Solarbots

Beambots are small robot's who are reacting on their environment.

We are building some like these:

Solar bot by Wilf Rigter and Eric Seale
http://www.solarbotics.net/library/circuits/se_t1_zener.html

The basics are really simple, a solar cel is charging the capacitor(s) and when they are charge the voltage rises. The diode will power the transistors which will release the power charge in the capacitor(s).