The TCRT5000 is a simple reflectance sensor with integrated infrared LED and phototransistor. This all in one sensor can be used as a part of a line following sensor array, short range object detection, edge detection, and even as a part of an optical wheel encoder.

Optimal detection of objects is within 2.5mm but ultimately the distance will vary depending on the reflectiveness and color of the object. White and light colors will reflect the IR light, while black and dark colors will cause the IR light to be absorbed. The phototransistor has an integrated daylight blocking filter that helps boost performance in brighter environments.

Because of its small size, these can be packed together to form a fairly dense sensor array.