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Old Colony CouncilMerit Badge University

March 2012

Joe MulcaheyLen Barrett

Sean Mulcahey

Based on the Electronics Merit Badge classes taught at the 2005 & 2010 National Jamborees

Rev. S, 01MAR12

Electronics Merit Badge

jkm@alum.mit.eduhttp://www.mulcahey.org http://www.crew748.org

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Class 1 Safety (Requirement 1)March 3 Electricity & Electronics Introduction

Circuit Diagrams & Schematics (2)Solving Circuit Problems using Ohm’s Law (5a)

Class 2 Job Opportunities in Electronics (6)March 10 Test Equipment Demos (5b)

Class 3 Proper Soldering Techniques (3)March 24 Kit Assembly (4)

Electronics Merit Badge Class Outline

Safety with Electricity and Electronics

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Electricity Safety• High Voltage ( 120V AC or greater) – Safety mainly

about not touching the wrong thing

• Current kills – Only 16 volts can kill when enough electrons flow through the heart or head

• Ventricular fibrillation – Electrons passing through the heart causes muscles to seize, leading to death

• If the shock doesn’t kill you, you can still be badly burned from touching the wrong thing

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How to Avoid Shock

• Turn power off before working on equipment• Don’t touch circuits that could have high voltage on them• Do not allow electrons to flow through the heart. I don’t

think the snake knew about this detail

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Electronics Safety

• Electronics generally uses lower voltages (less than 48 volts)

• You are usually working with DC voltage instead of AC voltage

• You are usually more concerned with sparks from connecting the wrong wires together, or burning yourself with a soldering iron, or some similar event

• Even when working with lower voltages, you may still receive an electrical shock from equipment you are using

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Personal Safety• Be aware of what you are doing, and

where you are placing equipment and yourself

• Pay attention to hot soldering irons• Keep a good distance between you and

those next to you• Know when you are working with high

current and/or high voltage circuits• THINK before you do something• Wear safety glasses when soldering 7

One Hand Rule

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• Prevents current from flowing in one arm, through your heart, and out the other arm

• Keep one hand in your pocket!

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Introduction to Electronics• Electrical and Electronics Engineering are both career

fields that are involved with Electronics Technology• Electrical engineers specializing in power work with

motors and generators, and design transmission lines and power plants

• EEs specializing in electronics deal with communications, such as radio, television and telephony, radar and digital & analog circuit technologies

• All engineers draw from the fundamentals of science and mathematics

• They design and work with electrical, electronic, electro-optical, and electromechanical devices, circuits, and systems

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Introduction (Continued)• Electrical Engineers collaborate with other

professionals in developing sophisticated software tools that support design, verification, and testing

• Electrical engineering is a discipline that integrates many other disciplines, such as physics, chemistry, mathematics, computer software and hardware, solid-state electronics, communications, electromagnetics and optics, signals and signal processing, systems science, reliability, engineering economics, and manufacturing

• In order to Learn about Electronics, we must first start by gaining an understanding of what electricity is, both AC (Alternating Current) and DC (Direct Current)

Types of ElectricityStatic Electricity

Static electricity is usually created when materials are pulled apart or rubbed together, causing positive (+) charges to collect on one material and negative (−) charges on the other surface. Sparks may result!

Examples of static electricity:

1. Lightning2. Combing hair3. Walking across carpet and

getting shocked4. Pulling out scotch tape

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Types of Electricity

Alternating Current (AC)

The common form of electricity from power plant to home/office. Its direction is reversed 60 times per second in the U.S.; 50 times in Europe.

Examples of AC usage:

1. Kitchens: Stoves, ovens, mixer, etc.

2. Computers (the plug)3. Lights in house4. Home air conditioners

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Types of Electricity

Direct Current (DC)

Type of electricity used in most electronics we have today. Current only flows in one direction (not both directions, like AC).

Examples of DC usage:

1. MP3 players2. Radios3. Electricity in cars4. Anywhere you use a battery

for power

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Basics of Electronics

• Current: Defined as “flow of electrons”

• Current: Units of current is the AMP• Current: Electrical symbol for current is I

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Current Flow – Water Analogy

1. Water flows in the hose, entering at the top and exiting the bottom

2. The water is the “current”; the flow of electrons

3. The more water flowing in the pipe, the more electrons are flowing in the wire

4. Different pipe diameters illustrates different resistance to water flow, which correlates to different resistor values 15

Current

• Current: Defined as “flow of electrons”• Current: Units of current is the AMP• Current: Electrical symbol for current is I• Common units for current are:

– amps– milliamps (mA): 1 mA = 0.001 amp– microamps (mA) : 1 mA = 0.000001 amp,

or 0.001 mA– nanoamps (nA) : 1 nA = 0.000000001 amp,

0.000001 mA, or 0.001 mA16

Voltage – Water Analogy

1. Gravity provides the force for water (current) to flow

2. This illustrates a small voltage, so electron flow is small

1. Gravity provides the force for water (current) to flow

2. This illustrates a larger voltage, so electron flow is larger

Small height = low voltage Big height = high voltage

heightheight

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Voltage

• Volts is the electrical force that causes electrons (current) to flow• Units of volts is the VOLT• The symbol of volts is E or V. We will use V• Common units for voltage are:

– volts– Millivolt (mv) : 0.001 volt– Microvolt (mv) : 0.000001 volt, or 0.001 mV– Nanovolt (nv) : 0.000000001 volt, 0.000001 mV, or

0.001 mV

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Resistance – Water Analogy

• Different pipe diameters represents different resistor values

• The smaller the diameter of the pipe, the larger the resistance

1Ω

10Ω

100Ω

1000Ω

10000Ω

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Resistance• Resistance is an electrical property of a

material that “resists” the flow of electrons

• The schematic symbol for a resistor is:• Common units for resistance are:

– ohms– kiloohm: 1KΩ = 1000 ohms, 10KΩ = 10,000

ohms– megaohm: 1MΩ = 1,000,000 ohms

• The units symbol for ohms is: Ω (ohms)20

Power – Water Analogy

• In electronics, power is equal to current X voltage

• The units for power is the WATT

• The symbol for power is W or P

• In our water analogy, power is• equal to water flow X pressure• You can see from the picture

that more water flow will mean more force, and more pressure will mean more force

Ohm’s Law• One of the most important laws in

electronics/electricity• V = I x R : Voltage = Current x

Resistance• Voltage is measure in volts, current is

measured in amps, and resistance is measured in ohms

• 1 amp, going through 1 ohm of resistance, results in a voltage drop of 1 volt

• 1 V = 1 A x 1 Ω 22

More Ohm’s Law

Volts = 10Resistance = 1000ΩCompute current:I = V / RI = 10 / 1000 = .01A.01A = 10mAQuestion: what would the current be if the voltage was 1 V? How about 1000 V?

Different forms of Ohm’s Law:V = I x R : Voltage = Current X ResistanceI = V / R : Current = Voltage / ResistanceR = V / I : Resistance = Voltage / Current

10V

1000 Ω

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+

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Ohm’s Law Pie Chart

If you know any two values, you can get the other two with these formulas

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Bonus Ohm’s Law Question: Resistor Cube

What is the resistance between points A and B?

R R

Resistances in series add: RTotal=2R

Resistances in parallel divide: RTotal=R/2

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Where Did the Names of the Electrical Parameters Come From?

• Volts: Count Alessandro Volta (1745-1827), Italian Scientist• Ohms: Georg Simon Ohm (1787-1854), German Physicist• Amps: André-Marie Ampère (1775-1836), French Physicist• Watts: James Watt (1736-1819), British Engineer• Farads: Michael Faraday (1791-1867), British Physicist• Henrys: Joseph Henry (1797-1878), American Physicist

• Other Units:• Coulomb, Gauss, Joule, Tesla and of course Smoot

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Smoot? What’s A Smoot?Smoot: A humorous unit of distance invented in 1958 by a fraternity at the Massachusetts Institute of Technology. The fraternity pledges of Lambda Chi Alpha measured the length of Harvard Bridge using pledge Oliver R. Smoot ('62). According to Smoot himself, the bridge turned out to be 364.4 smoots long "plus epsilon," but this has been recorded as 364.4 smoots "plus an ear." The bridge is still marked in smoots. Proposals to change the definition of the unit by remeasuring it with Smoot's son Steve (MIT '89) or daughter Sherry ('99) were rebuffed. One smoot equals 67 inches (170.18 centimeters). Oliver Smoot became an attorney but continued his interest in standards and measurement. He is a past Chairman of the Board of Directors of the American National Standards Institute (ANSI) and past President of the International Organization for Standardization (ISO).

Electronic Symbols

Single Pole, Double Throw Switch (SPDT)

Battery

Resistor

Light Emitting Diode (LED)

Buzzer

Fuse

Lamp

or

Capacitor

Ground

W NCNO

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+

SWITCH LAMP

GROUNDGROUND

FLASHLIGHT

TWO GROUND SYMBOLS IS THE SAME AS CONNECTING WITH A WIRE

GROUND = 0 VOLTS

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CIRCUIT DIAGRAM (SCHEMATIC)

BATTERY

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Design three different DC circuitsSwitch

BuzzerLight

PowerSupply

Switch

BuzzerLight

PowerSupply

Switch

BuzzerLight

PowerSupply

Wired to turn Buzzer On/Off

Wired to turn Light On/Off

Wired to turn Light On in onedirection and Buzzer On in

other direction

DC Circuit Wiring

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BuzzerLight

Switch Power+ 12

Fuse

Direct Current: Draw 3 different wiring test circuits

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Circuit to Switch Buzzer On / Off - Draw the rest of the wires

BuzzerLight

Switch Power+ 12

FuseBuzzer On

Direct Current

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Circuit to Switch Buzzer On / Off

BuzzerLight

Switch Power+ 12

FuseBuzzer On

Direct Current Answer

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Draw Circuit to Switch Light On / Off

BuzzerLight

Switch Power+ 12

FuseLight On

Direct Current

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Draw Circuit to Switch Light On / Off

BuzzerLight

Switch Power+ 12

FuseLight On

Direct Current Answer

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Draw Circuit to Turn Buzzer on in one Direction and Light in other Direction

BuzzerLight

Switch Power+ 12

FuseLight On Buzzer On

Direct Current

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Draw Circuit to Turn Buzzer on in one Direction and Light in other Direction

BuzzerLight

Switch Power+ 12

FuseLight On Buzzer On

Direct Current Answer

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PotentiometerVariableResistor

Power SupplyOutputs Volts

BatteriesIn volts

CapacitorsIn Farads

ResistorIn Ohms

Inductor or CoilIn henries

TransformerInput voltage

120VAC In

DC voltsOut

+

SpeakerCurrent → Sound

MicrophoneSound → Current

+

StepDown

StepUp

Isolated

Electronic Components

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DiodePN junction. Current flows in direction of arrow only

LEDLightEmittingDiode

TransistorElectronic Switch. Emitter, Base

& Collector terminals. Small current (B-E) controls a larger

one (C-E). Made of N (negative) and P (positive) sections

NPN(“Never Points iN”)

MetersCurrent MeterVoltage MeterResistance Meter

Switch Normally Open (n.o.)Normally Closed (n.c.)

n.o. n.c.

Slide SwitchCan connect the center

Pole to one of two Throws (SPDT)

PNP(“Points iN Proudly”)

Bonus Question: Which type is the Transistor on the Electronics Merit Badge?

Anode (P)

Cathode (N)

Electronic Components

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A Resistor’s value is indicated by its color bands and is measured in ohms

First Ring is First number / Closest to edge of resistorSecond Ring is second numberThird Ring is number of zerosFourth Ring is tolerance 1% or 5% or 10% etc.

First RingBlack = 0Brown = 1Red = 2Orange = 3Yellow = 4Green = 5Blue = 6Violet = 7Gray = 8White = 9

Third Ring MultiplierSilver = X .01Gold = X .1Black = X 1Brown = X 10Red = 2 = X 100Orange = 3 = X 1,000Yellow = 4 = X 10,000Green = 5 = X 100,000Blue = 6 = X 1,000,000Violet = 7 = X 10,000,000

Resistor Color Code Values

Second RingBlack = 0Brown = 1Red = 2Orange = 3Yellow = 4Green = 5Blue = 6Violet = 7Gray = 8White = 9

Fourth RingBrown = +/- 1%Red = +/- 2%Gold = +/- 5%Silver = +/- 10%None = +/- 20%

Resistor Color Rings

A Fifth Ring, if present, could indicate reliability or temperature sensitivity

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Black Brown Red Orange Yellow Green Blue Violet Gray White (Gold Silver None) 0 1 2 3 4 5 6 7 8 9

• Big Brown Rabbits Often Yield Great Big Vocal Groans When Gingerly Slapped• Big Bears Run Over Your Gladiola Bed Vexing Garden Worms• Black Bears Run Over Yellow Grass, But Vultures Glide over Water• Better Be Right Or Your Great Big Venture Goes West• Bye Bye Rosie Off You Go to Birmingham Via Great Western• Black Bart's Rambler Over Yonder Gave Bad Vibes Going West• Bright Boys Rave Over Young Girls But Veto Getting Wed• Big Boys Race Our Young Girls Behind Victory Garden Walls• Big Boys Race Our Young Girls But Violet Generally Wins• Black Birds Ruin Our Yellow Grain, Butchering Very Good Wheat• Billy Brown Ran Over a Yodeling Goat Because Violet's Granny Was Grumpy• Bad Betty Runs Over Your Garden But Violet Gray Won't• Billy Brown Revives On Your Gin, But Values Good Whisky• Better Be Ready, Or Your Great Big Venture Goes West• Black Beetles Running On Your Garden Bring Very Good Weather• Bowling Balls Roll Over Your Grandpa But Victim Gets Well• Batman Bests Robin On Yonder Gotham Bridge; Very Good, Will Get Superman Next!• Badly Burnt Resistors On Your Ground Bus Void General Warrantee• Big Bart Rides Over Your Grave Blasting Violent Guns Wildly• Bad Borg Raid Our Young Galaxy Before Vaporizing Good Walter

G-Rated Resistor Color Code Mnemonics

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First RingRed = 2Black = 0

Second RingRed = 2Red = 2

Third RingRed = X 100 = 2200 ohmsBrown = X 10 = 020 ohms

Example of Color Rings

First RingBrown = ____

Green = ____

Second RingGreen = ____

Red = ____

Third RingBrown = ____ = ___ ohms

Yellow = _____ = ____ ohms

Test of Color Rings

First Ring is first digitSecond Ring is second digitThird Ring is number of zeros

RingBlack = 0Brown = 1Red = 2Orange = 3Yellow = 4Green = 5Blue = 6Violet = 7Gray = 8White = 9

Resistor Value Examples

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First RingRed = 2Black = 0

Second RingRed = 2Red = 2

Third RingRed = X 100 = 2200 ohmsBrown = X 10 = 020 ohms

Example of Color Rings

First RingBrown = 1

Green = 5

Second RingGreen = 5

Red = 2

Third RingBrown = x10 = 150 ohms

Yellow = x10,000 = 520k ohms

Test of Color Rings

First Ring is first digitSecond Ring is second digitThird Ring is number of zeros

RingBlack = 0Brown = 1Red = 2Orange = 3Yellow = 4Green = 5Blue = 6Violet = 7Gray = 8White = 9

Resistor Value ExamplesAnswer

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TransistorNPN

A Transistor is an Electronic Switch

12 VoltBattery

12 VoltBattery

Computer cansend a signal to turnon the transistor whichthen turns on the light

NPN Transistor

Light

Mechanical Switch Circuit Transistor Switch Circuit

Switch openLight off = 0

Switch closeLight on = 1

Transistor come indifferent sizes dependingon the amount of currentand voltage required

Switch

Transistors

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Draw, Label and Explain this Schematic

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An integrated circuit (IC) consists of multiple transistors. The number of transistors can vary from just a few (circuits shown below), to over two billion that are in the latest Intel microprocessor.

6 Transistors in one ICThis IC has 6 invertersAn inverter contains 6 Transistors = 36 total

FunctionsInvertersGatesFlip flopsCountersMemoryMPUWatch ICsCalculators ICsMicrowave Timer ICsRadio ICsDialer ICsCar Controller ICs

Integrated Circuits

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Microprocessor Integrated Circuit: 60,000 Transistors

End of Class 1

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Education & Certification Required for Engineering Careers

• Engineering Assistant• 6 months to 2 years of Technical School during or after High

School• Entry-Level Design Engineer

• 4-year Bachelor of Science in Engineering Degree• Senior-Level Design Engineer, Engineering Manager

• 4-year BS Degree, 2-year MS Degree• 2-20 years experience• Some Engineering Positions Require State Registration (P.E.)

• Professor, University or Industry R&D Laboratory Researcher• Ph. D. or Sc. D. Degree in Physics or Engineering

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US Numbers by Type

From the American Society forEngineering Education, 2009

(http://www.asee.org)

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US BS Engineering Graduates By School, 2009

(Source: ASEE)

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US News & World Report 2011US Undergraduate Engineering School Rankings

(with Ph. D. Program)

Rank School ( * = public)

1 Massachusetts Institute of Technology

2 Stanford University (CA)

3 University of California, Berkeley*

4 California Institute of Technology

5 Georgia Institute of Technology*

6 University Of Illinois, Urbana-Champaign*University of Michigan, Ann Arbor*

8 Carnegie Mellon University (PA)

9 Cornell University (NY) Purdue University (IN)*

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Starting SalariesTop Jobs for 2010 Bachelor’s Graduates (www.jobweb.com)

35,00040,000

45,00050,00055,000

60,00065,000

70,00075,00080,000

85,00090,000

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Eng

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Chem

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Compu

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Mec

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Civil E

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Financ

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Accou

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Busine

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Mar

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About Joe Mulcahey• Before College

– Built lots of Heathkits, installed an intercom and an alarm system in my tree house, performed various dangerous high-voltage experiments

– Studied, passed FCC tests and became an amateur radio operator– Studied some more and passed more FCC tests, got a commercial

radio operator’s license enabling me to work as a studio and transmitter engineer at a 50,000 Watt radio station in Hartford

• College– Co-op student at Raytheon in the Antenna and Microwave

Department– Earned the BSEE and MSEE degrees from MIT in 1984

• Raytheon (since 1981)– My specialty is designing and testing really big and expensive

phased array radar antennas for missile defense– Raytheon is an industry leader in defense and government

electronics, space, information technology, technical services, business aviation and special mission aircraft, with more than 71,000 employees world-wide, including over 30,000 engineers

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About Sean Mulcahey• Eagle Scout with Gold Palm, 2009

– Merit Badges earned: Electronics, Engineering, Radio, Energy, Computers and 26 others

• Crew Guide, Venturing Crew 748• NEU Sophomore in Electrical Engineering• Currently on co-op at Bose, in the Product Safety Laboratory

– Test returned and not-yet-released products for safety– Take expensive and fragile audio equipment and set it on fire, apply

massive overvoltages, shake and drop

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• Power Supply• Power Equipment or Components for Test

• Volt-Ohm Meter (VOM) or Digital Volt Meter (DVM)• Check AC & DC Voltages, Resistance, Opens/Shorts• May also Measure Capacitance, Inductance, Gain, etc.

• Oscilloscope• Graphs one Voltage vs. Time or vs. another Voltage

• Radio Equipment Testing• Signal Generator• Receiver• Power Meter• Spectrum Analyzer

• Graphs Voltage versus Frequency• Network Analyzer• Field Strength Meter

Test Equipment

Now go get some hands-on experience!End of Class 2

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Safety Note: A Soldering Iron gets hotter than 300 F. Do not touch the soldering iron’s metal parts or you will receive a third degree burn

A good solder joint depends on the following:

1) Solder iron must have a clean, well-tinned tip

2) Parts to be soldered must be clean

3) There must be a sound mechanical joint

4) Parts to be soldered must be well heated before applying solder

5) Wait approx. 5 seconds after soldering to allow strong mechanical joint to form

Soldering

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Place soldering iron so that it touches both the PC board and wire. The heat from the soldering iron will transfer to the PC board and wire at the same time.

Iron

Wire

PC Board

Iron

Wire

PC Board

Iron

Wire

PC Board

WrongwayRight

waySolder melts at 310° F. The wire and PC (Printed Circuit) board must be the same temperature for the solder to melt on both items.

Soldering – Heating Junction

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When the board and wire are hot enough the solder will flow and create a cone shape. Ifthe board is not hot enough the solder will be rounded on the board creating somewhatof a ball. The finishing solder should also be shiny. Clip extra wire at board level.

Wire

PC Board

After 3 seconds place the solder on the tip of the iron, the wire and the PC board all together.The solder should flow to everything making a good connection.

WireIron

Solder PC Board

Wire

Iron

Solder PC Board

Rightway

Wrongway

Soldering – Applying Solder

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1. Use pliers to hold the component next to the lead to be unsoldered (If the lead is held with the pliers it will draw heat from the lead)

2. Apply soldering iron tip to PC board and wire3. Either use solder wick or solder sucker to draw solder off the

board, or simply pull wire from PC board when hot4. The soldering iron will damage electronic components if left on

device for greater than 15 seconds, so work quickly5. Sometimes it helps to put more solder on the solder joint to

improve the thermal conductivity6. Clean the soldering iron tip and keep it shiny

Un-Soldering

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WireIron

PC Board

Iron

Pliers

With pliers, hold device close to lead that is to be unsoldered. As heat is applied from soldering iron, pull with pliers. With one side out, do the same on other side.

PC Board

Un-Soldering

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PC Board

LEDNote Flat Edge

+Red

Black

1) Place components into PC board in the order recommended on instruction sheet

2) When components are placed into PC board, bend leads out slightly to keep parts from falling out, when the PC board is turned over for soldering.

3) Follow instructions as to proper orientation of components.

Clip wire at boardWrong

Correct

Kit Assembly

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Soldering Kit

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From the Kit Manual

Anode of LED1Q1 and Q2 are connected in a criss-cross fashion making a square wave oscillator running at about 1.5 Hz. The frequency is determined by C1 and R6. (Also C2 and R4.)

66The Oscilloscope is displaying plots of voltage vs. time

C2 Negative, Q2 BaseWhen Q1 conducts, Q2 gets turned off until the voltage at Q2 base rises above about 0.7V. C2 has to discharge through R4 for this to happen. This determines the time the multi-vibrator will stay in one state.

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IC1 pin 2 & 6IC1 is also an oscillator that drives the speaker at a frequency that we can hear. It oscillates at either the low tone of about 720 Hz or the high tone of about 980 Hz. C4 charges through R5 but discharges through R9.

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IC1 pin 3This shows pin 3 of IC1 that drives the speaker. This oscilloscope shot captured the 985 Hz tone. The output at pin 3 is a square wave (almost).

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End of Class 3