I'm working on a solar tracker. We have a general idea as to how it works, but it seems like it might be a bit too complex. Our current setup is running an Arduino Uno with 2 photoresistors and a separating board, casting a shadow on one. The code we have compares the value of the two, but we don't know how exactly to turn the panel. How are we supposed to activate a 12v motor with the Arduino?
With an H-Bridge motor driver. Buy one that can handle at least the voltage and current you need.
If you only have a small solar panel - say for a college demonstration project - it may be possible to move it with a hobby servo which would be very simple. Some servos are quite powerful.
I have 3 x 80W solar panels (which don't move) and you would need a very strong framework to support them. However they may not need a huge amount of power to rotate if the mechanism is well designed and constructed.
...R
google cerebral meltdown
he has the solar software and shows how to do much of the mechanical.