Having seen a number of solar panels on the web and some light tracking builds on Instructables, I thought it would be a neat idea to blend the two together. The solar panel charges best when it attracts the most amount of solar light so why not enable this in real time?
I have used an Arduino Uno and a motor shield to drive two servo motors both left and right, up and down. Adafruit sells a great motor shield for this very purpose and ServoCity stocks the Pan & Tilt mechanism that I used. In addition, I used an 17W solar panel and battery kit from Voltaic which comes with the necessary adaptors to hook up a battery which can charge an iPhone around seven times or a Macbook Pro once!
Step 1: Parts Used
The parts list used is as follows:
x1 Arduino Uno
x1 Motor Shield (product 1438 at www.adafruit.com)
x1 Pan & Tilt mechanism (SPT200 Kit at www.servocity.com)
x1 Battery and Solar Panel (17W Kit at www.voltaicsystems.com)
x4 analog light sensors (product: 1384 at www.adafruit.com)
Sufficient wires to connect the sensors to the motor shield.
I used two high torque motors so that I can disengage them when not in use. This prevents the panel from falling down when the motors are not in use!
Step 2: Arduino Code
You can download the Arduino Code here. I have documented most of the lines to make it clear what each part of the code does. In short, it averages out the readings of the two vertical and the two horizontal light sensors and moves the servos accordingly. To conserve battery power, the servo motors are disengaged when not in use.
Step 3: Wiring
I have uploaded the Fritzing file to help assist in the wiring of the build; I hope it helps!