The tracing module sensor has 3 way signal collection and output, respectively the left, the middle, and the right of the 3 pair’s infrared TCRT5000 photoelectric switches. The communication with Arduino is directly through the digital signal port communication. The Arduino handles the signals by collecting the signals from the 3 way sensor digital signal port. When the signal from the TCRT5000 was reflected by the close object, the signal port outputs high level. When meeting black object, the infrared signal will be absorbed which won’t be reflected back. Signal port will output low level.