Salom Mehdi,

From the other posts I am going to assume that you have no interest in tracking the sun. I am going to assume that all you want to do is accurately point at any localized light source, for example maybe a flashlight.


A Single Sensor with Shield

Mount a sensor with a shielded line of sight (only parallel rays from the source can reach the sensor through the shielding tube). Beginning with the sensor and shield tube facing horizontally, rotate clockwise until the sensor produces a maximum signal. This is the angular direction of a local source. Now raise the elevation until the sensor produces a new maximum signal. This is the 3-dimensional direction of the source. The accuracy is proportional to the length of the shield. The sensitivity will decrease with shield length. If you need to increase both you will want to try a two-sensor configuration.


A Two-sensor Application

I saw a two sensor application once on a tiny robot (I think it looked like a little clockwork mouse). Each of the eyes were photosensors. The right eye controlled the left wheel, and the left eye controlled the right wheel. The stronger the light in the sensor, the faster the wheel it controlled turned. The net result was that the little mouse would always move toward a light source (a pen light held by the guy demonstrating the little robot).

I hope these help. Good luck,

Joe