The sensor faucet refers to the principle of infrared reflection. 

When the human hand is placed in the infrared area of the faucet, the infrared light emitted by the infrared transmitting tube is reflected to the infrared receiving tube due to the blocking of the human hand, and the signal is sent through the microcomputer in the integrated circuit. For the pulse solenoid valve, the solenoid valve receives the signal and then opens the spool according to the specified instruction to control the water from the faucet; when the human hand leaves the infrared sensing range, the solenoid valve does not receive the signal, and the solenoid valve spool is reset by the internal spring,control the turning off of the faucet.