Sun Tracker or Irrigation Timer to drive motors
This is using two LEDs to sense the sun and send +- or -+ logic signals to a full bridge motor driver like L298 or http:/www.redrok.com LED3X schematic. I bought his. I recommend it.
I changed the front end logic to 4060 and 4011 ICs here, for fun. You could use this circuit to turn on an irrigation motor for a very short time every several hours (just omit the sun sensor and select appropriate timing pins and much lower oscillation frequency for the 4060).