The TCRT5000 infrared sensor continuously emits an infrared emitting diode when no infrared ray is emitted or reflected back, but the power is not large enough, the phototransistor is in an off state and the module's output pin is high, indicating that the diode was in an off state. When the object to be detected is within the detection range and the intensity of the reflected infrared rays is large enough, the phototransistor is saturated and the module's output pin is low, the LED indicator light is on.