In the interest of trying to determine my heading for the AVC robot competition, I have been working on a celestial solution. I am calling this device a SUNDAR as a hybrid of SUN and RADAR. In essence I am making a rotating platform with an optical sensor that will find the sun and therefore be able to report an azimuth.
My work and my hobby have a large overlap. One of the devices I am using at work is a device that determines attitude (roll, pitch, and yaw) using accelerometers and a camera system that will either find the sun or stars and based on some celestial mechanics can determine absolute heading. This device is very expensive and power hungry, but it did give me the idea for my SUNDAR along with a patent I found online.
So the basic concept is a small horizontal rotating platform with a photodiode sensitive in the visible light spectrum. As the photodiode rotates, its amplified output as digitized by a small microprocessor. The microprocessor then looks for the peak in amplitude and determines the platform orientation at that time.
I have started to prototype this system. So far I have picked out a photodiode and built the amplifier. The results are very possitive. I was able to get variations in light intensity of a two to one ratio. Next step is to build the rotating platform.