I'm trying to detect changes in light. Ultimately I want to transmit data from one unit to this circuit via lazer beam. The data speed doesn't have to be high. 24 bits a second is ok. I just don't want the phototransistor to assume other light is the lazer beam. I don't mind modulating the data, but to start with, I want the microcontroller to be able to detect when light is sensed and when darkness is sensed. An equation will help me if I knew what it was.