TCRT5000 IR Reflective Sensor Module, 3-Pin 5V Infrared Line Follower for Arduino & Microcontrollers

The TCRT5000 module is the classic eye of the line-following robot. Its infrared LED shines at the surface below and the phototransistor measures the reflection: dark tape absorbs, white floor reflects - and the onboard comparator turns that into a crisp digital signal with a threshold you tune by potentiometer.

Beyond line followers it detects object presence, counts items passing on a conveyor, senses paper in printers and reads simple rotary encoders from a striped disc. Analog output is available when you want the raw reflectance value.

Effective range: roughly 1-15mm from the surface; mount low and shield from bright ambient IR for best contrast.