No electronics needed. Follows the sun to the west, then moves to the east in the morning. The solar panel angle cuts down the power generated when looking toward the sun, while also allowing the position reset in the morning.
This tracker uses no electronics, just the 2 ea. 5 volt 160 mA solar panels and 1 ea. 6 volt gear motors 500 mA, see http://www.ebay.com/itm/DC-6V-37GB-100RPM-High-Torque-Gear-Box-Electric-Motor-500mA-37MM-4kg-cm-0-5A-/171643089674 (the torque spec is wrong, more like 0.4kg-cm)
Each panel is hooked to the motor oppositely than the other panel, the result being the panel with the most power moves the motor.