Solar Arduino tracker

To get Greenwich Time (aka UT) I use a DS1307 chip. Following the description of http://www.glacialwanderer.com/hobbyrobotics/?p=12 it worked immediately. Did not find any 2.2K resistors, it worked with 4.7K as well. I have taken the code from this site and tucked the complexity into an Arduino libary (DS1307.h)

Calculate Azimuth and Elevation

To calculate the solar azimuth and elevation exactly you need very involved formulas. However, for practical purposes like sun tracking of a heliostat there are simpler ones available. Widely used formulas for solar tracking are the one from the so called PSA-algorithm. It has been made avaible from Plataforma Solar de Almeria (Spain) and you can download it here as C++ code. There are adaptions neccessary for Arduino, though. The formulas for calculating the Juliand Day are not working properly on Arduino due to reduced double precision. (doubles have the same precision as floats on Arduino) Therefore, I have adapted them (expecting Julians dates from 1.Jan. 2000). These calculations I have put into another library (Helios.h)