In building Simple Bots
, we are going to use a series of photo-coupled devices called modules. But, before we can do this, we need a good photo-couple to use as a light-activated switch. To make one of these switches, we will be using a special OSRAM-brand photo transistor
and any standard NPN transistor (like a 2N2222, 2N3904, BC546, etc.). These switches will allow the motor to spin in direct correlatoin to how much light it senses. In other words, the more light, the faster the motor goes and the less light, the slower.