http://www.youtube.com/watch?v=2R2kqeTvESA
input is a 13v 1.5A adapter.
setup is a single wire run coil and 2 separate pickup coils bridge rectified and combined with the charge output. transistor is a tip42 switch by a reed relay, the reed came from a dollar store alarm kit.
needless to say it could be much improved to achieve much higher RPM's.