Infrared (IR) Sensor Module is a distance proximity sensor “switch”. When there is an object or obstacles that are close enough to block the view in front of 2 LEDs, it triggers the infrared trans-receiver module. The clear LED is the IR emitter while the black LED is the IR receiver. It uses the electromagnetic reflection principle where when the reflective surface (object) is closer, the receiver will receive stronger signal from transmitter due to shorter distance traveled of reflected of wave.

When there is a object that is close enough, the IR electromagnetic detection received by the IR receiver is higher than the threshold level (user pre-set level), the sensor will change the output switch mode so that microprocessor board such as Arduino can execute what is going to do next. IR Sensor Module has only 1 main output signal which is Digital Output. Digital Output either go high (5V or 3.3V depends on the input voltage) or low (0V), thus this module cannot be used as a distance measurement but just as a trigger switch.