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Low-Power Wireless Chargingby gripen40kon February 1, 2010

Table of Contents

Low-Power Wireless Charging ..................................................................................................

Intro: Low-Power Wireless Charging ..........................................................................................

Step 1: Theory of Operation ................................................................................................

Step 2: Needed Parts and Equipment .........................................................................................

Step 3: Coils and Oscillator .................................................................................................

Step 4: Slave Pickup and CW Generator .......................................................................................

Step 5: Putting it All Together (And Caveats) ....................................................................................

Step 6: References and Links ...............................................................................................

Related Instructables ......................................................................................................

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Comments ..............................................................................................................
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Intro: Low-Power Wireless ChargingHi and welcome to my first instructable!

I'm going to show you how to make your own low-power wireless charging circuits that will let you pass electricity through the air (or any other non-metallic mediushort distances. This is suitable for wireless battery and capacitor charging and powering of very small un-buffered circuits (such as a single LED).

Please make sure to check out the last page as there are tons of references and other sources I managed to gleam from the internet and other instructables. Alsothat I spent a GREAT deal of time experimenting and researching to get this right. I'm an electrical engineer, and even still it took quite a while to get my head arosome of the technical challenges. As such this is for experienced hobbyists only, unfortunately it's not easy to do although I tried to make it as simple as possibdoesn't take a lot of skill, just a lot of tinkering to get it to work right.

Now there shouldn't be current patents on any of this (Tesla, Colpitts, Cockcroft, and Walton all made this stuff yeaaaaars ago), but I would look into it first if you wsell anything using this design.

If you want the circuit then just skip ahead to step 2 and ignore the theory part :).

Image Notes1. Smaller secondary coil, primary coil underneath picture frame2. 2x 1.5F ultra-caps from Cooper-Bussmann used to store energy from slave coil3. Fancy circuit and part of a larger project (most of which isn't covered here)

Step 1:Theory of OperationThe short story: this is a Cockcroft-Walton generatorhanging off a resonant transformer. If you don't mind wasting a couple minutes with detailed theory then chaahead intrepid reader! Otherwise skip to the next step.

The long story, well, it's not much longer. Take a coil, make it resonate at a particular frequency using a capacitor, then place it near a similarly tuned coil and useoscillating magnetic field of the first to cause the second to resonate. Use a clever AC to DC converter and voila, you have a method of wireless energy transfer.

After some sleuthing on the internet, I went about devising the first part, an oscillator. Various homebrew methods have been used (see: Wireless Power Instructaweren't very good or just temporary solutions. I used the suggestion on wikipediaof using a Colpitts oscillator. This is a decent solution because it's dead simple tand, most importantly, it's a current oscillator and not a voltage oscillator. As current through an inductor is what generates the magnetic field, this is what will drivecoils.

The second part is fairly easy to understand, that being the two coils. Although they don't have to be the same physical size, they do need to resonate at the samefrequency. The combination of number of turns and diameter determine the inductance, and some capacitors were added to obtain the correct oscillating frequencgets tricky when you get into the details however (and they get very, very detailed, so I won't put the majority down here) as you need to select the diameter of wirwith the amount of current going through your coil, which will determine the amount of resistance in the coil, which will impact the viability of your oscillator. To masomewhat easy, go with 24AWG enamled magnet wire.

You now get to pick a some-what arbitrary frequency for your circuit. This I decided to go with 80KHz, it happened to be a nice middle ground between easiness aefficiency. Then you pick a capacitor value that's commonly available, I picked 150nF. This took a while to select because you need to get an inductance that is wrealm of being hand made. Using the equation:frequency = 1/( 2 * pi * sqrt(inductance * capacitance / 2) ) (from Colpitts oscillator)we use the capacitor value to try to get the inductance in and around 20uH to 70uH. Air-core inductors around those values are easy to make. I used a value of 53

From here you need to use this handy inductor calculatorto try to figure out what diameter and number of turns are needed. I used values of ~22 turns at 6cm diawith an arbitrary length around 4-5x the wire thickness for the secondary, and ~13 turns at ~15cm diameter for the primary. These values will be your STARTING ONLY. You have to experiment to get it right (covered in the next couple steps).

Note that you are using the same inductance and capacitance for both the resonating coils, this is so it's easy to tune. Don't go crazy with different inductances ancapacitances or else you won't get it to work.

OK, the last part of this picture is the AC to DC converter. This is what will shape the received AC into something we can use to charge a capacitor or a battery at usable voltage. I used a CW generatorhere to great effect; it allowed me to tune the slave coil to produce exactly the right voltage without going over the chargingvoltage. I determined (through experimentation) that a two stage generator would be enough, and that will generally be fine when trying to generate ~5V. For thecapacitors I arbitrarily chose 2.2uF caps, and for the diodes I chose a nice Schottky diodearray with a very low 0.38V forward voltage drop. The P/N is BAS40TWhowever these are VERY small parts so you will probably have to order individual schottky diodes for this one. Just use ones with a low voltage drop AND a low releakage current.

OK! Enough of this long-winded theory and background info, let's get to the actual good stuff!
http://en.wikipedia.org/wiki/Schottky_diodehttp://en.wikipedia.org/wiki/Cockcroft%E2%80%93Walton_generatorhttp://www.pronine.ca/multind.htmhttp://en.wikipedia.org/wiki/Colpitts_oscillator#Theoryhttp://en.wikipedia.org/wiki/Colpitts_oscillatorhttp://en.wikipedia.org/wiki/Resonant_energy_transferhttp://www.instructables.com/id/Wireless-Power-Transmission-Over-Short-Distances-U/http://en.wikipedia.org/wiki/Transformer#Resonant_transformershttp://en.wikipedia.org/wiki/Cockcroft%E2%80%93Walton_generator



Image Notes1. Colpitts oscillator2. Tuned resonant circuit to 20KHz (53uH inductor and two 150nF capacitors)3. Slave coil tuned to the master4. Two stage Cockcroft-Walton generator.

Image Notes

1. Primary (Master) coil2. Any 5V source will do, try to get one that can source 500mA-ish3. These, along with the coil, determine the operating frequency. Remember,in series divide the total capacitance (so 75nF).

Image Notes

1. Secondary (Slave) coil2. The caps we use to change the frequency3. CW Generator, capacitors are fairly arbitrary in value.

Step 2:Needed Parts and EquipmentI hate to let a lot of people down, but an oscilloscope is absolutely needed here. Without it you won't be able to tune your horrible handmade inductor and the circuwon't match. These things are really finicky, even if you went with the relatively large bandwidth that my values provided.

If you have access to one, then great! That, a soldering iron, some wire cutters, and pliers are all the tools you need.

As for materials, you will need a few different parts, but nothing too fancy.Master coil/oscillator:24AWG enameled magnet wirePrototyping board2 150nF capacitors2 10K Ohm resistors1 100Ohm resistor

1 100nF capacitorA bunch of 2N2222 transistors (I used 3, you can use more or less depending on availability)5V regulator and DC jack to plug it into the oscillator

Slave coil/CW generator:More wireAnother prototyping board2 150nF caps4 2.2uF caps4 low forward-voltage drop schottky diodes (search digikey for ones with Vf



Image Notes1. Simple pliers and cutters2. Solder and 24AWG enamled wire3. The star of the show, my oscilloscope (20MHz Gould from god-knows-when)4. Soldering iron

Step 3:Coils and OscillatorOk, so what we will do here is build the oscillator first and then the coil. Using the oscilloscope, we will tune the primary coil until it resonates at the desired freque

The oscillator is pretty simple and was tested both in simulations and in a practical circuit. I derived it from the one hereon wikipedia, however values had to be chand more BJTs (transistors) were added after I discovered that max current transfer improved. Rough schematic and pictures are below. Note to add more BJTs jconnect them in 'parallel' to the one in the schematic, pin-to-pin.

The primary coil started as ~18 turns at ~15cm diameter, then I removed turns based on the final shape/diameter. If you look at the picture of the jig you see how made the coils to a certain size. Just cut out some holes in a cardboard box and use pens on an angle to wrap the wire around.

In the other picture of the completed circuit/coil, I forced the coil into a roughly rectangular shape, so the inductance changed. Simply make the coil with a few extrand then connect that up to the oscillator (directly, solder it without cables or any other wires). Place the 'scope probes across the coil and check the wave period.Remove coils until the period matches what you want (in my case, it was 12.5us). By remove coils I mean physically remove a turn by cutting the wire and re-soldthe end. Excess wire will lead to more inductance and you won't get the right value.

After you are finished with the primary coil you'll do essentially the same thing for the secondary coil. Just unsolder the primary and repeat. However when makingyou are welcome to change the diameter and number of turns. I used my hand for the second one and started with ~30 turns, to make i t smaller and easier to fit in

Once completed you can wrap the coils, although this is risky as you will change the inductance significantly so you'll have to do a considerable amount of trial anto get it right. The inductance changes because you are forcing the wires closer together.

Now onto the slave pickup and CW generator!
http://upload.wikimedia.org/wikipedia/commons/f/f6/NPN_Colpitts_oscillator_collector_coil.png



Image Notes

1. Primary (Master) coil2. Any 5V source will do, try to get one that can source 500mA-ish3. These, along with the coil, determine the operating frequency. Remembecaps in series divide the total capacitance (so 75nF).

Image Notes1. Here I tested the frequency of oscillation while the coil was still on the jig tomake it a bit easier to work with.

Image Notes1. You can 'fray' the coil to lower the inductance and increase the frequencyyou should really just remove a turn.

Image Notes1. Primary coil completed2. Secondary coil completed and wrapped in electrical tape to protect it



Step 4:Slave Pickup and CW GeneratorAh, almost done! This step consists of adding 2 capacitors in parallel to the slave coil and connecting that up to a ladder of schottky diodes and capacitors.

Note that in the pictures below, you are looking at my heavily modified original PCB. Because of the simplicity here, this can be made on some protoboard or evenbugstyle.

The schematic and pictures really say it all, simply connect the secondary coil to the capacitors and then connect that up to the diode ladder. The 'bottom' line of tis selected as the ground and the top of the ladder is the output, in my case it was a bit under 5V.

The next step is simply putting it all together with some sort of storage element.

Image Notes1. Secondary (Slave) coil2. The caps we use to change the frequency3. CW Generator, capacitors are fairly arbitrary in value.

Image Notes1. Coil and caps2. Verrrrry small and hacked together CW generator3. Switching boost converter and LDO for the rest of the circuit (not covered h

Step 5:Putting it All Together (And Caveats)Great, now we have the primary coil and oscillator, a secondary coil, and a CW generator.

Of course the purpose of this instructable is that there isn't any 'hooking up'! If you power the oscillator and have the secondary coil inside/on/around the primary cwill notice that a fairly decent voltage is generated on the secondary coil. Although usually just over half the voltage on the primary, the CW generator takes that Avoltage and conveniently produces a clean 5V. Ideally this can be used to charge a large capacitor bank like I did, or a low power 5V circuit. Now for the caveats.

This first one being that you can't really use this for any high current applications, such as driving motors or a bunch of LEDs. Charging is a different matter of couwill work perfectly ok for that. When you try to pull too much current out of this circuit the voltage will start dropping considerably. For instance when you connect adepleted capacitor bank to it the voltage across the secondary is considerably reduced. If you take a look at the primary during this time you will also see that thefrequency and amplitude of the wave is considerably different. This frequency shifting is what prevents you from using high current loads. I'm sure there are better

oscillators and other measures that can be taken to improve the voltage regulation, but this works as a preliminary model.

The second caveat is that you can't put ANY metal in between the primary and secondary, particularly iron based metals (steel, stainless or otherwise). Even placoscillating circuit inside the primary effects the performance, creating drop-out zones on the upper surface of the picture frame that prevent charging when the secis placed in certain spots.

The third caveat is that the distance between the primary and secondary coil must be kept to a minimum. This isn't WiTricity, it can't power anything over a distaneven 20cm.

Working around these limitations is quite easy though. My method was to use the circuit to charge a large capacitor bank (3F @ 5V) and then use that bank to powswitching regulator (to keep a constant 5V even when the capacitor voltage drops) and LDO so I have both 5V and 3.3V to work with. It takes about a full night to the capacitors, and I can get a considerable amount of run time with proper power saving attention to the rest of my circuit.

Up next? Well maybe a larger, more robust version to trickle charge a car battery, or a nicer looking version to charge a cell phone battery. Maybe some experimein flat-wrapped coils or other methods. Feel free to expand upon my methods and improve this tech, and heck, take my idea and integrate it into some of your exisprojects. Just as long as you promise to make an instructable or something out of it, I'm interested to see what people will do with this! Also make sure to respect mcreative-commons by-salicense ;).

Happy Hacking,-Devin
http://en.wikipedia.org/wiki/Creative_Commons_licenses#Original_licenseshttp://en.wikipedia.org/wiki/WiTricityhttp://en.wikipedia.org/wiki/Point-to-point_construction



Image Notes1. LED magic! Note that there isn't any CW generator here, the LED is justplaced across the coil. In theory the LED should be twice as bright if a full waverectifier is used2. Not connected in this picture but can be to store power3. Primary coil housed underneath picture frame

Image Notes1. LED running entirely from the slave coil. Much brighter than this pictureinsinuates, stupid 'scope is too bright.2. 'Scope showing the voltage across the primary coil.

Step 6:References and LinksK, first off, links to people who have come before me!Instructables user robotkid249: wireless power transmission over short distancesInstructables user puffin_juice: I need your help. IPTRobert Coup and Monique Ryan (U of Auckland): Inductively coupled universal battery charger

Now for links from wikipedia (all accessed on or around Dec '09):Wireless Energy TransferResonant Energy TransferColpitts OscillatorResonant TransformerCockcroft-Walton GeneratorWiTricityPoint-to-Point ConstructionSchottky DiodeStripboardSecondary Coil: LC circuit resonance

Other links from around the web:Inductor Calculator

Colpitts OscillatorCommon capacitor values

Wireless power links (just fyi):Neat RGB LEDproject, similar setup to this oneUsing large capacitors and small inductorsinsteadQuick-and-dirty method for high power outputusing a CFL bulb.

I'll reserve this space below for anyone that uses this in one of their projects, just let me know!

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Comments

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erfesqualsays: Aug 17, 2014. 10:06 AMsir is there any problem is i use battery... i just notice.. my circuit is using 12vdc from a (12v 9AH)battery then i use a voltage regulator to get 5vdc.. i doknow about ur source.. this might be the problem of not having oscillation. can my battery give the required currrent? i really need help sir.

thank in advance. i really appreciate it

erfesqualsays: Aug 18, 2014. 6:14 AMi am using L7805 voltage regulator to regulate the voltage to get 5vdc. From the spec of the voltage regulator, max output current is 1A. While for ysource, u mention try at least 500mA which 0.5A, so did i pass the condition for the oscillator to work out?

i am building a wireless power transfer base on solar. so far using dc as is my priority.

gripen40ksays: Aug 31, 2014. 3:30 PMThe DC regulator won't matter too much as long as you have some caps on the output of it to provide clean power. If i t oscillates too much yoube getting really weird effects in the oscillator circuit. Follow the manufacturer's recommended circuit for your regulator.

erfesqualsays: Aug 7, 2014. 11:45 PMHello sirGreat sharing. . can i ask u the type of capacitor u had used for these:Primary Coil.150nF capacitors ;

100nF capacitor

Slave coil/CW generator:150nF caps2.2uF caps

it is non polar capacitors right? but what kind?

erfesqualsays: Aug 8, 2014. 5:28 PMand sir, what if i use higher voltage source for the same circuit. for example i use 12v dc source using same design.

gripen40ksays: Aug 13, 2014. 9:16 AMYou'll need to redesign the oscillator, I don't think it will work at 12V.

erfesqualsays: Aug 13, 2014. 10:17 AMthanks a lot for the fast response sir.i've try this circuit using 9v and 12v dc. i notice that the led was about to light but just for very small time. maybe split second. when i testedthe oscilloscope but i unable to get any oscillation sir. that is the problem. Is that bjt limit up to only 5 volt.

in term of redesigning sir.. any recommendation or suggestion sir.and how to parallel the bjt sir. thank in advance. sir.

gripen40ksays: Aug 13, 2014. 11:46 AMThe highest I've gone on this oscillator is 6V, I'm not sure 9V would even work. Try finding a 6V source somewhere and starting with thayou'll want to check that there is a voltage across the primary coil before you try to do anything else. Once you see AC voltage on the pyou can double-check it's the right frequency.

erfesqualsays: Aug 14, 2014. 7:50 AMnow i use a voltage regulator so that my input is 4.98v which is almost 5vdc. i build the circuit using 1 bjt only. what worry me is, howcome i could get any oscillation. When i tested for ac or dc voltage across the primary coil, the value is zero. there is some problemto troubleshoot sir?

fyi, the inductor value of the coil is just estimation, i cant tune because no oscillation.

gripen40ksays: Aug 13, 2014. 9:16 AMI don't think it matters what kind of cap you use. Almost everyone uses ceramic caps these days and those are widely available. They just have to non-polarized.
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bobjoe1234says: Mar 11, 2014. 5:44 AMHello, I have a lot of problems making the coils. How can I select my resonance frequency and How do I know the dimensions of the coil??

gripen40ksays: Mar 13, 2014. 7:22 PMAll of the details are explained instep 1: theory of operation, including links to inductor calculators and such.

apravinsays: Mar 3, 2014. 10:32 PMHello i wanted to build a wireless charger to charge a 9V battery..... plz helpme yar... thanx

arhodes18says: Feb 14, 2010. 11:28 AMsorry this may be another stupid question, but what are the caps in the diode bridge section for, the 2.2 uF ones.

gripen40ksays: Feb 15, 2010. 8:47 PMHaha, nope, not a stupid question.

Thewikipedia articledoes a good job explaining the CW generator, but I'll try my best to simplify it. The capacitors are a temporary storage for eithpositive or negative cycle of the AC source. So when you have a negative swing, the current flows through the first diode and charges the first cap2.5V (in our case). Then the AC source swings positive and current flows through the first cap and second diode charging the second cap to 2.5V pthe voltage stored on the first capacitor (2.5V + 2.5V = 5V). Of course this is simplified and doesn't take losses into account, but you get the genera

Now I picked a fairly arbitrary value, just guessed and it worked out pretty good. If you only have 1uF ones or whatever, then those will be fine. Jusget them roughly around the same values.

Mel007says: Jan 3, 2014. 11:18 AMI made the circuit but the power input in my primary circuit is not the same as the power output in the primary circuit. I am attaching 5V at the inbut check the flow I see that the voltage drops to 1V.looks like there is voltage loss and as a result the led in the secondary doesn't lit up.Do you have any suggestions.

gripen40ksays: Jan 27, 2014. 7:07 AMUh, I'm not entirely sure.

The primary oscillator is a current oscillator, so measuring the voltage on the primary coil may not mean much (it won't be 5V). Could you cthe values of all the components you are using, there could be a chance you're using a wrong value resistor or something.

arhodes18says: Feb 16, 2010. 6:26 AMoh ok that makes sense...Thanks for the help!

wwasanthasays: May 2, 2012. 6:22 AMTHIS IS MY PROJECT PHOTOS
http://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/FUF/GHH1/H1JU5CPY/FUFGHH1H1JU5CPY.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/FUF/GHH1/H1JU5CPY/FUFGHH1H1JU5CPY.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/FUF/GHH1/H1JU5CPY/FUFGHH1H1JU5CPY.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/FUF/GHH1/H1JU5CPY/FUFGHH1H1JU5CPY.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/FUF/GHH1/H1JU5CPY/FUFGHH1H1JU5CPY.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/FUF/GHH1/H1JU5CPY/FUFGHH1H1JU5CPY.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/FUF/GHH1/H1JU5CPY/FUFGHH1H1JU5CPY.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/FUF/GHH1/H1JU5CPY/FUFGHH1H1JU5CPY.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/FUF/GHH1/H1JU5CPY/FUFGHH1H1JU5CPY.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/FUF/GHH1/H1JU5CPY/FUFGHH1H1JU5CPY.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/FUF/GHH1/H1JU5CPY/FUFGHH1H1JU5CPY.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/FUF/GHH1/H1JU5CPY/FUFGHH1H1JU5CPY.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/FUF/GHH1/H1JU5CPY/FUFGHH1H1JU5CPY.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/FUF/GHH1/H1JU5CPY/FUFGHH1H1JU5CPY.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/FUF/GHH1/H1JU5CPY/FUFGHH1H1JU5CPY.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/FUF/GHH1/H1JU5CPY/FUFGHH1H1JU5CPY.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/FUF/GHH1/H1JU5CPY/FUFGHH1H1JU5CPY.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/FUF/GHH1/H1JU5CPY/FUFGHH1H1JU5CPY.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://cdn.instructables.com/F3U/539E/H1JUH6UO/F3U539EH1JUH6UO.LARGE.jpghttp://cdn.instructables.com/F9M/NMTI/H1LWPU0O/F9MNMTIH1LWPU0O.LARGE.jpghttp://www.instructables.com/member/wwasantha/?utm_source=pdf&utm_campaign=commentshttp://www.instructab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agarwalprashant80says: May 6, 2012. 2:45 AMhello wwasantha, sir i was working on a similar project n need a little assistance in that regard...sir i was not able to get the output..so i just wanted to more about the coil that u have used..sir i have made a coil of 26G with the specifications on specified by u.. i.e. 26 turns on primary and 200 turns onsecondary.. do i need to change this..?

wwasanthasays: May 6, 2012. 1:00 PMagarwalprashant,dear i think u can get complete idea about it if u gone through what i uploaded.MASTER COIL-24 GAGE, 26TURNS, DIAMETER 7.5cm(READ MY POST IN Apr 27, 2012. 9:57 AM)SLAVE COIL - 40GAGE, 150TURNS IN A 2cm x 2cm SQUARE(READ MY POST IN Apr 30, 2012. 11:32 PM)ABOVE TYPE OF COILS PLUSWITH OTHER ALTERATION OF OSCILLATOR AND CW GENERATOR CIRCUITS I MENTION SURELY U ALSO GOT 5.5V TO 6.25V OUT FROM CW GENERATORI JUST MADE SOME CHANGES OF GRIPEN'S PROJECT.BUT ALL WE GIVE THE CREDIT FOR HIM.THANKS.

agarwalprashant80says: May 6, 2012. 9:22 PMsir i was working on this but then i found out that i'm not able to get any voltage across the master coil..can u guide me on this..?

more over i hav gone thru your post and i'm working on that..i wanted to know this too..sir i'm using a a 12v adopter followed by a 7805 regulator circuit to generate 5v supply..n in the data that u hav uploded i saw 5v written on thenegetive leg of the oscillator circuit..so my question isis this the ground of the regulator circuit or do i have to generate -5v and connect it to this terminal?

sayma91says: Oct 28, 2013. 9:27 PMI am also trying to develop this circuit on project board but I am unable to get any voltage across the master coil..What can I do?

wwasanthasays: May 6, 2012. 11:07 PMsorry i just wanted to tell positive and negative supply of 5v for oscillator circuit,so you dont need generate minus 5 voltageim not very good in knowledge of electronicshow ever select proper capacitor value with a digital multi-meter149nf CAPACITORS INSTEAD OF BOTH 150nf IN OSCILLATORA 100nf CAPACITOR FROM 102nf CAPACITORS - FOR SLAVE COILAND USE 3 OF 2N2222 TRANSISTORS IN OSCILATORUSE GAGE 24 FOR MASER COIL AND GAGE 40 FOR SLAVE COIL (NOT GAGE 26)NICELY IT WILL WORK FOR U AS WELLno magics behind that strictly follow my post to make ur project,u will win.
http://cdn.instructables.com/FUF/GHH1/H1JU5CPY/FUFGHH1H1JU5CPY.LARGE.jpghttp://cdn.instructables.com/F6T/ZCNI/H1JUIZHP/F6TZCNIH1JUIZHP.LARGE.jpghttp://www.instructables.com/member/wwasantha/?utm_source=pdf&utm_campaign=commentshttp://www.instructables.com/member/wwasantha/?utm_source=pdf&utm_campaign=commentshttp://www.instructables.com/member/sayma91/?utm_source=pdf&utm_campaign=commentshttp://www.instructables.com/member/sayma91/?utm_source=pdf&utm_campaign=commentshttp://www.instructables.com/member/agarwalprashant80/?utm_source=pdf&utm_campaign=commentshttp://www.instructables.com/member/agarwalprashant80/?utm_source=pdf&utm_campaign=commentshttp://www.instructables.com/member/wwasantha/?utm_source=pdf&utm_campaign=commentshttp://www.instructables.com/member/wwasantha/?utm_source=pdf&utm_campaign=commentshttp://www.instructables.com/member/agarwalprashant80/?utm_source=pdf&utm_campaign=commentshttp://www.instructables.com/member/agarwalprashant80/?utm_source=pdf&utm_campaign=commentshttp://cdn.instructables.com/FSI/LHGO/H1JU5CQ1/FSILHGOH1JU5CQ1.LARGE.jpg



agarwalprashant80says: May 6, 2012. 9:13 PMsir i was working on this but then i found out that i'm not able to get any voltage across the master coil..can u guide me on this..?

more over i hav gone thru your post and i'm working on that..see the image below question enclosed in that..!

wwasanthasays: May 6, 2012. 11:37 PMbe sure not to heat 2N2222 while u soldering them in oscillator circuit keep contact metal piece to suck heat before heat transmit to 2N2in my case i used that safety measure and i soldered 3 of 2N2222 at last (after soldering all other component of oscillator)

agarwalprashant80says: May 7, 2012. 9:49 PMsir, i'm using a breadboard to develop this circuit. i did every thing as u said but still i'm not able to get any potential across the masterc

agarwalprashant80says: May 7, 2012. 9:50 PMis there a special way to check these 2n2222 transistor....?

wwasanthasays: May 9, 2012. 5:17 AMdid u set transistor pins correctly. it is impossible to non function.coz i did it that way and succeeded.i will upload a video clipprove it any time.did u use 2 coils as i said in same gauges?

wwasanthasays: May 13, 2012. 8:53 AMagarwalprashantpls change capacitor which parallel y attach to slaved coil into 100pf (102pf ceramic cap) not 100ufor else pf variable capacitor which using in pocket radio to select radio channels

wwasanthasays: Apr 27, 2012. 9:57 AM

HI GRIPENI DIDN'T HAVE AN OSCILLOSCOPE TO TUNE BOTH COILS.BUT I SUCCEEDED UR PROJECT WITH FEW EXPERIMENTATION.BEFORE TELLING ABOUT THAT I NEED TO THANK U A LOT FOR UR KIND UN INTERRUPTED GUIDANCE

# I CHANGED MASTER COIL & SLAVE COIL( BECAUSE(1) I WANTED TO GET 5 TO 6V OUT PUT FROM CW GENERATOR FOR CHARGE MY NOKIA C6-01(2) I WANTED TO MAKE SMALLER COILS TO ARRANGE THEM IN SMALL BOXES) THESE DAYS I'M TRYING TO SLAVE COIL MAKE MORESMALLER# I USED 3 OF 2N2222 TRANSISTORS IN OSCILATOR# I USED 149nf CAPACITORS INSTEAD OF BOTH 150nfCAPACITORS ( I SELECTED 2 OF 150nf CAPACITOR WHICH ARE GIVEN149nf VALUE FOR MULTI-METER CAPACITOR TEST)# SAME WAY I USED A 100nf CAPACITOR FROM 102nf CAPACITORS - FOR SLAVE COIL

I GAVE 4,92V TO OSCILLATOR THROUGH 5V REGULATOR CIRCUIT( link for it-> http://www.youtube.com/watch?v=CKS6zHo5T9k )I GOT 5.50V TO 6.25V OUT PUT FROM CW GENERATOR

THIS IS THE CIRCUIT DIAGRAM I USED

Lightening Ghostsays: Sep 22, 2013. 10:48 PMhey can u help me out with a circuit by which i can transfer charge from one device to another device.i want a circuit that can absorb charge from adevice.

Moin Skylarksays: Jun 6, 2013. 8:29 PMI follow uf circuit and setup it each & every point as like u.but i don't got any efficien output that the Tx portion can't made 20KHz frequency.do u use ecomponent for its.i want to make ur circuit.pls help...
http://www.instructables.com/member/Moin+Skylark/?utm_source=pdf&utm_campaign=commentshttp://www.instructables.com/member/Moin+Skylark/?utm_source=pdf&utm_campaign=commentshttp://www.instructables.com/member/Lightening+Ghost/?utm_source=pdf&utm_campaign=commentshttp://www.instructables.com/member/Lightening+Ghost/?utm_source=pdf&utm_campaign=commentshttp://cdn.instructables.com/F5V/FZTJ/H1EMI71V/F5VFZTJH1EMI71V.LARGE.jpghttp://www.instructables.com/member/wwasantha/?utm_source=pdf&utm_campaign=commentshttp://www.instructables.com/member/wwasantha/?utm_source=pdf&utm_campaign=commentshttp://www.instructables.com/member/wwasantha/?utm_source=pdf&utm_campaign=commentshttp://www.instructables.com/member/wwasantha/?utm_source=pdf&utm_campaign=commentshttp://www.instructables.com/member/wwasantha/?utm_source=pdf&utm_campaign=commentshttp://www.instructables.com/member/wwasantha/?utm_source=pdf&utm_campaign=commentshttp://www.instructables.com/member/agarwalprashant80/?utm_source=pdf&utm_campaign=commentshttp://www.instructables.com/member/agarwalprashant80/?utm_source=pdf&utm_campaign=commentshttp://www.instructables.com/member/agarwalprashant80/?utm_source=pdf&utm_campaign=commentshttp://www.instructables.com/member/agarwalprashant80/?utm_source=pdf&utm_campaign=commentshttp://www.instructables.com/member/wwasantha/?utm_source=pdf&utm_campaign=commentshttp://www.instructables.com/member/wwasantha/?utm_source=pdf&utm_campaign=commentshttp://www.instructables.com/member/agarwalprashant80/?utm_source=pdf&utm_campaign=commentshttp://www.instructables.com/member/agarwalprashant80/?utm_source=pdf&utm_campaign=comments



gripen40ksays: Apr 30, 2012. 4:01 PMAwesome, glad to hear it worked out for you :) However using an oscilloscope can allow you to tune the coils and get the maximum power transfer

agarwalprashant80says: May 11, 2012. 12:30 PMwhy are the radii and the shape of the two inductor coils are different ???could you please explain.thank you

wwasanthasays: Jun 4, 2012. 2:51 AMhey dude wt about ur project does it work now?

gripen40ksays: May 19, 2012. 2:15 PMThey are different so I was able to fit them into their two containers, that's all. You can make them any size/shape you want, as long as theinductance is still the same.

wwasanthasays: Apr 30, 2012. 11:32 PMthank you gripenfinally i made a smaller slave coil which gives same voltage out put (5.5 to 6.25v) from CW generatorthis simple description is about it

agarwalprashant80says: May 3, 2012. 4:45 AMsir i hav a small questn n that is what kind of wire can we use for the coil?is normal copper wire of 24G is acceptable or not..?

agarwalprashant80says: May 5, 2012. 6:53 PMi'm using 26G wire n not abl to get the o/p voltage..can u help with no of turns in d coil at primery and secondary.

gripen40ksays: May 3, 2012. 5:22 AMAh cool, good idea with the coil form, it makes winding a lot easier.

agarwalprashant80says: May 3, 2012. 4:45 AMsir i hav a small questn n that is what kind of wire can we use for the coil?is normal copper wire of 24G is acceptable or not..?

gripen40ksays: May 3, 2012. 5:21 AMUse insulated magnet wire, the guage doesn't matter because this is a low power application

Lightening Ghostsays: Sep 9, 2013. 7:33 AMhii i am looking for a circuit with which i can transfer charge from one gadget to another gadget ... i can make use of the circuit designed by you to trancharge but i need a circuit by i can absorb charge from the battery of one gadget so that i can transmit that to another gadget . can u help me please...

gnimrezt88says: Apr 17, 2013. 9:24 AM(From Apr 10, 2013. 10:02 PM)Hi, is there any recommended oscillator which produces higher voltage rating? Besides that, how will the frequency chosen in the design affects theefficiency of the system?

Thanks.
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gripen40ksays: Apr 17, 2013. 3:32 PMNo recommended oscillator, you'll have to figure that one out for yourself. The frequency effects the Q factor, which in turn effects the total efficiencbe honest I don't have the equations anymore so again, you'll have to figure that one out for yourself :)

mohmed.kadorasays: Apr 12, 2013. 12:07 AMhi mr ...in my area we dnt use awg we just use desem which=0.1 mm so can i use slave coil 2*2 ...150 turne ...0.0799 mm

master coil 9.5*4.5....26 turne ....0.511 mm to get 5 v.i have problem whith the diameters plz help me

gripen40ksays: Apr 12, 2013. 6:36 AM

Hey, the AWG doesn't mean much, I just used wire that I had on hand. As long as the wire is able to handle the current you're putting through it (indesign at most a couple hundred miliamps, if that) then you should be good.

The diameters/measurements don't mean as much as the overall inductance. If you follow the instructions for tuning the coils with an oscilloscope you can easily change the diameters of the coils and still get them to oscillate at the same frequency. The total inductance is what's important.

gnimrezt88says: Apr 10, 2013. 10:02 PMHi, I'm currently doing this for my degree project. Among all the tutorials, I find out that your's is one of the most understandable. My questions are:i.) What is the max voltage and current can be transmitted from your design?ii.) Will it be possible if I add 1 power amplifier circuit after the oscillator circuit in order to boost up the voltage to be transmitted so that I can charge upmobile phone?

Thanks in advance. Hoping to get replies from you soon.

gripen40ksays: Apr 11, 2013. 9:10 AMHey, well I would suggest you come up with a higher-voltage oscillator instead of using my design if you want to transfer any more power across th

As it stands this oscillator design is cheap and easy to make, but it doesn't have too many benefits other than that :)

i) ~6V, not sure how many amps, maybe a couple hundred mA?II) Yes, that would work, but you're probably better off designing a new oscillator

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low-power-wireless-charging.pdf

Documents

lowpower wireless charginghi

wireless battery

lot of skill

lot of tinkering

tons of references

small unbuffered circuits

table of contentslow

single led