electrical to mechanical and back....

I've managed to wedge an idea I had earlier about springs into this weeks project.  It was only in conversation though that we figured out to use a magnet and coil as both motor to wind spring and generator to light LEDs.

The spring slowly winds over the course of a day as the PV current in the coil spins the magnets.  At night, the arduino senses motion and releases the pawl on the ratchet.  This spins the magnets charging the coil and lighting the LEDs.