This type of input is a far cry from our incredibly complex sensory systems, that God has given us as humans. Creating real life actions from these limited inputs is one of the robot designer's hardest jobs. For the remainder of this article we will be discussing these types of sensors and how to interface them.
Light sensors range from simple CdS cells to complex video cameras.
One of the most popular light sensor is the near infrared sensor, which uses near infrared light to detect obstacles in its path. The humble CdS cell can be used to create light following, or negative phototropic behaviors. To start off our discussion of light sensors we will begin with the Cds cell or photo resistor. The photo resistor is basically just a potentiometer that changes its value based on the amount of light striking it. A photo resistor can be easily interfaced to a analog to digital converter using one other resistor in a voltage divider scheme pictured below.