This application explains how to make a light detector for ARobot. This can be used to tell when a light is on or off, whether the robot is inside or outside, or for light following. This is a simple expansion and does not require soldering if using a breadboard.
It does assume that you have attached a breadboard and an expansion cable to the ARobot . This circuit and the light sensor could be mounted and soldered to a perf board and located to a movable head. Multiple light detector sensors could be used to detect the direction of light.
Light Detector Application: [Link]