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Wireless Power TransmitterBy Radu Motisan Posted on July 13th, 2011 , 7686 Views (Rate 10.87) |
Using induction, it is possible to transfer electrical energy remotely, without any wires.
Similar to the Radio broadcasting technology, I have designed an emitter and a receiver. They are both tuned to work on the same frequency, in this case 63.1KHz. Their purpose is to transport electrical energy.
The oscillator in the emitter is a Royer push and pull type, using two IRF2807 mosfets. The emitter coil, is a circular 18 turns coil, with a tap at the middle (9+9 turns).
The receiver, uses a similar 18 turns circular coil, but no middle tap is required. I've used PVC insulated 1.5mm copper wire for both coils. A 440nF capacitor is connected in parallel to this coil, and then the load - a simply 12V bulb. See the circuit diagram for more details.
Circuit diagram:
This is a good alternative to recharging my autonomous robot . The robot can automatically detect the power emitter, and approach it to recharge its batteries.
Note: In free space, all electromagnetic waves (radio, light, X-rays, etc.) obey the inverse-square law which states that the power density of an electromagnetic wave is proportional to the inverse of the square of the distance from a point source.
Doubling the distance from a transmitter means that the power density of the radiated wave at that new location is reduced to one-quarter of its previous value.
The power density per surface unit is proportional to the product of the electric and magnetic field strengths. Thus, doubling the propagation path distance from the transmitter reduces each of their received field strengths over a free-space path by one-half. Radio propagation.
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July 14th, 2011 at 1:13 pm
Witricity!
July 14th, 2011 at 5:54 pm
Actually, I had a different name in mind
July 22nd, 2011 at 5:18 am
what was ur input voltage ? i also did this project in college so i was curious to findout ur efficiency ?
July 22nd, 2011 at 8:20 am
12-24V . Efficiency will be measured soon but seems to be high.
August 16th, 2011 at 8:54 am
Would be interesting if you could measure efficiency for different distance and misalignment. Does the primary current rush when the secondary side is removed, or does it stop? I.e. how is the reflected impedance related to the airgap, secondary load resistance etc?
August 16th, 2011 at 10:48 am
@Tomas, hope to find some time for all this, soon.
August 16th, 2011 at 11:18 am
@Radu Motisan, when you have studied the efficiency with the coils you have now, it would be really interesting to see how much it could be increased by using litz wire instead of solid copper wire. Maybe I’d better build one myself and try, your circuit diagram is excellent!
August 16th, 2011 at 11:52 am
Thanks, Tomas. The red wire is actually litz, but the internal thin wires are not insulated from each other. One can use regular emailed copper wire , and twist several wires together for the desired size.
September 16th, 2011 at 8:48 am
I want make similar project and I want more details about this so please help me to make concept of your or our project clear
September 16th, 2011 at 10:49 am
All the details, including circuit diagram are presented in the post.
September 23rd, 2011 at 9:41 am
cool….
can the power be focused? just like a laser beam line sending from source coil to target coil?
December 19th, 2011 at 11:09 pm
Ar merge si cu driver ZVS ?
December 20th, 2011 at 10:09 am
Salut Stelian, ZVS e chiar un oscilator Royer, deci asta am folosit si eu aici, intr-o varianta usor imbunatatita.
January 3rd, 2012 at 8:33 pm
Salut Radu, ce curent maxim poti transfera, am vazut pe schema ca scrie max 10 A ? Se poate 10A ? Multumesc
January 4th, 2012 at 8:28 pm
Salut Bogdan,
Din pacate nici pana acum nu am facut masuratorile, asa cum scriam in articol ca doresc sa fac.
La cum vad eu lucrurile, poti fara probleme sa ajungi si la 10A intensitate. OScilatoarele de acest tip (royer) au servit cu succes puteri de pana la 300W , ar trebui sa mearga si in acest caz.
February 1st, 2012 at 1:39 pm
Hi Radu
Any idea what current the demonstration was drawing?
On your schematic you show a 1000uH 10A inductor but I can’t see anything this big on your pcb in the video.
Thanks
Warren
February 1st, 2012 at 2:23 pm
Yes, my inductor was for smaller current, still you should use one rated for higher power to make sure the circuit will run cool for longer amounts of time.
I didn’t do the current measurements yet, sorry, I need to do them and post result on efficiency. Hope will be able to do this soon.
February 12th, 2012 at 1:40 pm
the input voltage is in dc or ac actually?
February 12th, 2012 at 3:47 pm
the circuit diagram clearly shows a + and a – . so it is DC input
March 30th, 2012 at 12:01 pm
give me detail information & file of that wireless projects
April 18th, 2012 at 12:57 pm
Hi
I am first year EE student. Because I want to understand the circuit more, I start reading electronics book and it was really nice and helpful to understand the basics of some of the components in the digram. But till now I did not fully get it. Please, it will be kind from you if you explain your circuit…
May 30th, 2012 at 5:29 am
This is magnetic induction. It has a limited range and not too practical…This is not what you are looking for… You want to send high power energy with no restrictions to very long distances using longitudinal electric waves, just like Nikola Tesla did.
June 19th, 2012 at 7:13 pm
Hi
how did u take a center tap in the transmitter coil?
June 19th, 2012 at 10:00 pm
@Deepal: it is so easy! You wind 18 turns, then puncture the plastic coil former, at the 9th turn, and solder an external connector, that would be the center tap.
So the emitter and transmitter coils are at first identical, until you puncture the emitter to create the center tap. 18 turns both as explained above.
If you build this send me pics so I can post them here.
July 11th, 2012 at 10:38 pm
What did you use for the 10 volt zener diodes?
Also, do you think this would work if I used slightly different dimensions for the coils, but stayed with the same number of turns and kept both proportional? Like, if I just used 22 gauge hookup wire for the coil, in stead of 1.5 mm wire?
P.S. Keep experimenting, bro! This type of research is very cool. Just for a suggestion, to see if you could make it work, I remember reading where someone was making a circuit like this to power a flyback transformer. It would be like transmitting a few kV wirelessly.
July 12th, 2012 at 9:08 am
Hi John,
I don’t remember the part name for the 10V zeners, but they were like 0.5W .
You can use any zeners in the 10V-16V interval, so choose what you have.
Yes you can use different wire for the coils.
July 12th, 2012 at 3:14 pm
Thanks for all the help, Motisan! I’ll check and see the transition frequency of the IRF2807, just in case: AWG 22 wire is pretty thin, and I’m worried the frequency may be too high for them to handle. Plus, I really love how you laid out the circuit in the videos and pictures. Whenever I make a project, half the fun in it is in making it look awesome or futuristic, and this one really hits the nail on the head.
If you like, I’d love to talk more with you about your ideas and experiments. It’s so hard to find any good circuits or ideas for a concept like remote power transmission, which has been around for well over 100 years. I ordered the parts, and am working on a few projects myself at the moment, but when I get the chance to make this (if the damned thing works right – I always mess things up!), I’ll fill you in on the results: I have an oscilloscope that I need some practice using, so I could do my best to tell you the efficiency and the waveform. I might try to adjust it to make a sawtooth waveform, which (because the magnetic field around the coil collapses so much more abruptly) can transmit power more efficiently.
Sorry if I am talking too much, I have a bad habit of doing that.
August 25th, 2012 at 11:37 am
the capacitor we are using is ac or dc?
October 11th, 2012 at 4:45 pm
to avneet, actually, its just a film capacitor and it stores a very little electric charge so its not necessary for it to be polar, it doesnt have any polarity so just ask for a capacitor and they will give you that,
October 12th, 2012 at 7:52 pm
actually i have used ac capacitor of 44uf,250 v & the power transmitted from transmitter to receiver is about 1-2v
which lights up only led so what should i do to light up 12v bulb & one more question how can i increase the range of wireless power transmitter
October 12th, 2012 at 8:44 pm
to increase the range, you should try to increase the diameter of the coils.
October 24th, 2012 at 6:30 am
regarding those center tap, i cant still understand how to have the tap. if im going to wind the wires at about 19 turns, then unfold it again and find the center by measuring, will it do?
im wondering because like what you did in your video, the center tap isnt actually at the center because the way you wind the wire isnt like in a coil where the wires are just in one side..
sorry, im really confused
October 24th, 2012 at 6:32 am
i mean 18 turns
October 24th, 2012 at 9:58 am
It will NOT work, as each turn has an increasing length – measuring it will place you way before the middle turn. So better use a transparent case like I did, and simply puncture it to insert a connector at the 9th turn.
October 27th, 2012 at 10:33 pm
se puede usar un condensador de 0.47uF en el receptor en ves del 0.44uF
October 27th, 2012 at 10:35 pm
can use a 0.47uF capacitor in the receiver in the 0.44uF see
October 28th, 2012 at 3:28 am
so im just going to coil the wire and count the turns and on the 9th turn, i will just puncture the wire and insert the center tap?
in short.. the center tap is not pertaining to the length of the wire but to the number of turns of the wire right?
thanks..
October 28th, 2012 at 4:03 am
hello, can i use other capacitors or should i use WIMA capacitors?
October 28th, 2012 at 1:56 pm
@joem, yes, you got it right.
@natan, you can try other caps as well.
October 31st, 2012 at 12:17 pm
Is it required for you to design your own oscillator or could you simply buy an oscillator chip and hook up the voltage regulator to it and output of it to the primary coil in parallel with the 0.47uF?
Can you do this?
October 31st, 2012 at 12:35 pm
Also, why did you pick a planar coil as your primary coil? Why not a single loop of copper? Are they not more efficient in setting up a better magnetic field rather than the planar coil?
Thanks!
October 31st, 2012 at 1:18 pm
For this oscillator I needed more than a single loop coil, to make it work.
November 1st, 2012 at 9:48 am
And as for my initial question: Is it possible I use a standard oscillator chip with a single loop coil and capacitor in parallel. Would this work for a setup of this kind?
November 1st, 2012 at 10:48 am
HB, what is a standard oscillator chip?
November 1st, 2012 at 10:57 am
I mean an oscillator you can buy which is contained in a chip/block.
November 1st, 2012 at 11:00 am
Wait a minute, how come you don’t have an oscillator? How or at what frere you driving your coil? Is this not resonant magnetic coupling?
And I’m sorry, I confused “oscillator chip” with power amplifier.
November 1st, 2012 at 11:19 pm
@HB actually, it oscillates ’cause it’s indicated on the description that it oscillates at 63.1 KHz.. and i think mosfets do these oscillation
November 2nd, 2012 at 8:15 am
@Joem: Yeah I was wondering ‘how’ it was doing the oscillation…I thought you were supposed to use a signal generator or crystal oscillator to provide the necessary signal @ whatever the frequency desired.
Anyways I got a question: What do the mosfets do in this design other than provide the oscillation? Does it amplify the current into the LC tank? Do we want a high current in the LC tank circuit end anyway? I would assume having a higher current at the primary coil LC end would create a really powerful and large magnetic field and hence increase the distance of transmission. Is this correct?
November 6th, 2012 at 11:20 am
mm,, i dont know how it does but accdg to its name.. MOSFET or metal–oxide–semiconductor field-effect transistor, a device used for amplifying/switching electronic signals..
so i think it amplifies the current.. but i cant answer some of your questions, maybe we shall leaave it to the author.. thanks..
November 13th, 2012 at 4:38 pm
Hmm thank you Joem. I see what he’s doing now I think. This is basically a Royer Oscillator which is an oscillator that operates at high current and high frequency. Right now my design consists of a regular oscillator that I made which is fed into a power amplifier. Only problem is, the power amplifier part could be expensive so that’s why these Royer Oscillators are used most often. Please correct me if I’m wrong Radu.
November 13th, 2012 at 5:42 pm
@HB, another reason for using a high frequency power electronics converter to energize the primary coil is the efficiency. With an analog power amplifier, you will get terribly low efficiency.
@Radu Motisan, did you have time to test efficiency vs different air gaps etc? (just repeting my previous question:”Would be interesting if you could measure efficiency for different distance and misalignment. Does the primary current rush when the secondary side is removed, or does it stop? I.e. how is the reflected impedance related to the airgap, secondary load resistance etc?”)
November 13th, 2012 at 5:46 pm
@Tomas, from what I remember there was an interesting effect of power consumption in direct relation to the efficiency of the energy transfer: connecting a simple ammeter in the emitter circuit, one could see a massive current increase with the receiver properly aligned and the bulb shining, and a decrease as the receiver is moved away. The primary current will not stop, but will surely tend to a minimum, negligible value.
November 14th, 2012 at 5:26 am
Tomas: Ah yes, thank you for that. I know there are a few oscillator circuits out there (Wien-Bridge, Hartley, Colpitts, Royer, etc) but I think the Royer is the only one that can achieve high frequency power oscillations…do you know any other way I can make a circuit that gives me high power (3-4 Amps) at high frequencies (from 100 KHz to 1 MHz)?
November 14th, 2012 at 1:28 pm
@HB, a couple of years ago I build a inductive power transfer device that was able to transfer a power of a few hundreds of watts (40 V, max 9 amps, if I remember correctly) over a distance of 5 cm with an efficiency of 87%. The resonant frequency was 20 kHz, and I used a MOSFET full bridge (H-bridge) to energize the primary coil. For the triggering signals I used a simple square wave signal generator.
November 15th, 2012 at 9:01 am
@Tomas: Wow that’s very cool. Would I be able to do the same if my resonant frequency is @ 1 MHz instead? I doubt it … however, it might work with some sort of RF power BJT. Oh and why was the distance so short? Was it because your coil Q low or something?
November 15th, 2012 at 7:33 pm
@HB: the distance was fairly short because of the relatively low frequency. The lower the frequency, the better inductive coupling you will need between the coils to transfer reach the same power and efficiency levels. There were several reasons why I choosed 20 kHz frequency. One were hardware limitations (eaier to work with lower freq) and an other was that 20 kHz seems to be what they choose for the wireless EV charging standard.
November 15th, 2012 at 8:28 pm
@Tomas: I’m having a hard time proving on my paper why a higher frequency is better to use. I know there are hardware limitations but we were thinking of using around 1 MHz. Can you suggest me some theory I should look at as to why a higher frequency is better please? The only parameter frequency seems to affect in my calculations is the Q of the resonators, anything else? It also affects the impedance of my coil, jwL, and I kinda need this too to allow maximum power transfer to my load by matching the impedance of the source.
November 25th, 2012 at 2:53 am
isistes windings as the issuer and resector to stay that way you move and well connected and did you use as a source
November 25th, 2012 at 3:19 am
1000UH coil is necessary? which is the core of this air or coil which
December 17th, 2012 at 8:00 pm
Hello Radu and thank you for your prototype.
I read all the reviews and I was wondering who has come realize your prototype?
I’m still missing the 1000 uF and inductance calculation for connection to half of the primary coil to throw myself;-)
If testers had réussient this prototype and could give me some details on the implementation not to deceive me.
Thank you, didier
December 26th, 2012 at 11:33 am
Hello Radu ,I have some project like you did and i want to know how do you know your device works on 63.1KHz? and what tools do you use to measure the frequency? because i had different result when i used oscilloscope and network analyzer(to know the resonance frequency for antenna).
what happens when the frequency higher or lower from 63.1KHz?
December 28th, 2012 at 11:41 am
@didier: it’s very easy to build. not much to add here, you have full description and everything you need in the article.
@jess: I used a multimeter to measure frequency. You can use any frequency you want, just make sure the receiver is tuned to emitter’s frequency. For this purpose I used the receiver’s capacitor, adjusted in the LC circuit for the frequency required.
January 14th, 2013 at 5:01 pm
Efficiency was pretty high. i want to know how was the Induction coil turns
January 18th, 2013 at 2:04 pm
in which component does the frequency depends on? Can we use other mosfet ? Does this circuit can work in MHz range?
March 2nd, 2013 at 10:38 am
we are doing this project we need to know the complete working of this project and how each component works,please sent the website address in which we should search
March 22nd, 2013 at 8:06 pm
Hello Radu,
Would you be interested in building one for me? Could you let me know your price and shipping to Finland? Would be an incredible help!
sinrev at gmail dot com
Thank you!
March 26th, 2013 at 6:44 pm
sir i am really impressed with this amazing thing of ur and i am making it for my collage project but i have little problem with that .i have to print a thesis of my own for this project which have to contain upto 80 pages so please help me for having them in one place i am wating for u r response . i am in big trouble pls help me sir
April 17th, 2013 at 6:41 pm
we r trying this project we are not getting the idea about transmitter coil and receiver coil , can you tell me what rating copper wire you used as soon as possible
April 17th, 2013 at 7:48 pm
@YESHU: 1.5mm^2 section , PVC insulated, copper wire. the receiver 18 turns. So is the emitter coil, but with a tap at the middle (so it is 9+9 turns).
April 20th, 2013 at 2:15 am
Hi, may I know what is the maximum voltage and current can be transmitted and can the receiver charge up a mobile phone at 5v, 500mA? Thanks.
April 22nd, 2013 at 6:38 pm
Hi Radu,
I can not find any 0.44uf or 440nf capacitor on ebay or other electronic websites, the standard is 0.47uf. Do you have a link where can I buy 0.44uf capacitor you used in your circuit? Can I substitute standard 0.47uf on both transmittor and receiver side? Will that make any difference? I am asking this b/c I a novice user. Thanks for your time to reply me.
April 26th, 2013 at 11:37 am
@JP: yes it can.
April 26th, 2013 at 12:02 pm
@Mike: it is always fun to try , to experiment. this is my advice.
May 7th, 2013 at 11:00 am
Thanks. Can the MKP capacitors replaced with other types of capacitor, etc electrolytic? Thanks in advance. Nice day.
May 8th, 2013 at 4:41 pm
Hi, may I know what is the diameter of the center of the coil? Does the number of turns affects the frequency or it will still be functioning if Im using the same number of turns and same value of cap for both side of the coils? Thank you.
May 8th, 2013 at 5:00 pm
@JP: other types yes, but not electrolytic.
@Jean: aprox. 1cm . the coils are not critical, but after you build them, you’ll probably need to adjust the values of the capacitors you use, to tweak the working frequency (given by LxC ).
May 9th, 2013 at 2:57 am
I can only find X2 275 VAC MKP in my local stores, can those work? For example, if I fix 470 nF at the transmitter, I will need to change the value of cap at the receiver in order to have the same frequency with the transmitter part ( like your’s 440 nF)? Thanks.
May 9th, 2013 at 2:15 pm
Hi Radu, could you tell me how you came up with the coil size/ number of turns required?
May 9th, 2013 at 2:19 pm
A short answer would be: based on my previous experience, but why are you asking, Mark?
May 10th, 2013 at 12:49 pm
Just curious about how crucial the number of turns and the size of coil are to correct operation
May 10th, 2013 at 1:19 pm
Also what power rating resistors would you advise to use?