> I have never experimented with inductive power transfer, but it does
> look ideal for the task. Apparently it improves in efficiency as the
> frequency goes up? I am reading up on it right now. If it's as simple
> as hand-winding some 1" diameter coils, then connecting each to a
> capacitor and full wave bridge.. then connecting all the bridge
> outputs in paralell.. could it be that easy? Of course some
> experimenting to get all the details right. but a roll of magnet wire
> and a few dozen diodes.. not a bad start!
> If "many" can be ganged easily, I could fill the inner surface of the
> sphere with as many as will fit. From there a supercap would be ideal,
> perhaps with a zener across it just in case the voltage transfer works
> better than expected.

It's not mainly that efficiency rises with frequency but that useful
inductive element physical size reduces with frequency.

Read the notes on IPT that I wrote re Vitaliy's project as cited recently.
As I said there, and it's just as true now (as you might expect),
resonance will make an utterly vast difference to what you can
achieve.

It is easy to get a reasonably close to frequency resonant receiver
coil using even 5% capacitors (1% better) and identical cores with the
same number of turns with hand winding and no great attention to tidy
layering or tidy winding. You will have trouble achieving useful power
transfer and range without resonance, and should have no great trouble
achieving the range you want with resonance. If using aiur cored coils
then largest diameter you can fit will help.

There are many wireless power transfer projects on-web and some good
you-tube examples.

FWIW I have a long expired 1999 US patent relating to Inductive Power
Transfer and have notes on prior art from 1972 (for work which I
looked at but had no part in the development of) so if anyone ever has
issues with people  rerere-patenting Tesla originated material I may
be able to help.

Read my 20 Feb 2012 answer in the "[EE] DIY Inductive Power Transfer"
thread for some useful material.

Or, here are the  links from my 22 Feb post re the MIT IPT (Inductive
Power transfer) system.

Gargoyling ...

http://web.mit.edu/newsoffice/2007/wireless-0607.html

BIG coils :-)

Smaller
http://www.instructables.com/id/Wireless-Power-Transmission-Over-Short-Dist=
ances-U/

You Tube
http://www.youtube.com/watch?v=3D2ODW-ntPHSU

Nissan
http://www.greencarcongress.com/2009/07/nissan-wireless-20090720.html

Images, misc
http://www.google.co.nz/search?q=3Dmit+inductive+power+transfer&hl=3Den&saf=
e=3Doff&prmd=3Dimvns&source=3Dlnms&tbm=3Disch&ei=3DrjpET9bhBYefiQeopuGfAw&s=
a=3DX&oi=3Dmode_link&ct=3Dmode&cd=3D2&ved=3D0CB4Q_AUoAQ&biw=3D1536&bih=3D86=
4

Some value
http://www.youtube.com/watch?v=3DTIhPayFBE9c&feature=3Drelated

http://www.youtube.com/watch?v=3DHw1h-cFGxdI&feature=3Drelated



         Russell McMahon
         Applied Technology ltd
         Auckland, New Zealand
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