I think you will have trouble getting enough power out of a magnet
and coil. I was curious about this, so I built a test setup. For a
coil I used the coil that drives a pendulum in quartz clocks. These
coils are wound from exceptionally thin wire and so have a very high
number of turns. I rectified it with a common bridge, filtered it
with 220 ufd, and put a load on it. I was spinning a neodymium magnet
at 3,000 RPM.

I had to reduce the load to 10K before I got more than 5 volts. 10K
at 6 volts is just 0.6 mA. I think you'll never get to 30 mA without
quite a large coil and magnet.

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Bryan Mumford
Santa Barbara, California
http://www.bmumford.com

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