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Miniature wireless power demonstrator

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mccoywm72

Thu Oct 15 2009, 02:11AM

Registered Member #2042 Joined: Sat Mar 21 2009, 03:44PM
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Posts: 9

I have had the pleasure of seeing one of these in action. It really is a great demo especially when considering how abstract many of the E-Mag lessons can be.

Conundrum

Fri Oct 16 2009, 06:27PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

Similar to an induction heater methinks...

ChrisO

Wed Dec 02 2009, 09:09PM

Registered Member #2495 Joined: Wed Dec 02 2009, 08:30PM
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Hi,

I'm new to the forum and I have a question about the capacitor C9 in your schematic. I and my team are trying to build a working wireless power transfer device off of your plans but we are having the problem of one mosfet getting stuck closed. We want to know what size capacitor we may need to ensure our oscillations start. Would a higher capacitance work?

Resistors, indcutors L1-L2, Diodes, and capacitor C9 are the same as per your schematic. The mosfets are irfz44rpbf n-chan 60v 50amp. The capacitor bank is 8 4.7uF 300v polyprop caps. The primary loop inductor is 1/4inch copper coil with 15 turns of diameter 7inches.

Any help or advice would be amazing. Thanks,
Chris O.

Pankaj Patel

Sat Jan 02 2010, 02:34PM

Registered Member #2581 Joined: Tue Dec 29 2009, 09:08AM
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Posts: 18

hello to every one,
interesting forum, i have developed the total project here as by your(MARKO) schematic, i have not used the copper pipe but but i have made the coil in pcb with size of 100mmx100mm, 13 turn in the board with 2 mm thickness of track and one more change i have done is .022 uf capacitor i have used in the board fo c1 to c8, in receiver the same of pcb used and the 2 nos same 0.022 uf cap parallel to the coil and then i have rectified the circuit. but the capacitor c1 to c8 gets heat up and current to coil is 14 amps, and so the wire also gets heat up. please suggest the guidance for how remove the heating of coil and capacitor and decrease the current. And one more experiment i have did was making 4 nos of pcb parallel coil to increase the area of transmission. I was experimenting for mobile charger, it is charging the 4 nos of mobile. but only problem is heating of coil and capacitor, pls guide me for that.

samedsoft

Mon Jan 04 2010, 04:55PM

Registered Member #2601 Joined: Mon Jan 04 2010, 04:45PM
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Posts: 1

Hi ALL

Does anybody know why Marko's design oscillates at 400 kHz?

Anybody has methodology or calculation technique of this circuit?

Thanks

BigBad

Wed Jan 06 2010, 03:13PM

Registered Member #2529 Joined: Thu Dec 10 2009, 02:43AM
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Posts: 600

scott fusare wrote ...

Hi Sulaiman,

Agreed on the regulations, although using the word "radiator" contributes to the misunderstanding of the principal involved. Pardon my being pedantic. The fields generated in the high power, across the room demos (MIT) will make the authorities apoplectic!

I'm not completely sure that's right. Nearly all the energy ends up in the resistance losses or the receiver. The transfer is near field which is non radiative, and as far as the residual far-field goes the receiver coil creates a pretty much 180 degrees out of phase wave that cancels the transmitter; and you're within a quarter wavelength.

There will be some radiation, but it's not likely to be watts, and these kinds of systems are already being fielded apparently without any huge drama in RFID situations and similar.

Scott Fusare

Wed Jan 06 2010, 05:22PM

Registered Member #531 Joined: Sat Feb 17 2007, 10:51AM
Location: Burlington, Vermont
Posts: 125

That was my point, the system is "non-radiative". Using the word "radiator" obscures the operating principles.

As for regulatory issues; No one has (or will) field a system to the consumer market that generates the field strengths encountered in the MIT demo. RFID tag readers are not permitted to use the output power levels encountered in the MIT work nor do the tags themselves have a particularly high Q.

Recall that the MIT resonators had unloaded Qs of ~1000 and were excited by a 833A driven power oscillator. Big power in and big fields from the circulating current built up by the resonant rise. The high Q is the reason this works to begin with, you can't avoid it if you want the efficiency over distance.

There is no way this device, as reported, would be vetted by the authorities.

dgzilber

Tue Jan 12 2010, 02:40AM

Registered Member #2620 Joined: Tue Jan 12 2010, 02:32AM
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Posts: 1

Hello all,
I am constructing a project that requires wireless power transmission. This thread is fantastic; the successful results posted from Marko, Strider, and Scott Fusare are truly the best gifts to any curious tinkerer, such as myself. I just have one quick question: are you both using formulas as detailed in the MIT report? Or did you find them from elsewhere?

I am familiar with the concepts involved but my project has tight demands, and I have been unable to find any satisfactory equations to help me build my system. If you could point me in the right direction (books, papers, or even the equations themselves), I would be much obliged, and would definitely post detailed results here, along with the rest of the project.

Thank you so much, and looking forward to meeting you all.

David

Scott Fusare

Tue Jan 12 2010, 02:51PM

Registered Member #531 Joined: Sat Feb 17 2007, 10:51AM
Location: Burlington, Vermont
Posts: 125

dgzilber wrote ...

I am familiar with the concepts involved but my project has tight demands, and I have been unable to find any satisfactory equations to help me build my system. If you could point me in the right direction (books, papers, or even the equations themselves), I would be much obliged, and would definitely post detailed results here, along with the rest of the project.

Personally I would avoid the MIT papers as they only serve to confuse things IMO. I like Terman's treatment of loosely coupled dual resonant systems that appears in "Radio Engineers Handbook". He is talking about band pass filters but fundamentally the "wireless power" device is the same thing - loosely coupled, high Q, dual resonant network. For a more modern reference there are a number of papers out there covering the topic. Most deal with the powering of sub-cutaneous implants. I can suggest a few if you would like?

EDIT: Sorry, I see you already requested suggested papers, here are a few:

Ko et al., "Design of radio frequency powered coils for implant instruments", Medical and Biological Engineering and Computing, 1977, 15, p634-640

Donaldson, "Analysis of resonant coupled coils in the design of radio frequency transcutaneous links", Medical and Biological Engineering and Computing, 1983, 21, p612-627

Stielau, "Design of loosely coupled inductive power transfer systems", IEEE Power System Technology, 2000. Proceedings. PowerCon 2000. International Conference on. Volume 1, Issue , 2000 Page(s):85 - 90 vol.1

Low et al., "Design and test of a high power high efficiency loosely coupled planar wireless power transfer system", IEEE Transactions on industrial electronics, Vol 56, no. 5, May 2009

Pankaj Patel

Wed Mar 10 2010, 06:32AM

Registered Member #2581 Joined: Tue Dec 29 2009, 09:08AM
Location:
Posts: 18

Hi everyone,

I have done a small work on wireless power transfer so please check out this small demo video.
Where the mobile is charged, and led lamp glows wireless.

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