> Hi all, perhaps someone can help with a wee power problem. I've
> got a circuit board mounted on a motor shaft. The circuit is there to
> measure the movement of an escapement mechanism (kind of
> like a governor) as the shaft turns from 100 to 3500rpm. The
> circuit itself is not a problem, I've managed to attached a small
> slider pot to the escapement and it's measuring OK with an ADC.
> What I'd like to do is induce power to the circuit using some kind
> of magnet/coil system. I need around 15mA at 6VDC. A possibility
> is to use a 7-segment LED (synched with the rotation) to indicate
> the escapement movement, hence the power requirement. Using
> batteries is not really an option because of the duration of the
> measurements and particularly if the LED idea goes ahead. I've
> got plenty of envultured materials - strong HDD magnets and
> more scrap transformers (enamelled wire of all gauges and
> laminate cores) you can shake a stick at. I thought I may be able
> to attach a small DC motor to the main motor's shaft as a
> generator but that's proved too tricky because of space limitations.
> So, any ideas on the most efficient way to induce power into coils
> on the PCB from stator magnets ?

How about starting off with a brushless DC fan, but fixing the fan unit, and
mounting the (what used to be) drive coils on your PCB, rectifying the
output for your circuit. Use an old fan from a PC power supply or similar
(although from your description it may be a bit big, but would be a starting
point).

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