TCRT5000 infrared sensor emits infrared emitting diode continuously when no infrared rays emitted or reflected back is reflected back but the strength is not large enough, the photo transistor has been in the off state, and the output terminal of the module is high, indicating that the diode has been in the off state; in the object to be detected within the detection range, and the intensity of the reflected infrared rays is large enough, photo transistor saturated, and the output terminal of the module is low, the indicator LED is lit.