford St.Davis, CA 95616
530-757-3737 Fax: 530-757-3792Email: [email protected]
Web: www.zworld.comCircle #85 on the Reader Service Card.
New Product News
SEPTEMBER 2004 39Circle #80 on the Reader Service Card.
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THE NEWBLUETOOTH OEM
PPROMI-ESD-02 is an OEMboard type of the Promi-
SD, Class 2 Bluetooth version.This unit is easy to use and can be embedded in applications, including virtually any type of machinerythat requires a wireless, serial communication link. It islong range, easy to install, low cost, and provides point-to-point connection without RS232 cables. Additional fea-tures include:
• Class 2 output power: 2.5 mW (4 dBm)• 3.3 VDC power supply• Integrated antenna on the board with setup software and
manual on CD • Output interface UART• Compliant Bluetooth spec. v 1.12• Transmission power class 2 (max. 4 dBm)• Dimensions 18 x 20 mm
For more information, contact:
LEMOS INTERNATIONAL CO., INC.1305 Post Rd. #305Fairfield, CT 06824
Email: [email protected]: www.lemosint.com
Circle #97 on the Reader Service Card.
LANDMARK LR SERIESEXPANDS TO EUROPEANFREQUENCIES
LLinx announcesthe newest mem-
ber of the LRReceiver Series of RFmodules. The 433MHz LR receiverinterfaces to virtuallyany data source,including microcon-trollers and decoder chips, making them ideal for applica-tions such as remote control, keyless entry, and periodicdata transfer. Capable of operating at distances in excessof 3,000 feet, LR receivers deliver 5-10 times greaterrange than previous solutions. They are also the lowest incost of any Linx receiver product.
The modules operate over a 2.7-5.2 VDC range andfeature low power consumption, wide operational temper-ature range, adjustable transmitter power, and a receiversensitivity in excess of -115 dBm. A precision, crystal-locked PLL architecture allows for transparent data trans-
fer at rates of up to 10 kbps. No external components arerequired (except an antenna), allowing for easy designintegration — even by engineers without previous RFexperience.
LR series modules are designed for regulatory com-pliance and interference immunity and are available infrequencies suitable for both domestic and export wire-less applications. The modules are housed in a tiny SMDpackage that is footprint compatible with the popularLinx LC-S receiver, allowing existing customers an instantpath to improved range and lower cost.
433 MHz LR receivers are in production and priced atapproximately $6.78 in volume production quantities.
For more information, contact:
LINX TECHNOLOGIES, INC.575 SE Ashley Pl.
Grants Pass, OR 97526Tel: 800-736-6677
Web: www.linxtechnologies.comCircle #100 on the Reader Service Card.
LATEST GEN/CMOS CAMERA
SSUPERCIRCUITS ofLiberty Hill, TX has
released the new PC300camera series, which incor-porates the latest layeredCMOS imaging technology.
The PC300 series camerasproduce 280 lines of resolutionand a low light rating of 1 lux.The PC300 series cameras are
available with two different lensoptions, a micro lens measuring 0.5 inches in diameteroffering a 35 degree field of view and a covert pinholelens option. The covert pinhole lens needs only a 1/16”inch unobstructed opening to obtain a 25 degree field ofview. The PC300 series is also flexible when it comes topower. It can operate between 7 to 14 volts and draws lessthan 10 milliamps.
The combined performance of this camera makes itgreat for a variety of scientific, robotic, and securityapplications. The PC300 series is being introduced at aground-breaking low price of $11.95, making it withinreach for many applications.
For more information, contact:
SUPERCIRCUITSOne Supercircuits PlazaLiberty Hill,TX 78642
800-335-9777 Fax: 866-267-9777Web: www.supercircuits.com
Circle #33 on the Reader Service Card.
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New, by Infineon. Has lasertransmitter and receiver inone package! 1.25 Gb/sdata rate up to 700 M onlow cost multimode fiber!Super small size, completespecs on the web. Makeyour own fiber optic link!0125461R (Set of two) ............................$19.95
ORDERING INFO: Add $6.95 for shipping, handling andinsurance. Orders under $25, add $5.00 small order fee. NJresidents add 7% sales tax. Sorry, no CODs. Foreign orders:use credit card and specify shipping method desired.
See more surplus electronic goodies at:
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16 character by 2 lines 5x8dot matrix character 64.5 x13.8 mm viewing area STNneutral mode reflective LCDrecently discontinued by
Hitachi but a very common and most used part.Directly crosses over to the Optrex DMC16249,brand new stock!0123260R ................................................$4.95
Hitachi LCD display
Wow! What a a cool item!Brand new laser scannermodule includes red laserdiode, beam splitting mirror,opamps, photo sensor, tran-
sistors, etc. From handheld laser barcode reader.No specs, $50 in goodies to first person who figuresout the hook up! Only 5 pins, so it should be easy!0128525R ................................................$14.95
Laser Scanner
Bar Code Module
Phihong PSM4954AUniversal 100-240VAC input14 VDC output @ 1.8 ampsSmall size, 2x1x5”0123815R ..............................................$4.95
Switching Supply
CCFL Florescent Light Inverter
Fiber Optic Transceiver
Powerful DC Motor
Cellular Bi-Directional Amp
Super Micro Tiny Speakers
Amplified Speakers Truck Stereo
Ericsson Desk style speak-erphone unit contains niceamplified speaker as well asMotorola MC31118 speaker-phone IC. Includes detailson converting to a sweetsounding amplified speakerfor iPod! Runs on 6 VDCand we even include the ACadapter!
0124605R .........................................$12.95
New power inverterdrives 2 lamps up to5W each! Simple touse, 12 VDC in, con-nect florescent lampsto output. Module gen-
erates correct starting and operating voltage, lampcurrent and is even dimmable!0128520R ...................................................$9.95
Motorola Hands-free amplifiedspeaker and switching powersupply. Contains a PhilipsTDA1519 stereo 6 watt perchannel IC amplifier, 5 VDC @1 amp switchmode regulator(adjustable from 4.8 - 7.5VDC), sensitive electret microphone with pre-amp, cigarette lighter cord, plus a universalmount with handy spring clip to attach any-where! Super rugged ABS plastic enclosureand fine sounding speaker! Works great asamplified speaker for CD and MP3 players,and the internal power supply has plenty ofpower to run any player! (5 volts replaces 4 AAcells) Brand new with hook up instructions onhow to connect to any CD or MP3 player.0123853R ...........................................$9.95
New in-dash cassettestereo AM/FM radio, LCDdisplay, drives 4 speakers(80 watts!) Even hasWeather band! Quality
fully enclosed case, easy hookup, great for inwall home installations! Runs on 12 VDC. 0128872R..............................................$29.95
Super nice Motorola amplifiedspeaker, runs on 12 VDC, 6watts. 5x5x2” metal case withadjustable mounting bracket.0124871R ....................$11.95
Real tiny full rangespeakers as usedin cell phones.Very small, approx.0.75”dia 0.15”thick, quality goldcontacts. You get 2 pcs of each,
Style A is 110 ohm, Style B is 32 ohm. Style Bincludes double stick foam mounting.0123338R Set of 4 spkrs ....................... $1.25
OEG Relay, Model # OJ-SS-109TM, 9 VDC SPST, NO contacts,180 ohm coil, 3 amp contacts,Small size .4" x .7" x .6"
0124685R (pack of 5)...........................$1.95
Quality speaker includes swiv-el mount and is 4.5x2.5x2.5”Includes 6 ft cord 3.5mm plug.
0127567R .........................................$4.95
Made by Johnson Electric12 VDC @0.85 A no load, 17,000rpm, 3 vdc @ .51 amps 4,200rpm, 6 vdc @ .6 amps 8,500 rpm.
Similar to Johnson Electric HC313MG series buthigher power. Actually runs as low as 1 volt oper-ation! (1200 rpm .46 amps). Size: 2" l x 1.5" dia7/8" long eccentric brass shaft end - easily brokenoff to form a .5" long x .312 dia round shaft end.0123850R .............................................$4.95
Rugged Speaker
9 VDC SPST Relay
Well made quality3 piece plier set.Includes deluxepadded zipper
case. Pliers are big 8” in size,you get: needlenose, diagonaland lineman style with handycrimper and stripper dies oneach tool! Get a few for thecar, gifts and toolbox, they are that nice!0128871R .............................................$12.95
Tool Set
Rechargeable Battery Blowout!
Made by Motorola, features powerful 3 wattRF amplifier for transmit and sensitivereceive amplifier. Utilizes diplexer ceramic fil-ters. Additional circuitry for protection, regu-lation, etc. Sorry, we have no specs on this,but its a treasure trove for the experimenterand RF guru. Brand new. Size: 4.5 x 5 x 1.5”in rugged extruded aluminum heat sink stylecase. Uses mini-UHF connectors.0127460R ......................................$14.95
Ion GeneratorBuild your own IonBreeze air purifier! Newmodule, 120 VAC in,
7.5KV out! Surplus from air cleaner makerwho sold them for $200! 0128873R ....................................$7.95
Nice, new 5 AA cell nicad pack.6 Volt 700mah with 6” wireleads. Great for projects orcordless phone replacements.0125345R.....................$2.50
Big box of 50 brand newAA button top NiCads. Fitanywhere an AA batterydoes. 1.25V 800mah.Best price in the USA!0128870R.............$19.95
Lithium Ion Rechargeables !!
Our web site has lots more greatdeals - in both small and large
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RechargeableLithium batteriespack the highestdensity of powerfor size andweight! Ideal rec-tangular size iseasy to fit in yourproject. All 3.6
Volt and approx rated Amp-Hour capacity.A: 1Ah 1.95x1.34x.4” 0125337R.....$1.50B: .8Ah 1.95x.1.34x.25” 0125349R.....$1.25C: .8Ah 1.95x1.24x.23” 0125350R.....$1.25
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A B C
C
Popular Nicad batteries, 1.25V all brand new,recent stock. A &B are NiCad and C is NimH.A: AAA 400mah 0125339R 2 for $1.00B: Sub C 2500 mah 0125443R 2 for $1.75C: 3.6 Volts 750mah 0125348R 2 for $3.00
A B
Circle #52 on the Reader Service Card.SEPTEMBER 2004 41
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The Audiophile's ProjectSourcebook: 80
High-Performance Audio ElectronicsProjects
by G. Randy SloneThe Audiophile’s ProjectSourcebook is devoid of thehype, superstition, myths,and expensive fanaticismoften associated with high-end audio systems. Itprovides straightforwardhelp in building andunderstanding top qualityaudio electronic projects that are based onsolid science and produce fantastic sound!$29.95
Robot Mechanisms andMechanical Devices Illustrated
by Paul SandinBoth hobbyists and professionals will treasure this unique anddistinctive sourcebook— the most thoroughand thoroughly explainedcompendium of robotmechanisms and devicesever assembled.Writtenand illustrated specificallyfor people fascinated with mobile robots,Robot Mechanisms and Mechanical DevicesIllustrated offers a one-stop source foreverything needed for the mechanicaldesign of state-of-the-art mobile bots.Written by a leading designer of robotsused at the horizon of mobile robotics,this resource offers a collection of bothnew and classic robotic mechanisms anddevices unmatched in scope — from suchhigh-level sources as the mechanical engineers’ mainstay, Mechanisms andMechanical Devices Illustrated. Paul Sandin’ssuperlative reference also brings you newrobotic mechanisms and devices that havenever before been collected! $39.95
Troubleshooting & RepairingConsumer Electronics Without
a Schematicby Homer Davidson
In this book, HomerDavidson gives youhands-on, illustratedguidance on how totroubleshoot and repaira wide range of electronicproducts — when youcan’t get your hands onthe schematic diagrams.He shows you how todiagnose and solve circuit and mechanicalproblems in car stereos, cassette players,CD players,VCRs,TVs and TV/VCR combos, DVD players, power supplies,remote controls, and more. $34.95
The Amateur Scientist 2.0Science Fair Edition
from “The Amateur Scientist” column This CD contains thecomplete collection —73 years — of articlesfrom Scientific AmericanMagazine's legendarycolumn "The AmateurScientist," plus a secondScience SoftwareLibrary CD with dozensof shareware and free-ware programs to feedthe passion of any science nut.With over1,100 projects to challenge science enthusiasts of all ages and skill levels —rated by cost, potential hazard, and difficulty— this is the ultimate resource for anyoneinterested in home-based science. If that'snot enough, it also contains over 1,000bonus pages of additional how-to sciencetechniques that never appeared in ScientificAmerican. Great for science fair students,hobbyists of all ages, and home-schoolers!In fact, The Amateur Scientist 2.0 contains aspecial primer for science fair students.Fully text-searchable and packaged in anattractive double-CD case, this remarkablebrowser-based product runs seamlessly onevery platform — Windows, Macintosh,Linux, and Unix.$24.99 — Subscriber$29.99 — Non-subscriber
Schaum's Outline of ElectronicDevices and Circuits
Second Editionby Jim Cathey
This updated versionof its internationallypopular predecessorprovides introductoryproblem-solving textfor understandingfundamental conceptsof electronic devices,their design, and theircircuitry. Providing aninterface with Pspice(the most widely usedprogram in electronics), new key featuresinclude a new chapter presenting the basicsof switched mode power supplies, 31 newexamples, and 23 PS solved problems.$16.95
Building Valve Amplifiersby Morgan Jones
Building Valve Amplifiers isa unique hands-on guidefor anyone working withtube audio equipment— as an electronicsexperimenter, audio-phile, or audio engineer.Particular attention hasbeen paid to answeringquestions commonlyasked by newcomers tothe world of the vacuumtube, whether it’s audio enthusiasts tacklingtheir first build, or more experiencedamplifier designers seeking to learn theropes of working with valves.The practicalside of this book is reinforced by numer-ous clear illustrations throughout. $29.99
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Robotics
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Build Your Own Printed Circuit Boardby Al Williams
With Build Your OwnPrinted Circuit Board, youcan eliminate or reduceyour company's relianceon outsourcing to boardhouses and cut costs significantly. Perfect foradvanced electronicshobbyists as well, thiseasy-to-follow guide isthe most up-to-date source on makingPCBs. Complete in itself, it even gives youPCB CAD software — on CD — ready torun on either Windows or Linux. $27.95
The Nuts & Volts Hobbyist BookstoreS e l e c t e d T i t l e s f o r t h e E l e c t r o n i c s H o b b y i s t a n d T e c h n i c i a n —
CNC Roboticsby Geoff Williams
Written by an accomplished workshopbot designer/builder,CNC Robotics gives youstep-by-step, illustrateddirections for designing,constructing, and testinga fully functional CNCrobot that saves you80% of the price of anoff-the-shelf bot — and can be customizedto suit your purposes exactly because youdesigned it. $34.95
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Electronic Gadgets for the Evil Geniusby Robert Iannini
The do-it-yourself hobbyist market — particularly in the areaof electronics — is hotter than ever.Thisbooks gives the “evilgenius” loads of projectsto delve into — from anultrasonic microphoneto a body heat detector,all the way to a Star Wars Light Saber.Thisbook makes creating these devices fun,inexpensive, and easy. $24.95
SEPTEMBER 2004
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BookstoreSep04.qxd 8/11/2004 5:34 PM Page 42
43
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Homemade Lightning: CreativeExperiments in Electricity
by R. A. FordEnter the wide-openfrontier of high-voltageelectrostatics with thisfascinating, experiment-filled guide.You'll discoverhow to make your ownequipment, how electricityis used in healing, andhow experiments in highpotential physics work!$24.95
Encyclopedia of ElectronicCircuits, Volume Sevenby Rudy Graf
Designed for quick reference and on-the-jobuse, the Encyclopedia ofElectronic Circuits,VolumeSeven, puts over 1,000 state-of-the-art electronicand integrated circuitdesigns at your fingertips.This collectionincludes the latest designs from industrygiants, such as Advanced Micro Devices,Motorola,Teledyne, GE, and others, as wellas your favorite publications, including Nuts& Volts! $39.95
Electronics Demystifiedby Stan Gibilisco
Best selling Demystifiedauthor and electronicsexpert Stan Gibilisco has penned the perfectintroductory book forconsumers, hobbyists, andstudents alike. Coverageincludes essential topics,such as current andpower supplies, wireless,digital principles, measurement and moni-toring, transducers and sensors, locationand navigation, and more. $19.95
Phase-Locked Loopsby Roland Best
The fifth edition of thisclassic circuit referencecomes complete withextremely valuable PLLdesign software written byDr. Best.The softwarealone is worth many timesthe price of the book.Thenew edition also includesnew chapters on frequencysynthesis, CAD for PLLs, mixed-signal PLLs,and a completely new collection of samplecommunications applications. $79.95
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This is a practical guideto one of the hottestfields in electronics and optical circuits.Acollection of hands-onexperiments and projects for the student,technician, and hobbyist,it explains optoelectronicsin nontechnical terms.Projects show how optical circuits workand how to use them in practical and efficient ways.You’ll save time, money, andenergy with dozens of do-it-yourself projects — from laser alarm systems tohigh-speed fiberoptic data links. Circuit dia-grams, schematics, and complete parts listsaccompany each project and an appendixlists suppliers for needed parts. $29.95
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by John CrispAssuming only a generalscience education,this book introducesthe workings of themicroprocessor, itsapplications, and pro-gramming in assemblerand high level languages,such as C and Java.Practical work andknowledge-check questions contribute tobuilding a thorough understanding with apractical focus.This book concludes with astep-by-step walk through a project basedon the PIC microcontroller.The concise butclearly written text makes this an idealbook for electronics and IT students and awide range of technicians and engineers,including IT systems support staff and main-tenance/service engineers. $34.99
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we are using the definition ofresistance and we are not usingOhm's Law. We can find variousexpressions for power by using thedefinition R=E/I. These are valid fornonlinear devices (diodes, light bulbs,varistors, etc.), as well as for lineardevices. That is, the expressions donot depend on Ohm's Law. My viewson Ohm's Law might be consideredtoo picky, but still, it would make myday to come across an article forbeginners that explains why Ohm'sLaw really is a law and not just adefinition. Even though that didn'thappen this time, I think the articlewas quite well done and useful.
Bob E. BakerCarmichael, CA
Dear Nuts & Volts:I read with great interest the article
entitled “Smith Chart Fundamentals”in your August 2004 edition of Nuts &Volts. The Smith Chart is a device thatI wanted to learn more about for sometime and this article was a goodstarting point. I hope you will featureadditional information about the SmithChart in future editions.
What prompted me to write wasthe notation of three citations in thearticle that — as best as I could tell —were not printed. Citation number 1was associated with the last sentenceof the first paragraph under thesubheading “The Inventor” after thewords “... match the line to space.”Citation number 2 and 3 wereassociated with the first sentence of thefirst paragraph under the subheading“What Is a Smith Chart?” after thewords “Although there are manycomputer programs ...” I appreciate ifyou could provide me the citations, aswell as publish them for other readers.
Ed Wilkvia Internet
The references were accidentallyomitted in the article, though theyare printed here. — Editor Dan
References(1) “Phillip H. Smith: A BriefBiography by Randy Rhea,” NoblePublishing.(2) The ARRL Radio Designer alsohas a Smith Chart utility.(3) Smith Chart computer programwritten by The Berne Institute ofEngineering. A demo version canbe obtained at http://sss-mag.com/zip/smith_v191.zip
Dear Nuts & Volts:I noticed two errors in the July
issue. The first is in the “Let's GetTechnical” article, where a “Table 1”is referenced that I can't seem to find.The second is in the “MicrocontrollersAre Great” article, where it is statedthat “it is sufficient to understand thata NAND gate's output only goes highwhen its two inputs are low,” which isincorrect. I guess the author meant tosay that the output only goes LOWwhen the two inputs are HIGH.
Karl Arndtvia Internet
Dear Nuts & Volts:Your readers should be aware of
the potential danger in building theLED Night Light project as describedby the author. Ping pong balls aremade of nitrocellulose which is anextremely flammable substance. Aspark on the AC input wiring due tosloppy construction of the night lightcould cause the ping pong ball toburst into flames rapidly and violently.
Ivan Zuckermanvia Internet
Dear Nuts & Volts:In the article “Stamp Application,
Expansion Made Easy” in the May2004 column by Jon Williams, theauthor compares a new expansionchip to an older one, calling the oldera “schoolyard sissy.” I bristled at theuse of this derogatory term. The use ofsuch terms in any publication —technical or otherwise — promotesprejudice and encourages violenceagainst certain groups of humanbeings. I realize it was only a casualreference, but many times we just donot concieve of the damage that termslike this can cause.
Andy LaTorreOtto, NC
Dear Nuts & Volts:The following might add to the
understanding of voltage, as anelectrical analog of pressure. I thinkwe all have an intuitive feeling for thefact that, when pumping compressedair into a tank, the added potentialENERGY is equal to the PRESSUREtimes each small addition ofVOLUME. When pushing moreelectricity into a capacitor, theadditional ENERGY is equal to theVOLTAGE times each small additionof CHARGE.
Dan Shanefield via Internet
Reader Feedback(Continued from Page 6)
ShowcaseSep04.qxd 8/11/2004 5:27 PM Page 45
Be the envy of your colleagues with thisüber-nerd coffee mug that generatespower from heat using the same
energy converters that are used on deepspace probes! Equipping a mug with thermoelectric energy converters andheatsinks will allow you to drive a smallmotor or other electrical device. You caneven claim to be environmentally responsibleby extracting useful work out of heat thatwould otherwise just go to waste.
Deep space probes like Cassini orVoyager are too far from the sun to use solarcells. They derive their energy instead fromRTGs (Radioisotope ThermoelectricGenerators), which are basically armored canisters holding plutonium dioxide fuel,which stays hot due to radioactive decay.Because these generators must work reliablyfor decades in space with no intervention foradjustment or lubrication, NASA needed a no-moving-parts way of generating electricity,instead of some kind of piston engine. Theanswer is thermoelectric converters — semiconductor junction devices that generatea current as heat flows through them.Although they are not very efficient, they arerobust and reliable.
Thermoelectric devices were once ratherexotic and difficult to obtain, but the perform-ance of modern microprocessors is such thatthey produce enormous amounts of heat,which must be removed efficiently to preventoverheating of the chip. So, little thermoelec-tric plates have become widely available.Here, I will show how you can use these inreverse to generate electrical power.
Thermoelectric Devices
The thermoelectric effect is the genera-tion of an electrical current at the junctions oftwo dissimilar materials (originally metals, butthe effect is larger for certain semiconductorslike silicon-germanium and lead telluride) ifthe junctions are at different temperatures. Itis quite a small effect — only a few microvoltsper degree Centigrade. The effect is reversible— if the temperatures of the two junctions areswitched, the voltage reverses. It is alsoreversible in that if a current is supplied to thejunctions, one will become cold and the otherwarm — heat is being transported by the electrical current.
The thermoelectric cooling modules we’lluse in this project are an array of around 100
pairs of p-n junctions, wired inseries. They are sandwichedbetween two thin ceramicplates to make it easy tomount them with good thermalcontact to a heatsink. This alsoallows the device to be cooled.Typically, these are suppliedwith a few amps of current at12-15 V and they can transportseveral tens of watts of heat.Note that the heatsink and fanon a typical CPU installationmust reject not only the heattransported from the CPU bythe cooling plate, but also theadditional heat produced bythe plate — that 12 V, timesseveral amps, is another
SEPTEMBER 2004
Java PowerBuilding a Thermoelectric Mug
46
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TThhiiss MMoonntthh’’ssPPrroojjeeccttss
Java Power . . . . . . . .46Electronic Sniffer . . . 50Enigma Machine P4 . . 54Floating Light Show . . 61
TThhee FFuuzzzzbbaallll RRaattiinngg SSyysstteemm
To find out the levelof difficulty foreach of these
projects, turn toFuzzball for the answers.
The scale is from 1-4, with four
Fuzzballs being the more difficult
or advanced projects. Just lookfor the Fuzzballs inthe opening header.
You’ll also find information includedin each article onany special tools or skills you’ll
need to completethe project.
Let the soldering begin!
Project by Dr. Ralph Lorenz
Close-up of the Thermoelectric mug.The blue enameled steel mug hasbeen hammered flat in places. Five thermoelectric modules are strapped
on with their heatsinks using bare tinned copper wire.The output ofthe modules is wired to a small motor with a balsa wood propeller.
RLLorenz.qxd 8/10/2004 1:16 PM Page 46
several tens of watts of heat.In this project, we’ll supply heat to the converter and
draw a current from it. When heat is flowing through theconverter (which will have an efficiency of typically 1% ifthe temperature difference across it is about 30° C), negative charge appears at the heatsink side (the “coldend”) of the converter in the N-type legs. Note that aneffective heatsink is crucial — it is no use making the whole converter hot: one side must be hot and theother cold.
Improving Performance
Thermal conduction is like electrical conduction —the flow of heat is like a current and temperature is likevoltage. The thermal circuit is a chain of resistancesfrom the high voltage (the hot liquid) to “ground” — thecool air. If the thermal resistance is low, then the “current”or heat flow will be highest.
One of the resistances in the circuit is the thermal converter itself. Ideally, this is the largest resistance in thecircuit, so that most of the power is dissipated in the converter and not in useless resistances elsewhere.
So, the other resistances (thickness divided by ther-mal conductivity) should be minimized — this means athin-walled mug made of a thermally-conducting materiallike metal. Similarly, the heatsink should be effective. Thebetter the heatsink, the cooler it will be and, thus, the temperature difference across the converter will be maximized.
Poor contacts between surfaces can introduce veryhigh thermal resistances — unless surfaces are groundexceptionally flat and perfectly aligned, a lot of airgaps fillthe contact area with contact being made only through little bumps in the surfaces. The way to minimize theseresistances and the temperature drops they cause is to usea thermal grease or heatsink compound that fills these little gaps with a relatively conductive material.
The voltage produced by the converter is proportionalto the temperature across it — this is, after all, the way thermocouples are used as temperature sensors. The current produced by the converter is proportional to theheat flow through it. The heat flow through the converter is
proportional to the temperature difference across it. So,the power produced by the converter (current times voltage) is, therefore, proportional to the square of thetemperature difference. This is why it is vital to maximizethe temperature difference by hot liquid, conductive mugand contacts, and a good heatsink.
To extract the most electrical power from the convert-er, it is important to choose the load impedance carefully
SEPTEMBER 2004
nz Java Power
47
Switch(optional)
Motoror otherload
MUG
Converters wiredin series
Circuit diagram. Five converters are wired in series (note polarity!).They are in thermal parallel (i.e., the same temperature difference is
driving them all). Heatsinks are omitted for clarity.
Thermoelectric Cooling Modules can now be found in manyelectronic parts stores and catalogs. One manufacturer/vendor isMagaland Technology, Inc. (www.leadingtechnologysales.com).I used several of their ICE-IT TEC 1-12705S cooling modules (40 x 40 x 3.8 mm, rated max 15.4 V at 5.2 A for cooling).
Another manufacturer is TE Technology (www.tetech.com)with a wide range of modules ($100.00 minimum order). I have alsoused their TM-TB-127-1.4-1.05(P) modules (40 x 40 x 3.8 mm, rated15.7 V 8.6 A).TE Tech’s website also has a lot of technical papers youcan download.
Resources
Circle #117 on the Reader Service Card.
RLLorenz.qxd 8/11/2004 1:26 PM Page 47
(just as for a photovoltaic cell). Using a very high imped-ance load measures the open circuit voltage, but admitsa very small current. On the other hand, a low impedance
gives a high (short circuit) current, but a tiny voltage.Somewhere in between, there is an optimum impedance(usually just a few Ω) that sucks a decent current out ofthe converter without letting the voltage drop too far. Forthese kinds of converters, the short circuit current can berather high, so you more or less want as low an impedance as possible.
Constructing Your Mug
One difficulty is that a mug is cylindrical, whereas theconverter is flat. One possibility is to find or make asquare or hexagonal mug — or perhaps bash some flatsurfaces onto a tin mug. Another approach is to makesome adapter pieces to help mate the converter to themug; if you’re ambitious, you could machine these out ofmetal. My quick-and-dirty approach is to wad up alu-minum foil, which acts as a fairly conductive — but moldable — material.
You could make the construction of the mug asrobust as you like — using machined parts or glue. On theother hand, if — like me — you just want to try it for awhilebefore using the converters in another project, you couldstrap the converters on to the mug using some steel orbare copper wire, twisting the wire tight on the mug handle to hold everything in place.
I found that, with 40 mm heatsinks and a steel mugwith flat sides, I could typically get about 0.3 volts andseveral tens of milliamps out of each converter. To get
higher voltages, the simplest approach is tomount more than one converter (in thermal parallel, but electrical series). I used five — aboutas many as there was room for on a large mug —to get about 1.5 V. If someone can come up witha circuit that can multiply DC voltages of a fewhundred millivolts up to several volts, it wouldmake these converters much easier to use! Notethat thermoelectric devices are like solar cells orbatteries — they have a polarity, which dependsnot only on their internal wiring, but also thedirection that heat is flowing through them. Somake sure that you wire them correctly to addtheir voltages!
So, what can you drive with this sort ofpower? An LED works pretty well — 20 mA is certainly enough, but you’ll need to make sureyou have enough voltage from the converters toexceed the forward voltage drop of the diode.Some LEDs can have forward voltage drops of 2V or more, but some that are as low as 1.4 V willwork better. Some small DC electric motors willrun on a volt or less, but you’ll need to make sureit runs smoothly enough at low current. Motorssold in solar power kits may work well; one I usewas ripped from an old CD player. I glued a smallbalsa wood propeller onto it to make it very
SEPTEMBER 2004
Project
The mug in action.The propeller spins for around 20 minutes.
48
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P
P
P
P
N
N
N
N
+
_
~ ~ ~ ~ ~~ ~ HOT ~ ~
~ ~ LIQUID ~ ~
~ ~ ~ ~ ~
MUG
WALL
Current Out
AIR
∆Tmug∆Theatsink
∆Tconverter
THOT
TCOLD
∆Tcontact
There is a cascade of temperature drops from the hot liquid to the air.In order to maximize the power output, we want ∆Tconverter as high as possible, so ∆Tmug must be low, as well as ∆Tcontact (e.g., heatsink compound, represented by the long, thin ellipses)
and ∆Theatsink (large heatsink).
RLLorenz.qxd 8/11/2004 1:26 PM Page 48
obvious when the motor was spinning. My mug, with fiveconverters on it, ran this motor for about 24 minutesbefore the voltage dropped too low.
Some Closing Thoughts
Be careful! Hot liquids can cause nasty burns.Remember also that the cooling fins may be hot, so don’tjab them into your face if you drink from the mug. Also, ifyou hammer an enameled steel mug to make flat surfacesfor attaching the converters, beware of the enamel spalling(glass flakes).
Of course, if you want to explore or demonstrate theperformance of thermoelectric converters, you needn’tuse an actual mug. You could attach the converter to a die-cast aluminum box and use that as a receptacle for hotwater. A limiting performance factor in the mug is the“cold end” temperature afforded by the heatsink. You canget much higher performance from the converter if yousandwich it between two boxes: one with hot water and theother with cold water — or better yet, ice.
Don’t be tempted to go too far with pushing power outof your converters. If temperatures exceed 100° C signifi-
cantly, the semiconductors can degrade and the solderthat bonds the junctions can melt — a eutectic bismuth/tinsolder that melts at only 138° C is widely used to makethermoelectric modules!
This is a somewhat expensive project, given its ratherfrivolous nature. New thermoelectric modules sell forabout $20.00 apiece, so there is about $100.00 of converters in the five-converter mug. You might want toexperiment first with a single converter. However, as thesedevices become ubiquitous in CPUs, they may startappearing in surplus outlets and become available at lower prices. You might be able to salvage some fromold PCs. NV
Java Power
SEPTEMBER 2004 49
Close-up side view of a thermoelectric cooling module.0
0.5
1
1.5
2
2.5
0 0.5 1
Voltage (V)
Cur
rent
(A
)
18 C9 C26 C35 C1 Ohm0.5 Ohm5 Ohm
I-V characteristic of cell.The datapoints are the voltage and current Imeasured with various temperature differences (9, 18, 26, and 35° C)across the converter (∆Tconverter).The higher the current drawn,
the lower the voltage, although it is a very nonlinear function.Arrows show schematically how the curves must turn over to reach
a “short circuit” current, though I didn’t measure that.The dottedlines show schematically how different load impedances will drawpower.To be efficient, a load impedance of 1 W or less is ideal.
Circle #140 on the Reader Service Card.
RLLorenz.qxd 8/11/2004 1:27 PM Page 49
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My wife and I were taking our morning constitu-tional walk up the hill when I noticed the smell.The wind was from the south.
“Do you smell that?” “What?” she said, “I don’t smell anything.” “Our neighbor must be gluing some PVC pipe or
fiberglassing something.” I didn’t think much more aboutit, but the smell continued off and on for the next coupleof weeks.
A month later, the wind was from the north and wehad taken a different route.
“Wow!” I said, “Is that ever strong!” “I don’t smell a thing” she replied. Then, it hit me
like a ton of bricks. I am a retired chemist and I don’tknow why it hadn’t clicked before: acetone or ether or a combination thereof. There was a drug lab in theneighborhood.
I went home and scrounged through my junk box andI found a Figaro TGS 822 gas sensor. I breadboarded it upto a 12 volt battery and hooked up a voltmeter. It stillfunctioned. Human noses quickly become desensitized toodors. The Figaro gas sensors do not. It didn’t take melong walking around the neighborhood to find the housethe smell was coming from. I called drug enforcementand explained my suspicions. Three months later, therewas a drug bust.
Everyone does not need one of these things to find aneighborhood drug lab, but it has many other uses. Bychanging the sensor, you can detect the following:propane, methane, hydrogen, carbon monoxide, ammo-
nia, hydrogen sulfide, organic solvents, CFCs, and carbondioxide, to name a few.
Methane is found in mines and is odorless. Minersused to carry a canary to detect it. So, if you are explor-ing mines, it might have a use. Carbon monoxide is alsoodorless and is a deadly killer and can be found in tunnels— or around your gas appliances. Ever wonder what thecarbon monoxide level is in the Holland Tunnel? The car-bon monoxide unit can be used for checking out bad gasheaters or has use with fire departments. The TGS 822 isgood for organic solvents.
The project is simple. It uses a round board that fitsinto the head of a four D cell Mag-lite that is available atany hardware store. You can find them for less than$20.00 if you shop around. The good thing about usingthis flashlight as a power source is that there are nomodifications required and you are able to still use it asa flashlight. Many of the sensors, like the TGS 822, havea heater and draw a hefty current 660 milliwatts or 132milliamps. The D cells will power the unit for 24 hours.The TGS 822 cost is $14.50, as of the January 2004price list. Other sensors vary in price. All are obtainabledirectly from Figaro.
Methodology
The heater requires a 5 volt regulated power supply. Iused a low drop out National LP 3875, which will allowoperation down to 5.1 volts, but doesn’t exceed 7 voltsinput. A Wheatstone bridge is used to provide the mostsensitivity and correct for the ambient temperature. Asthe sensor changes its resistance when it encounters agas, the voltage changes across the Wheatstone bridge.The brain of the unit is a PIC12C671 A/D microprocessor.The voltage from the Wheatstone bridge is fed into themicroprocessor and, with some simple math algorithms,is converted into sound. A bi-color LED is used to makesure you are on the right side of the crossover point of theWheatstone bridge.
Construction
You will need a programmer to program the PIC chipor it is available pre-programmed (see Parts List). Thecode is listed on the Nuts & Volts website: www.nutsvolts.com
All of the components — with the exceptions of the
The Electronic SnifferAn Electronic Nose That Knows ...
Project by Ron Newton
Parts placement on the PCB.
RLNewton.qxd 8/11/2004 2:10 PM Page 50
terminal and the voltage reg-ulator — are soldered to thetop of the board with theword “Sniff.” The sensor’s sixpins are designed to bemounted, regardless of itsposition; however, the soundtransducer is marked withpolarity. The long pin of theLED goes to the pad marked+. There are four holes forthe different pin spacings ofdifferent sound transducers.
The voltage regulator issoldered to the bottom sideof the board, along with thetwo-pin terminal. Pin 1 ismarked for the voltage regu-lator. Take some red finger-nail polish and mark the ter-minal next to the R (red wire)for ease of wire connection.
To make the bulb adapter, use an extra PR4 bulb andbreak the glass. Clean out its base and solder a red wire to
the center and a black wire to inside the case. The wiresshould be about 1.5 inches long. Tin about 1/4 inch of theends. This adapter allows the unit to be connected to the
SEPTEMBER 2004
on The Electronic Sniffer
Most of the Figaro sensors use micro-grains of sinteredtin oxide (SnO2) that have been heated to a high temperature.This causes oxygen to be absorbed on the grains and providesa positive potential in the space charge between the mole-cules. When a reducing gas — such as acetone, alcohol,propane, etc. — is passed over the sensor, the sensor’s resist-ance drops.The resistance is linear logarithmically over rangesof a few parts per million (PPM) to several 1,000 PPM. Forthose not familiar with log scales, what it amounts to is that alarge change in PPM will cause a small change in resistance,e.g., 100 PPM may give a resistance of 2,000 Ω, but a 1,000PPM would give a resistance of 1,000 Ω. For those who wantthe formulations, here they are:
Rs = A[C]-α
where: Rs = electrical resistance of the sensorA = constant[C] = gas concentrationα = slope of Rs curve
It is normal for the sensor to have a large drop in resistance when it is first turned on. Once the heater warmsup, the unit will function normally.The sensors will respond ina matter of seconds.
Humidity and temperature will also affect the sensor’sresistance, whereas humidity is difficult to correct for (but notimpossible). I considered it a minor problem due to the natureof the project. Temperature is compensated for by the thermistor in the circuit.
Although the sensors are pretty rugged, avoid siliconvapors and corrosive vapors, such as H2S, Cl2, HCl, and SO.Don’t get the sensor wet and, if it does get wet, don’t allow itto freeze or it will crack the sensing material.
Prices vary with the sensors. Here is a short list:
The following models sell for $14.50 and detect these gases:TGS813 LP-gas/propaneTGS822 Alcohol, toluene, xylene, acetone, etc.TGS842 Natural gas/methaneTGS24420* Carbon monoxideTGS2600* Air contaminantsTGS2610* General combustible gas* Require different mounting configurations
These models sell for $23.25 and detect:TGS830 CFC R-22 and R-113TGS831 CFC R-22 and R-21TGS832 CFC R-22 and R-134a
Finally, these models sell for $56.30 and detect:TGS821 HydrogenTGS825 Hydrogen sulfideTGS826 Ammonia
Figaro also makes oxygen sensors, but they are ratherbulky and will not fit on the flashlight. Visit them atwww.figarosensor.com for spec sheets and order info.
How the Sensor Works
5 +
5+
IC1
IC2
+
-
C1
+
R6
R3
2-5
1-3
TH R2R5
S1
2
5
1
1
R1
4 DCELLS
NC
2 3 4 5
2
3
45
7
8
6
+
R4
R7
The schematic showing the regulator, sensor,Wheatstone bridge, PIC processor, and output indicators.
51
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Project
SEPTEMBER 2004
flashlight without having to split the knurled nut that holdsthe bulb.
Using the Unit
Remove the lens, reflector, and the bulb from the flash-light. Place the bulb adapter into the bulb holder and screwon the knurled nut. Connect the wires to the board, mind-ing the polarity. Put the board into the lens holder andscrew it onto the flashlight. Prevent the board from turningby holding the components.
Turn on the flashlight. The LED should light either redor green. The sound transducer may be squeaking. Let theunit warm up for about two minutes. Adjust the poten-tiometer until the LED turns green. As the unit stabilizes,the pot may need adjusting.
Open a bottle of rubbing alcohol and place the unitnear the top of the bottle. Any bottle of alcohol will workjust as well. The LED should turn red and the speakershould change tone. The higher the tone, the more partsper million of vapor are present. When you place the unitin clean air, the tone should fall and the LED should switchback to green.
The unit can also be used to check someone’s breathto see if they have been drinking. Just have them blowtoward the sensor from about two feet. The unit is, howev-er, qualitative and not quantitative. It does not mean theperson is drunk. Do you need to check to see if a drink hasalcohol in it? Just place the unit over the glass. Try it witha glass of wine.
Check out www.figarosensor.com for more specifi-cations on using gas sensors and their detection limits.
Happy sniffing! NV
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The assembled sensor board installed in the Mag-lite body.
Ron Newton is a retired clinical scientist with degrees inchemistry and electronic engineering. He volunteers his time tothe Republic of Georgia Pediatric Hospitals (Asia) by providingconsulting and teaching in the fields of blood banking and bacteriology, and provides instruction in the repair of hospitalequipment. He also donates his time to NASA by providing R&Din the field of photonics and hopes to have his spectrometerdesign for the determination of ultraviolet light spectrums onone of the upcoming Mars shots.
About the Author
Circle #133 on the Reader Service Card.
RLNewton.qxd 8/10/2004 12:17 PM Page 52
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Circle #75 on the Reader Service Card. 53SEPTEMBER 2004
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SEPTEMBER 200454
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This is the last part of the Enigma series. In someways, it should really be the first because TheEnigma Machine grew out of these high power
observations. It was only after the electrical, physical, andchemical experiments were performed that enough infor-mation became available to design it.
In this article, we won't use The Enigma Machine.Instead, we'll look at its big brother and see what it cando. We'll see how Kirlian pseudo-science is just a flawedand fanciful misinterpretation of actual science. We'll alsodiscuss ELF (Extremely Low Frequency) effects (usuallyfrom power lines) that have been linked to health
problems. Finally, we'll look at some current research thatcould have significant practical applications.
Nomenclature and Apparatus
Since the effects are created without the movementof electrons, there is no electrical current flowing (see previous articles). It's not really electricity in the commonly used sense of the word; therefore, I will use theword "force" to refer to this transfer of an electrical chargewithout an electrical current.
I'm not going to describe the high power apparatus indetail. This is done to prevent unqualified and inexperienced people from getting hurt. The high powerapparatus does have the potential to give very painfulshocks and burns. (I know from experience.) An experi-enced and qualified person should be able to recreate theapparatus from my general descriptions and the previousarticles. I will be happy to provide details to academicinstitutions or other research interests upon request.
Anatomy of a Spark
An electrical spark of the same length, using thesame electrodes, must be the same, right? That's what Ithought. However, that's wrong. Figure 1 shows the basicsetup, which creates about 3/16 inch sparks. Figure 2 isa composite photograph showing the difference betweena common current carrying electrical spark to groundand a force spark under identical conditions. You can easily see that they are very different.
The photographs do not show exactly what the eyesees. In real life, the force spark has a lighter blue colorand looks continuous (no break in the middle). There isalso a very significant audible difference. The commonelectrical spark is very loud. The force spark can be nearly inaudible. Both sparks can be drawn to the samelength (> 1/4 inch). The force spark has no current flow(no deflection with a 50 µA meter). The electrical sparkhas significant current flow (slams the meter full scale).
At one time, I found that a very substantial amount offorce was passing through my body without any sensation. The amount was sufficient to draw sparks(about the same length as in Figure 2) from the tips of
Mr. E. Machine: TheEnigma Machine — Part 4
De-bunking Kirlian Pseudo-science
Project by Gerard Fonte
Figure 2.This is a composite photograph that shows the difference between a non-current-carrying spark (top) and a conventional current-carrying spark (bottom).
There is a significant difference in sound, as well.
Figure 1. Conventional sparks are made with the switch connectedto ground. Non-current-carrying sparks are un-grounded and
pass to large, lead mass.
RLFonte4.qxd 8/10/2004 1:07 PM Page 54
insulated wire-cutters I was holding to ametal plate. This is very different from highfrequency or RF skin effects. The operatingfrequency was nowhere near high enoughto create RF skin effects. I know thisbecause I have inadvertently allowed cur-rent to flow in several occasions, giving mea very painful shock. As we saw last month,the charge-transfer mechanism is different.
How can there be a spark without current, though? Isn't a spark electricity?Actually, it is not. When you see a spark, youare seeing ionized air (mostly nitrogen andoxygen). It typically has a blue hue, depending on the intensity of the charge. (Lightning looks white becausethere is so much current that the air is significantly heated.)
Electron transfer in a vacuum is invisible. If you've everlooked at an operating vacuum tube, you know that thereis nothing to see other than the glow of the filament.Sparks occur whenever there is enough energy to ionizethe atoms in the air.
Corona Discharge
A more general ionization — called a corona discharge— also occurs for the same reason. However, a corona discharge is not a simple point-to-point ionization. It occursover many points or even a whole area. Visually, it can bequite striking. Figure 3 shows the basic setup for perform-ing the corona discharge experiments. Figure 4 is what theexperiment looks like in normal light. If you look closely,you can see the force wire enter from the left. The tip of analligator clip, which goes to the lead bar, is barely seen atthe top. Figure 5 is what the corona discharge of the silverdollar looks like in a darkened room. Since it's hard to photograph without light, a 16 second time exposure wasused. This blurs the discharge somewhat. The eye seestiny tendrils of glowing blue that dance about.
You don't have to use metal to create the corona dis-charge. Anything that is either an electrical or force "conduc-tor" will work. I used an ordinary leaf for Figure 6. Initially, Iwas going to scrap that photograph because of the burn-through in the middle of the leaf (that bright white area in themiddle) that washes out the corona. However, I realized thatthis also shows something important. There is enough elec-trical charge to burn and char organic tissue. In other words,polar conductivity (see previous articles) has the capabilityto transfer real and significant power without any measura-ble electrical current or its associated magnetic field.
I should probably mention that I have unintentionallyfound myself holding a well-insulated wire with a coronadischarge that traveled into my hand. There was no sensa-tion of electrical shock. It felt more like touching spiderwebs. On one occasion when this happened, I squeezedthe wire between my thumb and forefinger and the wire feltwarm. I don't think the actual wire temperature had
increased, since the wires were never warm when the powerwas off. I think my skin was heating up, just like the leaf.
Another aspect of corona discharge is that materialfrom the charged object can actually be removed and re-deposited. Figure 7 shows the plastic container after a fewminutes of corona discharge with the silver dollar. You cansee that the deposits exactly match the corona dischargethat is illustrated in Figure 5. Most of this residue (which is,presumably, silver) is easily wiped off, but some seems tobe embedded into the plastic.
Kirlian Photography
Kirlian Photography is quite different from the picturespresented here. Their setup places photographic paper orfilm in close contact with the object, as shown in Figure 8.If the metal plate is large enough, no additional "conduc-tive mass" may be needed. Sometimes, they use a systemground that has the potential to allow real current to flow.For large objects (like a person's finger), they place thephotographic film (with or without the glass ) on top of themetal plate and have the person touch that. The person
SEPTEMBER 2004
nte The Enigma Machine — Part 4
Figure 4.The corona discharge photographs are taken through awater filled, thin, plastic container.The power goes in from the left,
up through a hole in the wood, and touches the bottom of the coin.The tip of the alligator clip is just visible at the top center.
It connects the water to a lead mass.
Figure 3.The basic setup for corona discharge photography.Refer to Figure 4 to see the physical layout.
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Project
SEPTEMBER 2004
then acts as the conductive mass. Note that, with standard Kirlian photography, the corona is not actuallyseen, only its effects on the film are recorded.
Kirlian followers believe that they are witnessingsome special "life aura" in these photographs. (They havemany colors and are certainly interesting and pretty.) It istheir belief that this aura is metaphysical or paranormaland has little relation to actual physical conditions. Sincethey believe rather than understand, no amount of logicand reason can cause them to consider any alternativeexplanation. (If it's an aura of life, why do ordinary metalobjects also show an aura?)
However, to an objective observer, the aspects of the
Kirlian "force" are quite clear. Their apparatus generatesa large electrical charge. The charge orients the molecules in the target — be it a leaf, a human being, ora house key — and creates a corona discharge. The "aura"they see is air ionization, also known as St. Elmo's Fire.The peculiar measurement effects are due to polar conduction rather than conventional electrical conduc-tion. There is nothing paranormal about it.
If the target is in contact with photographic paper,impressive colors are observed, but this is explained bythe fact that photographic emulsions are also sensitive toelectrical charge. The colors are simply the result of theemulsions reacting electro-chemically. That is why thesame colors are not seen in non-contact photography.
The "phantom leaf" experiment is easily explained.This is where an intact leaf is photographed first. Then,part of the leaf is cut away and another photograph istaken. Sometimes, the outline of the whole leaf is seen inthe second photograph. The Kirlian interpretation, as Iunderstand it, is that the leaf still feels that it is whole, sothe aura is complete. (This is somewhat similar to the real"phantom limb" effect, where human amputees feel alimb that is no longer there. However, this effect occursbecause humans have a complex central nervous system.Plants do not have a central nervous system.)
Here's what I see happening. During the first photograph of an intact leaf, Kirlian photographers typically press the leaf under the glass. This pressure canbe up to several pounds or more. This physical contactwith the glass — along with the electrical ionization —deposits moisture and/or small amounts of plant materi-al. When part of the leaf is removed, this materialremains. (Take another look at Figure 7 to verify this.)
The high conductivity of water conducts the molecu-lar orientation force even though it may be invisible.(Note, engineers working with high voltage apparatusknow the problems of invisible films of moisture or othercontamination. I have personally witnessed sparks skipping several feet over an old, wooden desk to an out-let ground with my apparatus.) I confidently predict that,if the Kirlian apparatus is thoroughly cleaned after everyphotograph, no "phantom leaf" effects will be seen. I alsopredict that, if the only photograph is of the leaf after ithas been cut, no phantom effects will be seen, either.
The "kissing" effect is also easily explained as a moisture film effect. In this experiment, two volunteerseach place one finger in very close proximity to theother's finger. However, the fingers are far enough apartthat no Kirlian "force" is seen passing between the fingers.Then, the volunteers kiss passionately. As they do, the"force" is seen between their fingers (as a small spark).
It can, however, be seen that there is nothing mysterious here. It is well known that there are manyphysiological changes that occur during sexual stimula-tion. Some of the very obvious changes are the generation of sweat, the increase in body temperature,
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Figure 6.The corona discharge of the leaf is washed out byburn-through.There is plenty of power to char the leaf,
even though no current is measured.
Figure 5.This is a time exposure of a corona discharge.
RLFonte4.qxd 8/10/2004 1:08 PM Page 56
and the increase in blood pressure. The result is that a per-son's hands get moist. This film of moisture conducts bet-ter than dry skin. Thus, while dry fingers are far enoughapart to prevent air ionization, the moist fingers are not.
We've seen that skin is an insulator. The moisturebreaks down the insulation of the skin. Thus, sparks areseen. It is confidently predicted that anything that causessimilar physiological effects will show the similar Kirlianeffects — or will simply show that wet fingers "spark" clos-er than dry fingers.
I do not claim to know all there is about Kirlian effects.However, I do know that whatever I have found can be sim-ply explained with polar conductivity, corona discharge,and/or the poor execution of experiments. There is noth-ing mysterious or magical about this force, regardless ofwhat some people would have you believe.
ELFs
Recently, there has been a great deal of interest indetermining if Extremely Low Frequency (ELF) RF radia-tion has harmful effects. These studies have looked at highvoltage power lines, police radar, cell phones, and otherfairly common sources of low power and/or low frequencyradiation. (Note, radar and cell phones are included, eventhough their operating frequency is not "extremely low.")
In general, the answer (so far) seems to be that thereis no connection between these sources and humanhealth. However, the methods of measurement are generally conventional electric current or RF power tech-niques. It has been shown that these methods can be misleading when measuring this force. It suggests thattesting for molecular rotation might be useful.
Additionally, the seed germination experiment dis-cussed in last month’s article is very suggestive. It seemsquite reasonable to expect subtle cellular effects when large,complex polar molecules are rotated by an external force.Many organic molecules' shapes and orientations are criticalto their function. It also appears reasonable to expect thatmolecular rotation at different frequencies would have different effects, depending on the natural resonant frequen-cy. It seems to me that the seed germination experimentshould be replicated independently. This could be important.
Other Research
In the mid 1960s, unconventional scien-tist/experimenter Wallace L. Minto crested aflurry of interest in "Plasmonics" or"Hydronics," which was described as a newform of wireless communication (PopularElectronics, March 1966, Volume 24, No. 3,pages 50-53). There are many similaritiesbetween the research and demonstrations heperformed and the effects described here overthe last few months. These similarities were
only recognized after I had done the bulk of my researchyears ago. Additionally, Minto's devices were black boxes andhe kept everything secret about the process. So, it cannot beknown for certain what his equipment consisted of.
Minto's work was mostly concerned with communica-tion. "Voice transmission via Plasmonics through the singlewire was unaffected when the wire was cut and capacitors,resistors (extremely high values), chokes, or even diodesback to back were inserted and the 'circuit' completed"(reference above). We saw a similar effect with the battery/ground effect last month, where a large resistanceto ground made a significant difference in performance.
You can reproduce his results by physically groundinga battery lead through various components and valueswhile The Enigma Machine runs on batteries. Back-to-back
The Enigma Machine — Part 4
SEPTEMBER 2004 57
Figure 7.This residue is from the corona discharge of the coin.Some could be wiped away, but some was permanent.
Figure 8.Typical Kirlian photography goes directly to photographic film or paper;the photographers don't actually “see” what they’re photographing.
That makes it seem much more mysterious.
RLFonte4.qxd 8/10/2004 1:08 PM Page 57
SEPTEMBER 2004
diodes (small signal type) and a straight wire connectionshow no significant difference.
There is one demonstration that Minto performed thatI have not yet been able to directly replicate. He showedthat the conductivity of a 5% sucrose solution varied significantly with frequency; peaks and valleys showed ona chart recorder. I've tried this several times without success. However, since Minto's equipment was secret, it'simpossible to determine if he was seeing a real phenome-non or if it was just a bad experiment.
The Future of PolarConductivity
Polar conductivity seems to be an area where very littleresearch is being done. This means that there is a potentialfor novel discoveries and applications. Expensive or sophis-ticated equipment is not needed to explore these effects atthis time. Therefore, enterprising experimenters and hobby-ists could — quite possibly — make significant contributionsand breakthroughs. Let's look at some areas of application.
Proximity Chemical Analysis. This is an area that Iam currently researching whenever I get the time (whichisn't all that often). Take a test tube of some solution andplace it between a force emitter and sensor. Measure the
conductivity with metal attachments to the outside of thetest tube. Different solutions have different conductivities.
Currently, I can easily discriminate between saturatedsolutions of table salt, sucrose (cane/table sugar), dextrose (glucose/blood sugar), plain water, and cookingoil. It's important to note that the test tubes are closed andthat these measurements are made without touching theliquids. In theory, this means that it could be possible tomeasure someone's blood sugar level or blood alcoholcontent (and perhaps other things) simply by placing theperson’s hand on an electronic device.
Underwater or Underground Communication.The Navy communicates with submarines with a huge,land-based, low frequency transmitter. It doesn't penetratevery deeply into the water, so the submarines must be fair-ly shallow to receive it. Since the transmission facilities areso big, the submarines can't directly respond. They have tosurface and transmit with more conventional equipment.Minto demonstrated point-to-point, wireless communica-tion from dockside to a scuba diver in the water. It seemsreasonable to suggest that polar conductivity through theground is also possible.
Medical Applications. The seed germinationexperiment (last month) seems to be quite notable. It was awell-controlled experiment in an academic setting. It sug-
Project
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Circle #43 on the Reader Service Card.
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gests that living things can be directly affected by polar conductivity. Admittedly, this is just speculation; however,consider an electronic medical device that could be tuned toprevent specific pathogens from replicating. Obviously, sucha product would have a tremendous impact at many levels.
Full Circle
This series started, "This is one of those things thatseems just a little interesting at the start; however, as youlook closer, it gets stranger and stranger." There does notseem to be an end to the strangeness. Like the batterybunny, it just keeps going and going and going.
This series was developed to illustrate a number ofaspects of science and learning. The first and most obvious was the actual development of The EnigmaMachine from concept to product. Next was the scientificapproach to gathering information and learning from it.Common sense and attention to detail are absolutely necessary. There was also the convoluted path of discov-ery from the first odd observation of hearing a sound whenmy ear brushed an electromagnet to the present.
Learning from mistakes is still learning. Hopefully, youfound this series interesting and fun. That's what scienceand engineering is to me. NV
The Enigma Machine — Part 4
SEPTEMBER 2004 59
Please use common sense ...
1. This article deals with high voltage and high voltage effects. Whenbuilt and used as described,The Enigma Machine is felt to be complete-ly safe. Improper use and construction can cause electrical shock.
2. Several Enigma Machine experiments demonstrate effects that passthrough the body of the user.Therefore, it is not recommended thatanyone with a pacemaker or other embedded electrical device participate in these experiments, nor should it be used in very closeproximity to any electrical equipment where electromagnetic interference could cause safety concerns.
3. Several experiments have shown subtle biological effects on plantswith continuous exposure of days to weeks. (See last month’s article.)
4. The high power version of the Enigma Machine presented hereshould not be built or operated by anyone who is not experiencedwith high voltage circuits. Severe electrical shocks or burns are verypossible.
5. It seems reasonable to suggest that the high power version couldhave significant biological effects, especially with long term exposure.
Enigma Machine Safety Notice!
Circle #71 on the Reader Service Card.
RLFonte4.qxd 8/10/2004 1:09 PM Page 59
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PIEZO BEEPER WITHADJUSTABLE VOLUME
120 Vac, 3 Watt, 60 Hz. Timing-style motor. 2.62” x 2” x 0.93” thick. Two mounting holes on 1.9” centers. 0.85” long brass shaft with 6-32 threaded stud at end. 10” pigtail leads. CSA.CAT# ACM-119
3 RPM, 120 VAC MOTOR
$350each
SUBMINIATURE DPDT SLIDE SWITCH
Shogyo #3650VC. Solid-state audio indicator emits a medium-loud, high-pitched tone. Screwdriver adjustable trimmer on back of device controls volume. Operates on 4-28 Vdc @ 6 mA. Black plastic face is 1.45” diameter x 0.16” thick. 1.25” diameterthreaded mounting bushing with large plasticnut mounts in panels up to 0.5” thick. 0.187”qc or solder terminals. CAT # SBZ-365
$395each
10 for $3.50 each100 for $2.75 each
Noble # SS-300A22K4C-2. Tiny DPDT slideswitch. 0.335” x 0.155” x 0.135” high exclud-ing slider. Six pc leads on 0.1” x 0.15” centers.CAT # SSW-40
$100for5100 for $15.00 (15¢ each)
600 for 72.00 each (12¢ each)
2 AA CELL NIMH PACK2.4 Volt, 1500 MAh nickel metal hydride battery pack. Two AA cells with a 2-conductor female connector on 2" leads. Used in many cordless phones. CAT# NMH-2AA
$200each
Originally marketed as Christmas lights, these LED covered stars and bars would make excellent attention-getting marketing displaysor disco-type lighting. Exceptional reliability,they last for over 200,000 hours and consumevery little power. In-line pattern generator provides more than 24 different light effectsincluding, chasing, burst, wagon wheel, rainfall, progressive and pulsating. Each star orbar has its own mounting holes. Each group of eight stars or twenty bars works indepen-dently; cannot be daisy-chained. Includes 5 Vdc 2 Amp wall power supply.Two styles available:
EIGHT 6.25” DIA. STARS:9’ long display. Each 8-armed star has 32 leds, eight each of red, yellow, amber and green leds (256 LEDs total).CAT # LVL-1$ 6.50 eachCase of 12 for $5.75 each
TWENTY 6.5” LONG BARS:11’ long display. Each bar has 8 leds, 2 each of red, yellow, amber and green leds (160 LEDs total).CAT# LVL-2 $ 5.50 eachCase of 9 for $4.75 each
COLOR HEAT SHRINK TUBING ASSORTMENT
154 PiecesHave the right piece of heat shrinkable tubing when you need it. Unbreakable clear plastic box with dividers contains 4 inch lengths of 6 differnet diameters.
ASSORTED COLORSblack, red, clear, yellow
green blue whiteCAT# HS-4900
ALL BLACKCAT# HS-4901
$1195each
1/16” - 56 pcs3/32” - 35 pcs1/8” - 28 pcs3/16” - 18 pcs1/4” - 9 pcs3/8” - 8 pcs
EDT # EW162C16 character X 2 lineLCD module with LEDbacklight. 5 x 7 dot characters.Module size: 3.35” X 1.41” X 0.52”. Display size: 2.5” X 0.63”.Includes hook-up diagram.
CAT# LCD-97
Circle #49 on the Reader Service Card.60
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After opening the pool thisyear, I decided to purchase some sort of
lighting system so we could enjoythose muggy Virginia nights. Iwanted a color system that lit thewater inside the pool. Manyexisting lighting systems had 12V lights that used a transformerto lower the voltage from 110 V,but I did not want to chancesomething going wrong with oneof these. Plus, the fiber optic sys-tems were much too expensive,so I decided to break down and build something.
My requirements were simple:
• It must be powered by four rechargeable AA batteries. This will give a nominal 4.8 volts, which eliminates theneed for a voltage regulator.
• It must last at least six hours on a single charge. Longer would be a plus.
• It must have three colors and cycle slowly between them to change the mood of the pool.
• It must be self-contained and float on the surface of the pool, yet it has to shine light onthe pool floor.
• It must fit in a small, waterproof tub. • It must be easy to build and inexpensive, so that
I can build more than one. I will probably buildfour for my pool.
The AA batteries and six hour durationpretty much dictated some sort of LED lightsystem. For the multiple colors, I decided to useblue, red, and green ultra bright LEDs. I wantedto use 5 V LEDs that pulled less than 25 ma so Icould power them directly from themicrocontroller’s IO port. For more brightness, Iwould use two LEDs for each color, each on itsown port.
For the microcontroller, I decided on anAthenaHS for its speed, cost, and simplicity. Ineeded to generate six PWM signals for mixingthe colors. The AthenaHS can source or sink 25ma on each port. This is perfect for the LEDs
that I have chosen.The AthenaHS also has a very
small carrier board that will allowme to build the light very easily.
Circuit Hookup
Figure 1 shows the hookupto the carrier board. We onlyneed six ports on the AthenaHSto drive the six LEDs. I decided touse a 2 x 6 female header, so Icould just plug the LEDs inplace. While this is not the most
rugged connection method, it would allow me to experi-ment with different colored LEDs.
Figure 2 shows the slightly modified carrier board. Youcan also use two 1 x 6 female headers glued or stucktogether with double-sided foam tape. Connect the freeends of the header together and tie to Vss, as shown inFigure 3.
The carrier comes with some snap connect maleheaders and you will only need two of them — one eachconnected to the + and – leads, as shown in Figure 2. This
Floating Light ShowMix Colors and Software for a Neat Effect!
by Michael Simpson Project
61SEPTEMBER 2004
Figure 1
RLSimpson.qxd 8/10/2004 1:27 PM Page 61
male header will be used to connect the batteries andfemale header. Other than the headers, the carrier board isbuilt step by step, according to the instructions. When usingthe AthenaHS with the carrier board, you will need a 20 MHzresonator.
Once the LEDs have been inserted, you can slightlybend them into groups, as shown in Figure 4. The shortLED lead connects to the outside header (vss). If you areworried about the leads touching, you can use some 1/16heat shrink for insulation. You only need to insulate the IOport side of the LED.
Use double-sided foam tape to attach the circuitboard to the battery holder. The LEDs should be centeredon the battery holder, as shown in Figure 5. To turn on thelight, slip the battery header over the two pin header onthe board. The negative side of the battery is connectedto the header pin closest to the LEDs.
The ProgramThe program must generate six PWM signals on ports
0-5. Three counter variables — named bluecount,redcount, and greencount — set the duty cycle of thecorresponding colors.
The color pattern is set in the main loop. We startwith red and green turned on and proceed as follows:
Fade out red.Fade in blue.Fade out green.Fade in red.Fade out blue.Fade in green.
Start over.
This pattern assures that all the LED color combosare met. It also means no more than four LEDs are on atonce, which will go a long way in reducing powerconsumption.
The actual call to the PWM routine is what lights theLEDs. At the start of this routine, we retrieve a randomnumber to set the number of times we will actually cyclethrough the PWM counts. The more times we cycle, thelonger it will take a particular color to fade in or out.
AthenaHS
dim bluecount,redcount,greencountdim curcount,cycle,rnd
‘LED Portsconst portblue1 0const portred1 1const portgreen1 2const portblue2 3const portred2 4const portgreen2 5
const maxcount 150‘Sets up the PWM fre-quency and resolution
setio 0,1,2,3,4,5
‘Start Point for lights
Project
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Figure 2
Figure 4
Figure 3
Figure 5
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bluecount = 1redcount = 150greencount = 150
loop:gosub Red_Downgosub Blue_Upgosub Green_Downgosub Red_Upgosub Blue_Downgosub Green_Up
goto loop
‘——————————————————Blue_Up:‘——————————————————for bluecount = 1 to maxcountgosub pwm
nextreturn
‘——————————————————Blue_Down:‘——————————————————for bluecount = maxcount to 1 step -1gosub pwm
next
return
‘——————————————————Red_Up:‘——————————————————for redcount = 1 to maxcountgosub pwm
nextreturn
‘——————————————————Red_Down:‘——————————————————for redcount = maxcount to 1 step -1gosub pwm
nextreturn
‘——————————————————Green_Up:‘——————————————————for greencount = 1 to maxcountgosub pwm
nextreturn
‘——————————————————Green_Down:‘——————————————————for greencount = maxcount to 1 step -1
gosub pwm
Floating Light Show
63SEPTEMBER 2004
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‘————————————————————-‘ Generate the light‘————————————————————-pwm:
random 40,rnd ‘This will determine how long‘we stay with a color
rnd = rnd + 5 ‘With a minimum of five counts
‘To create the six PWM signals we turn all ports on‘then turn them off as each color count is reached.for cycle = 1 to rndconfigio 0,1,2,3,4,5for curcount = 1 to maxcountif curcount = bluecount thengosub offblue
endifif curcount = redcount thengosub offred
endifif curcount = greencount thengosub offgreen
endifnext
nextreturn
‘You may want to place this code directly in the if‘statements. The KRcompression technology built into‘the Athena engine is centered around modular code so‘this particular way is more efficient than single if‘ statements
‘Port Handlersoffblue:
input portblue2input portblue1return
offred:input portred1input portred2return
offgreen:input portgreen1input portgreen2return
TubConstruction
The actual tub construc-tion is very simple. Using aRubbermaid #5193 tub, sim-ply set the battery and circuit board assembly intothe tub with the LEDs facingup, as shown in Figure 6.This is a one pint containerand the battery holder cen-ters pretty well without mucheffort. If you use a differentsize tub or battery layout,you will have to make sure
the assembly is centered so that the tub does not tilt to one side.
In order for the lights to illuminate the pool bottom,you need to reflect the LEDs downward. I have usedseveral reflectors, such as compact mirrors or convexmirrors. Out of all the tests, aluminum foil seems to workthe best at reflecting the light because all the littlecrinkles tend to mix the colors more evenly. You can usedouble-sided foam or tape to attach the foil to the insideof the lid. Make sure the shiny side is down, as shown inFigure 7.
That is pretty much it for the tub construction. Youcan add some flowers or a rubber ducky to the top of thetub, if you wish.
How Well Does It Work?
My wife loves them and can’t wait for the long, hotdays of summer. My hard-to-impress daughter wants thefive units I made to be used at her next pool party.
I’m getting over 12 hours of use out of the lights, somy next step is to add a small solar cell to charge thebatteries during the day.
Be sure to visit Kronos Robotics at www.kronosrobotics.com for project updates, as well as more lightpatterns. NV
Project
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AthenaHS Kronos Robotics #16277Athena carrier 1 Kronos Robotics #1630020 MHz resonator Kronos Robotics #16140Four cell battery holder Kronos Robotics #16323Snapable 1 x 36 female header Kronos Robotics #16291
Plastic Tub Rubbermaid # 5193
Ultra bright LEDsBlue LED All Electronics #LED-74Red LED All Electronics #LED-94Green LED All Electronics #LED-57
Sources
Figure 6
Figure 7
RLSimpson.qxd 8/10/2004 1:29 PM Page 64
A glimpse into the future of robotics!When we announced Tetsujin 2004 back in March, we knew it would raise some eyebrows.The
concept — a live competition where people step into strength augmentation suits to lift weights — was groundbreaking.As expected, it has attracted the attention of the best and brightest fabricators and engineers from around the country. Move over, DARPA Grand Challenge!
Next month is your chance to see what these seven amazing teams have come up with! Join the topminds in industry, as well as the worldwide media at RoboNexus — the nation’s largest event foremerging robotics technologies. Online registration is simple and quick — don’t delay!
If you are a decision maker for a company that wants unique and positive exposure, the exosuits ofTetsujin 2004 may be the channel you’ve been looking for.To exploreadvertising and marketing opportunities further, drop an Email to [email protected] or call (951) 371-8497 and we’ll pairyou up with a team that embodies the spirit of innovation, as well as the positive discipline of a “can do” attitude. www.robonexus.com
Tetsujin ad.qxd 8/12/2004 2:05 PM Page 65
SEPTEMBER 2004
On April 3, 2000, when President Clinton’s JusticeDepartment issued its ruling that Microsoft had vio-lated US antitrust laws and the NASDAQ plummeted
349 points (or 7.64%) — its worst single-day performanceever — it signaled the end of the Internet bubble. The nextyear, the horrific terrorist attacks on the US occurred onSeptember 11th. As a result, we’ve seen much less ofwhat Tom Wolfe once dubbed the “digibabble and fairydust” that ruled the 1990s and, somehow, technology hasslipped a bit below America’s collective radar screen.
Yet, in many ways, the rapid speed of technologicalprogress hasn’t abated. In the late 1970s, we saw the birthof the personal computer, the VCR, and the laser disc. Inthe 1980s, compact discs, cell phones, and fax machinesentered the picture. Today, average consumers aresurrounded by more technological goodies than we knowwhat to do with and keeping pace with what’s availableand their benefits can be a daunting task.
The Digital Consumer Technology Handbook is anew book (published by Newnes, go to www.xilinx.com/esp/dct_handbook.htm) written by Amit Dhir, amanager in the strategic solutions marketing group atXilinx — a 20-year-old, San Jose-based semiconductormanufacturer. Dhir has a Bachelor of Science in ElectronicEngineering from Purdue University and a master’s degreein the same field from San Jose State University.
At 656 pages, The Handbook would make a heck ofa doorstop or paperweight, but it does a pretty nifty job asan encyclopedic look at just about every major technologythat competes for your money, time, and living space.
Not Bad — but Not Perfect
It’s not perfect, however, and its minor flaws only
serve to highlight how — with a little more work — thisbook could have been flawless.
Occasionally, Dhir gets a bit too cute. On page one ofthe book, he refers to “Generation D — The DigitalDecade.” Well, is it a decade or a generation? Since ageneration is about twice as long as a decade, I’d saythose are mutually exclusive terms. Shortly thereafter,Dhir writes, “Anything that is digital is superior.” I’m as farfrom a Luddite as can be imagined, but I’m not sure if I’dwant to make a blanket statement like that. There are fartoo many professional photographers who love their 35mm and 4 x 6 format negatives and professional record-ing engineers who love the warmth of 2” wide analog tapewho might seriously blanche at having to switch to digital.
From time to time, Dhir throws in a buzz word andassumes that the vast majority of his readers will knowwhat it means. He mentions Moore’s Law and explainswhat it is and then mentions Metcalf’s Law without anyexplanation. At times, Dhir’s book makes the reader feellike it would be handy to have Google running in the back-ground while reading it. (About half of the folks readingthis just rolled their eyes and said, “Geez, is that Driscolla dummy or what?”)
Much later in the book, Dhir’s otherwise excellentchapter on video games is marred by an unexplainedphrase noting that Microsoft’s Xbox appeals most to“game artists and aficionado players.” Say what?
Chapter 4 does a thorough job of explaining how CDswork, but, at one point, Dhir writes that CDs are facingextinction. Well, the sun is facing extinction, too — give itfour, maybe five billion years, tops. Between commercialrecordings being released on CDs, computer programson CD-ROM, and people using CD-Rs for both, I’d say thatcompact discs have a few more years left in them before
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by Ed Driscoll, Jr.
A Stellar Book ... but With Many Minor Flaws
RLDriscoll.qxd 8/11/2004 2:02 PM Page 66
extinction occurs. What could hasten the speed of the CD’s demise are
its successor formats — DVD-A and SACD (short for SuperAudio Compact Disc). It appears that Dhir could havedone a more thorough job of explaining how the growth ofthese formats has been retarded by interference by theRIAA (Recording Industry Association of America), whichfears consumers copying their discs. (Which is why theseCD replacement formats need their own proprietaryreceivers with individual digital inputs for each of the sixaudio channels, rather than the single Toslink or coaxinput that the original video DVDs and audio CDs use.Also, this is why the RIAA has made the Dolby Digitalreceiver you bought five years ago obsolete.)
In Chapter 7 of The Digital Consumer TechnologyHandbook, Dhir has a through explanation of the benefitsof DVD and how the format was created. Then hementions Divx — the Circuit City-backed early attempt atcreating a rental DVD format that was loathed by the earlyadopters who first put DVD on the map. Dhir writes thatthe format “played a useful role,” but fails to note the back-lash it caused and the confusion it created by introducinga Beta/VHS format war so early in the DVD’s lifespan.
Later in the DVD chapter, he writes, “The number of[DVD] titles will be limited in the early years.” Early years?The format is seven years old! Limited? According to theofficial DVD Faqs (available online at www.thedigitalbits.com/officialfaq.html among other locations), bythe end of 2002, there were about 23,000 DVD titles avail-able in the US — and that number has only grown since.That doesn’t sound too limited to me.
A Few Missing Technologies
Aficionados are bound to see one or two technologiesthey would have liked to have seen mentioned. While PCsand spin-off technologies are well represented, I personal-ly would have liked to have seen some information onweblogs. Their inherent ease of use and flexibility arecausing them exponential growth in popularity, since theyallow for instant self-publishing on any topic imaginable.
Seemingly a Must-Have
All of this may sound like nitpicking and, in a way, it is;as I said, Dhir has written a terrific book that seems to bea must-have title for anyone with an interest in consumerelectronics, where most of us have expertise in one area,but have blind spots when it comes to knowledge of othertechnological niches. Hopefully, The Digital ConsumerTechnology Handbook will inform its readers — and allowthem to make informed decisions when it comes tospending their hard-earned money on electronics. It readslike it could have used another round of editing before itwas released, though. A book like this will need fairlyfrequent revisions if its sales are successful, so let’s hopethings get tightened up the next time around. NV
Schematic and PCB Layout• Powerful and flexible schematic capture.• Auto-component placement.• Rip/entry PCB routing.• Polygonal gridless ground planes.• Library of over 8000 schematic and 1000 PCB foot prints.• Bill of materials, DRC reports and more.
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MicroChip PIC 18• Supported models of the PIC 18 includes PIC18F242, PIC18F252,
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Basic Stamp BS1 and BS2• Proteus VSM for BASIC Stamp contains everything you need to
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“PROTEUS stands out as the best all-round program in this review. Other programsreviewed have strengths in the pcb design process, Proteus maintains a constant highlevel of capability throughout. Whether a schematic, user-friendly interactive routing,configurable autoplacing, competent autorouteing, or a combination of the above,PROTEUS handles everything very well.” Electronic & Wireless World CAD Review Roundup
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SEPTEMBER 2004
Circle #50 on the Reader Service Card.
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Last month, I explained how LORAN (LOng RAngeNavigation) worked as a navigational aid system and
how it was originally implemented using vacuum tubetransmitters. This month, we will continue with the storyof the retirement of the world's most powerful vacuumtube LORAN transmitter of 1.6 megawatts at the USCoast Guard station at George, WA. The vacuum tubetransmitter went on air in September of 1976 and wasofficially taken off air on December 8, 2003. Afterswitching the antenna transmission line from the vacuumtube transmitter, a new solid-state transmitter wasoperating within about two hours. Read on to learn aboutthe new solid-state concept and LORAN's future.
The Solid-State Transmitter
The differences between the vacuum tubetransmitter(s) and the new solid-state transmitter are like
night and day. This should be the case because of a 25year period to improve transmitting efficiency andfrequency/control techniques from computer technology.
The transmitter known as the Accufix 7500 ismanufactured by Megapulse of North Billerica, MA.Megapulse has supplied earlier versions of the Accufix,known as the AN/FPN-64, which were of lesser outputpower capability for USCG LORAN stations, primarily inthe inland areas of the US. Megapulse has recentlyfinished supplying units to the nation of Japan for theirLORAN chains.
The new frequency/control equipment is shown inFigure 1. At the left are two Transmitter ControlSubsystems (TCS) — one active and one standby. TheTCS controls precise timing of the transmitted LORANpulses and also monitors the “quality” of those pulses.
Third from the left is the Transmit FrequencyEquipment (TFE), which generates George, WA’s
LORAN rates of 9,940 and 5,990 as the oldequipment in Figure 2 of last month’s article did forthe vacuum tube transmitter. To the right of theTFE is the AUX rack containing three HewlettPackard HP-5071A Cesium Beam FrequencyStandards. Each Cesium costs over $28,000.00and they are the reason the LORAN signal is sorepeatable with time to its users. In a one dayperiod, HP rates the frequency stability as betterthan 3 x 10-14. You don’t get that kind of stabilityfrom a TCXO (Temperature Compensated CrystalOscillator), which is a common option in our HFamateur radio equipment.
Two racks on the far right (only a portion ofone is shown) are the RAIL (Remote AutomatedIntegrated LORAN) equipment, similar to whatwas used for the vacuum tube transmitter. TheRAIL — consisting of commercial grade Dellcomputers — provides timing corrections, systemalarms, a means to input “commands” to the TFEand TCS, and also acts as a communications toolto the control monitors. For the Canadian WestCoast Chain (5,990 rate) the control monitor is
by Clifford Appelby Clifford Appel
Figure 1.The frequency/control equipment for the solid-state transmitter.The two left racks are the TCS, then there is the TFE, the AUX rack withthree cesium beam frequency standards, and two RAIL racks on the right.
Love that alphabet soup! Photo courtesy ETC K.Anderson.
RLAppel2.qxd 8/10/2004 1:48 PM Page 68
located in St. Anthony, Newfoundland. For the US WestCoast Chain (9,940 rate), the control monitor is locatedin Petaluma, CA. The control monitor insures the propertiming and synchronization of all the LORAN stations inthe chain.
The TCS rack mentioned earlier controls the pulses inthe new solid-state transmitter, shown in Figure 2. You willalso notice there are vertical panels consisting of foursections. Each section is called an HCG (Half CycleGenerator). Two sections work in parallel to form thepositive half of the LORAN pulse and the other twosections form the negative half of the pulse. The HCGconsists of beefy inductors, hefty capacitors, large diodes,and large SCRs (Silicon Controlled Rectifiers), which“bang” a tuning coil to “build” the LORAN pulse. In a way,this transmitter can be thought of as a sophisticated,electronically controlled, spark-gap transmitter. This is atotally different concept than what was used in the vacuumtube transmitter that can be described as a super largeclass B linear amplifier.
The HCGs are fired in groups at various time intervalsto resonate and amplify the 100 kHz pulse. This is nosimple task because the whole output network must takeinto account the LORAN antenna. Once the peak of thepulse is reached, some means must be made to dampenthe trailing edge of the LORAN pulse.That dampening of resonance isaccomplished by a network with the dis-tinguished title of “tailbiter.” The TCShas a lot of responsibility for HCG firing,tailbiter operation, and output networktuning. The output network is constantlybeing massaged as the antenna sways(changing impedance) or environmentalconditions change (rain, snow, icing, lowhumidity, dust storms).
The Accufix 7500 transmitterproduces 1.3 megawatts — a bit lessthan the AN/FPN-45 vacuum tubetransmitter’s 1.6 megawatts — but the
solid-state unit has some virtues that the vacuum tube riglacks. If an HCG should fail, the Accufix will still put out asignal, albeit at a slightly reduced output power. An HCGcan be swapped out while the transmitter is operational.Corrective maintenance for the Accufix is simpler, lesstime consuming, and a lot cheaper than what wasrequired for the vacuum tube transmitters. There is onlythe one solid-state transmitter running 24/7, as opposedto the two vacuum tube rigs which were alternated everytwo weeks.
If you remember, earlier I mentioned that the vacuumtube transmitters could require an electrical “demand” ofnearly 1,000 kilowatts and that I calculated that eachtransmitter required 100 kilowatts just to light thefilaments. The entire building that contains the newtransmitter, frequency/control equipment, heating/coolingequipment, and lighting uses about 170 kilowatts. That’s adramatic reduction of electrical energy consumption bynearly six times. Utility bills will go from about $9,000.00per month for the vacuum tube LORAN equipment toabout $2,200.00 per month for the solid-state LORANequipment.
LORAN Antennas
There are three basic types ofLORAN antennas used at the US CoastGuard stations (see Reference 3). Twoare common monopoles (towers) —either 625 feet tall or 700 feet with toploading elements (i.e., “capacitancehats”) to decrease capacitance toground. Under each type of monopole isa counterpoise of radials buried in theearth. The monopole sits on a stoutglass insulator which isolates the towerfrom ground. At the LORAN frequencyof 100 kHz, we can calculate that onewavelength is 3,000 meters. Therefore,the 625 and 700 foot towers are about
SEPTEMBER 2004 69
New Life for LORAN — Part 2
Figure 2.The new Accufix 7500 solid-state transmitter.The right side
is a mirror image of the left side,prominent in the picture.
Photo courtesy of ETC K.Anderson.
Figure 3
RLAppel2.qxd 8/10/2004 1:48 PM Page 69
SEPTEMBER 2004
7% of a wavelength. As a result, the impedances of the625 and 700 foot tall antennas are 2.5-j25 Ω and 4.0-j23Ω, respectively. Not much there, huh? You can bet thatgreat effort is made to produce a good counterpoise toreduce ground loss as much as possible.
The third type of LORAN antenna — the one used atGeorge — is the SLT. I’ve seen “SLT” defined several ways,but the drawings at LORAN Station George call it a“Sectionalized LORAN Transmitting” antenna. There arefour other LORAN stations using an SLT, so it’s notunique to George. The SLT is a wire antenna consisting offour “T” sections slung between four towers. Each toweris 695 feet tall and arranged in a perfect square — 1,451feet on a side. One “T” section held up by two towers isshown in Figure 3. The horizontal sections are suspendedand insulated from the towers; the towers do not radiate
electromagnetic waves. None of the “T” sectionsare connected to another. The bottom of thevertical wire is connected to the bottom of the otherthree vertical wires from their respective “T.” If youuse your imagination, you can think of the SLT asa conical monopole with the upper half sliced off oryou can think of it as a “fat” monopole.
I will relate to you this “sea story” regardingthe SLT, although I have yet to find the source ofthe story. More than 30 years ago, when the CoastGuard was modeling SLT antennas, the computerpredicted an impedance of “about” 5.5 “real” Ω.Compared to a 700 foot monopole resistance of4.0 Ω, that’s a big increase and, hence, morepower radiated (in theory, assuming lossresistance is a fixed value). However, when the SLTwas erected and impedances were measured onthe actual antenna, it was found to be 3.3-j15 Ω, atrue disappointment. My guess is, though, that the
bandwidth of the SLT is much broader than that of amonopole. If nothing more, the sight of flashing aircraftwarning lights makes an impressive display from 25miles away, as seen while driving on Interstate 90 atnight!
Backup Power
I mentioned earlier that the vacuum tube stationcould use as much as 1,000 kilowatts at one time andthat the new solid-state station uses about 170 kilowatts.What happens when the lights go out? The Coast Guarddoesn’t want that LORAN signal off air for very long.Despite the very good service and reliability of the localutility (Grant County Public Utility District), powerinterruptions do occur.
New Life for LORAN — Part 2
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Figure 4. Backup generators for the vacuum tube transmitter.Each unit is rated at 400 kW. Photo courtesy of ET1 K. McKinley.
1 — www.navcen.uscg.gov/loran — then click on “LORAN-CUser Handbook.” Although this publication contains informationregarding LORAN stations long since shut down, it is a goodtutorial for providing insight as to how LORAN works.
2 — Private correspondence 5 March, 2004, with Bill Roland, aretired engineer from Megapulse, Inc.
3 — www.navcen.uscg.gov/pubs/rnavbull/rnbull38.pdf —then go to page 13 for details.
4 — www.loran.org/Newsletters/NewsletterIndex.htm —then click on September 2003. www.loran.org is the homepage ofthe ILA (International LORAN Association) previously known asthe Wild Goose Association.
5 — www.loran.org/Newsletters/April,2003.pdf — page 3,“US Coast Guard reports interference to GPS from TV antennas;”
an incident involving certain powered (active) UHF/VHF marine tel-evision antennas creating interference to GPS receiver operation.
6 — http://webhome.idirect.com/~jproc/hyperbolic/loran_c_future.html — “Excellent though GPS may be, itsproblem is that it is so low powered that the signal can easily beblanked out or disrupted — as demonstrated at a 1997 Moscow airshow, where a jammer destroyed the signal over a radius of 200km.” The website — maintained by Jerry Proc — is loaded with allsorts of information regarding LORAN and its history, as well asinformation regarding other forms of radio navigation.
7 — A nautical mile is approximately 6,076 feet or about 1.151statute mile. It is defined as one minute of longitude at the Equator— 1,852 meters.
8 — www.megapulse.com/how%20used.html — A concisearticle with diagrams explaining the extension of LORAN use.
References
RLAppel2.qxd 8/10/2004 1:49 PM Page 70
The vacuum tube station has three400 KW diesel generators, which willimmediately start up, parallelthemselves, and operate an automatictransfer switch (ATS) to provide stationpower when utility power is lost. Despitethe fact that under emergencyoperation some of the station’s load isshed (“non-essential” circuits), it stilltakes at least two of those generators inparallel to put George back on air. Aview of the three generators is shown inFigure 4. The generators can be up tospeed and supplying three phase 460 VAC in less than 30 seconds. The trans-mitter can then put itself back on airabout 30 seconds after that, so the totallost signal time lost is about one minute.
By contrast, the solid-state stationhas two physically smaller diesel generators, rated at 400kW each. When loss of utility is sensed, they both startup, but only one picks up the load. They do not parallel.After five minutes, the “loafing” generator shuts itselfdown. All load is carried; there are no non-essentialcircuits, but the major difference is that the LORANsignal does not go off air at any point because there is a240 KW UPS (Uninterruptible Power Supply) thatcontinues electrical power to the solid-state transmitter.There’s also an 8 KW UPS that supplies power to thetiming and frequency control equipment shown in Figure3 of last month’s article. The UPS equipment reallydoesn’t power the station for long because the generatorcan pick up the load in about 10 seconds. Wow!
The combinations of reliable, solid-state transmittingequipment, computerized control equipment, and the UPSequipment will result in LORAN signal continuity of from99.85% to a target of 99.99% (see Reference 4). Thevacuum tube equipment was achieving signal continuity of99.70%, on average. The Coast Guard prides itself onkeeping that signal on air and in tolerance for its users asmuch as possible.
The Future of LORAN
Where do we go from here? After spending approxi-mately $100 million — so far — upgrading the vacuum tubestations to solid-state transmitters, will anyone use the sig-nal? Yes, but probably not in the way LORAN was original-ly intended to be used.
Without question, the dominant form of electronic nav-igation around the world is GPS. The units are so small,inexpensive, and packed with features that a lot of ama-teurs have them married to a TNC (Terminal NodeController) and two meter FM rig for APRS (AutomaticPosition Reporting System).
GPS is not infallible, though. Since the system wasbuilt for military purposes, the owner can move satellites
around in orbit to meet whatever needthere might be. This would leave otherareas on the globe with “holes” of cover-age. The GPS signal operates at L bandand, therefore, doesn’t penetratebuildings or heavy foliage very well. Itssignal is so weak that it can be jammed(unintentionally) by something assimple as a poorly maintained activemarine TV antenna (see Reference 5). Itcan also be jammed (intentionally) by asimple, low wattage, portable transmitterin the hands of the wrong people (seeReference 6).
The LORAN signal can be used asa backup to GPS because of its robustsignal-to-noise capability and its lowfrequency of operation. It does not,however, have the pinpoint accuracy of
GPS — which can be as good as 10 meters and as pooras 100 meters. The US Coast Guard lists LORAN’saccuracy as 0.25 nautical mile (NM) nominally with 0.1NM at the best of times (see Reference 7). The signal’scoverage can be from 600 NM to 1,000 NM, dependingupon the time of day and path.
LORAN’s strong suit is that the position displayed is
SEPTEMBER 2004
New Life for LORAN — Part 2
Figure 5.The crew at LORSTA Georgewho helped put the new equipment
on air and shut down the legacy vacuum tube transmitters. Standing
left to right: ET1 Ken McKinley,ETC Kevin Anderson, ET3 Ross
McDermott, MK1 Richard Boxleitner,SK1 Sterling Van Horn. Kneeling:
FN Ryan McDermott (no relation).Photo courtesy of ETC K.Anderson.
71Circle #89 on the Reader Service Card.
RLAppel2.qxd 8/10/2004 1:49 PM Page 71
repeatable every time the user returns to that sameposition. In other words, even though the Lat/Londisplayed on the receiver readout may not be precise, auser can return to that exact geographical position eachtime that those Lat/Lon numbers are duplicated.
The Coast Guard is attempting to create an extremelyaccurate clock among LORAN stations known as Time ofEmission (TOE) control; the Coast Guard prefers its ownjargon, using Time of Transmission (TOT) process. Asimple explanation of how it works is given in Reference 8.This will enable a position fix using only two stations,
stations in multiple chains, or even two GPS satellites andone LORAN station.
The LORAN signal can be used for more thannavigation. Because of the stable cesium beamoscillators used at every LORAN station, the LORANsignal can provide precise timing for commercial users.Wireless telephone services, the radio and televisionindustry, satellite communications companies, and thebanking industry can use LORAN to keep TDM (TimeDomain Multiplex) format signals synchronized. Theelectric utilities can use LORAN as a clock to “time tag”
all their events and circuit breakeroperations. A precise coordinatedtime tag will assist in determiningthe order of occurrence ofhappenings, such as the northeastUS blackout in August of 2003.
LORAN C Station George wenton air September 29, 1976. Theoriginal station complement was 10people. With computer technologybeefed up in the late ‘80s, the crewwas reduced to seven. The new, solid-state transmitter will require a crew ofonly four. The savings in peoplecosts, maintenance costs, andelectricity costs will eventually pay forthe up-front expenditure. The Georgecrew that helped make it all happen isin Figure 5. As a Coast GuardReservist, I’m honored to haveworked with these professionals atthis premier LORAN station. NV
New Life for LORAN — Part 2
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SEPTEMBER 2004
Clifford J. Appel, K7SPS, wrote thisarticle for three reasons: First, he wantedto inform people that there is more to navigation than just GPS. Second, it is hissalute to the Coasties, past and present,assigned to LORSTA George who’ve keptthe equipment in top operational formsince 1976. Third, he wrote it as a tributeto a deceased friend; Stan Pickarski was hisworking mate when he was stationed atthe Coast Guard District 14 office inHonolulu, HI, from 1974 to 1976. Stanhelped erect the LORAN A and C stationsin the Pacific region and helped shut downthe A stations decades later. He died inFebruary, 1999, at age 78. He is missed forhis friendship and his wonderful sea stories. You can contact Cliff at P.O. Box241, Electric City,WA 99123, or by Email [email protected]
About the Author
Circle #103 on the Reader Service Card.
RLAppel2.qxd 8/10/2004 1:50 PM Page 72
SEPTEMBER 2004 73
Long before the Internet, dedicated hobbyists devel-oped their own world wide web of amateur radio sta-tions. Often using gear they had built themselves,
these radio amateurs — or hams — visited, exchangedinformation, passed along vital communications, andhelped out in countless emergencies. Hams have con-tributed to fields of research as diverse as antenna theory,sunspot activity, atmospheric conditions, rocketry, andsatellite communications.
Starting out in ham radio can be fun, but — as withany high tech hobby — there are plenty of hurdles to over-come. Ward Silver’s new book, Ham Radio forDummies, published by Wiley, offers a well-written andfriendly guide to starting and growing your new hobby ofamateur radio.
Ward, known by his ham call sign N0AX, draws on hisdecades-long ham career to explain the many aspects ofham radio, demystify the licensing process, and describehow to build and operate your own ham shack. His edu-cation as an electronics engineer provides the basefor the technical material in the book. He is also acontributing editor and columnist for QST — a pop-ular monthly ham radio magazine — and his writingskills go a long way in making this book easy to read.
The first section of the book introduces you to theham radio hobby. The material here provides anoverview of the hobby, not the fine details. You get ageneral description of a ham shack; much more detailappears in later sections.
Similarly, Ward devotes a few pages to topics such asradio fundamentals, basic gadgetry, how to make contactwith others over ham radio, ham contests, and organiza-tions dedicated to ham radio.
The second section gets down to the serious busi-ness of preparing for your ham radio exam. Operatinga ham radio station requires an amateur radio license,which must be earned by passing an examination bythe Federal Communications Commission (FCC).There are several levels of licenses available, with
increasing privileges granted to those passing the moredifficult tests. Ward spells out the different requirementsand privileges of the Technician, General, and AmateurExtra Class Licenses. He follows this with excellent material on preparing for the exam and what to expect onexam day.
Once you earn your ham radio license, you areready to move to the third section of the book, whereWard delves into the culture and vocabulary particular toham radio. Bagging a QSO (making a radio contact)requires several skills — including patience and knowl-edge of how the different radio bands behave. DistantQSOs can really test your technical abilities and Wardprovides pages of tips for working the different hambands.
by Karl Lunt
RLLunt.qxd 8/9/2004 4:29 PM Page 73
Though it is easy to think of amateur radio as a geekhobby, it has a large social element to it and Ward spendspart of this third section on ham etiquette, clubs andorganizations, and common courtesy.
He also uses this section to cover the more seriousside of amateur radio. Hams play a major role in emer-gency response following disasters and knowing how tohandle such situations can literally mean life or death to others.
Other specialties of ham radio — including DX (longdistance contacts), contests, QRP (low power operation),video transmission, and awards — get good treatmenthere.
The fourth section is where you get your hands dirty,so to speak. Setting up your station can be a lot of fun andWard describes some of the more important elements toconsider in your shack layout.
Here, you also find much of the technical informationneeded to get out a strong signal and to pull in a weak one.This section also includes good tips on used versus newequipment, safety considerations, and troubleshootingproblems that keep your station from running at top effi-ciency. Ward also provides considerable information onantenna theory and construction — a vital element of awell-built shack.
The fifth section of the book contains a set of tipsand guidelines — arranged in groups of 10 — for gettingthe most from your new hobby. This is followed by thebook’s appendices, including a glossary of terms, a col-lection of technical references, and a fairly extensiveindex.
I enjoyed reading this book for its technical contentand for Ward’s light and concise style. As mentioned pre-viously, he is an accomplished writer, which goes a longway to making this admittedly technical hobby easy tounderstand. He covers a huge range of material in thebook’s 350+ pages. Open the book at random and youcould hit a discussion of contacting ham radio satellites,accessing amateur radio repeaters, or finding resources for studying for your ham ticket (license). The paragraphsare short and all “meat.” The book’s page layout is easy to follow.
This book is an excellent starting point for your hamradio hobby. Ward takes much of the mystery out of ama-teur radio and helps you understand its fun and chal-lenges. His enthusiasm for amateur radio is apparent, as ishis conviction that ham radio plays an important role whencalled upon during emergencies. With this book, WardSilver may well become an Elmer (mentor) to a new gen-eration of hams. NV
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SEPTEMBER 2004
Personal Robotics by Mike Keesling
Some of us build robots for theeducational aspects, others fora creative outlet. Some of us
undoubtedly have a god complex orparenthood issues, but there is onething that you can’t deny and that isthat robots are great for impressingyour friends.
Unfortunately, after your third orfourth rolling robot (you know theones — two hacked R/C servos and acaster or a skid), you start to cravemore — more motors, more wires,more everything. You know what Iam talking about; you have beenthere or will be, eventually. You wanta walker. Not just any walker — youwant a hexapod.
Hexapods are amazing to watchas they do their magical cockroachdance. They roam around on yourworkbench or living room floor, withtons of behavioral aspects to exploreand myriad motions to perfect. Justgetting the code running for all thoseservos is a challenge, let alone theintelligence behind them.
Hexapod walking has a lot to it.
Even the simplest 2 x 6 presents amajor technological leap over yourold, two-motored carpet crawler.Efficiency, construction, geometry,and torque all take on anotherdimension of complexity as you sizeout motors for the job. Just thegeometry of the joints can have ahuge impact on the overallperformance.
While some of us are braveenough to attempt designing andbuilding our own walkers, others ofus turn to the commercial market tosatisfy our need for walking wonders.Predominant in the walker market isLynxMotion. They have been in therobot biz for as long as I can remem-ber and it had always been a dreamof mine to own one of their creations.
Apparently, they have inspiredmore than just admirers.CrustCrawler is relatively new to themarket, but offers a slightly “higherend” mechanism than LynxMotion, ifthat is possible. CrustCrawler hasalso partnered up with the industrystandard — Parallax — to provide a
distributor and acomplete solution.
TheHexCrawler
Since CrustCrawler’soffering — the HexCrawler— is a 2 x 6 with just 12servos, I chose to beginmy review with it.
To begin, when Iopened the box, I wasstunned. You have tounderstand that I haveworked in the movie andadvertising industries,
where everything must be pictureperfect: not a speck, not a hair out ofplace, no blemishes, creases, folds,or tears. Anything less than perfect isunacceptable.
It takes a lot to impress me, butParallax’s presentation of theHexCrawler did more than that; theyfloored me. They could havepresented some nice, reeking hakarl(fermented shark) fresh from thesand pits and drying sheds ofIceland and I would have gladlydowned it. The presentation wasbeyond good; it was stellar.
All the parts were in nice, labeledzip-lock bags. The glossy, spiralbound instructions beckoned to meand the shiny, anodized aluminumpieces — carefully shaped and bent— called to me. Then bags of spac-ers, hardware, and wire ties greetedme next — dazzling, taunting, andinviting me.
The next salvo on the senseswas the bags of electronics, servocontroller, processor, and compo-nents: so much to play with, so muchto do. Then the wave of Hitec servoshit. Occupying nearly two-fifths ofthe box, they clued me in to the workahead, but I was still willing, ready,and able. Everything about this kit isluxurious.
Assembly was almost seamlessand took less time than I hadoriginally thought. There were nosurprises and things were reasonablyillustrated and documented. Theinstructions are mostly clear andconcise, but not preachy or pedantic.There were some ambiguities in theinstructions, but they were easy toovercome.
The only difficulties I
A Walk on the Wild Side!
Understanding, Designing, and Constructing Robots and Robotic Systems
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The HexCrawler with a BASIC Stamp II brain.
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encountered were a PEM nut that haddamaged threads and a few missingpieces, like #2 washers. I decided toclear every PEM nut with a tap, just incase. I also decided to inventoryeverything and was able to rummagethough my junk box and get what Iwas missing.
The core issues I have are alsofeatures in their own ways and theyare the fairly limiting geometry that a2 x 6 walker possesses, along withthe simplicity of the processor — theBASIC Stamp II. In a way, this is sortof an equal match. The BASIC StampII isn’t capable of the intenseprocessing that is required to do theinverse kinematics that a 3 x 6 walk-er could use to more accurately walk,but I believe that it is also not neces-sary (more on that later, though).
Overall, this kit embodies theessence of what I think most of us seeas the core of walking robots — lots ofintricate, moving parts. While thesimple 2 x 6 design and its processorare ill-suited for complicatedkinematics, they do provide a great,simple start. A beginner should beable to jump into this right away and,in a few evenings, have a very highlevel of satisfaction. Additional thirdaxis leg extensions can be added,along with an additional servocontroller, as well, but, at that point, Iwould consider a processor withmore horsepower to fully utilize theadvanced geometry available.
Straight out of the box, this kitlacks the real complexity that Isomehow thrive on, but I have to keepreminding myself that — just becauseI have been programming for 30years and design insanely expensivemotion control systems — not every-one else has or even wants to dealwith that much wholesale madness.
Overall, a small degree of skill isnecessary and be prepared to usesome basic hand tools, as well as a1/8” drill. I give this kit a solid A.
Extreme Hex 3R
Now, to kick things up a notch, Icome to LynxMotion’s EH3-R —
Extreme Hex 3R. While the EH3-R lacks the
refined presentation of theHexCrawler, it is a beast of akit and very satisfying. Madeof laser cut Lexan® (not justgeneric polycarbonate) and18 Hitec HS475-HB servos,this kit is a formidablechallenge. The resilience ofthe Lexan gives the EH3-R analmost meaty feel as youassemble it, as though it weregoing to lurch into life on itsown. Replacing the cleangleam of the HexCrawler wasthe slightly acrid tinge of lasercut plastic, but that reallyadds to the feeling ofelemental life that the EH3-Rconveys as you build it.
In fact, the actual buildwas relatively easy. I onlyfound myself wanting an easyway to secure the servo wires, but atrip to the electronics store solvedthat with a variety of fastened andadhesive-backed wire anchors. Iwould also like to get my hands onthe metal standoffs that are nowshipping with the kits, as I see myselfaccidentally breaking some of theseeventually. I did take artistic license
with the build geometry, making eachleg identical, rather than mirroredimages of each other, but more onthat later.
The build of this kit is a lot moreintensive than the HexCrawler, due tothe additional six servos, but, in away, it’s a bit less complex due to themolded plastic pieces used to make
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The EH3-R makes its escape.
Circle #73 on the Reader Service Card.
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the hinges. There is just a lot ofrepetition involved. The otherdifficulty I came into was peeling theprotective plastic off the Lexan. Ittook me nearly an hour toaccomplish this. Before peeling, Ishould have taken some time to cleanup the laser-singed plastic cuts.
The three-jointed legs addanother dimension to hexapodwalking. With a two-axis leg, you getsome scrubbing on the ground as thehip swings the leg fore and aft. Youcan mince about, taking little steps,but it is somewhat unappealing. Here,with the third axis and a lot offloating-point mathematics and
inverse kinematics, youcan start to calculateyour path based on thegeometry of the robot.You can set the rideheight of the robot andtrace the tip of the footthrough a straight line or an arc to get much smoother walking.You can even crab-walksideways.
The symmetricaldesign of this kit hasalways appealed to me ina hexapod, but it alsoopens the door for someinteresting challenges.
Take, for example, the standard 3 x 6hex; it has two banks of legs: left andright, each leg on a side moving sim-ilarly, but out of phase with its leadingand trailing neighbors. In effect, eachleg mimicks the legs around it. Thelegs on opposite sides are mirrorimages, yet again, out of phase.
In short, there is a lot ofsymmetry. According to the instruc-tions, that is how this kit is meant tobe built. I however, decided to torturemyself by building the kit withoutmirrored symmetry. I, instead, optedfor a single axis of symmetry, with allof the legs built identically and simplymoving as rotations of each other
around the vertical axis.What this means is that, by
building and thus commanding eachleg identically with no head or tail, thesoftware is identical for each leg.There are no exceptions or reversingservos; each leg is a carbon copy ofthe others.
The commands that drive thelegs will simply be coded as vectors —angle and magnitude — for the wholerobot, and each leg will follow thispath according to its position relativeto the vector of commanded motion,not relative to the chassis. Thismeans that there really is no “forwardmotion,” just crabbing. This can befurther extended to arcing motions,where the whole robot follows an arcthrough space.
I chose to outfit this beast with aServoPod from New Micros, Inc., bothbecause the 18 servos do not evenphase the 80 MHZ DSP onboard, butalso because the language onboard —IsoMax — was specifically crafted torun highly optimized floating pointcalculations.
My first shot at the software —written over the course of twoevenings — employs a lot of interest-ing elements. The first is a 36 step,pre-canned gait. This gait pattern isnon-scalar and can be offset from thebody along the axis of the hip,
SEPTEMBER 2004
Personal Robotics
The EH3-R shows its tripod gait.
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rotated in space, and scaled in bothheight and length. The phase of thegait can be rotated to performdifferent gaits, as well. This gaitgenerator gets fed into the inversekinematics engine, which takes thedesired ride height of the robot, thedesired position of the tip, andcalculates the joint angles required toproduce that tip position.
Overall, this kit gets an A, as well.I would like to see the pieces cleanedup somehow and see someprovisions for anchoring the wires. Asimple Allen wrench and pliers wereall I needed to build it, but beprepared to spend some timeprogramming, if only because thereare 18 servos to deal with.
Shelob
Not content to leave well enoughalone, Phil Davis — a consummatehobbyist by night and computerscientist by day — has realized thateven three joints per leg leave a lot tobe desired. To counter this, Phil hascreated Open Source Shelob (www.IsoBots.com).
I have been in this hobby formany moons, but I have never heardof a 4 x 6 before. The addition of thefourth joint allows for better jointpositioning and trajectory tracking. Itis like a 3 x 6 on adjustable stilts. In a3 x 6, you have to accept that, as thetips of your feet translate through aline on the ground, you will generatea small amount of scrubbing unlessyou account for the geometry of thetip and, if you do, you generatewaggle or bumping in the body. Youare effectively constrained, not beingable to adjust the angle of the lastsegment to the ground. The fourthjoint allows this, but Phil wasn’t evenhappy with that. He has alsodesigned in an articulated, segment-ed body to better accommodateuneven terrain.
Shelob is constructed from 1/8”plywood from www.Filener.comThis perfectly valid building materialis easily cut, finished, and paintedand is relatively inexpensive. People
even build houses andboats out of the stuff andrumor has it that theyused to build airplanesout of it, too.
What is especiallyimportant about Shelobis that her construction isopen source in nature. Byplacing all the costsassociated with the intel-lectual property into thepublic, everyone canbenefit from the efforts ofall who contribute. Thisshould drive the qualityup and the price down.
Phil’s processors of choice areseveral IsoPods — one per segment— on a CANbus network. This willhardly task each IsoPod, but it willleave a lot of possibilities open forsensing by utilizing the extra timerchannels and A/D converters. Thiscan also remove some of theburdens of inverse kinematics fromthe main processor, which is meantto perform sensor synthesis anddecision making.
Presently, the code is based oninverse kinematics, as well, but Iknow that the eventual goal is based
on sensing, not calculating, thoughsome forward kinematics will beuseful for tracking the joints them-selves through space. The code alsoincludes velocity and accelerationprofiling to keep things smooth andprecise and — I guarantee — lots andlots of trig.
Walker Theory 102
Earlier, I alluded to not needingquite so complex of a trigonometryengine to perform walking. I believethe key to “real” walking is to
SEPTEMBER 2004
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The HexCrawler kit is quite a spread!
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The EH3-R in its parked position.
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transcend past highly calculativemethods and rely more on sensing —perhaps neural networks or simplepattern generators, modified by sen-sors. After all, if I use a trigonometryengine to generate a perfect gait,maintaining a uniform ground clear-
ance and tracking a perfect plain, Iam still moving to a pre-canned gait.Without being able to sense the feetrelative to the terrain, any walkingdone will simply be a coincidence ofthe ground meeting my expectations.
To this end, Phil and I are workingon three axis force sensors for thetips of the feet. This will allow us tosense the terrain and meter it; we caneven use the sensors to providefeedback to sense whether the feetare tracking arcs or straight lines. Bycomparing the vector of the forcesensed with the vector being generat-ed by the motion of the leg, the shapeof the surface can be ascertained.
A company called BokamEngineering (www.bokam.com)makes some very nice three axisforce sensors and amplifier boards.This would enable the measuring oflateral and vertical forces on the legand accommodate the terrain. Itwould also allow the traversing ofmore difficult terrain (anything notflat) by feeling for obstructions.
An alternate method would be touse strain gauges on the spansbetween the joints themselves ormetering the current consumption ofeach servo. These methods are more“integrated,” but would then requireyou to do more kinematics todetermine the vectors of force basedon the values you sense and the posi-tions of the joints. I will likely try this,as well, if only because it iscomplicated.
Through the method of sensingand reacting, rather than calculating,I believe simpler processors may bepreferable, as they do not require asmuch high level math. In some ways,this is more in line with what my ideaof a biological entity must be doing.
Please keep an eye open for fullcoverage of Open Source Shelob inthe future. I hope to build one of myown out of carbon fiber rather thanplywood. I also hope to fit it withstrain gauges and may go to acustom board with a TiniPod,amplifiers, voltage to frequency con-verters for the strain gauges for eachleg, and a single IsoPodX for a brain— but only if it is complicated. NV
SEPTEMBER 2004
LynxMotion — www.lynxmotion.comCrustCrawler — www.crustcrawler.com
Parallax — www.parallax.comOpen Source Shelob — www.isobots.com
Filener — www.filener.comBokam Engineering — www.bokam.com
Resources
Personal Robotics
One of Shelob's three segments. Notice the details, like engraved pieces.
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There is probably no other pro-fession that depends uponspecifications as much as
engineering does. You createsomething to meet some set ofrequirements or you rely on the per-formance data of variouscomponents. Very often, bothaspects are employed at the sametime. Knowing how to make, read,and understand specifications is animportant part of engineering.
Conflict of Interest
Arguably, the most importantaspect of specifications tounderstand is their inherent conflictof interest to the company. Engineerswant the most conservativespecifications possible. This makesthe product easy to produce, repair,and design.
Obviously, it's easier to make a25 watt amplifier with 1% distortionthan a 100 watt amplifier with 0.01%distortion, but who wants a 25 wattamplifier with 1% distortion? It won'tsell. It's easy to make, but there's asmall market.
On the other hand, there is agood sized market for the betteramplifier. Clearly, there must be abalance between what people wantand what you can make. Differentcompanies have different points ofview on this matter.
Hewlett/Packard (now calledAgilent) is a good example. Fordecades, they have been recognizedas producers of world class testinstruments. However, in the 1980sand 1990s, their products becamemore and more expensive relative to
the competition. There was noquestion that their quality wassuperb. However, would you spend$20,000.00 on an H/P oscilloscopewhen LeCroy would sell you one for$5,000.00 that did the "same thing?"The "same thing" was defined by thespecifications. Suppose bothmachines were spec'd with a band-width of 500 MHz. Which one wouldyou buy?
The truth is that the H/P oscillo-scope was clearly better and everyengineer knew it. The LeCroy 'scopewas certainly good and it performedas specified.
However, the H/P performedbetter than specified. Yet, when thejustification for the expense of anoscilloscope came, H/P had troublecompeting. It's hard to convince
financial administrators to spendfour times as much for the "same"instrument.
H/P sales started to decline andtheir name became associated with"over-priced" test equipment. Isuspect that this is a major reasonbehind the changing of their univer-sally recognized name, which theyworked so hard to get, in the firstplace. Agilent now sells testequipment that still is excellent, but itis more reasonably priced andspecified.
Specifications areNot Black and White
It's important to realize thatspecifications are not always fixed,although specifications are — some-
Specifications
The Business of Electronics Through Practical Design and Lessons Learned
In The Trenches
SEPTEMBER 2004 83
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by Gerard Fonte In The Trenches
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SEPTEMBER 2004
times — pretty much outright lies.Way back when the number oftransistors in a radio was significant,manufacturers would simply solder innon-functioning transistors to padtheir count. Early stereo amplifiersused to be rated in "music power"watts. (This was, apparently, themaximum peak power reached justbefore the amplifier exploded.)
Currently, there is the ridiculouswattage rating of some computermultimedia speaker/amplifiers. I'mlooking at one in the May 2004catalog of a very well-known hobbyistelectronics/computer supplier. Thesespeaker/amplifiers are rated at 480watts and cost $39.95. It's interestingto note that they look identical tomine — which are rated at 80 watts(also a joke). I took my speakersapart and found that the amplifier is aBA5406, which is rated at 3 watts perchannel.
Note that I use one specification(and common sense) to contradict adifferent specification. This is notuncommon in engineering.
After all, a specification is just ameasurement and measurements ofthe "same thing" can differ bymethod.
Let's look at a fictional — but
realistic — example. You've designeda logic chip with a propagation delayof 5 nS. Suppose this is typical forthis type of device. Your companywants a chip that's faster than thecompetition’s. Can you accommo-date your company withoutredesigning the chip?
How did you measure thepropagation delay? You reply, "Withthe standard 20 pF load." Supposeyou measured it with only a 10 pFload? That would reduce theapparent propagation delay.
Now, you have a chip with only a3 nS delay. You've "improved" yourchip considerably — with noincreased expense. The company ishappy, marketing is happy, and youget a raise.
People continuously find loop-holes in standard measurement tech-niques in order to give their product aperceived advantage in the market-place. This is called "specsmanship."While it's not really good engineeringpractice, it's fairly common inmarketing (again, engineering vs.marketing).
You clearly show on the specsheet that all measurements werewith a 10 pF load, so you are beingcompletely honest. Nowhere is it
said that your chips are faster thanthe competition’s. If thosecompanies choose to use 20 pF tomeasure their chips, that's theirdecision. You have presented yourmeasurements and how youobtained them. It is up to theconsumer to determine if yourproduct will suit their needs.
This illustrates the constant tug-of-war between engineering andmarketing. Engineering likes stan-dard methods so that measure-ments are easy and consistent.Marketing wants a product thatstands out so it will sell. It'simportant to see that both points ofview are valid. There is nothingunethical about making your prod-uct look good. There is nothingwrong about emphasizing the strongpoints and down-playing the weakpoints, but it is also important torealize that, in this case, your chip isreally no better than the competi-tion’s. If you compare your chip inthe same circuit as your competi-tor's do, they perform the same.
Two Types ofSpecifications
There are two general types ofspecifications: performance andtarget.
Performance specifications arethose that the product is guaranteedto meet (hopefully).
Target specifications are thosethat the product is designed to meet.
Engineers usually define the per-formance specifications. Marketingusually defines the target specifica-tions. Generally, these targetspecifications are based upon feed-back from customers who say thatthey need a product that does "___."It's important to keep these types ofspecifications in their proper place.
Unfortunately, too few engineersunderstand target specifications. Allthey see is that marketing has com-mitted them to create a product with
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specifications that are mutuallyexclusive. Marketing replies that thisis what the customer wants to buy. If we can't provide it, someone else will.
As you can see, specificationsare the weapons that the engineer-ing/marketing war is fought with.
Instead of arming the photontorpedoes and targeting marketing,what can you do when faced withimpossible target specifications?First, calm down. Remember, market-ing is not engineering. Their idea ofspecifications is not the same asyours. It's really a different word andconcept. They're simply repeatingwhat the customer wants. Often,they've combined requests from dif-ferent customers into a single productand it may simply be that theyhaven't reported the specificationsaccurately. Remember the three lawsof selling:
1. Marketing is not engineering.
2. Marketing has a potential sale.
3. Everything in marketing is nego-tiable.
Turn Lemons intoLemonade
Suppose you are given animpossible task. Let's say that mar-keting has promised a client a prod-uct that can measure temperaturefrom 0 to 200 degrees F in 0.1degree intervals using one of yourstandard products that has a simple,eight-bit processor.
Unfortunately, the processoronly has an eight-bit A/D (analog-to-digital converter). You need 2,000steps (200 degrees by 0.1 degreeintervals) and the A/D only provides256 steps. It's impossible to do!(Actually, it may be possible if youemploy the statistics we discussed afew months ago.)
First, calmly examine theproblem in detail. Then, create yourbest design. In this case, let's saythat you feel that an outboard 12-bit
A/D is necessary. Price the systemwith the new A/D. You may need tocreate a completely new productbecause the existing one can't bemodified. That may be an absurdapproach, but examine it anyway.Try to anticipate every comment,criticism, and observation thatmarketing can make. Have a goodanswer for each and every one. Thencall a design review.
In this review, explain in simpleterms what impact the requestedspecifications have on the existingproduct and then present yourdesign. Always have a workabledesign to present. It may not be costeffective or practical, but it is political-ly necessary. If you simply object tothe design, you'll be considered anobstructionist.
If you provide an alternativedesign, you will be seen as a teamplayer. They may complain about thecost or the delay or the form factor,but, if you have clearly explained yourposition and provided a design thatmeets the specifications, you will beseen as trying to help.
Note: You should generally justpresent your new approach. Letthe questions lead you into com-
paring the new and old designs.Non-technical people generallyfind this easier to follow, but becompletely prepared with graphs,tables, etc.
It often happens that, during thisdesign review, new information orspecifications emerge. In thisexample, the reason for 0.1 degreeaccuracy was because the productwas to be used for measuring thebody temperature of animals in azoo. Since very few warm-bloodedanimals have a body temperaturebelow 85 degrees and above 110degrees, the eight-bit A/D canprovide the 0.1 degree resolutionrequired (256 steps in 0.1 degreeincrements gives a 25.6 degreerange).
Did you notice that we're talkingresolution rather than accuracy?They are two entirely differentspecifications.
Unfortunately, they are oftenconfused. The resolution of a systemis its ability to separate closemeasurements. In this case, it's 0.1degrees. The accuracy is the abilityto measure according to a standard.This has not been discussed at allhere.
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SEPTEMBER 2004
Many inexpensive temperaturesensors have an accuracy of ±2degrees. A reading of 100 degreesmay actually be anywhere from 98 to102 degrees. Obviously, this is notvery good for determining if a baboonhas a fever.
Therefore, a special thermistorwill be needed. Understanding thedifference between accuracy and res-olution specifications is criticallyimportant in engineering.
Note: It is not unheard of foran engineer to identify "impossi-ble" specifications at a designreview while having a solutionalready in hand. This solution mayor may not be presented at thatmeeting.
However, sometime soon, thatengineer will "realize" that such asolution exists and provide it to thesurprise and delight of allinvolved. This saves the companytime and money. It also improvesthe engineer's reputation.Theatrics and good timing are notunethical.
Hard and SoftSpecifications
How long a battery will last in aheart pacemaker is a hard specifica-tion. How long a battery will last in aboombox is fairly soft. It's surprisinghow often engineers fail to considerthis aspect. Not all specifications arecreated equal. Making sure the multi-meter measures the correct ACvoltage at 60 Hz is importantbecause that's the frequency that ismost commonly measured. If themultimeter is off by 5% at 250,000Hz, it's not as important. Most userswould rather have a meter thatmeasures 60 Hz accurately and250,000 Hz with 5% error than ameter that was off by 2.5% acrossthe frequency range.
Obviously, the most important —or hard — specifications are thosepertaining to personal safety. It iscritical that these specificationsalways be conservative. What is the
AC leakage current? Is the fuserating correct? (Do you know how toproperly choose a fuse?) The twogreatest personal hazards electricalengineers need to consider areelectric shock and fire hazard. Theyshould always be considered in everydesign — even in battery-operatedproducts.
Suppose you have to design asimple linear power supply — just atransformer, rectifiers, and a filtercapacitor. It’s easy, right? It shouldbe, but it doesn't seem to be. Youneed 18 volts DC at 750 mA, so youchoose a 24 VAC transformer thatprovides 2 amps, to be conservative.The filter capacitor should be conser-vatively rated. Let's add 50% over the24 volts and use a 35 volt filtercapacitor. That seems reasonable,right?
Wrong — possibly dangerouslywrong! The transformer is rated inRMS voltage and under full load (2amps). Multiply the 24 volts by1.414 to get the peak voltage. Thiscomes to 33.9 volts. Add about 10%to compensate for the loadedvoltage drop and the unloadedpeak voltage out of the transformeris 37.3 volts. The filter capacitor isreally a bomb waiting to explode(and they do!). The absoluteminimum voltage for a filtercapacitor is twice the transformervoltage. In this case, that's 50 volts.To be conservative, 63 volts ormore is needed.
The rectifiers can be 1 amptypes, right? After all, we're onlydrawing 750 mA. Again, wrong. Thetransformer is rated at 2 amps andcan provide considerably more for ashort time. At power-up, thecapacitor acts like a short circuituntil it gets charged up, so the inrushcurrent will be over 2 amps. Thelarger the capacitor, the worse thisproblem is.
Admittedly, rectifier diodes arepretty rugged and can take substan-tial inrush overloads, but this is stillnot a conservative design choice. (Aninrush-limiting resistor can be asimple and effective solution.)
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Of course, the transformerdoesn't have to provide 2 amps. A 1.0amp or 1.2 amp transformer could beconsidered. It will also be lessexpensive.
There are a number of pointshere. A conservative transformerchoice (2 amps) makes other parts ofthe design non-conservative. Thespecification of an RMS voltage (24VAC) is not the specification of apeak voltage (37.3). Safety requiresthe full understanding of every detail.Cutting corners or carelessness issimply unacceptable when safety is involved.
It is also interesting to note thedance between target specificationsand performance specifications. Wemake our design meet our targetspecs by choosing parts with properperformance specs. When we'redone, we'll have a product with per-formance specifications. Further, ourproduct may be used in anotherproduct to meet its target specs andso forth and so on.
SoftwareSpecifications
First, stop laughing. There issome truth in calling softwarespecifications an oxymoron. If youdon't believe this, read Microsoft's
"End User License Agreement." It istruly educational.
With software, if it works, then itmeets specifications. There is noeasy way to determine if standardengineering practice is employed.There is usually no outside reviewof the actual code. This is verydifferent from hardware. A circuitboard must not only work, but mustmeet specific design rules (AKAspecifications) in regard to partsplacement, layout, trace widths,trace spacing, hole size, and soforth.
There are no equivalent rules forsoftware. There should be. Therehave been attempts to analyze codewith software, but this has not beengenerally accepted, nor, as Iunderstand it, is this softwareparticularly good.
The target specifications forsoftware become its performancespecifications.
However, these are not the same.The target specs say what theproduct must do. The performancespecs say how well it must do it. Ihave never seen actual performancespecifications for software, with theexception of benchmark ratings. Theonly way to compare similar softwarepackages is to actually try them,side-by-side.
Objective software standards arenot impossible to create or measure.How about measuring the ratio ofbranch to in-line statements or acode-line to comment-line ratio?What about providing the number ofstandard library code-lines and thenumber of custom code-lines? Thesevalues would allow the comparisonof one program to another. It seemsto me that they would be useful to have.
Unfortunately, I don't see thishappening soon.
The Root of AllLegal
One of the most commonsources of customer complaintsand legal action is because thecustomer feels that the productdoesn't meet specifications: Thisclock doesn't keep time. The radiodoesn't pick up my favorite station.The air conditioning doesn't keepthe whole office cool. I want mymoney back!
There will always be unhappypeople. However, your productshouldn't make them that way.Properly specifying your product cango a long way in reducing these com-plaints.
Additionally, good specifications
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can educate the user about what to expect from your product.Remember, unfulfilled expectationsare probably the biggest source ofcustomer dissatisfaction.
Put yourself in the your cus-tomer's place when you write thespecifications. What would like tosee? What's important to you? At theminimum, the spec sheet shouldinclude what your product needs towork (the voltage, frequency, andpower), what the product produces(output power, distortion, etc.),proper operating conditions (loads,environment), operating limits (frequency range, bandwidth, poweroutput, etc.), and the physical charac-teristics (dimensions and weight).Always include notes about otherequipment needed for operation (ACadapter, blank disks, computerrequirements, etc.).
Next, you can provide the softerspecifications. Sometimes, these
are called "typical" specificationsand are more like guidelines ratherthan guaranteed performance. Anexample is the highest frequencythat an AC voltmeter can reliablymeasure. These may not beabsolutely necessary for the customary use of your product, butthey are informative and useful to know.
Don't overspecify your product.You don't want to create problems.Say things like "high brightness LEDdisplay," instead of "2,000 MCD LEDdisplay."
In the future, it may be that3,000 MCD displays are the sameprice or that cheaper 1,000 MCD displays are necessary for cost.Think carefully because the specsheet may outlast your involvementin the product.
There is nothing inherentlyunethical or improper about omittinga bad specification. (It is unethical
and improper to include a false specification.)
For example, if the frequencyresponse of your voltmeter only goes to 100,000 Hz and all your competitors' go to 250,000 Hz, youmay choose to omit it. You want yourproduct to sell. You are not forced toidentify every weak point in thedesign (except for safety, of course).Naturally, if it's a major specification,it will be noticed and it will causeproblems.
Conclusion
Specifications are used indesigning, defining, and comparingproducts. There are different typesand definitions of specifications, soit's useful and important to understand them. Since your job andyour company's health depend onspecifications, using, creating, andproperly reading them is vital. NV
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Stamp Applications
Have you ever noticed yourself when you’ve noticedyourself? I seem to do it all the time, suddenlynoticing some behavior I had that — until that
very moment — had been completely unconscious of.Often times, the thing I notice is quite humorous. Likemost humans, I’m a creature of habit. My typical dailyhabit is to wake up, check Email quickly (in case there’sbeen an overnight customer emergency), jump on thetreadmill for about 30 minutes, grab a bite to eat, andthen pop by the neighborhood Starbucks for a cup ofcoffee and a quick chat with a very pleasant lady namedLindsay.
On a recent return trip from Starbucks, I noticedmyself doing something that actually made me laugh.While steering with my left had, I would reach down withmy right hand to adjust the coffee spout such that coffeewould not slosh out while I was cornering. Honestly, Ilaughed out loud, then immediately thought that, if I hadan accelerometer, a stepper motor, and a BASIC Stamp,I could keep both hands on the wheel. An idea was born ...
Was it a practical idea? Well, probably not — and I’mcertainly not going to tear apart the center console on mynew SUV to install such a device — but the exercise indesigning the circuitry and code tosolve my coffee sloshing problem isstill worthwhile. I receive a lot ofEmails asking how one gets “sogood” at programming the BASICStamp microcontroller. Like getting toCarnegie Hall, it takes practice,practice, practice. Imagine how manytens of thousands of practice shotsMichael Jordan shot before andduring his career; every one of themserved to prepare him for all thosechampionships. I guess my point isnot to wait for a “real” project toimprove your programming skills.
Many times, it’s worth doing a project just for theexperience of doing it.
Leaning To and Fro
If you’re new to the BASIC Stamp microcontroller orweren’t around for my article in the November 2003 issueon using GPS, you may be wondering how we’re going totake the output from an accelerometer and use it to pointthe spout of a coffee cup lid.
To be honest, it’s dirt simple: We’re going to use theATN function. ATN (arctangent) returns the angle (inbinary radians: 0 to 255) that points to the intersection oftwo vector values.
The first thing to do, then, is to read theaccelerometer outputs (x and y axis) to establish theg-force vectors. You may remember from our previouswork with the MEMSIC 2125 that a 0g output is a fivemillisecond pulse. Negative g-forces are shorter than fivemilliseconds; positive g-forces are longer. Reading thepulse outputs is no trouble; we can use PULSIN to do it.Here’s the trick: The resolution of PULSIN gets better asBASIC Stamp modules get faster. Code that will workproperly with a BS2 module will not return the correctresults when using the BS2p.
You know where I’m going with this: conditionalcompilation. I covered it briefly in the past and I think it’sgood to remind ourselves that this feature is now availablein the Version 2.1 compiler. So, what are we going to do
No More Coffee Spills
Ideas more crazy than this havebecome successful products!
Putting the Spotlight on BASIC Stamp Projects, Hints, and Tips
Figure 1. Memsic 2125 Connections. Figure 2. ATN Output.
SEPTEMBER 2004 89
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SEPTEMBER 2004
Stamp
with it? We’re going to use a conditional compilationconstruct to set a constant value that will be used to scalethe raw input from PULSIN to microseconds, alwaysreturning the correct value, regardless of which BASICStamp module is being used.
#SELECT $STAMP#CASE BS2, BS2E
Scale CON $200#CASE BS2SX
Scale CON $0CC #CASE BS2P
Scale CON $0C0 #CASE BS2PE
Scale CON $1E1#ENDSELECT
When we compile a program, the first thing that thecompiler does is look for conditional compilation symbols(created with #DEFINE), then look for conditionalcompilation constructs like ours above. The constructworks as we’d expect, but only at compile time. Thesection that evaluates as true will get compiled into theprogram; all others will be ignored.
If, for example, we had selected a BASIC Stamp 2module, our program would compile and assign the
constant called Scale a value of $200 (same as 2.0decimal when used with */).
Once you get used to conditional compilation, it canbe a very powerful tool. How many times have yousprinkled DEBUG statements through a program, onlyhaving to go rip them all out when everything is working?With conditional compilation, you can do this:
#DEFINE DebugMode = 1
Then, in the body of the program, we add a bit of logicaround our DEBUG outputs:
#IF DebugMode #THENDEBUG “Program Status”
#ENDIF
Once the program is working properly, we can turn-offall the DEBUG statements with one small change:
#DEFINE DebugMode = 0
How much easier is this? Also, as we’ve all seen,programs are ultimately updated. When that happens, wedon’t have to go back through and drop in DEBUG
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statements to check on our updates — we simply re-enablethe ones that are there with #DEFINE.
Okay, let’s get back to reading the accelerometer(connections are shown in Figure 1). The first thing to dois scale the raw input from it to a known value. By usingour Scale constant, we will end up with microseconds andat 0g on either axis, we should get around 5,000 (fivemilliseconds).
Remember that the */ operator works likemultiplication, with the parameter being expressed in unitsof 1/256. This lets us multiply by fractional values between0 and 255.996.
Get_Memsic:PULSIN XPin, 1, xG PULSIN YPin, 1, yGxG = xG */ ScaleyG = yG */ ScaleRETURN
If we run this code in a loop and look at the results,we’ll see values that range from 3,800 to 6,200microseconds. Okay, but what we need is something thatfits into the -127 to 127 range required by ATN. It’sactually very easy and uses the “round up” math welearned as kids in math class.
Get_Memsic:PULSIN XPin, 1, xG PULSIN YPin, 1, yGxG = xG */ Scale + 50 / 50 - 100 yG = yG */ Scale + 50 / 50 - 100RETURN
Right after Scale, you’ll see “+ 50 / 100.” This roundsup the value and scales it down to 50 as the 0g point. Then,we subtract 50 so that 0g returns a zero value. There’s animportant note here: We need to do the subtraction lastbecause, if we attempt to divide a negative number, we willget incorrect results.
If we look at the output now (using the SDECmodifier, of course) we should see values from -12 to+12. Don’t be worried about the apparent loss ofresolution of our vector. The reason we’ve divided downso much is to eliminate minor jitter from the sensor thatwould just cause the stepper to quiver back and forthunnecessarily. What we’ve done, in fact, is a bit of simpledigital filtering.
Okay, now that we can read the output of theaccelerometer as vectors that will work with ATN, let’smap the output of ATN vis-à-vis the g-force loading onthe sensor. Figure 2 shows the values I read from my
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SEPTEMBER 2004
Stamp
setup. We can simulate acceleration of the car by tiltingthe front end of the sensor (pins 1 and 6) up. We cansimulate braking by tilting the front end of the sensordown.
Main:GOSUB Get_MemsicDEBUG HOME,
SDEC xG, CLREOL, CR,SDEC yG, CLREOL, CR,CR,DEC (xG ATN yG), CLREOL
PAUSE 200GOTO Main
So, under simulated acceleration, we getzero, under braking, 128, turning right, 192, andturning left, 64. Let’s think about this for amoment. Wouldn’t it be a bit more convenient ifthe output matched the number of steps of ourstepper motor? It might be easier to deal with,mentally, if the values increased in a clockwisedirection, as well.
I happened to grab a stepper that has a 3.6degree step; this means that there are 100 stepsin each revolution. Here’s how we can do it:
angle = 100 - ((xG ATN yG) */ 100) // 100
This may look a bit convoluted, but I promise there isa reason for every bit of it — let’s work from the inside out.By using */ (star-slash) with a parameter of 100, we scalethe output of ATN from 0–255 to 0–99. Our next issue,then, is reversing the direction so that values increasegoing clockwise instead of counter-clockwise, as they donow. By subtracting from 100, we’re able to do that — withone tiny glitch: what was 0 ends up being 100. Okay, then,we can use the modulus operator on the whole works andnow our output is 0 to 99.
Accelerating means we should point the coffee spouttoward 0 (front of car); when braking, it will point toward50 (rear of car), to 25 when turning right, and, whenturning left, 75. Let’s polish off our main loop:
Main:GOSUB Get_Memsic angle = 100 - ((xG ATN yG) */ 100) // 100IF (angle <> pos) THEN
GOSUB Move_SpoutENDIFGOTO Main
END
This is as simple as it gets: we read the new angle andcompare it to the current spout position. If there’s adifference, then we reposition the spout; otherwise, we goread the accelerometer again.
Before we can actually turn the spout, we need to findthe shortest path between the current position (pos) andthe new position (at angle). It actually took me a fewminutes to figure out how to code this one cleanly. While it
Figure 3. Stepper Connections.
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looks simple on paper — with circles and dots — it takes abit of thinking. Let’s look at the code that determinesrotational direction and work through it:
Move_Spout:IF (angle > pos) THEN
span = angle - posIF (span < HalfRev) THEN
stpDir = MCWELSE
stpDir = MCCWspan = RevSteps - span
ENDIFELSE
span = pos - angleIF (span > HalfRev) THEN
stpDir = MCWspan = RevSteps - span
ELSEstpDir = MCCW
ENDIFENDIF
Here we go: If the new angle is greater than the currentposition, then we get the span by subtracting the old posi-tion from the new. Next, we check to see if that span is lessthan half a revolution. If it is, then we set the stepper direc-tion to clockwise; otherwise, it will rotate counterclockwise.
Notice that we have to make a correction in the spanif we determine that the shortest path is counter-clockwise.If we don’t make this correction, the spout will overshootthe desired position. We can use a similar set of logic whenthe new angle is less than the current position — withadjustments, of course, to make sure that we turn in thedirection that provides the shortest path.
Okay, let’s finish up and actually reposition thestepper motor:
stpDelay = MoveTime / span
DOstpIdx = stpIdx + stpDir // 4 READ (Steps + stpIdx), CoilsPAUSE stpDelayspan = span - 1
LOOP WHILE (span > 0)
pos = angle
RETURN
The rest of the subroutine starts by calculating thedelay between steps. The value is set by dividing the totalmovement time (500 ms in our program) by the numberof steps in our move. Note that we must have some delay;the stepper motor needs it. Also, we’ll want to experimentwith this a bit. The largest possible move is half arevolution. Setting the time for that move to 500milliseconds seems reasonable — fast enough to get thereswiftly, but not so fast as to sling coffee out of the spout.
A DO-LOOP is used to send the step data to the
motor. We’re back to our old tricks with the modulus oper-ator; this allows us to set the direction with a variable. Thecoil data is pulled from a DATA table with READ andplaced right on the pins. Of course, we cannot drive a step-per directly with BASIC Stamp IO pins; we need a high-current buffer to handle the coil load. Figure 3 shows howto use our old friend, the ULN2003, to handle the load forus. Finally, we need to update the pos variable with ournew position and start the whole process again.
Short and Sweet Rules!
Okay, I know this project wasn’t a big mentalchallenge, but I do think it’s useful — even if we don’tautomate our car’s cup holder. I’m sure you’ll figure outsomething fun to do with it and, when you do, don’thesitate to share your results with me.
Until next time, Happy Stamping. NV
Stamp
SEPTEMBER 2004 93
ResourcesJon [email protected]
Parallax, Inc.www.parallax.com
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The study of electrostatics wasour first step in the field ofelectronics. In electrostatics,
electric charges are relativelystationary. So, the natural philoso-phers (early scientists) who studiedthe phenomenon of electrostaticsconcentrated primarily on thecreation, storage, and interactionbetween the two types of electriccharges. One of their tools was theelectroscope, a device consisting oftwo metal foil leaves draped over ametal rod and protected within aglass jar.
The electroscope indicates thepresence of electric charges by thespreading of its two metal foil leaves.The presence of charges of theopposite polarity is indicated by thecollapse of the previously chargedleaves. If no opposing electriccharges are present, the leavesshould remain spread apart aftertheir initial charge.
Instead, it was discovered that,once charged, the leaves of theelectroscope did not remaincharged. The electroscope slowlyloses its charge — no matter how dryor clean the air. The source of thisdischarge was unknown.
Viktor Hess’ ExperimentOn August 7, 1912, physicist
Viktor Hess began making balloonflights with electroscopes onboard.In his flights, he rode in an opengondola under a hydrogen filled bal-loon to altitudes in excess of 15,000feet. The experiments were notwithout risk. The hydrogen in hisballoons was flammable and, at highaltitudes, he found that there wasless oxygen to breathe and that theair would begin to get cold.
On these flights, Hess discov-ered that his charged electroscopeswould discharge more quickly athigher altitudes. The effect becameapparent once his balloon climbedabove 6,000 feet and the interferencecaused by natural radiation emittedby the ground.
Hess’ electroscopes dischargedmore quickly because the air was asource of ions that neutralized thecharge on his electroscope. Sincethe electroscope discharged morerapidly at higher altitudes, he
concluded the ionization of theatmosphere increased as he rodehigher in his balloon.
The increase in ionization withincreasing altitude indicates that theionization is caused by an extrater-restrial source. In other words, therewas a source of radiation in spacethat was ionizing molecules in theatmosphere and causing hiselectroscopes to discharge. Thissame source of radiation was alsodischarging electroscopes on theground, but more slowly than in hisballoon experiments.
In 1936, Hess was awarded theNobel Prize for his discovery ofcosmic rays, the extraterrestrialsource of radiation. Cosmic radiationwas a fascinating topic for people inthe last century. As I recall, there iseven an old black and whiteFrankenstein movie that mentionscosmic rays as being responsible forthe origin of life on Earth.
Initially, it was believed that cos-mic rays were a form of electromag-netic radiation, like microwaves orgamma rays. Electromagnetic radia-tion is carried by photons, which areparticles without rest mass or elec-tric charge. Photons are not affectedby magnetic or electric fields.
However, since cosmic rays areaffected by magnetic and electricfields, they must consist of chargedparticles, like electrons andprotons.
It took several decades tostraighten out this error in bookswritten for the general public. I canrecall seeing cosmic rays listed at thehigh end of the electromagneticspectrum in high school sciencematerials. Because of this cosmic
SEPTEMBER 2004
Near Space by L. Paul Verhage
Approaching the Final Frontier
Near SpaceThe History of Cosmic Rays
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error, I got burned when correctlyanswering a question about theelectromagnetic spectrum duringtryouts for the College Bowl in 1981.
Cosmic Rays as a Tool of ScienceThe first particle accelerators
were built less than 100 years ago.These first generation devicescouldn’t reach very high energies.
So, to study subatomic physics,physicists launched their experi-ments in high altitude balloons,where they could use cosmic rays astheir source of high energy sub-atomic particles. The results of theseexperiments led to the discovery ofseveral important subatomicparticles.
One subatomic particle discov-ered in cosmic ray experiments wasthe meson. The meson was predict-ed to exist and be responsible forholding the nucleus of the atomtogether. There are actually severaltypes of mesons — like the mu and pimesons (called the muon and pion)— and only one is responsible forkeeping the protons inside thenucleus together. As it turns out, thefirst meson discovered was not theone found inside the nucleus.Another particle discovered fromcosmic ray experiments was the firstanti-matter particle — the anti-electron or positron — which waspredicted by physicist Paul Dirac.
Today, particle accelerators canreach such high energies that it’s nolonger convenient to do subatomicresearch with cosmic rays. However,that doesn’t mean cosmic rays areno longer an item of research. Now,cosmic rays are researched in aneffort to understand astronomicaland nuclear processes occurring inthe Sun and beyond the solarsystem.
The Nature ofCosmic RaysTheir Composition
The vast majority of cosmic raysare energetic nuclei — high speedatoms stripped of their electrons.
About 86% of cosmic rays are pro-tons or hydrogen nuclei (remember,the hydrogen nucleus doesn’t have aneutron). Twelve percent are heliumnuclei (alpha rays), 1% are energeticelectrons, and the remaining 1% areatomic nuclei heavier than helium;these are elements that astronomerscall metals. There are some highenergy gamma rays and neutrinosthrown into the mix, as well.
Their EnergiesOne of the most amazing aspects
of cosmic rays is their level of kineticenergy. Some cosmic rays carry over100 quintillion electron volts ofenergy. That’s enough energy to boila thimbleful of water if all that energycould be transferred to it. (In reality,such a cosmic ray would travel rightthrough the water, scarcely noticingit, and leave only a tiny bit of itsenergy in the water.)
Put another way, this amount ofenergy is the same as the kineticenergy of a baseball thrown at about100 mph! Imagine the energy of afast baseball packed into a single,invisible proton. The high energylevels found in cosmic rays allowthem to make the trip to Earth atspeeds very close to that of light.
The Source ofCosmic Rays
In optical astronomy,astronomers can point theirtelescopes in the direction of the lightthey are observing and see the light’ssource. However, galactic, solar, andterrestrial magnetic fields sothoroughly mix up the paths ofcosmic rays that other methods mustbe used to determine their source.The possible sources of cosmic raysare determined by how they respondto the solar cycle, their composition,and their kinetic energy. So far, it’sbelieved that there are three sourcesof cosmic rays.
Solar Cosmic RaysThese cosmic rays originate with
the solar chromosphere (the solarlayer above the photosphere — thevisible surface of the Sun) duringhigh energy events like solar flares.Solar cosmic rays tell us the types ofelements and their proportionresiding in the outer atmosphere ofour Sun.
These tend to be the lowestenergy cosmic rays. Their presencegoes up shortly after a flare and canincrease by a factor of hundreds to
SEPTEMBER 2004 95
ge Near Space
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even hundreds of thousands. Suchevents can last for only a few hoursor several days. Solar cosmic raysrepresent a hazard for astronautstraveling outside of the Earth’s pro-tective magnetosphere. Fortunately,our Apollo astronauts made theirlunar expeditions during a time ofsolar quiet.
Anomalous Cosmic Rays These are the nuclei of difficult
to ionize atoms. They originate asneutral atoms drifting into the solarsystem from interstellar space. Whenexposed to solar ultraviolet radiation,these atoms become ionized. Onceionized, the solar wind can capturethem and carry them away from thesolar system. When traveling with thesolar wind, these ions are called“pickup ions.”
Pickup ions are carried to apoint where the solar wind is forcedto slow down from supersonic tosubsonic speeds by the resistance ofthe local interstellar medium. Thisregion — where solar wind flow goesfrom supersonic to subsonic — iscalled the terminal shock. Smallerversions of terminal shocks are seenwithin the solar system when thesolar wind plows into the magnetos-phere of planets.
The passage through a terminalshock can accelerate pickup ionsand change their direction of travel.
After multiple passes through theterminal shock, these cosmic rayscan break free and travel back into the solar system, where theycan be detected. The remaining,anomalous cosmic rays escape the solar system and travel betweenthe stars.
Anomalous cosmic rays haveintermediate energy levels and arerepresentative of the atoms found innearby interstellar space. They areinfluenced by the 11 year solar cycle,which changes the location of theSun’s terminal shock.
Galactic Cosmic Rays These cosmic rays are the high-
est energy cosmic rays we find. Theyare fully stripped of their electrons.Galactic cosmic rays probably origi-nate in supernova remnants, whichare the expanding clouds of gas anddust that were once the outer layer ofa massive star. The explosion itselfdidn’t create the cosmic rays.Instead, the powerful and expandingmagnetic fields and shock wavesassociated with supernova remnantsaccelerate ionized atoms.
After the ions pick up enoughenergy, they can escape from thesupernova remnant as galacticcosmic rays and travel interstellarspace. We know supernova remnants can accelerate chargedsubatomic particles because the
radio signals the remnants emit indicate the presence of powerfulmagnetic fields that are acceleratingelectrons.
When the charged electronaccelerates, it emits a radio wavecalled synchrotron radiation. Thestudy of the isotopes found ingalactic cosmic rays and their halflives indicates that these cosmic rayscan travel for several million yearsbefore being detected on Earth.
Most galactic cosmic rays havelow enough energies that the MilkyWay’s magnetic field bends theirpaths around a radius smaller thanthe galaxy. This effectively trapsthese lower energy galactic cosmicrays within the Milky Way galaxy.However, a small percentage of thegalactic cosmic rays contain moreenergy than is available in supernovaremnants.
Their energies are too great forthem to be held within the galaxy’smagnetic field. So, these ultra-highenergy cosmic rays must originateoutside the galaxy. However, thesehigh speed cosmic rays cannottravel for long through intergalacticspace before their collisions withphotons left over from the Big Bang(the cosmic microwave back-ground) significantly lower theirenergies.
It’s believed these ultra-highenergy cosmic rays originate innearby, active nuclei galaxies, whichappear to be powered by massiveblack holes. Perhaps, instead, thesecosmic rays are trying to tell usabout exotic physics occurring deepwithin intergalactic space.
One of the benefits of galacticcosmic rays is that their collisionswith atoms in interstellar gas createsome of the rare elements neededfor life, but that are not synthesizedby the fusion reactions within thestars.
Detecting CosmicRays
Geiger CountersThe easiest way to detect the
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In an effort to share current informa-tion with this column’s readers, I have created an Email distribution list underYahoo! Groups. My Email list is not designedto replace the many lists for amateur nearspace groups that already exist. I plan tomake announcements, update column information, and answer reader questions inthis list. I will also keep subscribers up-to-date on the status of my book on amateurnear space exploration.
To join the Near Space Email group, go tohttp://groups.yahoo.com/
Sign in if you’re already a member of Yahoo!
— if not, click under New Users, then ClickHere To Register.
Under the Join a Group field, typeNearSpace and then press Enter.
Under the list of groups displayed, clickNearSpace (it will be the only group listed).
In the upper right of the screen, click to jointhe group.
I hope you find the Email list useful in yourefforts to begin your own program of amateur near space exploration.
The Near Space Email Group
RLNearSpace.qxd 8/10/2004 10:38 AM Page 96
presence of ionizing radiation is withthe Geiger counter. The electronicsin the Geiger counter create adifference in charge between thewalls and the central wire of theGeiger-Muller (GM) tube. The gasinside the GM tube cannot dischargethis potential difference unless theair becomes ionized. The passage ofcosmic rays is just what the air insidethe GM tube needs to create anionized channel.
Once the gas inside the GM tubebecomes ionized, electrons begintraveling across the tube, furtherincreasing the level of ionizationinside the GM tube and creating asmall current that is amplified tobecome the familiar click of 1950s B-grade science fiction movies. (Ah, theclassics!) Gases inside the GM tubeeventually quench the ionizationinside it. If it wasn’t for the quenchinggas, the ionization would continue,preventing the detection of anothercosmic ray.
The time it takes to quench a GMtube is called its dead time. The deadtime for the GM tubes I use in mycosmic ray experiments is 90microseconds. As long as there is atleast a gap of 90 microsecondsbetween cosmic rays, my GM tubewill detect them all. This means that,on an average, I can detect a fluxgreater than 11,000 cosmic rays persecond with my Geiger counter.
There are several limitations withGeiger counters. The first is thatGeiger counters cannot measure theenergy of each detection, so myGeiger counter experiments onlydetect the increased cosmic ray fluxas a function of altitude and not thechanging energy of each detection.
Another limitation is that Geigercounters cannot indicate the directionof travel of a cosmic ray. In myexperiments, I have no way of deter-mining if the cosmic ray flux is trulyuniform in nature. One last limitationto mention is that Geiger counterscannot indicate which type of sub-atomic particle was detected. Mycosmic ray experiments cannot tellme if the composition of cosmic rays
changes during the experiment. That said, there are some tricks
to get around these limitations and I’ll discuss them in a future column.(I’ve been experimenting with one of them.)
Photographic FilmSome early cosmic ray experi-
ments carried stacks of photographicfilm with thick emulsion betweensheets of lead. When a cosmic raycollided with a lead atom, it created ashower of secondary cosmic rays thatleft dark streaks in the developedfilm. The photographic film stack wasplaced between the poles of amagnet.
From the dimension anddirection of curvature of the streaksfound in the emulsion, the type ofparticles created in the collision wasdetermined. I get the impression thatgrad students were the ones search-ing through the photographic stackswith a microscope and determiningthe composition and energy of theircosmic ray prey.
I didn’t understand how photo-graphic stacks were made up when,in 1998, I sent a sheet of dental X-rayfilm up on a flight in an effort todetect cosmic rays. Of course, there
were no signs of cosmic rays on thedeveloped film.
Plastic SheetsThe collision between cosmic
rays and some types of plastics dam-ages the molecules of the plastic. Anetchant will preferentially etch awaythe damaged plastic, creating a cone-shaped pit where the cosmic rayimpacted the plastic. The type ofetchant used depends on the type ofplastic, but most etchants are eitherstrong acids or bases.
The depth of the pit etched in theplastic reveals the energy of thecosmic ray responsible for thecollision. The plastic visors of someof the Apollo astronauts were treatedwith an etchant in order to detectsome of the cosmic rays that theastronauts were exposed to on theirway to the Moon. An excellent sourceof information on this process can befound in the book Nuclear Tracks inSolids, by Fleischer.
A Cosmic TripThrough Earth’sAtmosphereSlamming Into Air
To a cosmic ray, our atmosphere
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Circle #144 on the Reader Service Card.
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acts like a 13-foot-thick slab ofconcrete. This is a good thing for us,since we don’t handle extremeexposures to radiation very well. Acosmic ray diving into the Earth’satmosphere is called a primarycosmic ray. The flux of primarycosmic rays at the top of the atmos-phere is about one cosmic ray persquare centimeter per second — or
about the same flux of raindropsduring a rain shower.
Secondary Cosmic RayProduction
When cosmic rays slam intoEarth’s atmosphere, they are prima-rily colliding with nitrogen and oxy-gen molecules. Upon impact, the pri-mary cosmic ray shatters the mole-
cule, creating a shower of lowerenergy particles from the subatomiczoo — subatomic particles, likeneutral and charged pions, neutrons,and more protons. Neutral pionsdecay into gamma rays, which latercreate electron-positron pairs.Charged pions decay into muons, aheavier relative of the electron. Thisshower of particles created by the
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As you will recall, in the July column, Iasked the question, “How can we provethat using a fixed resistor of a value equalto the geometric mean of the range of avariable resistor yields the greatest range invalues in the voltage divider circuit?” Well,the readers of this column replied with theanswer.
I will send Treasure Valley Near SpaceProgram patches to the first two respons-es because, together, they showed me theway to mathematically prove my observa-tion. By the time this column goes out,Erick McAfee of Texas and ColoradoCollege Physics Professor Val Veir shouldhave their patches. The patches were car-ried to an altitude of 104,571 feet onboardmy near spacecraft launches at the GreatPlains Super Launch on July 3, 2004.
From Erick and Val’s suggestions, plusA. A. Klaf’s book Calculus Refresher (greatbook, by the way) and some fooling aroundon my part, I have put together the follow-ing proof.
The Plan of AttackThe voltage range generated by a
voltage divider is equal to the maximumvoltage generated by the divider, minus theminimum voltage generated by the voltagedivider. If the output voltage of the voltagedivider is graphed with respect to thepossible values of the fixed resistor, we geta curve that is low on its two extreme endsand has a peak value somewhere near themiddle.That peak value of the voltage rangewill occur at a point over the fixed resistorvalue that is equal to the geometric meanof the maximum and minimum resistancevalues of the variable resistor.
By using calculus, we can make thisinto a max-min problem and find the pointat which the slope of the output voltagecurve goes to zero (this is at its peakvalue). At this point, we will find that the
value of the fixed resistor is equal to thesquare root of the product of the minimumand maximum resistances of the variableresistor or, in other words, the geometricmean of the maximum and minimum valuesof the variable resistor.
The ProofWe begin with:V = Vmax - Vmin
Note that:Vmax = VA · [Rfixed / (Rfixed + Rmin)]and
Vmin = VA · [Rfixed / (Rfixed + Rmax)]
I’m going to drop VA (the voltage applied tothe voltage divider circuit) from the math,since it’s just a constant and doesn’t affectthe best value of the fixed resistor.
Making my substitution, I get the following:V = [Rfixed / (Rfixed + Rmin)] - [Rfixed / (Rfixed
+ Rmax)]
Now, take the derivative with respect tothe fixed resistor value and set everythingequal to zero:V / d Rfixed = d[Rfixed / (Rfixed + Rmin)] / d Rfixed - d[Rfixed
/ (Rfixed + Rmax)] / d Rfixed = 0
According to A.A. Klaf, the derivative of theequation S = R / (R + A) with respect to Ris equal to A / (R + A)2
Making this substitution, I get the following:Rmin / (Rfixed + Rmin)2 - Rmax / (Rfixed +Rmax)2 = 0
Flip the ratios (by moving them to theopposite side of the equality), multiply outthe squared numerator, and we get:(Rfixed2 + 2RfixedRmax + Rmax2) / Rmax -(Rfixed2 + 2Rfixed Rmin + Rmin2) / Rmin = 0
Divide the terms by either Rmin or Rmax (thevalue in the denominator) and we’ll have:Rfixed2 / Rmax + 2Rfixed + Rmax - (Rfixed2 /Rmin + 2Rfixed + Rmin ) = 0
Note that we can move the minus sign intothe second half of the equation and sub-tract the 2Rfixed to end up with:Rfixed2 / Rmax + Rmax - Rfixed2 / Rmin - Rmin
= 0
Combining like terms and moving them toopposites of the equation gives us:Rfixed2 / Rmax - Rfixed2 / Rmin = Rmax - Rmin
Factor out the Rfixed2 and move theremainder to the other side of the equa-tion and we get:Rfixed2 = (Rmax - Rmin) / (1/ Rmax -1 / Rmin )
Now, at this point, I ran into a brick wall,but, knowing what I had and what I wanted,I discovered the following equation by play-ing around with some algebra:Rmin Rmax (1 / Rmin - 1 / Rmax) = Rmax - Rmin
I substitute in the left side of the equationfor the Rmax - Rmin in the previous equationto get the following:Rfixed2 = Rmin Rmax (1 / Rmin - 1 / Rmax) / (1/ Rmax - 1 / Rmin )
Divide out the like terms and we get:Rfixed2 = Rmin Rmax
So, the condition of having the maximumvoltage range occurs when:
Rfixed2 = Rmin Rmax
or when the value of the fixed resistance isequal to the geometric mean of the maxi-mum and minimum resistances of the vari-able resistor.
Solution to the Voltage Divider Question
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collision of a cosmic ray is called asecondary shower.
Particles in the secondary showercontinue traveling toward the surface,sometimes colliding with other mole-cules lower in the atmosphere andcreating more secondary showers.Eventually, secondary showers areattenuated by the Earth’s atmos-phere, protecting us from harm.There can be millions of subatomicparticles in a secondary shower andthey can cover several acres of landonce they reach the ground.
The secondary cosmic raysdetected on the Earth’s surface aremostly muons. On average, there areclose to 100 of these muons impact-ing every square yard of land persecond. Some of the surviving primary cosmic rays are so energeticthat they can be detected in deep mines.
EffectsAircraft pilots and their passen-
gers receive less protection fromcosmic rays by the Earth’s atmos-phere than we do at sea level. Evenresidents of Denver, CO (sorryEOSS) receive more radiation cosmicrays than do residents of San Diego,CA. Not only is the flux of cosmicrays greater at higher altitudes, butthe flux of cosmic rays also increasesthe closer the aircraft flies to thegeomagnetic poles. The flux isgreater near the magnetic poles ofthe Earth because the Earth’s magnetic field dips earthward andfunnels cosmic rays to the surface.
The muons found in cosmic rayshowers have very short half lives.Their half lives are so short that, if itwasn’t for the time dilation caused bytheir relativistic speeds, muons wouldnever live long enough to make thetrip down to the Earth’s surface,where we can detect them.
Cosmic rays may modify theEarth’s ionosphere, influence cloudproduction, affect the ozone layer,and possibly have an impact on ourweather. Cosmic rays convert someof the nitrogen-14 atoms in ouratmosphere into the carbon-14
isotope, giving archeologists a greatmethod of dating (radiocarbondating) organic artifacts that are lessthan 50,000 years old.
There are several good sourcesof information on cosmic rays, likethe book A Thin Cosmic Rain byFriedlander and several Internetsources. (I didn’t have a problem withfinding nonsense when doing myInternet search — unlike what occurswith some topics.)
Detecting CosmicRays with the AwareElectronics RM-60
My tool of choice for measuringcosmic rays in near space is the RM-60 Geiger counter. This Geiger count-er is manufactured by AwareElectronics (www.aw-el.com) as aPC- or laptop-based radiation detec-tion system. The RM-60 measures 1-1/4” by 2-3/8” by 4-3/8” and weighsa mere 4 oz. It’s designed to take itspower (5 to 9 volts at about 2 mA)from the serial port of a PC.Software loaded on the PC recordsand graphs the detections from theRM-60.
The manual that comes witheach unit is very thorough and even
contains background information andsuggested experiments.
The output from the RM-60 is aconstant +5 volt signal until an eventis recorded. At that point, the voltagedrops to 0 volts for the length of theGM tube’s dead time. The BASICStamp is quite capable of detectingradiation from the RM-60.
You only need to modify a phonecable to interface the RM-60 to theBASIC Stamp. Imagine adding aradiation detector to your BOE-BOT.To interface the RM-60, you will needa telephone cable (the kind with RJ-11 jacks on both ends) and a methodto connect one end of the phonecable to your BASIC Stamp.
In a future column, I will discussthe flight computer I use and how Iinterface sensors to it.
For now, however, you can wirethe RM-60 to a Board of Education(BOE) and launch that on your nearspacecraft. Let’s modify the phonecable. You’ll need about 10 minutesto do this.
1. Cut one end off the telephonecable (the other end is left in place soit can plug into the RM-60).
2. Strip about 1” of outer insulation
Near Space
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RLNearSpace.qxd 8/10/2004 10:38 AM Page 99
from the cut end of the phone cable. (Be careful not to damage the insulation around the wires inside
the cable.)
3. Carefully strip about1/2” of insulation fromeach of the four wiresinside the cable. (This isa very small gaugewire.)
4. Bring the two outer wires togetherand solder them together. (They are
connected to ground.)
5. The second wire is the 5 voltsignal from the RM-60. This wireis connected to a BASIC StampI/O pin.
6. The third wire is the 5 voltsupply to the RM-60. This wireis connected to the 5 volt out-put from the BASIC Stamp.
Even in high radiation environ-ments, its current draw does notexceed 20 mA — well within thecapability of the Stamp’s built-involtage regulator.
The diagram in Figure 3 islooking into the open socket of theRM-60. I have accidentally crossedmy wires without ill effect to theRM-60.
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Figure 2.The RM-60 Geiger counter.
Figure 3. RM-60 pinouts.
The OnSet Computer Corporation(http://onsetcomp.com) has generouslyagreed to sponsor a prize for the highestaltitude amateur near space flight duringthe 2004 calendar year. This is the largestsponsorship to amateur near spaceexploration to date. By achieving thehighest altitude flight this year, you will winthe following OnSet products:
• A four channel, eight-bit HOBO DataLogger that measures relative humidity,temperature, light intensity, and one exter-nal voltage of your choice.
• Boxcar Pro 4 software for programmingthe HOBO, downloading data collected bythe HOBO, graphing and analyzing data, andexporting the results to other file formats.
• An external temperature sensor (on a sixfoot cable) for the HOBO Data Logger.
This award is a miniature weather sta-tion for your near spacecraft and would bea part of an awesome science fair project.With the OnSet Prize, you can measure theinternal temperature of your near space-craft, the outside air temperature, the rela-tive humidity of the air, and the Sun’s inten-
sity during flight.With these measurements,you can determine the height of the strato-sphere and how it varies over the course ofthe year.You can also determine the rotationrate of your near spacecraft. It’s very difficultto get this kind of data from a near spacemission at the extremely low weight of theHOBO Data Logger and its sensors.
To be eligible for the OnSet Prize, youmust accomplish the following:
1. Announce your flight at least a week priorto launch (the general launch location, callsignof the near spacecraft, and its frequency).
2. Use a GPS receiver and APRS totransmit position data during the mission.
3.Transmit APRS data such that other ama-teur radio operators can record the data.
4. Obey FAR 101 requirements.
5. Recover the near spacecraft.
6. Announce the results of the flight(include several packets or posits aroundthe peak altitude).
I monitor several amateur near space
group Email lists. I recommend making yourannouncement either on the EOSS BalloonLaunch Announcement list, the KNSP Emaillist, or the GPSL Email list.All these groupsare available to the public from YahooGroups.
If at all possible, please transmit yourflight related packets or posits to a gatewayand to the Findu website. In this way,everyone can monitor the flight.
Be sure to get my attention when youannounce your peak altitude. I’ll Email areply to all announcements.
In December or once no other nearspace groups announce that they willlaunch a mission before the end of the year,I will announce the winner. Since I’m a highschool teacher and take road trips duringChristmas break, I will try to present theaward personally. If that can’t be arranged, Iwill send the award through the mail.
I’d like to thank OnSet ComputerCorporation for sponsoring this prize.You’ll find their products in the NASASpace Grant Consortium’s BalloonSatProgram. Be sure to check out the OnSetwebsite and get a look at the greatproducts they offer. You’ll find a lot ofjustifications for launching near space mis-sions with OnSet Computing Corporation.
The OnSet Prize
RLNearSpace.qxd 8/10/2004 10:39 AM Page 100
However, I do notrecommend you do this,as I may have beenlucky.
I like to solder thewires of the telephonecable to a straight maleheader with 0.1” betweencenters. This type ofheader is available fromJameco as part number109575. I tin each wireand then slide thin heatshrink tubing over it.
Next, I tin the shortpins in the header andpress a tinned wire in con-tact with a header pin andheat them with a solder-ing iron.
The solder on thewire and the header pinmelts and fuses the wire to the pin.After it cools, I slide the heat shrinkover the soldered connection andshrink the tubing. Afterward, I canplug the RM-60 into the BOE’s bread-board or my flight computer, like Iwould a servo.
I use the following code todetermine the counts per minutefrom the RM-60. My code is writtenfor the BS2pe, so you will need tomodify the count time if you use adifferent flavor of BASIC Stamp. Onmy flight computer, I store theresults into a RAM Pack B. If you aresending up an RM-60 with your BOE,then you can store the results in theEEPROM of the Stamp. After recov-ery, you can download the results ofthe flight.
gm CON 0radiation VAR WORD
Geiger_Counter:COUNT gm,34843,radiationDEBUG DEC radiation
This code assumes the RM-60 isconnected to P0 and counts thenumber of pulses from the RM-60 for10 seconds. Since I have so manyother experiments onboard my nearspacecraft, my flight computer can
only afford to count cosmic rays for10 seconds at a time. After recovery,I download the results from theGeiger counter into a spreadsheetand multiply the results by six to getthe cosmic ray flux in units of countsper minute.
In your experiments, you shouldcount cosmic rays at a fixed interval.Use the APRS data from your nearspacecraft to determine the altitudeat each measurement. When youcombine the cosmic ray count withthe altitude in a spreadsheet, yougenerate a chart like the one in Figure4. It shows data that was recordedand collected at the Great PlainsSuper Launch on July 3, 2004. Mynear spacecraft weighed nine poundsand made an altitude of 104,571 feeton a 1,500 gram balloon with 15pounds of lift.
This chart is typical of what mynear spacecraft measure. The fluxincreases with increasing altitude, asViktor Hess would be familiar with.The cosmic ray flux increases untilan altitude of 62,000 feet is reached.Higher than that, the cosmic ray fluxdecreases. t appears that the drop incosmic ray flux occurs because thenear spacecraft enters a regionwhere there are primary cosmic raysthat have not yet produced cosmic
ray showers. There really are fewercosmic rays to detect, but eachdetection on average contains moreenergy.
Had this flight occurred shortlyafter a solar flare, the cosmic ray fluxmost likely would have continuedincreasing above 62,000 feet. If themission had taken place closer to thegeomagnetic poles, the increase incosmic ray flux would have climbedmore rapidly.
So, get out there and start usingthe RM-60. For $150.00, it’s a greatlittle Geiger counter. I do not work forAware Electronics and I don’t receivecompensation from them. I’m just asatisfied customer. Let me know howyour Geiger counter experimentsturn out. Remember that you cancontact the amateur near spacegroup closest to you and arrange forthem to carry your experiment intonear space.
Onwards and Upwards,Your Near Space Guide NV
Near Space
0
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60000
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0 100 200 300 400 500 600 700 800 900
Flux (cpm)
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Figure 4. Cosmic ray flux.
SEPTEMBER 2004 101
Parallax — www.parallax.comAware Electronics — www.aw-el.com
Jameco — www.jameco.comOnSet — http://onsetcomp.com
Resources
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Tech Forum
QUESTIONS
We have a 2001 VW Eurovan thathad three keys, two of which are theremote control key fob type, and onesmaller "valet" key. My wife has lostboth of the remote keys, somewherehere in our house. The dealer wantsover $200.00 per key to replace them.I tried to copy the remaining key atour local home center. They were ableto grind a new key blank, but a testershowed that the original had an RFchip that prevents the copied keyfrom being used.
Can a device be made orpurchased that will emulate the signalthe car sends to excite the RF chipand detect if a key is nearby? I coulduse that to search our house for thekey. If it can tell me if a key is close
by, that would enable me to narrowour search and find it without tearingthe whole house apart. #9041 Jim Balderrama
San Diego, CA
I am trying to find info on a kitthat was offered back in RadioElectronics magazine, called theHyperClock. It was offered by anoutfit named SkiTronix, around 1991.I built one back in high school, and ithas just now failed. I cannot locate theschematics or magazine issue thatfeatured it. Searching the web has notyielded anything.#9042 Rich White
via Internet
Does anyone have a simplecircuit for taming the turn-on thump
from the charging of the outputcoupling capacitor of a bass guitaramp that uses a single 90-voltsupply? Manual switching is notadequate because it does not protectagainst someone messing with thepower cord wall plug.#9043 Dennis Green
via Internet
We use a Barcus Berry modelModel 4000N piano mic at ourchurch. Remembering to changebatteries every couple of monthsbefore we are in the middle of aservice is a pain. I want to convert ourmic to be phantom powered from ouraudio mixer. Has anyone done thisand can offer some advice?#9044 Steven Morgan
Cumming, GA
I do quite a lot of 35mm motionpicture projection work, and wonderhow close to 24 frames per secondthe projector is actually operating. Isthere a circuit for some sort of sensorthat I can hold in front of the lens andmeasure the FPS count?#9045 Edward Vanoverschelde
Buhl, ID
I have two questions. First, whathappens when an EXE file is run on aPC? I would like to know where thecontents of an EXE file will be loaded,and so on. Second, I am confusedwith partitions on the hard disk drive.I would like to know how thepartitions (i.e., C, D, etc.) arerepresented on the disk.#9046 Aditya
via Internet
ANSWERS
[6041 - June 2004]Does anyone know how I might
construct a relatively simple fieldstrength meter to orient a UHFantenna while I’m perched on aladder? The circuit would be tunedto one specific frequency — say 500MHz.
#1 I used to work on TV antennasfor Sears and couldn't stomach the$300.00 price of an antenna meter,
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Tech Forum
Tech Forum.qxd 8/12/2004 8:06 AM Page 102
so I bought a $50.00, AC/DC, 5 inch,B&W TV from RadioShack andbrought the AGC voltage to a jack inthe rear. It goes up the ladder just fineand runs on batteries if you don'twant to sling a 50 foot extension cordup on the roof. My DVM shows mewhen I'm aimed right, and the picturehelps me see if I have ghosts. It'sbetter than any expensive fieldstrength meter, and the frequency iscontinuously, manually, tunable.
C. L. LarsonLargo, FL
#2 In order to build a suitable UHFfield strength meter, you'd be lookingat a sizeable outlay to get thesensitivity required. An easier way isto borrow a pair of FRS radios, stationone with a viewer at the TV set whileyou orient the antenna on the desiredchannel. Moving the antenna backand forth until an average mid pointresults in best reception. The FRSradios serve as communicationbetween you and the TV observer.
This method is suitable for anyfrequency range of interest.
Ralph Cameron Ottawa, Ontario, Canada
[6044 - June 2004]If I were to take two 500,000
volt stun guns and connect bothpositive outputs together and bothnegative outputs together, would Ihave 1,000,000 volts? I’m planningan experiment which uses highvoltage.
#1 NO. In the first place, the outputshould be connected in series, plus tominus. But the outputs are not DCand not the same frequency, so theydon't necessarily add. However, Iwould expect the voltage to be morethan one alone.
Russ KincaidMilford, NH
#2 Such a simple question — butone for which a technically accurateanswer is horrendously complicated.
As for the proposed experimentation— DON'T TRY IT!!!
The insulation on those devices —while good enough for the voltagethey produce — is NOT adequate tocontain double that voltage, noranything even close to double it. Notto mention the difficulty you will havein finding something with adequateinsulation, to use to tie them together.
If you try this experiment, it isvirtually guaranteed that you'll havesome form of catastrophic failure,with destruction of the gear, andserious hazard to life and limb.
The semi-safe way to experimentwith 'very high' voltages is with staticelectricity. Search the Internet for'Wimhurst static machine' or 'Van deGraaf generator' for some startingpoints. (Also check out GerardFonte’s four-part Enigma Machineproject, beginning in the June2004 issue of Nuts & Volts. — EditorDan)
Robert BonomiEvanston, IL
Tech Forum
103SEPTEMBER 2004
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Tech Forum.qxd 8/12/2004 8:07 AM Page 103
104
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Tech Forum
[7041 - July 2004]I have three radios that use an LM386 for the audio
output. This chip tends to be noisy. (It produces audiohiss.) Are there any circuit modifications that can beapplied to this chip to make it less noisy?
The LM386 is a very old chip that is still aroundbecause it works well. It is also well known for generatinghiss. The most common solution is a 10K resistor and 0.01mF capacitor in series between pins 5 and 8. This providesfeedback that reduces the high frequency response andtherefore the hiss heard at the speaker.
Dave SarrafElizabethtown, PA
[7042 - July 2004]I have been looking for years for a circuit to sense
cars in my driveway. I know that the traffic lights use asingle wire loop in the pavement and I assume that it issome kind of tank circuit tied to a PLL. I wouldappreciate any information on the subject.
#1 I worked on a loop detector design in 1967. Thetechnology has changed, but the theory hasn't. Design anoscillator for about 100 kHz, with the loop as part of thetank circuit. Cut a slot in the pavement and lay outdoorinsulated house wire in the trench and backfill with epoxy.
A few turns are all that’s needed. When a car enters theloop, the frequency will increase by between 1% and 3 %.The frequency will also change with temperature,moisture, etc. The detection threshold has to be slowlybalanced in 10 minutes or so. We used phase locked loops,but counting the frequency with a microcomputer is mucheasier.
James VaughanBainbridge Island,WA
#2 Old traffic lights used the inductive wire you mention.Modern traffic lights use video cameras to sense whenvehicles are present. The cameras are usually mounted onthe horizontal support that the traffic light is on. Mostpeople think the cameras are monitored by people at acentral traffic office — they are not. They are just localcameras connected to the traffic signal control box. Thereason they went to video was that it was too expensive tocut the road to lay the wire. Plus, there were maintenanceproblems with the wire method.
If you wish to use the same method to "watch" yourdriveway, there is a plug and play solution. Resources Un-Ltd. (www.resunltd4u.com) has a VM10, which is a videomotion sensor. Attach a video camera to the unit andwhenever a change in the scene is detected, the unit willbuzz. It sells for $179.00 and also has contacts for a VCR.
Jon B. Busheyvia Internet
[6042 - June 2004]I would like to have my garage open automatically
when I pull in the driveway. Maybe an IR transmitteron my garage and a receiver in my car? The IR on thegarage could transmit a constant signal so that whenthe receiver (in my car) picked it up, the door wouldautomatically open. Any suggestions?
Wow! Too lazy to push a button! I understand yourneed to have the receiver in the car, so only your car willopen the door. But you need a transmitter in the car andreceiver in the garage to operate the motor that opens thedoor. I suggest that you remove the push button from theremote garage door opener and replace it with an IR
receiver module.These receiversoperate at afrequency of 40 kHz, so youwill need an IR transmitterrunning at thatfrequency. Thecircuit shownhere shouldproduce enoughpower, but you
may need some optics to direct it to the driveway.Russel Kincaid
via Internet
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Tech Forum.qxd 8/12/2004 8:07 AM Page 104
Atomic Time ..................................................................9Linx Technologies .......................................................88Ramsey Electronics, Inc. .......................................26-27SGC ............................................................................59Supercircuits .................................................................5Surplus Sales of Nebraska ..........................................63Windsor Distributors ....................................................41
Cunard Associates ......................................................44
Earth Computer Technologies . ....................................93Jaycar Electronics ........................................................21
Autotime Corp. ............................................................44Circuit Specialists, Inc. .......................................106-107Matco, Inc. ...................................................................44Polaris Industries .........................................................13Ramsey Electronics, Inc. ......................................26-27Supercircuits .................................................................5
Cunard Associates ......................................................44ExpressPCB ................................................................25Maxstream ..................................................................71Micromint .....................................................................72PCBexpress ................................................................58PCB Fab Express ........................................................90PCBPro .....................................................................103Pulsar, Inc. ..................................................................45R4Systems, Inc. ..........................................................67Saelig Company ..........................................................74V&V Machinery & Equipment, Inc. ..............................44
Bellin Dynamic Systems, Inc........................................44Electronix Express ......................................................19Front Panel Express LLC .............................................97Jameco ........................................................................29Lemos International Co., Inc. ......................................33Linx Technologies .......................................................17Maxstream ..................................................................71Micromint .....................................................................72PCBexpress .................................................................58PCB Fab Express ........................................................90Pulsar, Inc. ..................................................................45The Electronic Hoard ...................................................47Windsor Distributors ....................................................41
HardwareActiveWire, Inc. ...........................................................44Autotime Corp. ............................................................44Earth Computer Technologies ....................................93Halted Specialties Co. ...................................................3Imagine Tools ..............................................................39JK microsystems .........................................................91Smartronix ...................................................................23Surplus Sales of Nebraska...........................................63
Microcontrollers / I/O BoardsAbacom Technologies..................................................90Basic Micro, Inc. ..........................................................82Conitec DataSystems...................................................85EMAC, Inc. ..................................................................91JK microsystems .........................................................91microEngineering Labs ...............................................80Micromint .....................................................................72MVS .............................................................................58Net Media.......................................................................2New Micros, Inc. ..........................................................79
Parallax, Inc. .................................................Back CoverR2 Controls .................................................................44R4Systems, Inc. ..........................................................67Scott Edwards Electronics, Inc. .................................104Square 1 Electronics ...................................................87Technological Arts .......................................................99Texas Instruments .........................................................7Trace Systems, Inc. ....................................................84UltraDense ..................................................................45Yost Engineering, Inc. .................................................15
SoftwareEptsoft Limited ............................................................36JK microsystems .........................................................91PULSAR ......................................................................16Trilogy Design .............................................................59
ExpressPCB ................................................................25Front Panel Express LLC ............................................97Pulsar, Inc. ..................................................................45R4Systems, Inc. ..........................................................67Trace Systems, Inc. ....................................................84V&V Machinery & Equipment, Inc. ..............................44
Atlantic Int’l Institute, Inc. ............................................88Command Productions ................................................52EMAC, Inc. ..................................................................91Eptsoft Limited ............................................................36Hobby Engineering ......................................................95PCB Fab Express ........................................................90Syspec, Inc. .................................................................44
Integrated Ideas & Technologies, Inc. .........................28
Tetsujin 2004................................................................65
Autotime Corp. .............................................................44C & S Sales, Inc. .........................................................53Earth Computer Technologies ....................................93EMAC, Inc. ..................................................................91Hobby Engineering ......................................................95Imagine Tools ..............................................................39Information Unlimited ..................................................86Jaycar Electronics ........................................................21QKITS .........................................................................45Ramsey Electronics, Inc. .......................................26-27Scott Edwards Electronics, Inc. .................................104The Electronic Hoard ...................................................47
Information Unlimited ..................................................86
All Electronics Corp. ....................................................60Anchor Optical Surplus ...............................................33Front Panel Express LLC .............................................97Halted Specialties Co. ...................................................3Surplus Sales of Nebraska ..........................................63The Electronic Hoard ...................................................47Windsor Distributors ....................................................41
Anchor Optical Surplus ...............................................33
Basic Micro, Inc. ..........................................................82
Conitec DataSystems...................................................85Intronics, Inc. ...............................................................44microEngineering Labs ...............................................80
Lakeview Research .....................................................44Square 1 Electronics ...................................................87
Abacom Technologies .................................................90Linx Technologies .......................................................17Matco, Inc. ...................................................................44
Hobby Engineering ......................................................95Imagine Tools ..............................................................39LabJack .......................................................................92Lemos International Co., Inc. ......................................33Lynxmotion, Inc. ..........................................................20Net Media ......................................................................2New Micros, Inc............................................................79Robodyssey Systems ................................................103Rogue Robotics ...........................................................44
Lemos International Co., Inc. .......................................33Linx Technologies .......................................................88
Information Unlimited ..................................................86Linx Technologies .......................................................17Matco, Inc. ...................................................................44Polaris Industries .........................................................13Supercircuits .................................................................5
Jameco ........................................................................29
Linx Technologies .......................................................88
Bellin Dynamic Systems, Inc........................................44Brand Electronics ........................................................45C & S Sales, Inc. .........................................................53Circuit Specialists, Inc. .......................................106-107Conitec DataSystems...................................................85eBay ............................................................................11Electronic Design Specialists .......................................83Intronics, Inc. ...............................................................44Jaycar Electronics ........................................................21LabJack .......................................................................92Madell Technology Corp. ............................................49Pico Technology Ltd. UK..............................................37Saelig Company ..........................................................74Smartronix ...................................................................23Syspec, Inc. .................................................................44Trace Systems, Inc. ....................................................84
C & S Sales, Inc. .........................................................53Madell Technology Corp. ............................................49
Jameco ........................................................................29Smartronix ...................................................................23
WIRE/CABLE& CONNECTORS
TOOLS
TEST EQUIPMENT
TELEPHONE/CELLULAR
STEPPER MOTORS
SECURITY
SATELLITE
ROBOTICS
RF TRANSMITTERS/RECEIVERS
PUBLICATIONS
PROGRAMMERS
OPTICS
MISC./SURPLUS
LASERS
KITS
EVENTS
ENCLOSURES
EDUCATION
DESIGN/ENGINEERING/REPAIR SERVICES
COMPUTER
COMPONENTS
CIRCUIT BOARDS
CCD CAMERAS/VIDEO
BUYING ELECTRONICSURPLUS
BATTERIES/CHARGERS
AMATEUR RADIO & TV
Advertiser’s Index
Abacom Technologies ............90ActiveWire, Inc. .......................44All Electronics Corp. ...............60Anchor Optical Surplus ...........33Atlantic Int’l Institute, Inc. ........88Atomic Time...............................9Autotime Corp. ........................44Basic Micro, Inc. .....................82Bellin Dynamic Systems, Inc. ..44Brand Electronics ....................45C & S Sales, Inc. ....................53Circuit Specialists, Inc. ..106-107Command Productions........... 52Conitec DataSystems .............85Cunard Associates .................44
Earth Computer Technologies ..93eBay ........................................11Electronic Design Specialists ..83Electronix Express ..................19EMAC, Inc. .............................91Eptsoft Limited ........................36ExpressPCB ...........................25Front Panel Express LLC ........97Halted Specialties Co. ..............3Hobby Engineering ..................95Imagine Tools .........................39Information Unlimited ..............86Integrated Ideas & Technologies, Inc. 28Intronics, Inc. ..........................44Jameco ....................................29Jaycar Electronics ...................21
JK microsystems .....................91LabJack ...................................92Lakeview Research .................44Lemos International Co., Inc. ..33Linx Technologies .............17, 88Lynxmotion, Inc. .....................20Madell Technology Corp. ........49Matco, Inc. ..............................44Maxstream ..............................71microEngineering Labs............80Micromint ................................72MVS ........................................58Net Media ..................................2New Micros, Inc. ......................79Parallax, Inc. ............Back Cover
PCBexpress ............................58PCB Fab Express ...................90PCBPro .................................103Pico Technology Ltd. UK .........37Polaris Industries .....................13PULSAR ..................................16Pulsar, Inc. ..............................45QKITS......................................45R2 Controls .............................44R4Systems, Inc. .....................67Ramsey Electronics, Inc. ...26-27Robodyssey Systems ............103Rogue Robotics .......................44Saelig Company .....................74Scott Edwards Electronics, Inc. ..104
SGC ........................................59Smartronix ..............................23Square 1 Electronics ..............87Supercircuits .............................5Surplus Sales of Nebraska .....63Syspec, Inc. ............................44Technological Arts ..................99Tetsujin 2004 ..........................65Texas Instruments ....................7The Electronic Hoard ..............47Trace Systems, Inc. ................84Trilogy Design .........................59UltraDense ..............................45V&V Machinery & Equipment, Inc. ..44Windsor Distributors ...............41Yost Engineering, Inc. ............15
SEPTEMBER 2004 105
IndexSep04.qxd 8/11/2004 3:22 PM Page 105
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*Signal Levels up to 160Channels can be displayed simulaneously on the LCD
*PLL tuning system for precise frequency measurement and tuning
*Built-in Frequency Counter *LED Backlight LCD (192x192 dots) *All fuctions are menu selected. *RS232C with software for PC & printer interface *Built-in speaker
(Limited Offer)
(Includes Antenna)
>>> Test Equipment >>> Power Supplies
Details at Web Site
Protek 60MHz Dual Trace Scope
While Supplies Last!
SuperSuperBlowoutBlowoutPrice!Price!
Sold by othersSold by othersfor Over $700!for Over $700!
The FC5001FC5001 2-way FM radio tester has the ability to lockautomatically and almost instantly on to any FM signal with-in its frequency range. The FC6002FC6002 radio frequency traceris useful in locating stuck transmitters or bugging devices ina room or automobile. It excels at silent detecting RF signalsfor RF security and counter-surveillance applications.
<< RR FF SS ee cc uu rr ii tt yy >> FC6002: $149.00FC5001: $99.00
A 40 watt soldering iron with a 3-wire powercord, fast heating ceramic element and agrounded tip to protect static sensitive devices.
Comes complete with a soldering standComes complete with a soldering stand
and thrand three ree replacement soldering tipseplacement soldering tips,which include a conical tip, chisel tip and a 45°chisel tip.
>>> Soldering Equipment & Supplies
Details at Web Site
Complete Kitas shown
Circle #105 on the Reader Service Card.
Circle #60 on the Reader Service Card.
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Circle #154 on the Reader Service Card.
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