Comments for "Wireless Power Demo Circuit"

26th June 2014 19:47

Amer wrote ...

Hello Alan

Great educational video about wireless power transfer. I'm doing a similar project where I also need to get a LED to light. Also wireless. The crystal freq you are using is 14.91MHz. Where I buy my electronic components 14.91MHz is not an option.

Is it OK to use another crystal with the freq close to that of yours?

I would really appreciate your help on this.

Regards, Amer

16th November 2013 06:56

Gareth wrote ...

Hey alan,

I have been doing research on green energy... If you have the module (the one that releases the signal) coil is way bigger than the small reciever (the one that recieves the alternating current from the moduel) coil... And is it a transformer of some sort? I'd like to know.

I just came across your invention, and it is cool... Very good presentation, got my gears spinning..

Thank you Alan,


21st March 2013 02:30

Nicholas wrote ...

Hi Alan,

Fantastic explanation! Thank you!

I have a few questions.

1) What variables determine the amount of power that can be transferred? Frequency? Size of coil?

2) How does voltage play a role? If you were to supply the coil with power/voltage from a common household receptacle, would thus be a suitable/safe process?

Thanks in advance for any insight!

14th March 2013 09:10

Aimi Zainal wrote ...

Hello and Good Day Alan,

I've been really aspired with your video.

I have try to make the same circuit but I have problem in finding the oscillator..where can I find it..and can you explain me in detail about this circuit..I still having problem in understand the circuit itself..

thank u in advance

really appreciate your help..

looking forward for your reply

26th February 2013 18:34

Ahmed wrote ...


Thank you for you interesting videos. they are really helpful.

I'm making a wireless phone charger for my senior design project. I'm getting a DC Voltage from a battery as a input and would like to charge a phone from the rectifier circuit. Could you please help me if thats possible and what ICs I have to change ?


1st February 2013 00:23

Frank C wrote ...

Great presentation Alan. Thank you for a supurb effort. A complicated subject well covered and well explained in the time available.


16th January 2013 06:30

Drew wrote...

Hi Alan,

Loved your video! I wish I could understand it better. I've watched it several times, but have no real experience with electrical engineering.

You calculations are based about finding the best power output, but could you try to help me with this?; I want to wirelessly power a single 1mm LED at 3volts from about 6 inches away.

The power transmitter will be battery powered, I need to maximize the duration of consistent power delivery.

I'm not sure how to adapt your equations to calculate the most efficient design.

I would be so grateful for any advice!

18th November 2012 01:13

Mohit wrote ...


Alan Sir i really like this project but mosfet irf510 is not available in my area can i use some other here...

pleasw help me and also tell me that y cnt i use basic transistor here

1st November 2012 12:31

Mikhael Wijaya wrote...

Hey Allan, a couple of years ago, I was inspired by a show being displayed in a confrence on 'TED'. Where an MIT professor and some graduates created indcutive charging to a point where it could reach a couple of meteres. I'm planning to create one such as that for my MDP (DT) and using your principles as well as your brilliant explanation, but I myself can't create it as I have never done physics before or have the required euqipment. And as you said earlier, there were those 'PowerMats' that are considered as inductive charging... but I want to create one with amplifying range. Not one restricted to making contact with the mat. Is it possible you could give tips, euqpiment or tools? All critisms and help is very much appreciated.

Extra info:

- Still in highschool

- Needs lots of help to create this project :3 [The TED video]



18th October 2012 06:22

Shane wrote ...

Hello Alan,

Nice video explaining the principles of wireless power transfer so in-depth! I was wondering why you had a choke on the primary inductor circuit?

Thank you


21st September 2012 05:12

WeiTao wrote ...

Can I know the datasheet of the oscillator? Because I can't find it.

12th June 2012 13:46

Noah Z wrote ...

Do you have an image from an oscilloscope for what the wave forms look like at the transmitting coil and the receiving coil? As well as the frequency at both sides and the max voltage? I'm an amateur at this and trying to fumble my way through and if I had something to compare it to that might help me to figure out what I'm doing wrong. Thank you ahead of time!!

8th June 2012 11:49

Alan Yates wrote...


Connect the signal generator to the gate of the MOSFET.



4th June 2012 17:58

goku wrote ...

can u tell me a ckt with a signal generator instead of creating one and making a ckt out of it

18th May 2012 18:00

Kaustubh Chaudhari wrote ...

Hi Alan,

I am a newbie to this field. I tried to build the circuit similar to the witricity switching design simulation. But dont know something is going wrong. Can you explain me the exact functioning of the circuit. To be precise what exactly is the function of the 390pf in circuit. Can you tell me how these values are calculated?

Thanks in advance.

Looking forward for yor reply.

14th March 2012 08:44

Tamer wrote ...

does the temperature of the IRF510 increase with you ??

16th February 2012 10:15

Tamer wrote ...


i need the equation of solenoid coil inductance that you use , cause every calculator on internet or any formula doesn't give me the values you wrote in the picture.

and i need also all the expressions used for the generated field and received current and voltage as in that range of frequencies the circuit's behavior follows RF analysis not magnetic analysis coupling

thanks in advance.

waiting for your reply

24th January 2012 17:03

Arun kumar wrote ...

Hi alan

I'm halfway through the design.. There is no availability of cap inductor near my place.. Can u suggest me an alternative component instead of cap inductor..

3rd January 2012 06:13

Zhihao wrote ...

Hey There smart professor :)

I am a student from Bonaire, The Netherlands Antillen.

Kind in need of your help. We got stuck in our project. We couldn't build a working wireless transfer demo to show our classmates.

Please reply me asap. Would be so grateful if you can do it before 7th Jan.

I need your help of giving me a guide to build a small scale demo to show my classmate this wireless power technique.

and would really nice if you can give a description of each of the materials what they are for and why.

7th December 2011 13:42

Ron wrote ...

Hi Alan,

I built the exact same circuit you have as I am doing a study on wireless power transfer. I am not sure where I would be going wrong but I cant seem to get it to work. What is the average voltage I am looking at by the coil.Is there a way I can send you a picture of my circuit and you could take a look at to see what I am doing incorrectly. Appreciate any help you can provide. I used the same values you have for the circuit.

14th October 2011 03:05

Pete wrote ...


There's something that I don't understand :

Receiver is composed by capacitor and coil inductance where values give a resonant frequency of about 14Mhz so same than your quartz. But how do you choose values of capa and coil in the emitter part ?

Thx in advance for answer

23rd September 2011 16:35

deren wrote ...

Hi Alan,

I am currently working on a project along the line of wireless power transfer. Your demo has proved to be a real help. However, i am unsure about certain concepts such as the power being transferred by the transmitter and the received power. If i were to transmit 10W, does it depend on the class E amplifier? Any directions would be a great help. Thanks.

Best Regards,


25th August 2011 04:15

Dan wrote ...

For Kenneth,

Hint, I've run ~25W at a lower frequency with a similar circuit using ferrite cores to direct the flux into more useable patterns over 1/4 to 1/2 inch gap. The driving circuit was a bit more complex (Add PWM and frequency control), but basically the same idea.


3rd July 2011 21:16

Alan Yates wrote...


The oscillator is a canned "14 pin style" TTL 14.91 MHz square-wave oscillator module. It actually only has 4 pins, two for power, one not connected, and the other signal out. It runs from about 5 volts and delivers nearly 5 v peak-to-peak into an open circuit.

They are very common and many frequencies are available. I used this one because I have a few in the junkbox, it is not a critical frequency at all, any HF one should work, from a few MHz to 20 or so. Of course my tuned circuits were optimised for ~ 15 MHz.

If you really can't find any, I have plenty, I can send you one.



3rd July 2011 21:13

Alan Yates wrote...


Unfortunately I do not speak Spanish, but I translated your message using Google Translate.

5 Watts, shouldn't be too difficult, especially over short range. I'd be interested to see how it turns out.



3rd July 2011 18:24

Alan Yates wrote...


Are you running the complete system at resonance?

The efficiency will be really poor if both sides aren't resonant or have poor Q. You don't mention capacitors, so measure the inductances on both sides and add capacitors to tune the system to resonance at the frequency the 555 is running at.



22nd June 2011 14:04

anna wrote ...

what is the oscillator can give me details of the crystal oscillator

19th June 2011 16:08

rodrigo wrote ...

Hola Alan

Exelente la informacion disponibles, demasiado buena. Estoy en estos momentos en un proyecto en U, en donde como meta nos propusimos, transferir 5 Watt de potencia.

La verdad que me gustaria mucho pedirte si tienes algo en español, como por ejemplo tu video, o algo asi. Me gusta mucho el tema y quiero partir bien del principio.

Nuevamente te fecilito por la pagina, y ojala me puedas responder.


28th May 2011 13:34

Kenneth Dale Thomas wrote ...

Hi Alan - I really enjoyed your article. I have a couple of questions please. What is a good source for the 14.910 oscillator and:

I am attempting to build a miniature wireless charger for a 3.7 Vdc, 100 Mah/ 20C, Lipo cell. It's to fit inside a small robotic device that requires wireless charging of the Lipo cell. The receive side coils (size restraint item) I have available are 153 turns of # 38 AWG with a dia of 12mm as part of a LC tank feeding a FWBR. It produces 4Vdc but not enough Ma to barely light a LED. For the TX side, I have used a 555 feeding a npn/pnp pair and that into a LC tank. I have wound 80 turns of # 26 AWG for the TX coil. I am stumped on how to get more current and would ask you for any suggestions on what direction I should try. I would appreciate any response you might be able to provide.

Best Regards

Kenneth Dale Thomas


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