The TCRT5000 Reflective Optical Sensor is an IR-based switch ideal for DIY projects like line-following robot cars. It combines an infrared emitter and phototransistor in a compact, leaded package that blocks visible light for more accurate detection.

When the IR emitter projects light onto a surface, a white surface reflects the light back to the detector, causing the module’s output pin (S) to go LOW. If the light hits a black surface, it is absorbed, and the detector receives no signal, making the output pin HIGH. Sensitivity can be easily adjusted via the onboard potentiometer, making it versatile and easy to use.