On 27 Nov 2003 at 11:54, Koen van Leeuwen wrote:

> Hi all,
>
> I have a circuit mounted on a fan, doing about 3000 rpm. This circuit ha=
s
> to be powered with 5v, 30 mA. I can't use brushes because they slow down=
 the
> fan too much.
> I tried to make an "open transformer": an open coil (not rotating) with =
a
> smaller coil with iron core inside it (not touching the other coil, and
> rotating).
> Both coils have ~30 windings.
> Using 50 Hz 5v 500 mA at the primary side,=C2=A0only 300 mV shows up at =
th
> secondary side with short-circuit current of 1 mA.
> Should I use a higher frequency, or just make the coils larger with more=

> windings?
> (or is this never gonna work and you have a better idea?)

I think it could be done, but if you're playing with PICs anyway, check ou=
t Microchip's
RFID line.

As far as the magnetics go, google on "The ESU Advisor" and look for "Prod=
ucing
Wound Components."

HTH,
Mike
>
> Thanks in advance,
> Koen van Leeuwen
>
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