The Heliowatcher calculates the position of the sun using GPS and a RTC, and orients a solar panel to find maximally efficient paths. It uses a modified MightyBoard, the control electronics for the MakerBot Replicator, which has an atmega1280 and required stepper motor drivers on board. The system uses a combination of latitude and longitude data from a GPS module, the current time from a soft RTC*, and local light conditions as measured by a quadrature of LEDs. The system monitors the output voltage of the solar panel over the course of the day, and is intended to be used for data logging to calculate efficient placement of solar panels in areas with unusual light conditions, such as urban environments, areas with high cloud cover in certain directions, and polar or near-polar locations.
This project was done for Cornell's ECE 4760 Designing with Microcontrollers class.
*It would be ideal to use the timestamps encoded in GPS messages, but our module had issues with this.