Picture of Wireless Power
Quarter of a million views, thanks everyone!

The power cord, I know you hate it. Sometimes, you just want to cut it apart! Well say goodbye to your power cords, because with the power of inductive coupling your device will not need to be connected metal to metal. Seemlessly your device can be charged!

This instructable will show you the basics of creating your own cheap and easy wireless power mat, which you can use to power your device through the air!

New Update: complete list of components.

Check out my new project on sending a balloon into space!!

Remove these adsRemove these ads by Signing Up

Step 1: What is it? How does it work?

Picture of What is it? How does it work?
A few years ago MIT created a system for transferring power wirelessly. They transmitted power over a two-meter distance, from the coil on the left to the coil on the right, where it powers a 60W light bulb. Back in 2006, this was a pretty cool thing. You can only imagine what the implications of something like this would be. Well, unlike most of us, we do not have the time or material goods like MIT has. So i have made this simple and easy to follow Instructable, so all of you good people can experience the joy of wireless power.

Inductive Coupling uses magnetic fields to transfer power. There is a primary coil, which generates a magnetic field. Then there is another secondary coil which is composed of a capacitor and a coil, the capacitor creates a resonant circuit with the primary and secondary coils. Seem easy? Well, before publishing this instructable I found many useful and a lot of non-useful info on the subject.

In my research I found, that to transfer power in very complicated. Once i did it I found that you do not need to go to MIT do do this sort of stuff. With a little electrical know how, this is easy.

It all starts with the transmitter. This transmitter needs to create 147.7 kHz square wave AC signal. Let me take a minute to explain this all. Level one on the frequency scale is Hertzs, then there is kHz, then MHz. MIT used a 10 mHz wave to drive there coils, but for this we will be using a 147.7 kHz signal so it does not get too complicated.

The secondary coil has a 0.02 uF capacitor. This will allow the two circuits to be coupled therefore, transferring power efficiently. The 0.02 uF capacitor is used only for this frequency, and the value of this capcitor will change depending on the frequency.

The primary coil creates a magnetic field, when another coil is placed near it, energy will be induced into it.

Be in mind that i could not get a hold of a 0.02uF capacitor so i used two 0.01uF capacitors connected together.

shrawan981 month ago
where i get the circuit?
help me
shrawan981 month ago
where i get the circuit?
help me

how to make the primary circuit?

Ajith19951 month ago

how much distance will this take place....i want to increase the distance.. what is the method

dkimbril2 months ago
Does anyone know what the device is that is connected to the ground on the MOSFET?
freakqnc1 year ago
Quick question for anyone willing to pitch in. I am trying to use induction coupling to transfer power from a coil to another because I only need a contactless connection. I am using this in automotive to transfer 12v from standard light wires.
I can't find any simple schematics or info on how to accomplish that though looking at info I did find I should be able to use just 2 coils and perhaps just a couple condensers and resistors... I'd appreciate if anyone could be so kind to point me in the right direction! Thanks in advance! :D

I'm looking to do something similar, I'm needing a 14+V, 2-5A power transfer, using induction like this. I do in a way understand how this works, however I have no idea how to get a fairly large power transference. Everything I read is 3-5V, >500ma, not even close to what I could use =(

<500ma ***

ThatCatMan3 months ago

Also, if you think about it, this wireless power system is very similar to the way a simple transformer. Power goes into one coil, creates a magnetic field, and it passes to the other coil, but to a higher output.

ThatCatMan3 months ago
Hey robotkid! I like the Instructable and I had an idea for you. I don't know if you know about Electrostatic levitation, but I have seen work done where you can move a metal ball through a small space with magnets making it seem to "levitate." If you could do one of those, you could combine that with this wireless power in a larger scale to make something in a small sphere, as long as the magnetic field doesn't interfere with the wireless power, to make a free floating, free powered, circuit to move around in an open space. A nice challenge for you, I hope?
Like, if you could have a micro-camera inside a "globe" with a rotating center bar, all controlled with infrared signals, you could control the zoom and direction with an IR-Remote, while controlling the position with the above electromagnet control. A free floating camera. But then, I think the electromagnets to "levitate" might cause problems with the servos that turn the camera. Just a little idea I know wont work.

Oh I made a mistake. It is not electrostatic levitation, but instead Magnetic levitation.
The same concept that holds a levitating globe in mid-air. An electromagnet controlled by a circuit that keeps the object floating.
claudiopolis3 months ago
I see nobody here worrying about EMI. Electromagnetic interference will affect audio/video/PCs a lot. Shielding can not be used, it would hamper the power output. So we're left with a "dirty" (in EMI terms) power supply with less than 50% efficiency, for getting rid of a 3 inches long cable. I'd say wireless charging still has a lot to evolve.
gospina9 months ago
Hey guys! I'm planning on trying something like on a new project, but I'll need someones help who knows this area of study. What degree is related to this or what field of study is this related to? Also for anything wireless and electrical I guess.
zseys9 months ago
can i charge my phone with this? it has the backing to accept the charge.
Moin Skylark10 months ago
how may i create 147.7 kHz for Tx without using signal generator.have any efficient circuit diagram of ur project.i need it.
gnimrezt881 year ago
Hi, may I know what component is used in the design for the primary coil? (The one connected with function generator and dc jack, voltage regulator?)
randomtwig1 year ago
The magnetic "lines" created by the primary coil are at a right angle to the plane of the coil. to set up a current in the secondary coil it must also be at right angles to the plane of the coil. if the plane of the secondary coil is at a right angle to the primary one, the magnetic flux lines just kinda go past ineffectively. The effectiveness of a magnetic flux is B x i x L x sin θ where θ is the angle between the two planes
randomtwig1 year ago
Hi Hi. Just wondering if the power loss across the air gap is significant enough to render this inefficient?
kleomenid1 year ago
Does the number of coils matter? and do the sizes of the master and slave coil matter as long as they are proportionate?
could you use a 555ic to replace the function genorater?
robotkid249 (author)  MadScientist1012 years ago
Yes, but it wouldn't be efficient...
why, surely it would do the same job but less options
LM555's are power hogs...really !
dang i have heaps
Well, compared to their low powered cousins they are....still they are quite useful.....just not if you need to keep a battery fresh without recharge for awhile. I have a bunch of them too, as I use then for simple timing projects....
Sorry, I just didn't want to discourage your using them...., they can be very useful for the right projects.
you didn't disgourage me for using them
Ok, just making sure :-)
how can i do it?
It is entirely possible to use 555 ICs, if you use a MOSFET to convert DC to square wave AC from pin 3 of the IC.
where i get the circuit?
help me
Hey, thanks a lot for your guide! Based on this and a few other sources, I was able to make a wireless electricity system (for our school's science fair) using an IC-555 and MOSFET in place of the function generator! I'll post an instructable on the construction process in the near future.
Is "dimming" the receiving circuit by way of adjusting the transmitter voltage possible? Or does that mess with the tuning of the coils?
Could you just sell me one. Need 2 inch distance to charge 5 volts.
sshroff1 year ago
You have specified Gold for primary and Red for secondary.What would be the length of each coil?Have you used the same gauge in both the coils at the same time?
Kuzan1 year ago
Been doing a project like yours,I would like to ask if the phone really charging ??How Fast ,cause in our experiment it discharges instead
ehabcharek1 year ago
is it possible to connect the primary coil directly to the power source and the secondary coil directly to the (for example) LED?
also, is it possible to use metals other than copper?
agis681 year ago
whata you did there was also well descibe it by Tesla itself. But well you did it to remin us this cheap and safe energy transfer. Now my question.How did you make it to give this squire with smooth corners form of your coils. How many turns is the primary and how many the secondary.

thank you for sharing
alinneker1 year ago
What's the calculation that can be used in the experiment?
Calculations of electromagnetic waves.
jose15221 year ago
Hi guys! I was looking for an alternative for the Frequency Generator Kit since its not available and I found that a astable circuit with a 555 timer can do the trick; however, i'm not sure about the Capacitor and resistor configurators... I used an online calculator to obtain a configuration close to the 147.7 Khz frequency and it turns out I can get 146Khz with a 470 ohm R1, 47 ohm R2 and 0.01 micro farad C . Can someone double check the math for me? Thanks!
Sorry, another correction. R1: 33ohms, R2: 470 ohms.
I just reallized that with a 33 ohm resistor instead of the 47 ohm one I get 148Khz frequency. Still, can someone double check it?
are_pit2 years ago
hello guys...
i'am want to know...
how the secondary receive volt from primary...
can u explain to me....
thanks you..
Hi are_pit,

There is a common mis-conception that the power is transfered by induction.

This is not true. The power transfers by coupled magnetic resonance --the magnetic equivalent of Tesla's high-voltage resonance.

Check my time-line I'm still working on...

The coupling phenomena is more akin to nuclear magnetic resonance than common induction.

One company is already making a power-pad wireless power charger for electric vehicles.

Google the quoted term "wireless power transfer" for starts. There's lots of background, more almost every day.

Another company already announced a cell-phone wireless power antenna. See my wiki above... main page, top of the top-fifty list... Electromagnetic Coils.

Have fun... run the background... there's are hardly any experts out here yet!

There are a couple of things you should know before I begin to explain how this works.

Firstly, when electricity runs though anything (not just wires) it creates a very very very small electromagnetic field.

Secondly, this electromagnetic field has a spin around the conductor relative to the direction of flow of electricity.*

Thirdly, this spin is amplified by proximity to other conductors.

Fourthly, flow creates spin and spin creates flow.

Now that you know those four things I can begin to explain.

The primary coil is a coil and not just a solitary wire because the voltage being put through it does not create enough of an electromagnetic field to transmit power. So when the wire is looped around next to itself it acts like one big wire and creates a larger field than that of a single wire.

Once the field has been increased from a few micrometers to a few inches in this manner you can start to receive power. Due to the spin created by the field any circuit (electricity has to have a place to flow) placed within it will "resonate" this spin and begin to carry electricity on its own almost as if by magic.**

But this only goes so far. This field, while stronger than before and able to generate electricity, does not have quite enough power to be able to run a device receiving power through a single wire. And so it must be passively amplified (through another coil) before it can be sent to the components you are trying to use.

Once amplified in this manner there is enough voltage flowing through the receiving coil to power the device or components it is attached to.

PS This is a relatively basic and general explanation of how this works. A more detailed description of it can be found almost anywhere.
Wireless Energy Transfer
Electromagnetic Induction
Make Presents: The Inductor (Watch the whole series of Make Presents videos they explain almost all of the basic electronics components)

*Use the Right Hand Grip rule to determine direction of spin. Hold your right hand up in a fist with your thumb up. Your thumb represents the flow of electricity down the wire. Your fingers represent the direction of spin around the wire.

** This is the principle behind an Electro-Magnetic Pulse (EMP) the pulse creates so much voltage within the target's circuitry that it overloads all of the components, and destroys any form of magnetic storage.
I tried the links you've provided for the Function Generator but the links say that they are not manufacturing the products.
Is there a way to get the project done without the generator?
And how to make the secondary coil?
ausam1 year ago
Hi, I have a simple question. Do I need the function generator to produce AC square waves of approx.147 frequency? Can I just simply connect the primary coil to a power outlet or any other source of AC current? thanks.

PS. (pleeeaase do answer. i'm doing this for my school science fair)
akipfer1 year ago
hi, listen to me, i recently bought a mouse, wireless mouse, but i paid 6bucks tops
(dealXtreme) this mouse, more precisly '' no quotes
I want to make it fully wireless
with no need of batteries, this mouse can't hold up so much, 2 fresh AAA baterias, 2, maybe 5 days top, and the baterryes are dead...
can i do that?
won't harm my PC? i would put the large coil 'maybe under the table, wooden table, or make a case for it, tiny , so i put the mouse on it, 24\7 on wireless'

can i do that?
mouse uses 2 AAA bateries, 3V...
sujithZis1 year ago
Hey guys making making the instruct-able
and i am having small doubts ............... ............

desperately needing experts advice's
dmcintosh31 year ago
I've been working on developing a simple DIY inductive charger. I have schematic and low level details in there.

I used a PCB patterned coil for the transmitter/receiver.
A few years ago MIT created a system for transferring power wirelessly???? im pretty sure Nikola Tesla created wireless energy in 1891
minu.14072 years ago
is there any formula to find out the number of turns of the transmitting and receiving coils used for wireless power transmission?
noaddict2 years ago
The MOSFET (IRF520N) heat's up very quick at 12V. Is this normal?
I didn't get it working yet.
ls12446782 years ago
May be someone already noticed. From looking at the picture. The way you connected the capacitor the value will be 0.005uF not 0.02uF. Looks like the value is not that critical.
thebfs2 years ago
it doesnt light when u turn it vertical because they recieve power best when they are on the same plane. the primary coil creates a magnetic field. but fields are not even they have gaps and fluctuations. the coils are more sympathetic? efficient parrellel to eachother (the secondary coil accepst the field of the primary better that way
wmiddleton2 years ago
hi, i'm liking this small DIY project :)
umm, what do i need to put in my mobile phone, mp3 etc. to charge it from the coils?
hello wmiddleton!!!
are you found the solution in your case???
my case like your case...
i hope u can share u solution to me...
thank you...
nzemke2 years ago
Ok so I get everything your trying to do but I'm confused as to what model of rectifier to use? Or if that is even what your using? I picked up a full wave brdge rectifier (GBL005) from that the correct thing to be using? Thanks ahead of time for taking the time to answer.
TNThieding2 years ago
I was very surprised I got this to work! Through the process of building, I was scared of power spreading all over and ruining electronic devices. In the end I was in awe!
hi sir can u give me the exact number of turns of your transmitter coil and receiver coil?? also with the dimension
robotkid249 (author)  TNThieding2 years ago
NeMewSys2 years ago
Hi, great article!!
Your 147.7 square wave AC signal generator just retired from the market, are there any alternatives?

How do you know wich capacitor to use to get that frequency? Could you show us the math?

Thanks ;)
there's a newer version of the kit that can still produce the same output:
hey i checked that link and that one was retired too anybody have suggestions?
Theres a possibility.
I haven't tried it yet but I plan on it.
I am also very interested in this.

Can someone point me in the direction of a kit I could use to generate the 149KHz signal?
hrishikeshp2 years ago
anyone know a function generator kit like the one mentioned above that is cheap, because the one oin his post is retired, and someone posted a newone, but it is also retired Please help!!!!
Hamayal2 years ago
Hi Robotkid249, I had just finised reading your article on, Wireless Electricity, and it was very well written, and the eagar to see it for my self, I tried building the model explained, seeing the success before me. It's great to see some one who takes pleasure in expiressing their knowledge with others, such as yourself. I wasnted to implement this concept, into another situation, in which I would like to power a 9V motor DC motor. What guage of wire would I require in the primary and secondary coils to do make this work smoothly, and how would I, in the future, be able to determine this on my own? Thanks, Hamayal.
mirtunio2 years ago
Hey I have a question, what are the cons if I use a 18 - 20Hz signal and what capacitance should I use on the receiver end?
robotkid249 (author)  mirtunio2 years ago
Your frequency is way too low to transfer power. It wouldn't work.
adilvij92 years ago
Hi, we want do this project but the problem is we don't know

which type of copper wires to be used, ( i.e thickness of wire)

what are the dimensions to be used please tel the length and breath

1) primary coil dimensions

2) secondary dimensions

and last thing is "how/ can we glow the led about 10 inches from primary coil ".

please help .we really want to do this . please answer ...
robotkid249 (author)  adilvij92 years ago
Ok, i'd say it would be pretty hard to light an l.e.d. from "10 inches" away. Inductive coupling is a very short range approach to wireless power. My only suggestions would be to increase the power of the primary coil, but not too much or you'll blow up the mosfet. The wire is called magnet wire, and its insulated with some invisible plastic stuff.

1) It's like 4 by 6 inches, and maybe 20 windings. 22 gauge.
2) It's about 20 windings and 3 by 4 inches. 30 gauge.
blob8002 years ago
Very nice instructable!

I'm interested in learning more about inductors, LC circuits, etc. Did you find any good books on these subjects? (where did you learn that you need a 147.7 kHz square wave AC signal)?
M-Taimoor2 years ago
I wanna know that which copper coils these are, are they insulated or wiring copper coils
robotkid249 (author)  M-Taimoor2 years ago
Magnet wire coils, with a coating
adas112 years ago
i interested in this topic.i am an electrical engineering student. plzz any one send me perfect list of equipments my mail id is
robotkid249 (author)  adas112 years ago
I added a new step!
MIT copied Nikola Tesla, big deal
NeMewSys2 years ago
Hi robotkid249, could you provide a more detailed schematic of the coil number one (the most complex), with the values and part names, like you did for the second one? Thanks! Great device :)
DixonLam2 years ago
Can i know the input voltage is 6volts in DC or AC??

I had run testing on this project topic also but i could not get a high output from the receiver part.
rr52 years ago
please help me..........can u tell how many turn in secondary coil ..? very urgent & want to prepare 4 exhibition
robotkid249 (author)  rr52 years ago
As long as everything is vibrating at the same frequency, the coils cal be any size, as long as they are large enough to gather the EMF waves. (See pictures)
markee22 years ago
Nice instructables! got some problem in freq matching. Got similar idea of the project and gives some formula of the frequency you wish to use depending on the available capacitor , inductor, and supply frequency you have.

F1=F2= 1/(2π√(L2*C2))

resonant transmission.jpg
dlinvega2 years ago
While I have no knowledge of electronics, this is a really good intensive to learn and so, I would like to figure it out and teach other beginners like me.

It would be really nice if you could begin the instructable with a list of items one will need.


- 1 x Function Generator kit [link]
- # x Capacit..
Alternatively you can by the kit [link]

Anywho, keep up the nice work!
It's wont open... could someone send me the PDF file please,
jkline32 years ago
Hi Can some please send me a exact list of componets and/or simpler instructions.

My email:
heh can any1 send me the a perfect list of components required for it
The faster the list gets to me the better...
plz help on...
tcanters2 years ago
GETPOWERPAD is selling this solution already! With a great design!
robotkid249 (author) 2 years ago
jmg12712 years ago
Tesla transmitted power wirelessly a century ago. Anyone ever heard of Colorado Springs? How about the tower he never finished in Shoreham, NY?
vernors R.A.T.M2 years ago
(removed by author or community request)
can you give us some sort of ratio of primary to secondary windings or how you wound yours as it would be of great help
GaryCifers3 years ago
This is an awesome instructable and all... The only issue I have is everyone saying that this is a "New" discovery... and that we don't have the resources of MIT... Tesla didn't have these resources and he made well as a one wire energy transfer cause J.P. morgan didn't like his wireless design... In fact he made a design to power an entire town by pulling energy out of the atmosphere sooooo... It's not a "new" technology... just saying
Got a schematic for Tesla's version, both the power source and the receiver?
robotkid249 (author)  endolith2 years ago
His design was basically resonance without a function generator, meaning it was very very inefficient. He was basically blasting out EMF, and I'm pretty sure all the people in the room that day got cancer from it...
RF doesn't cause cancer.

This is his drawing?

His secondaries have lots of turns, and then really large capacitor plates. Hmm.

"Liquified air"? For cooling? Or reducing conductivity?
robotkid249 (author)  GaryCifers2 years ago
I never said it was new, I just said that MIT did wireless power.
lee_y_l3 years ago
Can I know how is the theoretical calculation of power efficiency for this circuit? I only manage to get efficiency of roughly 30%. And my current on the input and output is very low. (uA). Then I used the Vrms from oscilloscope to mutiply with this current to get the power. Is my method correct or my connection has something wrong?
robotkid249 (author)  lee_y_l2 years ago
If you don't have a mosfet, then that efficiency is very good. Try adding a mosfet and amplify the current with about 12 volts to the mosfet and that should give you a better efficiency.

Good Job!
oakvillan2 years ago
Can the turns in the primary coil overlap?
Also, how would you wire the capacitors to the terminals in the output? Or do you need to in the first place?
robotkid249 (author)  oakvillan2 years ago
Yup, magnet wire is insulated... Capacitors help with resonance.
Exactly how would you go about doing that?
I know what a Joule Thief circuit is and how you make one, but I want to know how you would wire it if you were to actually replace the function generator with the circuit.
n_cleaner3 years ago
Can you tell me the company of MULTIMETER?
lee_y_l3 years ago
Can anyone give some advise on how the IRF520 mosfet should be connected to the circuit? Thank you.
robotkid249 (author)  lee_y_l3 years ago
New circuit diagram, yay!
I've tried with the new circuit diagram but seems like not much difference on the o/p power of the receiving side. Can i know how much voltage (DC?) are you feeding the MOSFET?
robotkid249 (author)  lee_y_l3 years ago
12 VDC from a wall plug. Make sure everything is hooked up, because you should see a major jump into primary coil current.
Light_Lab3 years ago
Just wondering does this set up produce much RF interference? A 147.7 Khz square wave should produce a whole family of odd harmonics eg 738.5 KHz, 1033.9 KHz, 1329.3 KHz, 1624.7 KHz which are through the AM radio band.

BTW Nicola Tesla did this wireless lighting trick in1894 a long time before MIT and I think even he was not the first.
robotkid249 (author)  Light_Lab3 years ago
Yup, a lot...
beehard443 years ago
will 60Hz work? because i can rip off the diodes from my wall wart and use the wires coming directly from the transformer to get 60hz square wave
no .60HZ not work,
lee_y_l3 years ago
Can anyone tell me how the IRF520 should be connected to the primary coil? Any circuit diagram?
mgercak3 years ago
Can I have like just a list of materials I need to buy in order to make one that can charge an Ipod or something? thanks, my email is The faster the list gets to me the better.
deqwer3 years ago
is it a good idea to connect the primary power source to the wire plug
we now use the wireless power for led lighting,You'll enjoy its convenience: Do not need to take out the rechargeable battery for it's energy, Do not need to recharge the battery when the battery runs out,Do not need to look for flashlight everywhere when you need it.It can be recharged with wireless power ,recharging processing that relies on automated and Intellectual recharging,which can prevent the battery over charged and over discharged
you can view our
Oldstudent3 years ago
your goal was to make this work for iPod that consume much power than lighting a LED.
iT is exciting to know you are testing on using a irf520 mosfet to amplify the power input from the function generator, which increase the secondary voltage tremendously.
is the test OK? Wonderful if you cna post some pics and circuit.
A brand-new product developed by our company: Wireless charging flashlight. You can view our It is the only type of flashlight that has a battery charged by a wireless charger. It is convenient, durable and cost-efficient, and it will become a star in the flashlight field. Compared with traditional flashlights, wireless charging flashlight has following incomparable advantages: 1. Timely charging. The wireless flashlight is place in a wireless charger when not in use. When it is used, it is always fully charged. Traditional flashlight is charged only when people notice that it gets dim or totally dark. Power is in shortage when it is needed! 2. Convenient charging. You don't need to care for its charging. What you have to do is: Take it when you use it and place it back (to the wireless charger) when you don't use it. Traditional flashlight is troublesome in charging. First you should take the battery out and then place it back to the flashlight when it is fully charged. 3: Intelligent and automatic charging. All batteries are subject to self-discharge. The wireless charger will supplement the power quantity automatically, which protects the battery absolutely from over charging or over discharging. Its gradual charging will lengthen the service life of batteries. Chargers and batteries of traditional flashlights are not stable in quality, which leads to unstable service life of batteries. 4: Totally sealed structure: It can be used in water or for diving as it does not have a charging hole and is controlled by magnetic switches. But like traditional battery, it is also convenient to change its battery. Having charging holes or contact switches, traditional flashlights are not air-tight and have low waterproof level.
wireless power led flashlight.jpg
hshafiq3 years ago
can i know why must the secondary coil smaller than the primary? what a good ratio between them?
because most the current thought the Receiver is low than the wireless power,
you can view our new led lighting which's rechargeable li-ion battery is powered by wireless power
wireless power led flashlight .jpg
lee_y_l3 years ago
I've some extra coaxial cable( in my house. Can I use the copper core in the center of the cable to be used as the primary and secondary windings? Is it true that the turns of the windings does not affect the efficiency and distance of the power transfer???
 I dislike the following fact: There is no single Radio Shack store anywhere in this country!!! There used to be one, but it's now gone. That means I can't get enough magnet wire for this. Yes, I do have some, but only 2 meters of the stuff. 

Bottom Line:
Is there any other source of magnet wire other than the internet?
I pull mine out of old CRTs. It takes a while, but you can pick them up at e-wastes for free.
that's problematic because there clearly aren't any e-waste piles around here.
I heard you can get magneticwire from taking apart a electric motor.
right... about that... We don't use or even have any large electric motors around here so getting lots of wire is still a problem
i believe you can also find it in tvs if you have any of those to take apart
everyone's TV's around here still works, so I won't be able to grab one and tear it apart (carefully).
uuh, go to a motor rewinding shop and ask for some electromagnet wire. They might ask you to pay for it, but maybe 50 pesos for a kilo or two.
Or get an old transformer and start removing the coils
Collect old DC adapter wall transformers, break off the plastic cover. (Value Village, Salvation Army usually has plenty.) Some iron transformer cores can be disassembled: use screwdriver, needlenose, visegrips, and pull off a few thin sheet laminations from both sides. They're soaked with hard varnish, just crack them apart with an old knife. This loosens it enough so you can disassemble the whole thing. You end up with a plastic spool of wire. The AC 120V winding has the thin stuff. (Some iron transformer cores are welded together, can't take any thin iron plates out. Discard, try another.)

Solenoids often cost $1 or $2 from online junk suppliers. Some types can easily be opened. Get the plastic spool of wire. Try these:

Or just buy a $16 spool of wire... (Brocott in UK)

Right on Bill.
And another great source of Cu wire of all sorts are old discarded CRT type TVs. The yoke around the tube usually contains 4 flat coils that are practically ready made for this Instructable. Just be sure the TV has been off for a long time because the old CRT TVs can sometimes store high voltages for days.
Oz TV's contain a massive transformer with several kilograms of copper wire that comes apart easily (US TVs usually had no transformer.)
i didn't know that. I guess i have some electromagnet wire to scavenge from my old CRT...
Yeah, the tube has been sitting for 2 weeks without the control elecs
quarter kilo of wire's gonna yeild like 50m, good enough
and whats the point of getting the electromagnet wire off solenoids, waste of resources and money
> whats the point of getting the electromagnet wire off solenoids, waste of

DON'T BUY NEW STUFF. Solenoid wire is recycled wire. Don't buy a new spool of wire if you can recycle. Don't let manufacturers discard unwanted solenoids. They're melt them down for scrap copper, which wastes all the time and cost in making the wire in the first place. Instead keep on buying lots of old junk from surplus catalogs.

Also, recycle the plastic spools from the solenoid solder in large bulk spools, and split it up into many small plastic spools.
if you take the average transformer, and boil it for 20 mins or so, it usually comes apart nice and easy, and allows you to custom re wind the transformer if need be.
not sure if it works out too green to boil transformers, but hey, it works!
I like what your saying and will include it in my decision making when I can still meet my critera and objective. Thanx for that reminder.
Sorry, it doesn't seem that clear to me :/ You could try looking for people throwing out old or broken CRTs, perhaps on the streets. I don't know if that's how it works where you live, but there's a pickup every few months around here. Eh, sometimes you have to get a bit inventive. But hey! That's the fun part!
I bought some wire from my local local electric motor rebuild shop. This can be a car starter rebuild shop. Ask them to sell you what you need. Many people
are willing to help but you need to understand the following friend.
I mean nothing personal but you shoot every idea down people give you. We all have become self reliant as possible but we all need direction time to time. Be patient and stay with a determination to find your source materials. Electric motors and basicaly anything you have to unwrap from an existing coil is a mess. But it will work well enough to see if your ideas work. Otherwise avoid it.
Well, that's the reality of my situation. I guess I'll settle for something else then. You do realize this chain has been going on for a really long time. I have other things at hand right now so can't pay attention to everything.
Internet if you dont have a credit card just get one of those prepaid ones
here two capacitor of value .01 uf are connected in parallel or series???????
can you tell me the number of turns in secondary coil and size of sec. coil.
also tell the exact no. of turns and size of primary coil
tcanters3 years ago
I really like the idea of wireless power! And it seems this technology is getting more and more common. Today I read in my local newspaper about GETPOWERPAD, this product enables you to charge your iPhone 3 or 4 wirelessly! I found it on
rajatrain3 years ago
can you give me inforamation that how much voltage and frequency can be apply during making of this circuit...
oranges0da3 years ago
If you are trying to obtain .02uF out of 2x .01uF capacitors, aren't you supposed to wire them in parallel?
mehmet0023 years ago
YA BEN TÜRKİYEDEN BAĞLANIYORUM RİCA ETSEM ŞU ADRESE adresine projenin türkçsini yollarmısınız
REA3 years ago
didnt the powermat an mygrid just copy this?
when u mean ac signal do u mean a 555 push pull circut cuz i what to build me own gnerator so i can put it in a nice box thankx :)
Hmmm... I have a concern: If this puts out an EM wave, is there any possibility of it disrupting/erasing HDD memory? If so, it's only safe for devices that use Flash Memory such as iPods and phones.
I'd LOVE to have one of these suckers for my laptop so I could get off the wire. T_T
kledi4 years ago
Tesla did this 100 years ago... mit didnt invent anything, they just copied some 100 year old circuit.
no he sent his 26 miles and lit 100 lightbulbs
(removed by author or community request)
 Tesla used currents sent through the ground to light the 100 lightbulbs, using something called "Terrestrial Stationary Waves." He also invented this, but it isn't the same instance.
No. This is not the same instance. You are right.
However this is still a transformer.
It uses inductance.
Tesla was a pioneer in this field. (no pun intended)
odamen3 years ago
pls can i know the power rating of the wireless power produced. 4 further messages send to
The Function Generator is out of stock :( so I look for another and I found this one, Can I use it too?
Would some pre-wound RFID coils suffice for the job??? :)
Great instructable!
What sort of current have you been able to get from the secondary?
is 300ma-500ma feasable? I'm considering using this to charge some Lithium Ion batteries for a project of mine..
memo26343 years ago
How do you go about choosing the frequency for the primary coil in the project? I'm assuming if the capacitor value is different, the frequency will be different as well.

Also you mention using nails on a 2x4 to wrap the wire into a coil. Is that done to keep the wire bunched in a tight group?

Based on the size of the coils, what kind of distance were you able reach? Lastly how many feet of wire did you end up using?

I'm working on a project for school that will implement this and it would help if I could get some quick help. Thanks
Websteria3 years ago
Is there a way to do this with a smaller amount of coil?
calidude893 years ago
Im very confused. Is the capacitance of the primpary supposed to be the same as the secondary coil? I only see one capacitor on the primpary. but you said you used 2 capacitors to make .02uf. Also the instructions differ from the pictures in value of capacitance. I purchased a function generator just for this project. I have 2 .01uf caps in series on my secondary coiil and 1 .01uf cap on my primary as shown in ur pictures, but it doesn't work.
Forgive me if this seems like a dumb question, but could you use this to charge a marine/car/motorcycle battery? I want to make a larger robot that can be charged without a complex dock. Thanks for the instructable btw! Awesome job!
redbloomer3 years ago
if you will notice..the two 0.01 uf caps are in series.. and it reads us 0.005 uf not 0.02uf.. i think he have done it as "trial and error " on his experiment.. and the description of the number of turns for the primary and secondary is not properly discussed..and i think on step 6 , he includes a joule theif because he wants to have a larger voltage output that can be up to 5 volts.. actually it only reads 5 volts when it doesnt have a load. on his experiment he only have a led that only works for just a couple of miliiamps..eheheh... sir if you actually wound the primary and secondary coils a couple of hundreds of turns of wire . you will desirably achieve the voltage and current output you want..
robotkid249 (author) 3 years ago
Would anyone be interested in wireless data transfer using inductive coupling? I'm seeing a few comments about it here, and I need some motivation from you guys if your interested. The plan is to transfer some type of data using inductive coupling from about 3 inches away. Applications might include a mouse that is powered by a pad, but is also able to communicate with the pad, and can infer data. The applications are awesome, and I'm sure that i can make a system that does it. I just want to know if i should make an instructable on it? Anyone like the idea?
redbloomer3 years ago
dude i've been inspired by your so i decided to do something like that. and i successfully made it.. thanks for your ideas..
The only problem for a while, is that the function generators at Sparkfun are on backorder and won't be available for some time due to their production manager being gone. It is supposed to be several months until he's back.
tanvisarin3 years ago
m wrking on a similar circuit for a mobile battery charger dat i neeed 2W power...which m nt result so far is 5v with 100 ohm resistance 1.e only 250 mW....please help me ....itz very urgent could you please mail me
Cross_3 years ago
Any update on the data transfer instructable you were working on ?
ASCAS3 years ago
Does this have enough power to charge a cellphone wirlessly.
rafitf3 years ago
for that theoretical circuit I would add something like a simple switcher PSU instead of a regulator since the regulator is pretty bad with efficiency 
robotkid249 (author) 3 years ago
You can scavenge magnet wire from all most ALL electronic circuits, from transformers, motors, and computer hard drives and stuff.
-max-4 years ago
i figured out i can make wireless electricly with a transformer and a cristal set LED.  

the transmitter was just a step up transformer connected then diconnected to a battery!

 the recever was a led connected in parrelel with a 1N34A diode as my "cristal set." one end of the the led or Ne2 light woud flash!
fitousa -max-4 years ago
Hello Powermax,

Can you be more specific? Can you explain on the step-up transformer side? Transformers are supposed to work on AC, but you mention it was connected to a battery. So I assume you were manually turning ON and OFF at a very high rate, correct?

Second, on the receiver side I guess you had both anodes connected together and both cathodes together. You do not mentioned the secondary coil, but i assumed you hooked up each end of the coil to both diodes. Is that correct? Or did you go with no secondary coil when using
the diode?
By the way, how many turns in your circuit?
-max- fitousa4 years ago
sorry for confusion.on the transformer high voltage side, besides an antenna to one lead , and ground to the other, nothing...  also, i think the polarity of the 1n34a diode & LED didn't matter...

u can use a oscillator on the transformer side if you like.. and the transformer i used was from a wall adapter (or a mains transformer) but it really doesn't matter as long is it gives off over 80 volts or a painful shock!

NNOOOOOOOO!! there are two separate circuits!!

check out the two schematics  |

                      ant                            )  ||     __________
                         |                              )  ||   (                       |
            /---------------------|              )  ||   (                       |  
         LED                  diode           )  ||   (____battery_/
            |____________|              )  ||
                           |                           |
                       GRD                   GRD

wireless energy.bmp
i hope this answers your questions  =D

what's the extra hardware for?
for converting the ac input current into dc allowing you to connect cellphones, ipods and other dc appliances to the coil (it has its limitations)
 ok, so I don't need to build that because I'm building a wireless batterie free mouse and pad.
computer mice are dc!!!!!!
TS19904 years ago
this instructable interesting and I am trying to build one one my own. I am just a beginner and I have some questions, would you please help me out?
Q1. why did you choose 147.7 kHz for the frequency?
Q2. you said the two coils should be in tune, what is it that affects the frequency of the secondary coil?
Q3. what waveform comes out from the other end, is it sawtooth or something else?
Q4. how efficient it is?

thanks :)
diametal4 years ago

I have  a Q....

How can i figure out the number of coils?

I guess there is an interrelation of this...

But I couldn`t find it. 

I am going to use a 24AWG wire for my lab.

But I don`t know how to calculate the inductance value of the wire

please..!! somebody helps me out.... 

Dr.Bill4 years ago

Coils, as antennas, are polarized either horozontal or vertical. Turn the 2 meter antenna horozontal and your transmitted radio signal will be bad on the verticaly  polarized receiving end. 

A radio signal rotates as it travels from point 'A' to point 'B'.

You could take an HF transmitting radio antenna and hang the antenna so the elements pointed vertically, UP and DOWN. The received signal on the other side of the world will be just as good as if the transmitting antenna were hung so the elements were horozontal because the radio signal Rotates. Distance is the key here. 2 Meter radio does not go as far on earth as HF radio does.

This is on of the coolest subjects. Your coil is in fact a kind of radio transmitter. In fact you have tuned your coil to a radio frequency.

Go take the Amateur Radio Test now and become a Ham.

BOOOM! Dr.Bill4 years ago
While this may emit radio waves, it is not the principal method of power transfer. This particular setup is using inductive coupling
Dr.Bill BOOOM!4 years ago
Fine.  Turn your coils 90 degrees to each other and see how little 'Power' is transmitted via inductive coupling. Also the direction your coils are wound in relation to each other will make a difference. A study of crystal radio will reveal more on this.
A number of years ago there was an experiment Transmitting electricity from one mountain ridge to another using Microwaves to light a tower of tungsten light bulbs that was successful. Microwave energy is RF. So radio waves can carry electric current. All I was saying was if you turn the transmitting antenna, like the coil, 90 degrees to the other energy transfer will diminish whether it is magnetic or electric.

Don't get me wrong, I think this is a very cool 'ible and I have seen products like this now for sale. Very cool 'ible.

BOOOM! Dr.Bill4 years ago
"Fine.  Turn your coils 90 degrees to each other and see how little 'Power' is transmitted via inductive coupling. Also the direction your coils are wound in relation to each other will make a difference. A study of crystal radio will reveal more on this. "

First of all, magnetic fields are directional, so turning the coils will have an effect, does not prove that this is using radio waves

Second, The direction of coil winding will have no effect whatsoever, the only difference is that the voltage will be 180 degrees off what it would be otherwise

Third, crystal radio sets have nothing to do with coils interacting with each other.

"A number of years ago there was an experiment Transmitting electricity from one mountain ridge to another using Microwaves to light a tower of tungsten light bulbs that was successful. Microwave energy is RF. So radio waves can carry electric current. All I was saying was if you turn the transmitting antenna, like the coil, 90 degrees to the other energy transfer will diminish whether it is
magnetic or electric."

Your statement proves nothing, i never said you couldn't transfer power using radio waves, i said that this setup didn't, which you said it did.

"Turn the 2 meter antenna horozontal and your transmitted radio signal will be bad on the verticaly  polarized receiving end"

ubr.bzkr BOOOM!4 years ago
Yes it uses the magnetic field to transfer energy, not an electric field like with radio.
Dr.Bill Dr.Bill4 years ago
Oh yeah. A Variable Frequency Oscillator (VFO) would allow you to tune to any freq., you wanted to use.
Dr.Bill4 years ago
Electric power has been transmitted over distances with the use of microwave energy. Basically a radio transmitter. That was dond a number of years ago between two mtn ridges a mile apart. We all know what Tesla did and proposed to do. He was short circuited by Westinghouse, GE, Edisonand so on. My point is that this is only new again because people like you are interested in radio whether you know it or not.

Get your ham licencees. All of you. You'll see. Doors will open for you.

Well although what you say about microwave and radio energy transfer is true its not a very viable solution for transferring usable or large amounts of power for any type of consumer application. strong electric fields are unfortunately dangerous and  have been proven to cause cancer in excessive amounts (ie: X-rays and gamma rays) because of this they are only useful for transmitting small amounts of power like radios (why you cant just run your radio off of the radio wave energy that it revives, it may be transmitted in kilo-volts but by the time it gets to your radio it could have decayed down to only picovolts and is only useful as a signal :! ). luckily, magnetic fields have little effect on biological organisms so they are safe to transmit energy with, its just a matter of manipulating the magnetic field to get the most energy and range out of it.
Actually I do run my radio off transmitted RF.

******** It is called Crystal Radio. *********
I receive enough power to light an LED.

In the 50's there were plans to light homes with flourescent tubes but for the reasons you espoused (medical) they were scrapped.
won't the magnetic field screw the memory of an mp3 player or something?
(removed by author or community request)
 So my c200 Sansa won't be affected by it?
Yours Sansa C200 will be safe seeing as it is a solid state memory device so you can use this tech. with out erasing your MP3.
awesome! I think I might make one of these then!
 ipod touch 2g work? yes or no
should if made right
are you sure cuz i think touches use a hard drive?
I can assure u it has flash memory
THat being said i dont actually own one, but i'd like to.

 ok  thanks abunch
 It takes a significantly strong magnetic field (such as a lab deguasser) to do any 'damage' to hard drive memory mediums. 

I would be more worried about the RF noise this thing is emitting. 

06-04894 years ago
can the range be increased? it posible to increase it to about 1meter or longer?.
yes the higher the frequency the longer the range
gato667a4 years ago
i dont know what to use for a generator so am going to use my ps2 generator,it should work and i think probably why it doesnt work verticle is because the way u put the wire together their on top of each other not next to each other,well i think so cuz in all my classes i always see the wires of coils next to each other and not on top of each other.
mspark4004 years ago
Excellent design and instructable!

I have just recently designed a device that used many of these principals. My "leech" is designed to magnetically attach to the mounting screws of my universities rfid card reader system and use a coil to collect the energy that it is transmitting. Even without proper tuning it works quite effectively. As it is set up now, it charges a large capacitor which can (when I wire it to) use to power a usb device such as an ipod with a regulator etc. Now of course its not "free" energy since the existence of my coil puts load on the the rfid system and makes it work harder. However it's a very convenient way to grab a little juice around campus without a laptop or outlet present.  Hopefully I will finish the redefining and put up my 'ible soon.
[AV3NG3R]4 years ago

Transmitting data over inductive coupling sounds a bit tricky, considering every conductor with any sort of current  flowing through it will give off considerable electromagnetic interference.

samr37l4 years ago
I'm going to steer away from Tesla and MIT. How would I make a bigger and high power coil? Could I send wall power over this coil? if I could, can someone please give me instructions on how to do this? Thanks!
most devices these days charge on 5-6 volts. you could use one of the wall adapters to take the voltage down and could use different size coils for the different devices. you would need to know the pinouts for all of the devices you want to adapt. Go to your web browser address bar and type in "pinout for (insert device name here be as specific as you can)" without the parenthesis or quotation marks. this should take you to a site that tells you the pinout, the voltage needed to charge it, and what pins and resistors to use. if i were you i would put two coils, one where the walls meet the ceiling and where they meet the floor or wrap it all the wayaround your room if you don't care for looks.. before you hook anything up, you should test with a volt meter to make sure you're using the right voltage and amperage. this would be very expensive, as it would use a LOT of magnet wire. the rectifier would be built into the device, as it takes AC to make a good wireless transformer. you could also get a 12-110V inverter to power it, but it might not work as well as the wall outlet, even though it's pretty much the same.
dear  sir,
if it possible to send me the complete primary circuit and to describe the elements used in this circuit(simulation).
thanx Mr. tanmanknex
one more thing, you might want the FCC&FDA to approve this because of the radiation from it...
Dr.Bill samr37l4 years ago
Ya can't steer away from Tesla. You will just be reinventing the wheel. Tesla is our teacher.
that would, as u said, require a much larger coil with lots of complicated circuitry to produce the exact wave specifications required for this form of power transfer. If u are doing this, i would recommend using the loads of magnet wire u need to outline the entire perimeter of ur room on the floor, meaning that the wire should go where the walls and floor meet. That would be like super cool though, cuz then u could like automatically charge ur cell phone by just walking into ur room, and using very little circuitry on the phone itself, so it would just be a little snap in adapter, much like those bluetooth adapters for the ipod that snap into its docking station port I wish u the best of luck on this project and plz post pics if possible!
Thanks guys! I was just thinking of building it into a night stand or a table. Is there a way to run wall power to the coil? Because the square wave thing that the guy uses in the project will only give off 0-6v, and I need 50-100 to charge the devices. Thanks!
yeah, just use the wall directly. what devices are you charging?
i disagree with that logic because most devices, such as ipods and cell phones are charged through a wall wart, which knocks that 100v own to 12v or under in most cases For example, my env2 charger gives off 5.1 volts and my sansa express mp3 player charges from standard 5v usb power. Unless u want to power an entire desk lamp or something of that nature, 50-100v will not be neccesary at all
 can you give me instructions on the plug from the generator?
can you conect the generator to a usb plug?

please answer me soon
 I'm building a wireless mouse with a pad that will have the generator and coil.
robotkid249 (author)  happybuilder4 years ago
 It is a wall wart that plugs into AC wall power and rectifies it into 12V DC. I am not sure if 5 volts will be sufficient.
 so did you need it to just light the LED?
 (I'm a beginner at this)
raykholo4 years ago
 so, essentially, i could use this to wirelessly power a microcontrolled led blinker?
if I put the large coil inside a nice box and then the microcontroller circuit could be nicely  put on top of the box?
NeMewSys4 years ago
Can someone tell to a noob like my how do you know what frequency to use, how capacitance, what is this coupling and why is it achieved this way?
Jodex4 years ago
Now everyone should make big coils around their houses and replace the power plug of the devices with a coil! Well, it would be dangerous after a long time.. And won't probaply work : D BUT you COULD make a charging room to your house. ;-D You'd probaply understand ;-D

This is great!
ubr.bzkr Jodex4 years ago
Well if you use magnetic fields it wouldn't be dangerous and it could work. look up MIT's Witricity or e-coupled wireless power.
thexplanet4 years ago
I think i have seen these windings, in an Access Card from Honeywell or HID?

are they the same? or you made it, and did u use any enamel coating or varnish for the same, or is it just the Magnetic core wire?
the windings you saw in the access card were likly likerly thoes of anRFID tag used to identify the card. an electric field is passed through the winding and it creates a radio signal at a specific frequency or amplitude which is unique to that RFID chip and is picked up by a nearby reviver which identify's the card. first of all the windings in the card are very small and are basically circuit board wire so they are non removable. The wire that this guy is using is enamel coated magnet wire which you can pick up in a 3 pack at radio shack or buy on line in bulk. (i recommend 1lb spools and that is PLENTY)
KeviBear4 years ago
 Where the LED is this picture is, couldn't you just attach a female usb port instead and then be able to charge ipods? Or would you need to add a 5v regulator somewhere so you don't over charge it and kill the battery?
What i will do with mine is try to get the secondary coil to output 3 volts to emulate 2 AA batteries and then hook it up to my minty boost usb charger kit (Ada-fruit kit) and see if that will charge my stuff. its already a small neat package, works on my usb stuff, and will make a nice, neat demonstration piece. I just hope the amperage will be correct also. might take some calculations though :$ .
ubr.bzkr4 years ago
Anyone know how to calculate the mutual inductance and the capacitance of the coils? apparently in order to make them resonant you must tune them until they exhibit mutual inductance and capacitance. (I know that calculating the capacitance of a coil means calculating the capacitance between every point in the loop giving you the capacitance of one loop, multiplied by the number of loops in the coil but I cant find the equation for it.) if this is done the range and efficiency of the energy transfer will be significantly increased. this is also why MIT's Witricity is a bit more complicated then the simple inductive transfer shown in this 'ible.

I am building this for my high school senior project on wireless energy so any help would be greatly appreciated as I would like to optimize the resonance of this circuit as much as possible.. (and you will get to mentioned on my works cited page WooHoo!)
in the circuit used in primary coil, what are the 5 ICs used? pls answer asap...
we'll gonna do this as investigatory project...
arhodes184 years ago
 If you make this to operate at resonance it would be way more efficient... But great instructable nonetheless!
Zaeem Sagri4 years ago
i wanted to find out. if you were to put this experiment into a question what would it be? there are so many variables to be put into the question........

pipponum14 years ago
the led doesn't light because the two coils don't have the same polarization. moreover the maximum magnetic field is in the middle of the coil (if you try to take the secondary coil next to the border of the primary coil you will see that the range is decreased).
One question: you said that you needed a 0.02uF capacitor so you put together two 0.01uF capacitors. But in the picture it seems that the capacitors are put in series, so the total capacitance is 0.005uF, not 0.02uF. Is that true? are they in parallel?
Moreover do you have an oscilloscope? it would be nice if you post the shape of the received wave.
Thank you
Algag4 years ago
 anyone thats metric (even though I'm not) the measurements of the 2 by 4 he is talking about is 38*89 (millimeters) 
gxb54434 years ago
how big did u make the coil?
Algag gxb54434 years ago
 as big as you want, i would say about 6 by 12 (inches) but you cant do that on a 2by4....well obviously
koopatroopa4 years ago
is there anything inside the coild? is it and electro magnet?
 a coil of wire with energy running through it creates an electromagnetic field

sk.mobeen4 years ago
what do you mean by 2x4....can u specify sizes in centi-metres or inches for both primary and secondary coils. for ex....primary(10cms x 5cms). please HELP.
Algag sk.mobeen4 years ago
 look at my above message

robotkid249 (author) 4 years ago
When i said 2 x 4 i mean nails on a 2 by four as on a piece of wood.
2 inch by 4 inch??? what abt secondary coil....dimensions?? THANK YOU VERY MUCH
Algag sk.mobeen4 years ago
 a two by four is a peice of wood that is 2 in high and 4 in wide then it is so many feet long (you would chose) he is just using this as a base to put the nails in, then your wrap the wire around the nails like a pegboard
robotkid249 (author) 4 years ago
Okay, I need a little help now, funny. If someone could help me solve this dilemma, it would be greatly appreciated. 1. The LED on the secondary coil blinks. Can some one please explain this, and how can i prevent this. 2. The LED on the secondary coil does not light of when the secondary coil is horizontal. Why is this? Again, any answers would be greatly appreciated.
for the horizontal problem,

refer the Lorrentz force, it is due to Magnetic coupling: google and u may find the answer.
well i tried it...its working fine. Thanks. Coming to ur Qn. i didnot get any blinks.Well i think u might have prob of dry solder. The shape of antenna we are using is RECTANGULAR(which is directional antenna unlike circular, which is omni directional)..and if u take a look at the field pattern of Rectangular antenna u can easily understand why is it happening.Well my previous explanation of "we get output only when magnetic lines from primary cuts the secondary at 90 degs the amt of lines cutting the sec coil is minimum..hence LED will not light at that position." is also true. Refer the working of simple motor(esp the inner coil rotation).
mine system also blinked now but its ok now as i resoldered it. u too try.
1 maybe because of some kind of weird resonance of the secondary circuit, the circuit gets in resonance and then out of it again. 2 It normally shouldn’t. It is normal. The electromagnetic field can’t interact with it.
Does it blink rapidly?
1.may be a loose contact or battery prob or LED receiving less current or frequency of current received by LED is low(and also not DC).... it may also be due to ur joule-thief.... 2.its a rule that coils should not be at 90 degrees (we get output only when magnetic lines from primary cuts the secondary at 90 degs the amt of lines cutting the sec coil is minimum..hence LED will not light at that position.) JUST GUESS DONNO WETHER ITS RITE.....Forgive me if i misled you.
hafeez cool4 years ago
really nice keep the good work up. 
what if the smaller coil is placed inside a wireless mouse and the larger coil is placed under the mouse pad?  never mind what if the, real question is why not?
 or built into the mouse be the mouse pad, just one big coil
 I think I might try that, once I get the supplies.
vbman114 years ago
 could you supply the formulas for the capacitance<-kHz? A bunch of people have asked fo the formulas.
 um, whats the mathematic relation between the gauge of the wire, # of turns, size/shape of the coil, frequency and capacitance? or were I can find it?
ARRL 888-2775289 Toll Free
Dr.Bill Dr.Bill4 years ago
robotkid249 (author) 4 years ago
I want to remind people that this is electromagnetism not magnetism...
Pure and simple, this is radio.
KeviBear4 years ago
I will start off by saying i absolutely admire and love the idea of wireless power and i will hopefully get to make one from this instructable but i have one question, well at least a short series of questions. 1. What do i need to modify this and make it charge portable devices(iPods, Cell phones, ect.)? 2. How would i do this? I really hate to ask questions like this but i didn't understand the last part.
thexplanet4 years ago
hey gr8 work!!


well I have 2 things to ask, if you can answer:-

1>What is the use of Signal generator / or the Circuit u have attached, cant u use the stereo /mono output from the soundcard using a software like audio toolbox?

2>and what is the Amperage you are getting at the output side?
how do you calculate regarding how much you need at the output?? any formulas.
suppose I need for a mobile  to charge with input of 5V dc, and 550mA?
so, then how do i build this up?

Thanks in advance
If the same capacitor is used for both coils, wouldn't both coils have to have the same inductance in order to resonate at the same resonant frequency?
zack2474 years ago
ok. two questions:
1- can copper wire (also known as craft wire for some reason) be usd instead?
2- do i really need the power thingamajig for the larger coil?

awesome instructable, saw a commercial for something like this, just thought it was a heap of bs, now i understand
The wire needs to be insulated, which is why magnet wire has a thin coating of lacquer on it.  If the wire isn't insulated, then you are basically shorting out your coil over its entire length, and you won't be generating a magnetic field.
so i could use regular wire if i wanted to? just as long as it doesn't short out, i can use it. ok thanks
 As long as it's insulated, yes...regular wire will work.  It just won't be quite as efficient or compact as magnet wire would be.  That said, you can still get decent results from regular insulated wire.  I remember making a fairly powerful bar electromagnet when I was a kid, using either 14- or 16-gauge solid core wire.   I forget which gauge wire I used, or how many turns it was (this was a LONG time ago!), but I know it was quite a bit of wire wrapped around an iron rod about a foot long.
XTTX4 years ago
connecting two 0.01uF capacitors in series will give you .005uF not .02uF. You need to connect them in parallel.
pedroion XTTX4 years ago
Man, this was today's topic at school!
I'm so happy right now.

BTW: it's true.
XTTX pedroion4 years ago
Stay in school kids :D. I also learned it from my physics class a few months back.
knoxarama XTTX4 years ago
yes, and i've learned more about technology, biology, all that stuff outside of school. really, there isn't anything that you learn in school that a good apprenticeship wouldn't do better, just because it would be more focused into one job, specifialy (unless that job was to do many jobs) and everyone would be more efficient. then, advancement would speed up greatly and overall everything would work our better. School is therfore not the best option. even without apprenticeship, many schools are incompetent.
I agree!!! We should get someone to set up a self guided learning school and compare the test scores of the same grades. Like, we could teach them to read and write and then let them go free. That'd be the best...
This web site kinda sorta resembles a self guided school. Don't it. Mo Bettah to leave the Test Scores and competition at the schools and keep this fun and at the same time learn all kinds of stuff they will never teach you at school. I dare say that every person here knows more than the ones that are not. I have seen some pretty cool stuff here that I never saw in school. When I was 15 I built a Heilium Neon Laser and brought it to school and was lambasted for bringing such a dangerous thing to school. My school had a very closed mind. This place does not.
i hate the weapon policie. A pencil is more of a weapon than pliers.... but which do they allow? if only i was around when you could still bring guns before all those 'gangsters' or whatever started shooting everyone. I hope they realize that them agaainst the police, they would lose. Really, them against anyone with any gun, they would lose. From what i've seen, they can only hit something if they blow off ten rounds. Kill them all.
My LASER was not a weapon in 1968. What I had to deal with was a school full of closed minded teachers that knew I was not rich enough. I grew up in a wealthy town full of stuck-up snots.
most of the people i go to school with are stuck up snobs. even the ones who aren't rich. the rich people are kind of weird, they contribute the leat to town things. that's probably how they got rich, along with not tipping the waiter. i'm still telling them pencils are more dangerous than a laser pointer.
My home town was Darien, Connecticut. The people there are so stuck-up they walk around town with their noses so high up in the air (cause its free) they got to be careful when it rains they might drown. If they did they would be doing the world a favor.
maybe they'll develope neck problems from having their necks bent up like that.
WOW. It started with the properties of capacitors, and now it's about neck problems. lol
It's the power of the internets, brother. NAO STRAT FLOODING!111
 1 and 2... again
Today my weapon of choice is radio.
bash them in the head with it while listening to 'the drive'.
Mine is a transmitter. I will be supplying 2 way communications to the fighters when the Revolution Happens
I would have to agree with you, Im home educated and i wouldnt have known anything about electronics or other things if i stayed in.
Of course you learn more from a apprenticeship, but it's much harder to have one.
I was surprised to see something REAL from school. It's hard to use anything you learned there in real life, you know?
very true
lets not get off topic now...
Did your teacher demonstrate. If so, How? I would have liked to have seen that.
Unit042 XTTX4 years ago
Parallel does double capacitance, but series does not half total capacitance. The series capacitance becomes the equivalent of the smallest capacitor in the chain. (Or, at least, vwery close. See wikipedia for the math equation)
DavyBaby XTTX4 years ago
10 out of ten my good man. XTTX is on the money. Caps do not behave like resistors when connected in series or parallel but the inverse. Just switch around the formula. Great Instructable!!!!!
brunoip4 years ago
Awesome !!!
robotkid249 (author) 4 years ago
Sorry for the confusion the theoretical circuit diagram is only a ac to dc converter. The secondary circuit goes to the input of the ac to dc converter. I will post a different schematic showing all of the circuitry tomarow.
Would using this to charge an ipod touch a/o cell phone be too risky? doesn't magnetism ruin things like that? also, what would i have to do to get it to work for me?
cell phone should be ok but i still wouldn't do it but ipod touch or any ipod is a horrible idea (some have harddrives)
 Only the iPod mini and the iPod photo have hard drives. Unless, you have an old Classic. 
Ipod classic has also a hard drive...
also Ipod video V5 and older....
so I have had 2 ipods and both have had hard drives... so you can´t say that only the ipod mini and photo have hard drives...
if it's lagrer than 20gb it probobly has a hard drive...

What I mean is, the Mini and Photo are the only ones that weren't upgraded to flash memory. That's why I said have not had.
all of the newer ones are flash but i'm going to do it to cell phone only (probably) seeing as i already have a good charger for my ipod.
mattccc4 years ago
whats the length of wire you used for the primary and secondary coil?
zack247 mattccc4 years ago
im not sure if it matters, just as long as its a coil, and not a lump of wire
breadpig4 years ago

can anyone advise me how to determine the mutual inductance of two coils and coupling factor? can share with me any papers on those infomation?anyone did antenna radiation simulation for the coils?

pls advise me :(
cool project..i am doing this..what are the number of turns of secondary..i have 0.22uf capacitor instead of 0.022uf ...can any tell me about the no.of secondary turns and the value of frequency that must be set for this capacitance..does the led be capable of handling secondary current..please tell me the rating of secondary and frequency range.....
This is really cool, I had no idea it was so simple!

I've got a few questions, if one could get this circuit to resonate properly, how much current could you get? Would the output current diminish over distance(or would the voltage diminish)? Since this is esentially an air coil transformer, are the rules similar to ordinary transformers?

breadpig4 years ago
Hi anyone who has access to this pdf file can share with me?im doing my final year project on handphone charger. I have some problems with the coil, anyone can advise me? like which equation to use, how to determine the inductance without LCR meter? :(

Elite LED4 years ago
 I would like to say thanks for posting this.  Its been awhile since I've been on instructables, but last May/June we had a final project for AP Physics and my group decided to use this (build, explain it, modify it, etc).  It turned out great!  We got a 97 on the project.  Actually found out that you can just throw the entire thing in water without putting it in a plastic baggy (except the amplifier and alternator of course).  The only thing is the LED corroded and fell off.  But again this works just like you said it would/ THANKS!
tbird450394 years ago
you ever heard of a tesla coil. its basicaly the same thing but you can transfer electricity much farther distances.
Do you think this could work on a larger scale?
Say, a 1.5x2 ft outer coil with a 1x2 in inner coil.
And if it did could power be transmitted no matter where it is placed in the coil? (Perhaps use multiple outer coils)
and would that power something along the lines of a zip zap or other small car?
marzban1234 years ago
what is the power output on the secondary coil? could one use a 5v regulator to charge an ipod or is there not enough power. how does one adjust the power output of the function generator?
The power depends on how efficient your circuits are at transmitting the power.   The volts will be a function of the ratio of turns in your primary coil and your secondary, as well as how close to resonance the primary is ringing.  which direction the  coils are facing and how far apart they are will also factor in on the power. 
idogis14 years ago
So, what's the capacitor for? You said that it is necessary for magnetic resonance, but what does that mean?
This is a simple parallel inductor-capacitor (LC) resonant circuit.  For every combination of inductance and capacitance in parallel, there is a certain frequency where the circuit will resonate, i.e. there is the largest current around the loop containing the inductor and capacitor.  More current is good in this case.
hubi4 years ago
Very cool demonstration.
Seems it is a kind of Tesla´s wireless energy transmission with resonant coils.
short time ago i disassebled my old electric toothbrush it uses the same kind of technology for wireless charging.
I have not yet a purpose for it, but when i find one i will let you know.
greets Hubert
hubi hubi4 years ago
Please don´t try this with rectangle waves, you should make a lot of distortion in the RF band because of the harmonics, i have always tried so, got a 20Watt halogen bulb to light, but  there was no radio or tv functioning in the neighbourhood. by filtering the harmonics with a double t- filter or using a sine wave for the feed there were no more distortions.
As coil i used a flat pancake coil.
If you get enough power into it and no load at thesecondary, you can see tiny sparks on the sec, also if i pump ca. 80 W into it, neonligts up to 3m away will light.
to get enough power into it use a rectangle generator + driver + MOSFet H-bridge like used for Solid State Tesla coils or induction heating. you can find a good explanation of these drivers on richie burnettes site.
Unit0424 years ago
Uhhhh.... wifi and wireless power are both radio frequency electromagnetic radiation, both are affected by obstacles in the way, but wifi is lower power (less range) and higher frequency (higher tendency to bounce away).
Don't try to power your whole house with this, as a number of possible effects could occur:
1.There is energy lost in the transfer from electric current to an electromagnetic field and again from magnetic field to electric current. Much less effieciency than a straight wire.
2. Metal things (ferrous metals, in particular, along with neodymium magnets) could start vibrating at the frequency of your transmitting coil.
3. Following idea 2 further, there could be residual voltages built up/stored in anything conductive. Possible shocking hazard, but as long as it's below 35 volts or so, you should be OK.
4.Computers, cell phones, pacemakers, anything sensitive to large amounts of magnetic fields will not work, unless properly shielded.
("Um, Grandpa? Don't come to my house, because I turned it into a giant solenoid....")
5. Landline phones are robust, but a strong, pulsing electromagnetic field near your house's phone line may cause phone conversations to turn into a contest to see who can yell "what?" the loudest.

But an upside is: this is way cooler!

Also: would you need a full wave bridge rectifier to get double the current coming from the oscillating LC tank circuit? Is the capacitor really needed for general power transfer purposes(aside from creating a resonant frequency)? I'm gonna get my circuit simulator out....

 Wifi, in the 2.4Ghz, is microwave radiation (a specific band of electromagnetic radiation).  Microwaves are absorbed by water (as well as fats and sugar), which is why they're so useful in heating food.  Part of why WiFi uses microwaves is that the range is limited by the water in the atmosphere, so a small range of frequencies can be used for personal networks all over the place without much interference. Different frequencies of electromagnetic radiation can interact with materials differently.  Water is transparent to light (human visible spectrum of electromagnetic radiation), but opaque to microwaves. 
Unit042 Unit0424 years ago
Oh, wait, picture three of step 5 has the diode bridge. Sorry.
zygomatic4 years ago
Not sure if anyone's posted about why your secondary produces no voltage when oriented vertically, but it's simply Gauss' law.  Simply, your primary coil is creating a magnetic field, which flows through the center of the coil, creating a roughly toroidal magnetic field. 

Phi = Magnetic Flux (a vector quantity)
B = Magnetic Flux Density (a vector quantity)
A = Area
Theta = Angle between the coils

Phi = B * A * cos(Theta)

And when vertical, cosine of 90° is 0, you get no magnetic flux and therefore no current in the secondary.
efox4 years ago
 thats pretty cool.

seems to me like all this really is just a transformer ripped apart (with some obvious changes), but the principle is between this and a transformer is essentially the same.

good work tho 
mattccc4 years ago
it looks like your on
Magnet_Dude4 years ago
are the capacitors necessary for this to work??
shams4 years ago
whats the voltage on your primary ?.....I want make a higher power one........I am thinking of using the electronic ballast of an flurosent is rated 40 watt and also what do you think ?...will it work ??
gripen40k shams4 years ago
PLEASE, do NOT use the high-voltage ballast for this project, unless you have some sort of background in electronics.

I'm an electrical engineer and even I would be afraid of running high voltage through any coils that I make by hand. The chances for failure are massive for a number of reasons.

Just don't do it, for your own safety :)
shams gripen40k4 years ago
no I know something about electronics.....I ve made arc speaker with tl 494,amps,smps psu any many small I was jst asking that if u have tried it with any ballast or there is any chance that it will work cuz I can make some big arcs with a ballast nd flyback......
gripen40k shams4 years ago
Here's the thing though; the fly-wire you will use to make the loop has really thin insulation. Putting too much voltage through it will generate too much current and it may melt the wire/insulation. This will either cause a fire which would be bad, or burn out the ballast (if it doesn't have protection, no idea if they do or not). It's just too risky given that with no secondary coil you are basically driving a high voltage through a short-circuited wire.

Plus I don't know much about ballasts, but don't they output a sine wave? That wouldn't be usefull in this project. Part of the reason why it works is because you are causing 'ringing' in the coil, or overdriving it, by using a square wave. A sine wave probably wouldn't give you the same effect (although it would make a nice inductive couple without any resonant effects).

Now, having said that, there is something neat you can see in terms of spark-gaps. If you have an oscilliscope then you can put a really long wire on the input (without the grounded sheilding) and then make a large arc or spark nearby. You can see a large jump in voltage on the input to the scope. This is because the spark makes radio waves and the long wire on the scope picks them up; and is also another method for energy transfer (kinda, just without the spark part and dedicated electronics instead :P ).
Mr.NHRA4 years ago
 This is great. Have you heard of the Power Pad? All you need is a battery from Power Pad then you set your wireless devices on it and it charges them... without a cord. Great ible!
arhodes184 years ago
 I found a very easy to do function generator using 2 op amps... but im not sure how to "hook it up" to the primary coil, and how to tune it to exactly the right frequency, can you help?? here is the function generator... its at the top of page 9. thanks in advance!
BTW I love the idea of transmitting data over the inductive coupling, how do i subscribe?
godoggie4 years ago
Nice Instrutable! Very well done!
will this work like the power mat?
wolfkeeper4 years ago
The energy vampire thing is probably a bit overkill. I think all you need is a step up transformer and a single diode and capacitor. The bead might be all you need to make the transformer if you wind it right; and if the load is the LED, you probably don't even need the diode, just a resistor to limit current. If you do this though, you may need to up the frequency, the bead works best at high freq.
smtgr144 years ago
Um... my circuit is amplified (volt wise) when it passes through my glass of orange juice, i this normal? if yes what is amplifying it the plastic cup or the orange juice cuz i would like to know
SalemSnaKe4 years ago
Nice project, I have a computer mouse that works on this technology thus beeing wireless but having no bateries, I bought it like 5 years ago, it`s good to know how it works
samr37l4 years ago
Sorry to ask again but I'm having some some trouble with the 555 timer circuit. I'm using the astable 555 timer circuit but when I plug it into the coil the 555 timer gets really hot and the frequency goes way off (like it changes from 150 khz to 110 than back to 170 and then to 150 again). If anyone has any ideas please help me, and if anyone has any better ideas on how to make the 555 circuit can you please send it to Thanks a lot, SAm
The primary coil probably is drawing too much current for what the 555 can stably provide. It is a good idea to use a power transistor or something for the coil that way your don't draw your power from the 555 it's self. Also, because of the heat the current is making the 555 will mess up. It does it with temperature drift.... that is why it's probably better to get a function generator that is more resistant to this. It is a common problem, does the same thing with cold too.
do you have a good circuit to do this? like how could a put in the power transistor cuz I already tried that and I blew a 555 timer. Thanks, Sam
It's probably a voltage thing. The point of this system is that the sender coil has to ring strongly- you're probably overloading the 555 timer, because the volts on the ringing coil are tens of volts, in both directions, even though you're only feeding in a few volts from the oscillator. I doubt the 555 timer can take that. At the very least you need a transistor or two to decouple the timer from the coil.
I don't really have a circuit, but you just use it like any old transistor. A power transistor is rated for more current. Basically just hook up the output of the 555 to the base of your transistor, then have the coil power hooked up to the other two ends of the transistor. In this way the transistor acts like a switch and will pulse the coil on an off but the power transistor will take allow for more current to be drawn.
fkuk4 years ago
do the coils have to be uniform ?
railgunfuzz4 years ago
Couldnt you use a crystal resonator on the secondary coil?
zim09094 years ago
Wow, I always wanted to do something like this but never really understood how to. My dad had an old function generator, an oscilloscope, and this capacitive decade box thing. I used 0.022 uf because it was the closest value to yours. Then i hook up my scope and set it to graph volts and tweaked the frequency and it worked perfectly. Then i started playing with the amplitude settings and then i got some strange numbers. I got close to 45 volts ac when the coil was directly in the other one. I also checked the amperage and i was getting about 20 mah but i don't know how i was getting so much voltage. But great Instructable dude, 5 star.
Yes, it's a resonant circuit. You really can get stuff like that happening. It's like pushing a swing, you feed in a small amount of energy on each cycle and it gets bigger and bigger until the losses equal the energy you put in. These circuits are quite low percentage loss, so the voltage/current can go up many fold over what you feed in.
wolfkeeper4 years ago
For the function generator you might be better off using a Colpitts oscillator, it can give quite a bit of power. I'm also wondering a bit about your receiver circuit. Your circuit goes AC->DC which then feeds into the Joule thief which then goes DC->AC (at much the same frequency you started at) and then goes through the ferrite bead, which is essentially a step up transformer and then it gets rectified by the light-emitting diode again!!! It seems a bit tortuous. I think you would do slightly better to wire the ferrite bead onto the receiver coil- you're already at high enough frequency for that to work I think (more or less anyway, you could up the system frequency to make absolutely sure if necessary) and then feed the output of that straight into your LED. Also, the more turns on the ferrite on the LED side the better, you need the volts, particularly at long range.
robotkid249 (author) 4 years ago
You can use a transistor attached to, say, a 12v supply and run the coils through that...
lvam24684 years ago
how could i make this on a larger scale perhaps the main coil at 1 sq. ft.
tubbsey884 years ago
Isnt yur cap a little counterproductive? Should it not be inline with the positive line, rather than spliced into both leads?
robotkid249 (author) 4 years ago
I have updated it with a more clear view of the func. generator and primary coil circuit, for those of you who are trying to replicate this.
I would like to build the circuit by sparkfun by myself, i bought the components from a local electronics store but i have trouble reading the circuit, for example there are many 74hc04n ICs displaye in the circuit yet only one is needed and the 74hc04 IC has 16 pins but only one input and output is stated in the diagram so how do i connect this?
sorry, probably a little off topic but i have some comments about this project 1. Amazing, thank you. I needed a high voltage out for a few ion experiments i want to do. I am also wondering if this can be done strictly through vaccume tubes (modified or otherwise, i have a few compressors (one from canadian tire, and one from an old freezer) i'm still looking into whether this is enough vaccume pressure to operate thermionic tubes. 2. Nikola Tesla did NOT "invent" AC or DC. Many professors and students of the art at the time postulated on AC type movement and DC type movement. Long before Tesla arrived on the scene. DC was what more research had been done (probably cause no one wanted to do higher calculus). Through solving the math equations in 4 dimentions(xyz, and time) Tesla found a better description of atomic/ionic interactions through electric and magnetic fields. Infact he was able to utilize the vanderwaals forces in ways that even we havent tried properly (many people think HAARP but most situations and installations do not follow the principles outlined by tesla. Tesla found in AC, the components and infrastructure (that he invented or adapted from other inventors in europe at the time) would allow for a power grid. In Electrostatics (a more general form of DC found everywhere in nature) tesla found the movement of colombs can be more economical (i wont dicuss the mechanism here cause i feel its a right of passage reading his lectures to understand the ramification of this mode of energy. War would have to end or we would perish.. kinda like nukes). dick tracy said "he who controls magnatism controlls the world" what he didnt know was tesla had mastered the magnetic field and saw that electrostatic ion reactions controlled the universe. He didnt agree with two modern viewpoints. 1, einstein was taken advantage of; too many assumptions taken (einstein left out the electric universe!) 2, particles. When wave interactions can create particle behaviors he still understood that matter is a wave matrix. i could go on but no one has the attention span for true electrical theory any more, let alone any of tesla's lectures.
Your compressors won't achieve anywhere near the level of vacuum that you need to operate any sort of "vacuum tube". In fact, the level of vacuum will be so low that anything you would attempt would be considered "gas-filled". You need s very powerful vacuum pump, such as an oil diffusion pump, to build a vacuum tube.
this is very true, i've recently come across better data on the requirements. Though i've now thought about creating a partial vaccume with a conductive gas like oxygen and no wire inside the bulb. You could use a bifilar pancake coil (with magnetic fields reinforcing rather than cancelling) to acellerate the gas by a capacitance effect. Im not sure that it would be a more efficient way to light things though.
Xellers4 years ago
"Once i did it I found that you do not need to go to MIT do do this sort of stuff." While you're right about that, this doesn't compare to what they did. The device that you demonstrate here has been around for many decades. It is commonly used in devices such as wireless mice that don't use batteries.
aravindzzz4 years ago
how did connecting a capacitor makes the coil coupled???
gabe944 years ago
I am completely confused at what you mean about making either of the coils. Can you go into more details? I am kind've short on budget and can't afford to make several and test them.
toby5150 gabe944 years ago
Magnet wire is used in many types of transformers so can be stripped from old equipment and i beleive that old microwave ovens are cheap sources of magnet wire (coated in insulating material so that when 'coils' are made they don't just short circuit)
gabe94 gabe944 years ago
I am not sure how to make the coils, it wasn't very descriptive. Also i am not sure how to set up the function generator kit
you stick four nails in a board and wrap it around, over and over until it's the right size. then you pull some out and lift the coil off. wrap a bit of tape around each side and you're good to go!
nahyah4 years ago
Would a primary coil and the receiver coil having similar loop size increase the efficiency of the power transfer? Since maximum efficiency would require the receiver loop to be in the center of the primary coil, that seems to make sense. Any ideas?
I highly suggest you read up on MIT's recreation of Nikola Tesla's experiment (though modern society is so historically dense that they gave MIT the applause that had been waiting tesla for about 100 years now).

What you want to do is calculate the capacitance and inductance of the sending and recieving circuits. You want the circuits to be in "Resonance"

Here are two MIT Lectures that deal with this idea.
-The first link is on Resonance.
- The second link is on non conservative fields (the recieving circuit and how power is distributed with in such a circuit). VERY NON INTUITIVE!]

I highly suggest for anyone studying electricity to review Walter Lewins lectures on physics. He allways had an experiment of some kind to show you a physical representation of the theory, he does not leave holes in the explination, and he will admit faults in the theory. He does not assume you are stupid and "just dont understand" like most teachers i've come into contact with.
drchoc4 years ago
Hey your LED is in parallel to your circuit, in fact if you set it up that way you don't really even need the capacitors. I am beginning to question whether you are using a resonant coil; you said you used .02 uF but your capacitors are in series making the capacitance .005 uF. What I see here is either a simple air core transformer, or an extremely lucky resonant coil. I suggest you try and measure your inductance and then calculate and see if you are making a resonant circuit. Could you post some dimensions for your coils? and what gauge you used? Thanks, and nice job! Dr. Choc
samuraii4 years ago
guys u shold know that this is nothing new little more over 100 years ago a serbian scientist doctor Nikola Tesla invented wireless power transmission and the electricity could go over few miles - and yes he is the one that invented tesla turbine , dc motor and dc electricity and many other important thinghs we use in our daily lives.
b-stro samuraii4 years ago
Tesla invented AC and the AC motor, not DC. Tesla viewed DC as inefficient and wasteful, and eventually faced off against his original employer (Thomas Edison) to determine which system of current delivery would become the standard for consumer use. Tesla did do some groundbreaking work with electricity, if anyone's interested in wireless power, his old projects are worth looking into. He was decades before his time.
Tesla invented AC power
sk.mobeen4 years ago
did any one tried calc the input power and output power of the ckt?? what is the efficiency wid ur ckts?? and value of capacitance used is 0.005uF not 0..02uF.
and it'll work not only wid square but also wid sine and tringular waves. did any one notice?? what ever may be the input wave , output at sec coil is always sine. I figured it out why it any one else interested??
robotkid249 (author) 4 years ago
mattccc4 years ago
can this tharge a cellphone
robotkid249 (author) 4 years ago

This youtuber uses the same setup as me, but at a different frequency. A function generator, with a capacitor connected in parallel, a coil then air, then another coil with another capacitor connected in parallel and an led. Check it out, it might help you...
MagiWG4 years ago
I use this technology everyday at work. We have electronic price tags at my store, and each one is about 1.5" x 1.5". They draw enough power for a small LED, LCD display, and a wifi transmitter for changes that might come down. They are so awesome as they can go in the freezers and coolers because they are watertight.
robotkid249 (author) 4 years ago
Eye bot remember that the "schematic" is

The ll's are the 0.02uF capacitors in parallel.
Today, we ran out of time and couldn't get it to work (sorry, no new instructable this time!), and I had to do something else quick and dirty for my project... (I soldered one of those cheap little kits and I'll make a big poster, a scrapbook, and all that jazz) This morning, my dad had to help me look at it, and we tried to tune it. I used part of an ethernet cable to shield my wire from my primary coil to my generator from interference. No more interference! We checked the coils, and I was getting a fairly good signal through the coils, but the signal wasn't very pretty. It wasn't a square wave at all... So he had me change out a couple of different capacitors, and had me try to get a spike in the frequency (no luck), and so we ditched the whole thing (we were running out of time anyway). There was probably something key that I was missing, or wasn't doing, because I followed your instructions to the letter, and nothing seemed to work... Because you've bested me (for now; wait and see what I'm going to build next year!-this time, I'll start sooner), and because I'm overly impressed by your instructable, your reward for helping me is that I'll subscribe to you.
robotkid249 (author) 4 years ago
Eyebot, Make sure that the frequency going into the primary is 147 ish kHz square wave signal. Remember also that magnet wire is have a protective coating, which has caused me some problems, with a bad connection. Be in mind that the 0.02µF capacitors, only work at the 147 kHz signal! Good Luck
I tested my function generator with an oscilloscope. Works fairly well. The capacitors wouldn't read out on my multimeter, but I think that is due to a bad connection. So, I calibrated the oscilloscope, and hooked it up. I found the 147.7 kHz frequency. I connected the primary coil to the generator, and hooked the secondary coil to the scope. Instead of the square wave that was going in, I was getting some sort of shallow sine wave harmonic... I turned the generator off, and it was still there! It's noise or interference from something, I just don't know where. Also, the 32 guage wire has an awful connection (probably has something to do with the interference). I may end up using 26 guage wire like I used on the primary coil. I'm done working on it today though! I'm waking up bright and early tomorrow to get this thing working...
Still nothing.......Thank you for replying however. Could I ask you what is the purpose for connecting a .02uF capacitor in parallel to the primary coil? Does that do something? I'm no expert... It seems that my connections are good, but I can't seem to tune it right. Would 147.7 kHz and .02 uF capacitors not work with my coils because they're different than yours or something? Hopefully I'll get this thing working (with your help), and I'll be able to enter it in my county 4H fair.....
robotkid249 (author) 4 years ago
I am really not sure. I had some this magnet wire laying around. I have built some coils, using this green wire from radio shack, and seems to work well.<br/><a rel="nofollow" href=""></a><br/>
Hmm.....I used 26 guage wire (40 turns) to make my outer coil, and 32 guage (40 turns as well) to make the inner coil. I have about two days to finish this, and I'm still not having any luck. I found .02 uF capacitors, but I don't know If they're the right ones to use for my particular coils.... I don't know if my coils need to have the same size (guage) of wire or not. I connected a capacitor in parallel with the primary coil, and one in parallel with the secondary coil. And I can't figure out why it still isn't working..... The coils are only about 1/2-3/4 of an inch apart, and they should be pretty efficient... I would have to guess that my outer coil measures 8" long and 6" wide, while my inner coil measures 6" long and 3" wide... Also, I tried using a razor blade to remove the lacquer coating on the wire, and I haven't tried using a flame yet. If ANYONE could help me figure out why I'm not getting a signal, I'd REALLY appreciate it! I'll post a pic or two in a few minutes..........................................(I just have to find the camera...)
The pics I promised. These are just of the coils so you can get an idea of what size they are. I put a breadboard in the middle of the whole thing. Because it's for a 4H project, the judges like to take things apart. Especially the circuits themselves... But I don't know if I would be better off soldering my .02 uF capacitors directly to the coils themselves or not. The function generator that I'm using will be able to make the frequency I need, if I knew which frequency I needed. I may be losing my signal from a bad connection... I'll check those sometime today. Earlier, I checked with a multimeter across each coil on a 20 kHz readout... The primary was good, but on the secondary I got nothing. Ideas? Like I said both coils are 40 turns each... 26 guage magnet wire on the outside primary coil, 32 guage magnet wire on the inner secondary coil.
4H Project 012.jpg4H Project 009.jpg4H Project 015.jpg4H Project 010.jpg
thanks to reply but ....did u use same wire for both pri and sec coils?? Reply soon because i'm not sleeping for ur answer(u know its 4:30 am here now and i have not slept till now). is that ac-to-dc conv circuit must to put a joule thief on our diode?? did u try without it?? did u recharged any thing using the circuit.... what if the coils are of same there any specific reason for not using same sized coils??
recon5064 years ago
As to your question why the LED is not lit when the primary is turned vertical is because then the primary is transmitting in a different plane than the secondary is receiving.
Its similar to Wireless router antennas, they have a dead spot directly above the tip of the antenna and when you turn the device sideways your basically hitting that dead spot. I have a question what's the output voltage directly off of the rectifier bridge?
robotkid249 (author) 4 years ago
WOW! Great Job!
Awesome project, worked out great and didn't take much time or effort. Put mine in a plastic case which the secondary coil gets plugged into. Video here:
robotkid249 (author) 4 years ago
If they are the same size, you will see a slight reduction of power outputted from the secondary.
The primary needs to be larger than the secondary.
You can use the green magnet wire here from radioshack, which seems to wrok quite well.
eyebot1174 years ago
So, what exact guage of wire was used for these coils? Were they the same? Does the difference of size between the coils matter? I'm trying to build one of these using your instructable, and what I don't know is what's preventing me from finishing this thing. Could you help me out?
sk.mobeen4 years ago
PLEASE please ǝsɐǝld dlǝɐsǝ once more.........
sk.mobeen4 years ago
what are the gauges u used for the pri and sec coils???

please answer..........-

the gauge u r using is according to AWG or SWG??? please answer.
sk.mobeen4 years ago
what gauges did u use for primary and sec coils??

30-gauge for primary and 26 gauge for secondary my guess correct??.......PLEASE HELP.. :) _
Dr.Bill4 years ago
Actually, I saw a guy stand under high tension wires and hold a flourescent tube over his head and it lit. Then there's the case of the farmer out in Iceland that put a 3' diameter coil on his roof where he lived under the high tension wires and lit his whole house. The USAF saw it and went to investigate and could do nothing about it. Of course you have to think of the EM field all around you that might cause CANCER..............................
It doesn't cause cancer, as far as I know. They tested it on Mythbusters.

Think about it: power lines have been around since the end of the 1800's (these were the early DC power lines). If the field they created really did cause cancer, wouldn't we all be dead by now?
Just a thought.
Its probably what started all the cancers. Tesla had a horrifying idea to transmit power all over the world through the air. Think about what that might have caused.
Not through the air, through the earth!
I have a friend in Hawai'i that does just that with communications. He burys his antenna and listens to Japan. He also detects earthquakes in the 3 to 7 Hz range using 2-60 lb coils of wire and some associated electronics all home built. The man is an amateur extra licensed radio operator.
thats a great idea! then we wouldnt have to worry bout trees falling on the lines during storms anymore!
They didn't have cancer before power lines? And that is pretty scary when you think about it - lucky for us, Tesla changed his mind and decided that power through the Earth would be the better option.
Well, We still have a lot of other things that give us cancer, like the RF travelling through the air from TV stations, radio stations, WiFi, Cell phones (you can cook eggs with the RF produced by a mobile phone...) and a lot more things, So I really doubt Tesla's invention wouldn't cause any more damage to us. Tesla didn't change his mind, the power companys overpowered him..
The cell phones emit microwave energy. :-)
That's why I don't have a cell phone (well also because I don't feel the need to have one) because my grey matter
Haha! I don't have a cell phone, because I don't know how to use it. :-) Also, when people are talking on their cellies, just think of all that microwave radiation going in to their heads... -_-
mobile phones use radio waves at less power than a walkie talkie to communicate with the radio towers, then the information is then in turn sent via microwaves to satellites. I believe the FCC limits cell phones to 1 or 2 watt maximum output, a lot of people say "my head feels warm after being on the phone for an hour!" which is caused by either pressing something to your head which makes it feel warmer, and the because nothing is 100% efficient some energy being lost as IR, heat, to your head.

Basically no microwaves =]

Also im going to out one of these in the back of my mobile to charge it with a primary coil in a mousemat, also people should use this to charge wireless mice =]
sorry to disappoint but the egg this aint real
Why do you say that, do you have any evidence?
Cant remeber where but someone put 100 cell phones on top of an egg and then called them ( using another 100 phones), after they all finished ringing the egg wasnt even warm.
You try it. Put two phones on either side of an egg and start a hour long call between them, the egg should be cooked in about 40-50 minutes.
i ve only got 3 cell phones, and i would need to set up a price plan so that it doesnt cost me a fortune, but I would love to try it some time.
Yeah, You only need two cell phones anyway. But it is sure worth a go. I would send you the email, but it has been deleted so I can't find it ;-(
Been too long since I read the history of Tesla, to be %100 certain, there where other factors that lead to his experimenting with wireless power transmission, he was a proponent of it until the day he died.
Specific absorption rates are prescribed by the FCC for ham radio because too much electromagnetic radiation does produce tumors. I have 2 EMF detectors that I do home surveys with to find sources of EMF. A good source to start with is a paper; Biological Effects of Power Frequency Electric and Magnetic Fields. This is a background paper done for Congress and the Office of Technology Assessment a number of years ago. It might be found in the stacks in the library under R 621.319 N That would be a good starting place........
static Dr.Bill4 years ago
The FCC set exposure limited for all the radio services it regulates. Certainly there are situations where RF can harm a person, but the conclusion of numerous studies are all over the place. I had always felt the FCC decided to put exposure limits in place to head off oppressive US Congressional legislation. Anyway in regards to most EM and RF radiation, the genie is out of the bottle, not likely to be put back in it. Most likely any stray radiation from small scale transfer like this can be controlled by shielding without affecting it's designed purpose. Given that most likely will end up being one more phantom load, I don't see it going anywhere.
I see.
By "in the library," do you mean "in the library of congress?"
I just figured that if they really did cause cancer, we would have noticed it a while back (for all I know, we did; I'm not very good with current events).
And thanks, I'll take a look at that paper later.
Sure. And any big city library. Smaller libraries don't have the space for a place called "The Stacks" where they keep all the really cool research papers.
Dr.Bill Dr.Bill4 years ago
Also if you google search the title you will find the paper
Some people are just too paranoid. Radio Stations and Electric Fields does not mean cancer!
Are you sure about that ?
Mythbusters is not research doctors.
T-K Dr.Bill4 years ago
You know, I hate it when people say 'it causes cancer'. It seems as if everything can cause cancer nowadays! Before people say this sort of stuff, they should research. Make sure it's true or not. And drbill, I'm not trying to provoke you, I'm just saying that i don't like it used as an excuse for everything. What you said about the flouro tube and the house... Sweet! Good idea on transmitting power. Neat.
harley_rly T-K4 years ago
i know right! it seems almost everything nowadays has "warning: known to the state of california to cause cancer...." on it somewhere. like sassafras root, they banned it from being sold like back in the 60's or 70's saying that it was carcinogenic(also was banned because it could be used to make ecstasy)and my whole family way back in generations on my moms side drank it all the time, i still drink it myself, and none of them got cancer.
clarjon1 T-K4 years ago
Your negative words cause cancer! ;) Kidding, of course. Pretty cool idea, i remember doing stuff like this way back when... or was it a dream... Oh, now i remember it was a door alarm type of thing, and when the door opened, the one coil (on a string) would move out of the circuit and cause a charged capacitor to ring a chime :D Man i was creative when i was younger :P i think i was 12 then or so lol
Dr.Bill T-K4 years ago
I am not provoked. I know the facts with this application. Granted the power levels you are using are very low and Granted the Cancer risk is low but it remains. Biological Effects of Power Frequency Electric and Magnetic Fields, Google Search It. It is a very interesting study If you decide to follow a career path or hobby that involves higher energies you will need to know about this stuff. I use it in Ham radio to protect my family and neighbors from my undue releases of EM and RF fields. I am required by law to observe Specific Absorbsion Rate guidelines put out by the FCC. EM and RF fields do cause Cancerous Tumors. I just think that people should be aware of what they are putting in their lives that could cause problems in the future. And yes, nowadays there are a lot of things that cause Cancer. Sad but true. People unknowingly expose themselves to all kinds of carcinogens because they don't Study. lol. Not to worry I am not provoked. DrBill 73's
the farmer storry is fake, you would need an insane coil to gather enough power to light a house
Since we're on that subject, check this out:
this could be achieved by using a large tesla coil
That looks like Project HARP
Dr.Bill Dr.Bill4 years ago
Nope. My bad. Those are flourescent tubes. I wonder if they are wired or just standing there. This would be a cool project to do to the electric company all around the country. It would blow their minds.
They are just standing there... It was some artsy guy's project and he just planted a bunch of fluro's in a cow paddock under high voltage powerlines.. I'd add a link but can't remember where I saw it.
Thanks for putting that there, I forgot to cite my sources.
pretty cool huh ? I found it in just about 30 seconds.
I'm gonna search around a bit for it. Looks real interesting. I'll bet the power co went nuts on the guy if he left it up for any length of time.
Dr.Bill Dr.Bill4 years ago
There is a lot of juice flowing under power lines. I would not like to live under them.
sk.mobeen4 years ago
THANKS FOR UR REPLY... just 1 more help....PLEASE what gauges did u use for primary and sec coils?? 30-gauge for primary and 26 gauge for secondary my guess correct??.......PLEASE HELP.. :) _
Have you mentioned Tesla's experiments with wireless power transmission? His visions were realized in Colorado Springs, USA way back over a hundred years ago. Worth studying to discover what lies behind this "new" technology.
robotkid249 (author) 4 years ago
sk.mobeen please read the context of the sentence! I am talking about how to make the coils. Place nails on some wood (a 2 by 4)
That will help you make you coils....!

The primary coil is 3 inches by 4 inches. The secondary coil is 1 inch by two inches. Sorry for the misunderstanding
sk.mobeen4 years ago
what gauges did u use for primary and sec coils??

30-gauge for primary and 26 gauge for secondary my guess correct??.......PLEASE HELP.. :) _
sk.mobeen4 years ago
whats the guage of the wire you have used??? and please mention the dimensions of the coils to be winded clearly for both primary and secondary.....PLEASE
jelmain4 years ago
Watch the utility companies squelch it because they'll never be able to prove whose transmission you're pulling power from
What about using an AC power supply to create the alternating current in the coils?
brokengun4 years ago
Did you calculate resonance frequencies for this? Or did you just base your coils and frequencies off of someone else's design?
edfel014 years ago
for the next year or so im going to be studying this for a project that will hopefully make it far. just a heads up might ask some questions. thx!!
tinkerC4 years ago
Would you mind explaining the effect of the capacitors? Thanks,
Nice little project! Really simple...
To the reason why it doesn't shine when the receiving coil is vertical to the other: As you already said the principal concept behind this is the magnetic coupling. So there's a so called Lorentz' Force involved, which acts only on vertical directions. In detail: The moving electrons in the outer coil are inducing a magnetic field vertical to the way they travel. This field works mostly inside the coil and stands vertical to the plane of the coil. Then the magnetic field itself begins to move the electrons in the wire of the inside coil, which results in another current. So if one of the coils stands vertical to the other the Lorentz' Force can no longer move the electrons and so there isn't an electrical flow anymore.
Visit for more information on this and don't forget the three-finger-rule if you're using this concept ;)
DrChill4 years ago
I'm wondering if you considered using LEDs for your bridge rectifier...
samr37l4 years ago
Problem. The function generator that you show doesn't exist. I tried Sparkfun, but they are all out. I looked up the generator but couldn't find anything else. Any one have any good ideas for a CHEAP way to do this? (instead of the function generator. SAm P.S. The 555 timer thing didn't work; I just blew 2 amplifiers and burned my hand on a resistor that was malfunctioning, so I'm going to try a safer way.
robotkid249 (author) 4 years ago
Blakdragon19, all you need to make the coils is magnet wire. As long as you have enough you should get a stable power output in the secondary. samr37l, a 555 timer should work. Check the second instructable in the related box. He uses a 555 timer to do the same thing i am doing. Yet, it looks his is less efficient, keep that in mind....
I looked up on the second instuctable, but it was wayyyy to confusing for me. Also, I think I figured it out. You can use the astable 555 timer circuit and amplify it, then plug that into your primary coil. I think it might work, but I'm not sure, so tell me what you think. Thanks, SAm
I'm a little confused. is the second coil supposed to be the same guage/number of winds as the primary? also, did you use the 20 gauge wire for your primary and the 30 gauge for your secondary? is there a cheaper way to attain 147.7 kHz? please help!?:!?!?!?
Same problem... Need a cheep way. I'm trying to use the 555 time but let's just say IT IS NOT WORKING!!!!!! I'm working on a bigger scale and I need more voltage, like 12-20 and I can't get that with the kit that you showed. That's why I need something else. Any ideas???????!!!!! SAm
edfel014 years ago
ok i get it now.... how far apart can the coils be from eachother? or does the little coil have to stay in the primary coil? thx for help
I get it, but dose the coil on the outside have to be around the inside coil.
edfel014 years ago
i dont get the primary coil circuit how does it all hook up?
when a genious speaks everyone listens but no one understands
koopatroopa4 years ago
could you just plug this into some batteries instera of the genorator
jimvandamme4 years ago
Ya know, if you could get it to resonate somewhere in the 20 KHz range, you could use a secondary winding like the 5 volts out of an old computer supply. I've done it at higher power levels to make a VLF transmitter that went through 150 feet of solid rock.
Dude. You should get your Ham License.
Actually, I had a First Class Radiotelephone license, so I could run a radio or TV station. Now I just content myself with running a 200 KW radar transmitter. Oh, and a 30 KW L band one. I miss the old megawatt days, though.
wee_man4 years ago
How much meters of copper wire is needed?
edfel014 years ago
does the smaller coil have 2 be inside the bigger coil? and if not how far can it be and still light the led?
I'm not sure if someone's mentioned it before, but I saw a pretty funny webpage where the guy put the primary inductor in the base of his mousepad and the secondary in his mouse, so he'd never have to charge his wireless mouse. I guess it's truly wireless now.

Oh, found the link

Not the neatest job around. :)
How to connect the LED's and the capacitors to the secondary coil.
MJTH4 years ago
You should put it under a mat, and hook up a thing to charge your phone.. that would be cool. and put it into a type of charger station :)
robotkid249 (author) 4 years ago
Under the subscribe button, on the right of my instructable, are links to other instructables. If you are interested in doing my instructable with a 555 timer see the second link, I need help.... instructable.
samr37l4 years ago
How can I make a function generator using a 555 timer chip that can run at 160 khz and approximately 5-10v. Can you please give me some details instructions that I can follow to build this. Thanks, Sam
nolte9194 years ago
You said, "The 0.02 uF capacitor is used only for this frequency, and the value of this capcitor will change depending on the frequency. " Do you have a formula or explanation as to how to find what value capacitor goes with what frequency?
vince0864 years ago
I think i might build one of these in a year or so for a docking station for my robot. How much power does the coil you built provide for the LED?
senacharim4 years ago
"A few years ago MIT created a system for transferring power wirelessly." I believe you meant to say: "Over a century ago, Nikola Tesla created a system for transferring power wirelessly. Recently, educated people (like those at MIT) began working on the same thing." Aside from that, totally love it. Thank you.
You realize that not everything you read on the Internet is true, right?
Long before the internet I spent a great deal of time studying the life and works of Nikola Tesla. While there ARE many urban legends surrounding him, he demonstrated wireless power at the Worlds Fair in 1893--and was working on other, larger projects later. (Congrats on taking the internet with a grain of salt.)
Please provide some actual, reliable evidence. What technique did he use? What was his circuit?
Hey, man, what do you have against Mr. Tesla?

Just because someone's not 100% sane doesn't mean they didn't accomplish anything they ever claimed to. You can see footage of a Tesla coil, lighting up florescent light tubes without direct contact. Tesla's circuit was the tesla coil. The schematics for Tesla coils are available in many places. Also, florescent light tubes can be lit up under high-voltage power lines, again, without direct contact.
Yes, I've built a Tesla coil and lit up fluorescent bulbs with it. That's not the same thing as wireless power transmission over long distances. The books that claim this stuff are hokey crap.

"In 1976...I stumbled across a strange text entitled Return of the Dove which claimed that there was a man not born of this planet who landed as a baby in the mountains of Croatia in 1856...his name was Nikola Tesla."

I'd love to see some real evidence, but I have yet to find any.
I'm not sure but I think electricity can be transmitted via microwave. I seem to remember 2 towers set-up on 2 ridges. 1 tower transmitted a microwave signal contaning the electricity. The tower on the other ridge received with a microwave dish and lit a bank of spotlights.
Yes, you can transmit energy with microwaves, since they're aimable. It's not terribly efficient, though.
zaery endolith4 years ago
Norrie, H. S., "Induction Coils: How to make, use, and repair them".Norman H. Schneider, 1907, New York. 4th edition. Electrical experimenter, January 1919. Page 615 Go check these out :)
endolith zaery4 years ago
Q: How does WiTricity technology compare to traditional magnetic induction, like that used in a charging mat or electric toothbrush?

A: Traditional magnetic induction requires that the power source and capture device be very close to one another—usually within millimeters—to transfer power efficiently. That’s why many traditional inductive charging solutions require a cradle to hold the capture device, or a mat on which the capture device must rest. WiTricity technology is based on sharply resonant strong coupling, and is able to transfer power efficiently even when the distances between the power source and capture device are several times the size of the devices themselves.
zaery endolith4 years ago
Hrm...... I don't quite understand how that's a reply to my comment.....
endolith zaery4 years ago
I'm not sure how your post about induction coils is a reply to my comment.
zaery endolith4 years ago
It's a book that has a history of induction coils in it, what a surprise, you wanted evidence, you got it.
endolith zaery4 years ago
What do induction coils have to do with this instructable or with Tesla?
zaery endolith4 years ago
I suggest that you find out by yourself, but it's quite obvious how induction coils are related(i.e. steps 2 and 3) and Tesla used induction coils to wirelessly transfer energy, do some reading before you make prejudiced statements about Tesla, he has over a hundred patents, so don't be surprised if he invented something that you don't understand.
endolith zaery4 years ago
Tesla used induction coils to wirelessly transfer energy

Over long distances? Please provide some evidence of this, or an explanation of how this could be possible. Inductance drops off very quickly with distance. Think about how transformers are designed, with hundreds of coils tightly wound around magnetic cores to get the efficiency up to 85% or so. Now imagine taking the magnetic core out and separating the coils by 2 meters of air. What will the efficiency be?

The efficiency of the MIT experiment is 45% over a distance of 2 meters, with only 5 turns in the coils. Do you understand the difference yet?

he has over a hundred patents

Then it should be very easy for you to find the one that backs up your claim.
zaery endolith4 years ago
I give up, i forget what the efficency, but he got 200 lightbulbs to light from a distance of 26 miles, and go read Prodigal Genius, it is a book about Tesla, now stop making me do all of your research and assuming that i said things that i didnt, i never said that Tesla could transfer energy long distances, but now i did. And, go search your own 100+ patents, i hope you know what wikipedia is.
endolith zaery4 years ago
go read Prodigal Genius

I have. As I've been saying all along, it's hokey garbage with stories that don't have any evidence to back them up. Please read through my other posts.
Wow, really? 2 minutes to find this:

There's your evidence.
go buy a book.
Hey, I got a book and it says Tesla invented time travel and a beam that cures cancer, too. Whaddyaknow?
well you're obviously overly sceptical of the internet regardless of how many sources there are... you say not to believe everything you read on the internet then go on to demand "actual, reliable evidence."... on the internet... Do you want me to snail-mail you a book? There may be only stories to back some of the things Tesla did but they've been documented and replicated enough to assume they're probably true.
There may be only stories to back some of the things Tesla did but they've been documented and replicated enough to assume they're probably true.

Then show me the documentation and replicated experiment results. That would be "actual, reliable evidence" that I asked for. Not a book written for entertainment that indiscriminately parrots any fabricated story they could find.
This is about Tesla, not MIT.
"replicated experiment results."....
I know, for instance, that he proposed creating conductive paths of ionized air with X-rays for transmission of energy. If that's what he was doing, then it has absolutely nothing to do with the MIT research. Where's the evidence that he actually did this? What technique did he use? Why can't anyone provide any details or documentation?
I see MIT researchers transferring energy wirelessly several feet in the near field using resonant coupling. I don't see any documentation of what Tesla did, or that anyone was trying to reproduce his results.

All you've got is a story in a book that says he transmitted energy for miles and powered light bulbs and a motor. What technique did he use? What was his circuit?
Whew. Someone said so I didn't have to. Read a book people lol :D
If you power up a tesla coil (which creates high voltage charge) it will light up a fluorescent bulb without the bulb being connected to anything. I believe this is a static electricity phenomena, and not the magnetic induction that this project is related to.
You're right. Using the Tesla coil to produce the same result is different then this instructable.
check out Scalar Waves

yeah, uh about the pseudo-science tag on this topic, well turns out there is more going on than we fully understand at the moment. just ask the guys getting 150%+ Faraday efficiency from their little hydrogen electrolysis experiments. (HHO)

also on those pages are ZPE and while you're at it the Casimir effect. :)
If you put a lightbulb in a microwave, it will light up. Of course, you should shield the metal part by putting it in a cup of water. ;)

Tesla did have a theory on wireless electricity as well as electricity everywhere where you can simply plug stuff into the ground. Of course, Thomas Edison didn't like this very much.
Not sure if it's true or not... but I heard that horses kept getting zapped when Tesla tried this because their shoes would conduct electricity whenever the horses stepped on metal grates in the street. Could be science urban legend... I'd like to know for certain if there's a physics guru out there who could confirm/deny this one.
I find this instructables very cool, and I have some questions;
Should the coils to be "plate" (I'm french, plate=in a plan?)?
Does the number of turns should be about the same for both of coils? Should the primary coil need to be bigger than the other? Should it have more turns tha the secondary? Can we use others capacitors (the same for both coils) with an other frequency? How to calculate this frequency and how does this influence on the distance, ...
I know there is a lot of question , but if you could answer me, it would be great (and if someone french could send me a Private Mesage to explain me more precisely in french ... )
robotkid249 (author) 4 years ago
Ive gotten 4-5 inches which is good i think. It does not work when the coil is in a vertical pozition if you know what i mean.
the coils have to be wound in the same direction and parallel to each other. Antennas have a polarization too.
I would imagine that is due to polerisation of the induced magnetic waveform.
Dr.Bill4 years ago
Have you considered trying an air variable capacitor (as an experiment) to tune the secondary circuit instead of fixed caps ?
Dr.Bill4 years ago
Over 43,000 views. Holy Crap the thinking is happening. I can't wait to see what comes out of 43,000 look sees. This is beyond good.
Dr.Bill4 years ago
I still think this is one of the Cooler things I've seen in instructables. I don' really care that much about EM and RF radiation, you see, I like to see what kind of thinking comes out when the comment is made.
Speedmite4 years ago
But wouldn't you have to wear rubber boots/suits to keep from killing yourself with electricity and line the fool with like aluminum foil?
I take it back. But are you sure this is the best way? power cords dont bother me except on shop vacs.
fortnix9114 years ago
railgunfuzz4 years ago
What was the range like on the device and is there a calculation for working out the capacitor value relative to the frequency?
finnrambo4 years ago
can you power a dremel with some thing like this
Jakeg4 years ago
wow I just got a great idea. build the primary coil embedded in acrylic then put the secondary coil in the back plate in your ipod. so when you put your ipod on the acrylic it will charge
the hard-drive inside the i-pod may be afffected by the magnetic waves. may want to research how to prevent that.
You could shield the HDD with a thin steel plate. I believe that there are currently mag-shielded HDD's available for industrial uses that do that.
thats a great idea. if only i had an old crappy ipod to try it on. also you could just convert the ipod to flash memory. Wouldnt that work?
Yeah, I think flash memory is immune to magnetic interference. I actually thought most ipods had flash memory. I dunno, though, I don't have an ipod either.
Actually, all of the newer ipods are flash memory, and ipod touches/iphones have a metal backplate anyway.
eggman4 years ago
you could probably use a degauss coil from a CRT monitor as a primary coil. it's 200-300 feet of magnet wire already wound into a rectangular shape and wrapped in electrical tape.
edfel014 years ago
hm....i like it but it might be out of my league. GOOD JOB!!!
Dr.Bill4 years ago
This is pretty cool !
Dr.Bill4 years ago
WoW ! Shades of Tesla ! I do kind of the same thing with an X-Tal set that has 3 coils, 3-0 to 365 pF air variables, and a long antenna. My LED modulates to the announcers voice and I got 2 nice S-meters on it at the same time to tune each tank !
goboom4 years ago
gabe944 years ago
Is there a way to do this without a function generator? With just the coils and capacitors
i think it would be possible by using a wall outlet as the square wave generator, but you would have to use different values because wall outlets are 50-60 Hz. you'll have to do some research about it, but you should be able to find some information.
isn't mains electricity sinusoidal not square wave?
Yeah, It's sinusoidal, and it isn't really feasible to use the 50-60Hz from a wall outlet because the coils would have to be bigger. Same thing with transformers, a switch mode power supply need a smaller transformer to a wall wart because they work at a higher frequency...
yeah i thought about it and realized that... nevermind...what about just using direct current at 6V and taking it down to 5 with the coil sizes? i could do like 36 on the outer and 30 on the inner?
You would still need something to make a square wave because transformers still need some sort of osscilliation to work...
are you sure that transformers require oscillation? i hooked up a 9 volt to a wall wart and it sparked just fine.
Well, if there is just a transformer with no extra circuitry, hooking it up to the battery will get a spark on the input (because of the excessive current draw) and a spark on the output, but you will only get a spark on the output for a fraction of a second because they require oscillation.
okay, that explains why it only sparks for a split second.j but if not DC then how could i do it without a wave generator? i might be able to connect it to a wall transformer... okay how about this. i take a wall adapter transformer and remove the rectifier so it's output along the two wires is what the wall's is, only at 6 volts. I then put the rectifier in the receiver and wa-la, a wireless charger!
Well, you could use a relay to oscilliate, But you could use the output of a wall adapter as long as it isn't filtered(open it up and take out the capacitor)
filtered? okay, i'll just turn the breaker off for my room while i'm doing it. is it electrolytic or ceramic?
is filtered the one that protects against surges?
It doesn't protect against surges (i think) it just makes the output more smooth than really rough , but you want rough...
It shold be electrolytic...
where would the cap be?
It shows you somewhere in the Instructable
This will give you something to think about

Effect of frequency

The time-derivative term in Faraday's Law shows that the flux in the core is the integral of the applied voltage. Hypothetically an ideal transformer would work with direct-current excitation, with the core flux increasing linearly with time. In practice, the flux would rise to the point where magnetic saturation of the core occurs, causing a huge increase in the magnetizing current and overheating the transformer. All practical transformers must therefore operate with alternating (or pulsed) current.

Transformer universal EMF equation

If the flux in the core is sinusoidal, the relationship for either winding between its rms Voltage of the winding E, and the supply frequency f, number of turns N, core cross-sectional area a and peak magnetic flux density B is given by the universal EMF equation

The EMF of a transformer at a given flux density increases with frequency. By operating at higher frequencies, transformers can be physically more compact because a given core is able to transfer more power without reaching saturation, and fewer turns are needed to achieve the same impedance. However properties such as core loss and conductor skin effect also increase with frequency. Aircraft and military equipment employ 400 Hz power supplies which reduce core and winding weight.

Operation of a transformer at its designed voltage but at a higher frequency than intended will lead to reduced magnetizing current; at lower frequency, the magnetizing current will increase. Operation of a transformer at other than its design frequency may require assessment of voltages, losses, and cooling to establish if safe operation is practical. For example, transformers may need to be equipped with "volts per hertz" over-excitation relays to protect the transformer from overvoltage at higher than rated frequency.

Knowledge of natural frequencies of transformer windings is of importance for the determination of the transient response of the windings to impulse and switching surge voltages.

a capacitor to sync the two coils and provide for the oscillation.
What did you say was providing the oscilliation?
Do you have a diagram of some sort? I'm a bit lost...
yeah sure. download the diagram and look at it. couldn't get a pic...
That looks pretty good, altough you won't be able to get the secondary very far away from the secondary, because you need to match the inductance with a capacitor...
you mean very far away from the primary don't you? okay, It's just dawning on me how complicated and difficult this will be... got any ideas on how i could do it, based on the frequency, amperage, all that other stuff that i could use to my advantage? i really need to do this, and fast. so find a capacitor that matches the frequency? there's actually a capacitor in the rectifier, but will it be messed up because i'm changing the voltage? will i have to change the capacitance in the rectifier is what i'm asking i guess.
Well, the cap in teh rectifier will be very large, you need a cap around the value of 0.01 uF
k i'll try it... why 0.01uF?
Not exactly 0.01 just around that range, See in teh instructable....
okay. i see... thanks for your help. i might ask for more if i need help thank you SOO much!!! kind of a random question but are you like in india or something? it's midnight here.
You're welcome. No, I live in Australia, It's nearly 5pm on Sunday here...
12:53 sunday here. anyway i don't know how i could thank you enough!!! :)
Oh, lol. Hope you don't mind me asking, but how old are you?
i'll just send you an email.
and yeah, i realized that earlier. i wasn't really planning to charge across the room if you know what i mean. thanks for pointing that out though, for those who didn't know/think about that.
the outer coil is vibrating quite a bit with the power. just thought i'd let you know. i have continuity between everything but i still don't get voltage. would a capacitor fix this? i didn't use one yet... i'll try it and let you know how it goes.
Well, you wouldn't need a capacitor if you had them on a iron core or similar but try tapping the coil on and off the battery really quick, you might get something from the secondary coil then, if nor, try wrapping it aroung a piece of iron of similar..
correction, capacitorS.
1up tanmanknex4 years ago
Can't you simply use a 555?
tboehmer 1up4 years ago
Yes, tuning a 555 timer would work just as well.

To make a few other remarks, using a sine wave over a square wave will still work, and the differences between the two at higher frequencies shouldn't be that large since the inductor is resisting the change in current and will smooth out the square wave regardless.

Also, for 50-60Hz you wouldn't need bigger coils per say, you could get away with a huge friggin' capacitor : ) And it's only the secondary inductor that matters since the primary is being driven. The secondary just needs to operate with a natural frequency equal (or close) to that of the primary's signal frequency in order to achieve any reasonable efficiency. I suspect harmonics would work as well, but not as efficiently.

Note: natural frequency (Hz) = 1 / ( 2 * pi * sqrt( L * C ) )
1up tboehmer4 years ago
Tell me, how do you get an AC pulse from a 555?
tboehmer 1up4 years ago
A quick Google search brought up this tutorial:

That should help you a good bit.

555 timers are quite simple, they only rely on an RC (resistor-capacitor) time constant and a threshold voltage to trigger on. By connecting the two threshold pins (inputs to comparators) to the capacitor, the capacitor will continually charge and discharge between 2/3 Vcc and 1/3 Vcc, Vcc being the supply voltage. Make sure that R2 in their diagram is much larger than R1 in order to come as close as possible to a 50% duty cycle. Here's the equations of interest:

f = 1/(.693 x C x (R1 + 2 x R2))
t1 = .693(R1+R2)C
t2 = .693 x R2 x C

So just select your operating frequency and choose (read guess) some resistor values that seem reasonable. You can keep playing around with the values until you find a capacitor value that is in a reasonable (and attainable) range.
robotkid249 (author) 4 years ago
I am pretty sure that the fcc has approved products that use this technology. Yes, powering and ipod is what this is intended for. I will do that in my next instructable.
(removed by author or community request)
Most of what you say is right, but everything in this paragraph is wrong .
The capacitors, the way they are wired in series across the secondary coil doesn't add the capacitances, making the real capacitance .005uF. They also don't resonate or filter, as an RC circuit would, because there is no resistive element in series with it. LED's do not work with AC at all, forcing current backwards through them will cause them to breakdown. The capacitors actually only serve to allow the coil to put current through the capacitor rather than the LED backwards.

True enough, connecting capacitors in series won't add capacitances, but it doesn't divide them either. The capacitance would .01uF (same as a single cap.) and the voltage rating would double. He does need to put them parallel.

The circuit would resonate because the caps do have a resistive element in series; the coil itself.

LEDs will filter ac like any diode. (Hence the name Light Emitting Diode) They do have a relatively low reverse breakdown voltage, but the voltage in this circuit appears to be very low.

Capacitors do not serve to pass current so it doesn't go backwards through the LED. Capacitors do not pass current in the conventional sense. They pass voltage potential. The current goes backward through the coil itself as the capacitor discharges. The best physical analogy for a capacitor is a pair of hemispheres bolted together with a rubber sheet across the middle. As pressure is applied liquid is pumped in one side, the sheet is stretched and displaced, pressure is applied to the other side and liquid comes out . As the membrane is stretched, it exerts back pressure until it equals the pressure of the incoming liquid. Pressure, not liquid is transferred to the other side. When pressure is removed or reversed, the membrane reverts to (or beyond) the neutral position, and liquid flows back out of the first side. This explains why dc current will flow for a short time in a capacitor containing circuit.
Ever thought about using DC? maybe use a old gameboy wall adapter and use the two wires to power the coil. this is what i'm going to try, and i'll let you know how it works out Mr. This-will-never-work-in-a-million-years. (JK) =)=D=P
(removed by author or community request)
EXCEPT the primary coils would have to be GIGANTIC, like 720 turns. i'm using a modified gameboy wall charger, i made it output AC so it works and i don't have to have gigantic coils
servant744 years ago
I think the Saturn EV1 used an inductive charger 'puck' that slipped into a slot in the front of the car to charge the batteries. Inside the 'receptacle' in the car they had coils. I haven't seen any 'plugin electric cars' doing that though. (Could the losses be excessive?) I thought it was pretty neat! A year or so ago I thought I saw a 'deskmat' or table top that would allow you to lay your cell phone, calculator, or laptop on (with appropriate adapter) that would allow charging the devices just by setting it down on the table. I think they had some additional stuff to allow optimization for use with various devices. Still the same concept, different implementation.
Good instructable, But did you actually make the coils, they seem to look like the wireless mouse charging pad coils. Could you try to get a guage of the wire and the amount of turns so we can try to experiment?
i'm using 22 gauge wire and it's (kind of) working. just forgot the oscillation.
lioneyexp4 years ago
how much energy is lost from the large coil to the smaller one?
depends on quite a few things. one of them is distance. see comment further down about a 1:1 ratio.
poiu123404 years ago
like most people have said this is not new technology it is cool that you made it into something everybody can make. they would be selling this technology to power gadgets like laptops. they have the technology to make it practical but they are still testing health effects. so they do not sell them to the public.
NOT true. take a look at these links. to COMMERCIAL wireless charging mats.
just realized it but one uses conductance... the other is RF though.
kostaz94 years ago
Let me ask, if i dont use magnet wire and use copper wire is it going to work?.Because I am can't buy from the net can you post me a circuit diagram so i can create the generator by myself?
plain copper wire WILL NOT work unless it is insulated. it MAY work if it has plastic insulation but im not sure. i think it would be best to just use magnet wire.
plus, magnet wire is copper, but with an enamel coating.
avenant4 years ago
Cool, Very cool. And to think that Nicola worked on wireless electricity way back in 1891 !!! And through fear of the unknown people didn't believe it, didn't want it and some just plain called him crazy. Or maybe it was just economics speaking louder than common sense?. Keep up this "free-thinking" - it is what makes real inventors stand out from the sheeple.
fozzy13 avenant4 years ago
That's what I was thinking! This wasn't discovered a couple years ago, Tesla did this ages ago! I read his autobiography...
avenant avenant4 years ago
Sorry, slip of the fingers - was referring to Nicola Tesla.
Great Instructable! I don't understand it yet but I'll spend time re-reading everything.
I'm not a teenager any more . . . far, far from it. But I can't help seeing this Instructable and asking myself "How could I use this to raise some HECK?" This is just too cool not to exploit to it's fullest !!!! LOL

What kinds of tricks or pranks could I pull with this device? Even something that appears to be magic would be good. Like taking an LED, pluging it in my ear and it lights up? Or somehow it triggers some other phenomon to happen, hear, see touch or smell? Or I could move objects somehow without touching them.

Anybody have any good ideas for pranks or magic-like things that are feasible?

And you folks who unbderstand this, please help me weed out the "BS" from real possibilities will you please? I'm much too niave to know the difference.

Think out of the box. The more crazy your idea is, the more I'll probably like it.

I bet old Tesla is spinning in his grave !!!! LOL

Grand Rapids, Michigan
put the wave generator in your pocket. put the coil on your left shoulder or in your armpit or something. make the led and put it near your heart. it should light up and look cool. have fun.
get the firs coil and put it on a table and put cloth over it then put the second coil close to it and tell your friends you have energy power or something like that and the turn it on and make it look like its you doing it
syfire4 years ago
Well, Nikola Tesla discovered this in the early 1900's. This is NOT new, whatever people say. Try a google search on Tesla Coil.
Note to reader (not gabe, as he seems to know this): Tesla did work on wireless power transmission (which are not to be confused with Tesla coils, though he invented those too) Sure, this is nothing new. Heck, toothbrushes seem to use a similar device. He's just saying how to build one.
It's true that he just say how to build one, but MIT saying they discovered this, I say bullshit...
syfire syfire4 years ago
Oh, and Nikolas Tesla also gived a speech on wireless electricity, but people saw big loss of profit in that, so they destroyed tesla
Yeah. I said he "invented it" not "perfected it." (I think US Patent 382,280 and US Patent 382,281 detail this...)
gabe94 syfire4 years ago
actually if you want to be statisticly correct, a tesla coil has nothing to do with this wireless power technology. Wireless power involves magnetic induction and tesla coils involve stray electricity.
gabe944 years ago
If you put lets say 120 volts into the first coil, would it be possible to get 120v in the second coil? how about if you had 3 coils? Would you get 120v at each of the 3 coils? I am so confused with electrical engineering, but i want to know if its possible.
i would say that, if the 2 coils had a common core then yes that is possible. otherwise it is unlikely. you you wish to get a rough idea on how to work out the emf in the secondary coil, you will need to work out the mutual inductance, this is how the magnetic energy from the first coil applies to the second and vice versa, i imagine it has something to do with distance from each other, overlappin surface area etc. then if you multiply it by the current measured in the primary coil. this may be complicated if there is a load in the secondary. im afraid its not that simple.
gxb54434 years ago
Do the inductances have to match between the two coils have to be the same?
no, however the number of coils on both sides along with the distance between them (called the mutually inducive element) and the load you use will affect the applied emf to the secondary circuit.
oh so this will transfer power no matter what. If the the base and reciever were tuned to one another though there would be way greater efficiency, right?
If the Circuit reached resonance, there would be voltage/current magnification, which you may have to consider when choosing your components. the advantage would be that energy would only be dispersed A, in the resistive element, and in the space between the coils. i looked it up, and every time the distance doubles, you lose magnetic power by a factor of 4.
the load will have effect? How do you take that into account? So this way is just two arbitrary coils that will couple together. If you tuned the base and receiver to be in resonance, wouldn't that transfer as close to 100% power transfer as you can get?
gabe944 years ago
Do you get equal voltage/amps on the secondary coil? Or would you have to use a transformer to get equal?
gabe94 gabe944 years ago
i mean as in the voltage you put into the first coil.
It could be argued that this circuit is a transformer, the only difference being that a transformer would have a common coil. Regarding your question about secondary coil etc, you would have to research magneticly coupled circuits in order to understand this. msg me if u want more info.
Would it be best to treat this like a 1:1 transformer?
It would only be a 1:1 transformer if there were an equal number of coils on the input and the output.
i thought u may like to know some formulas for the EMF.
for the primary coil:
Emf = (current in primary circuit)*(load in primary circuit) + (current in primary circuit)*(inductive reactance of primary coil) ±(current in secondary*(mutual inductive reactance)
for the secondary coil:
0(as there is no power source) = (current in secondary circuit)*(load in secondary current) + (current in secondary circuit)*(inductive reactence in secondary coil) ± (current in primary circuit)*(mutual inductive reactance)
gabe944 years ago
Is it possible to loop power? Like connecting the second coil to a capacitor bank then charging the capacitor bank and then diconnecting first coil and connecting the second coil to the first? Or would it short? I am kind've new to electrical engineering
Nav4 years ago
How hard would it be to scale this up, and lay the larger cable into a workbench and attach smaller coils to various tools?
duct tape4 years ago
This is one of Tesla's inventions. It also reminds me of RFID tags.
if your really interested in wireless power, look up powercast co. they have been working at this for few years, I've seen them at a few trade shows, they never stop to amuse me. They have a wireless christmas tree and some decor last year, but they are talkng about doing game controllers, like have an xbox controler not have batteries or wires, so virtually never needs messed with, or the wii controllers with no batteries, they have a few lamps out now, and can run a calculator, but from my knowlage are having trouble with using it in usefull distances, but that was a few years ago, I'm going to a trade show at the end of the month, hopefully will see them there.
flydogfly4 years ago
I looked all over the place for something like this thnx
robotkid249 (author) 4 years ago
Yes, part of my "research" was looking at the mouse. I made other coils of the same size that worked the same. Those just happened to be the coils i used for this instructable.
rellik10004 years ago
My 10 year old Braun electric toothbrush uses a similar technique. Contactless charging provides a sealed,totally waterproof unit.
endolith4 years ago
I'm always annoyed by the constant comparisons to Tesla and toothbrushes that people yell on the Internet when they don't know what they're talking about.

I just found this link that explains the differences between the different technologies:
They use this technology in motorized toothbrushes to charge their batteries. Instead of having exposed contacts, there is just a coil of wire in the bottom of the motor head and a coil in the charger. Waterproof connectors basically.
acron4 years ago
Very nice Instructable. BUT, beware:
and the like. I am just the messenger, here... But, something to think about before we start changing the source to complement our abilities to go wireless.
endolith4 years ago
Be in mind that i could not get a hold of a 0.02uF capacitor so i used two 0.01uF capacitors connected together.

Looks like you connected them in series, though, so your capacitance is 0.005uF now. You need to connect them in parallel.

Can you include your calculations for the resonance frequency of these capacitors with the coil?

Inductive Coupling uses magnetic fields to transfer power. There is a primary coil, which generates a magnetic field. Then there is another secondary coil which is composed of a capacitor and a coil, the capacitor creates a resonant circuit with the primary and secondary coils.

Normal inductive coupling doesn't use any capacitors or resonance. This is what sets the MIT circuit apart. Inductive coupling drops off very rapidly with distance, but their coupling should reach a lot further. "The usual non-resonant magnetic induction would be almost 1 million times less efficient in this particular system."
sabre4 years ago
LED's arent meant for AC current. its a light emmitting diode, meaning it only allows electricity to pass through in one direction.
tboehmer sabre4 years ago
Since the frequency is so high our eyes can't perceive the difference (only in brightness maybe), so inserting diodes pointless (and redundant if you did a half-wave rectifier).
It does not matter, the LED will glow when the sine wave is on the positive side. You will not break the LED by doing so.
sweet! I've been looking for something like this for years.
HOMEPIE644 years ago
this could have a lot of use, but is the energy transfer limited to 2 meters or the magnetic field, also is it if you have them closer together more is transfered/it is transfered faster?
I think that the induced magnetic flux/flux density would reduce with distance.
gabe944 years ago
I am still unsure on how you made the coil. The schematic made me even more confused. Also how did you power the primary coil?
The coil was just insulated wire wrapped round 4 nails, bare in m ind the coil does not have to be a circle. the primary coil had a function generator apply power to the coil, which was inducted to the secondary coil.
1up4 years ago
For the secondary coil, can't you just use a simple bridge rectifier to make it DC?
He does in this image:
But you may have posted before he posted that image. the components after that are smoothinc caps i presume. then we have a specialised filter i presume with the resistor in series.
babbie4 years ago
can you use a battery to be wireless?
ardrhi4 years ago
How about "Over a century ago, Nikola Tesla...blah blah blah...AND electric toothbrushes have been doing the same thing since the 50's, so recently, educated but redundantly-minded people at MIT began..." Come on. Inductive coil battery chargers and such for small appliances, especially those that must be around *water*, have been around for half a century or longer. My dad had an electric shaver that used one. We had electric toothbrushes that had them when I was a kid. I have a $20 sonic toothbrush that uses one now. There's a PDA charging mat system that uses this method -- plug a tiny receiver coil into your PDA or phone, then put the PDA on the mat to charge. Now, develop a system that works at a distance of a kilometer or longer, and I'll be impressed. A low-loss system that will run or charge an electric car at a real distance from the base station would be truly useful.
MrMikeyMike4 years ago
MIT claimed to have used harmonic coupling for their supposed wireless transmission of electricity, but all they did was build a huge inductive coil with a 60% efficiency. Do the math as to how many volts they had to use to get a 60 watt light bulb to light up. The technique they claim to have used has been used by ham radio operators for years to tune their sets. There is a huge difference between a standard inductive circuit and actual wireless transmission. BTW the way Tesla's design worked, he use a huge Tesla coil to shoot huge charges into the air to basically what was a lightning rod on the top of a house connected to a deep earth ground, not very practical with airplanes and skyscrapers.
luvit4 years ago
it shocked me. so i touched it again.
Meggz luvit4 years ago
robotkid249 (author) 4 years ago
Ah, now im scared for my own safety! Maybe I should turn this thing off, haha
lemonie4 years ago
Nice work, and not a mention of Tesla?! L
this is just inductance not the wireless transmission that tesla worked withbut still nice to see people playing with it and learning
It's similar, other people would have tossed in his name (I didn't think you should have). L
I was using it to differentiate between the two ideas but your right its a very well done instructable
(bad eyes) - I didn't think the author should have - but you know that a lot of people do throw in popular names & phrases.
It's the sort of thing I might use, if it suited a purpose (but don't have one right now)

how big should each of the coils be?? (in terms of diameter and turns)
frontier4 years ago
This is nice and all but im curious. do you have any measurements of efficiency? Etc % loss of power on a scale of how much power is transferred?
sypher4 years ago
For interesting insight, look into how "arc" welding machines work. Their inner workings are very similar to this principle. In the case of welding machines, sans the techno bable; they make use 2 transformers spaced apart to switch out voltage from them master transformer to the slave transformer for amperage to generate the ever so useful electrical arc that is vital for "SMAW" type metal welding. They have been using wireless electrical transmission for over a century for use in welding, thanks to Tesla, Miller, Lincoln(not the president) and various other groups/inventors. It is an odd thing that most people think the wireless energy is a thing of the future, when it has actually been in use for a considerable time.
ChunkMunk014 years ago
Hey guy, Just wondering how much electronics experience you really have. When you wire two capacitors in SERIES as your picture shows, their series capacitance does not increase, only their breakdown voltage, as the voltage is divided by the two devices in series. To add capacitances with capacitors, you wire them in parallel. PS. on the last page of the instructable, your full wave rectifier schematic shows your 4 diode bridge, your two wires for dc out, and two capacitors of different values in PARALLEL, which is redundant unless you're adding the capacitive values to find a resonant frequency. Seeing as how their purpose is to smooth the output of the rectifier, in general, the bigger the better. done and done.
higgrobot4 years ago
I may be wrong but, basically the difference between this and an air-core ac transformer is... yours isn't as efficient and only works at 147.5khz :)
Would a non-resonant air-core transformer work across a greater than 1 meter gap? The point of using a resonant frequency is to concentrate the energy transfer, either boosting efficiency or increasing range. It's a feature, not a bug.
I don't know if an air cored transformer would work across a 1 meter gap very well? an extension cord would work great :) This might be a great way to power a toy helicopter or UFO though
How about keeping your cell phone charged, all the time, just by having it in the same room as a power coil? How about setting your laptop down on your desk and keeping it powered without a wall cord?
Let's call it POW, Power Over Wireless, the possibilities would be endless. I could run my Peltier beer cooler while I stumble around the house on my way to a drunken stupor :)
According to MIT it's called WiTricity.
>>It's a feature, not a bug. Did you formerly work for Microsoft?
robotkid249 (author) 4 years ago
LEDs are one of the only things that work in AC, that could be demonstrated.
robotkid249 (author) 4 years ago
I updated my Instructable with new circuit diagrams.
Notbob4 years ago
How far can the secondary coil be from the primary, before it stops working?
rocketguy4 years ago
Well, this is really cool and all, but this is one of those technologies that I really hope stays a curiosity. EMF exposure is still poorly understood in terms of biological interaction, and there is some evidence that it's problematic for health. While this isn't exactly a high voltage power line, it's a lot closer. Basically, if you're going to do this, don't put it right next to the baby crib... That said, I'm building a coil for custom solenoid work, so it was nice to see how this coil is built. -RG
If you could measure all the radiation being passed through the human body at any typical moment, you would be astounded. Radiation being all particle and wave energy hitting or passing through us... I don't know the actual power, but consider that most radio stations put out 50,000 watts or more, and power lines are surrounded by it, the sun puts out tons, etc etc. It's kinda like other environmental issues...misunderstood and generally overreacted. Not saying it's safe, but it may be no worse than walking around.
On top of that, is this not how artificial hearts and pace-makers are charged?(or am i mistaken?)
lorikix4 years ago
Do you have a simple circuit diagram you can show us?
bmake4 years ago
The Sonicare brand toothbrushes use this technique for charging. A Sonicare charging base might be a good off the shelf starting point. I imagine using the charging base and perhaps the lower portion of the toothbrush handle with the coil attached to an IPOD charging base would be a good start if you have the electronics worked out.
sageserver4 years ago
Hey this is cool. I tried to make one of these but i didnt know how to work my dads ac power supply. I wanted to make wireless earphones(very small) using inductance. I couldn't make it becuase of the power i needed to make the coil work that far. I was thinking you can make one of these. Like, you have a coil on your shoulders(under clothing) and you put a small coil connected to a speaker in ur ear. you can sell it at school (since lots of people want to listen to music without having there earphones taken away) for alot of money. can u help me make them or make an instructable for them. That would be super cool. Nice instructable, very good pictures.
Hmmm, I suggest using ferrite cores for the earphones. The transmitter on your shoulders is a good idea, buy a cheap shirt and glue the coil to it. Wear that under your uniform and you;re good to go. You also have to modulate the signal between the two, otherwise you will just hear an annoying hum...
I thought ferrite cores make the magnetic field closer and compact. Also, since sound is almost a form of AC, all I need is a amplifier. I made a coil ,similar like urs, and I got it to light a red LED. while doing this, my dad told me that the wire also has its own resonance. My coil resonated at about 1.56 MHz. If you go to .156mhz you get the same resonance but since its lower frequency giving smaller efficiency. the higher you go up an octave the more efficient it is until it starts to brake itself down. I put a scope to both my primary coil leads and to my secondary coil leads to measure it. also what would be good its to find the right MHz then to make a 555timer curcuit to match it and you have a working inductance wireless charging thingy-majig.
JReynolds094 years ago
The pictures in this are cutting into the 3rd step to this instructable. I would like to try this but can't make out exactly what the step is saying. please try to correct this or email it to me @ Thanks.
jimmyjo4 years ago
IIRC LEDs have a very low reverse breakdown voltage, it's generally a good idea to put in an anti parallel diode with the LED in AC applications.
srhadaham4 years ago
does this have the capability to do something practical such as charging an iPod?
wolfkeeper4 years ago

But don't tell the FCC, they'll have kittens- this will be radiating like crazy! And square wave... not so good for not radiating.

Incidentally, you would be much better off twisting or plaiting the wires in the primary, it massively reduces the resistance losses (you really want Litz wire for this)
correct me if I'm wrong, but using two capacitors to double the capacitance, they have to be connected in parallel.
You are correct. Those caps in the pictures are connected in series, thus halving the capacitance to just 0.005uF.
no not halfing the capacity only capable to store higher voltige at least that's been said to me by my teacher
That is true, though a single mylar capacitor like you used should be able to handle 120V on its own quite easily. It's still half the capacitance.
What kind of range did you get with this? I've tried super basic inductive coupling and gotten similar results to your photos (without using capacitors, even...). Also, I feel like there is way more helpful info on this instructable regarding wireless power...
thinker4 years ago
this is similar to the idea used by wireless radio headsets used in the navy for years they have a large magnetic ring around the circumference of the deck that way all the people on the deck can hear the radio tower but the signal isnt broadcast far enough for other ships to pick it up out of curiosity, if you made a ring going around the roof of your room would all objects in the room be powerable by said ring?
Mr Cheeseo4 years ago
agreed 110% I was just going to say the exact same thing, hmmmmmm great minds must think alike huh?
robotkid249 (author) 4 years ago
No, this form is really safe and there will be no cancer i promise.
eth3real4 years ago
Those caps should be setup in parallel to get 0.02uF, not in series which doubles the forward voltage instead of the capacitance.
Didn't see those other comments before I wrote this. :P
hg3414 years ago
dang if only i had a cell phoneoh wait i f!@#ing hate phones!!

anyway this was realy cool
I always thought about this but didnt know it was real until I read about it in popular science. I guess someone made a lamp that could send power to something next to it like a cell phone. Wouldnt it be cool if you could have one of those coils running through the walls of your house? You wouldnt have to plug anything in, it could be very useful.
The problem with inductive coils is that even when you are not using energy at the secondary, the primary is wasting energy keeping the magnetic field steady, so this would not be very good for a large scale application. Think of it as a giant wall wart.
Also, it would likely get very hot over time...
Exactly right. That heat also contributes to energy waste. There is also the noise factor a one large or multiple small transformers. At some point you may have a mutual impedance (crosstalk) between sets of coils which can cause all sorts of problems.
robotkid249 (author) 4 years ago
147.7 kHz is the best frequency to couple with a 0.02uF cap. Thats why it is high.
robotkid249 (author) 4 years ago
For now i would say that it is at 70% efficiency but once i work on it some more that percentage will go up.
Can I ask why you think it's that high?
wee_man4 years ago
wow this is realy cool. There isn't any possible side affects from use and how much power does the primary coil consume.
zomfibame4 years ago
yah, I second the phrase made by lemonie..... not a mention of Tesla?! cool instructable, even without mention of Nicola
robotkid249 (author) 4 years ago
Great idea, that would be really cool, the problen is though thst inductance only works really close together.

Get More Out of Instructables

Already have an Account?


PDF Downloads
As a Pro member, you will gain access to download any Instructable in the PDF format. You also have the ability to customize your PDF download.

Upgrade to Pro today!