solarwind wrote:
> Good idea, but the analog electronics part is wayyyyy too complicated
> for me.

Get someone to help you then.  If you get enough voltage from the coil, it
could be as simple as a single transistor with the coil driving the base
directly.

> * What kind of coil would need to be used? Thickness? Resistance?

As many turns around a magentic core as you can stand.  Several layers of
thin magnet wire around a steel bolt should to it.

> * Would a coil pulled out of an analog clock work? (Was formerly used
> in the clock to move the seconds hand.)

That depends on the clock, so I have no idea.

> * How much coil is needed and how will it be configured physically?
> Will it be wrapped around a pencil, for example?

A pencil is a bad choice since it's not magnetic and therefore wont
concentrate the flux thru the inside of the coil.  That's probably about the
right diameter though.  Some steel (magnetic) bolt with a few layers of thin
magnet wire should work.

> * I'll look at the signal produced by the coil through an
> oscilloscope, but what other electronics is needed to isolate the
> wanted signal? Or can a PIC alone and it's A to D converter tackle the
> task?

The coil signal will need to be amplified.  You want the PIC asleep betwen
pulses, so the A/D is not a good idea.  The pulse will also be very short,
so you'd have to sample fast to catch it at high speed.  You need something
that takes the coil signal and produces a digital edge into the PIC from it.


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