Working principle of passive infrared detector

The basic working principle of the passive infrared detector is: when a human body moves in the prevention area, the infrared light emitted by the human body is focused on the pyroelectric infrared sensor through the optical lens. The thermoelectric signal is very weak and mixed with a lot of interference signals. Therefore, it is necessary to design a special thermoelectric signal processing circuit to amplify the thermoelectric signal while filtering out the clutter signals that cause interference.

The detector uses an operational amplifier and cooperates with the surrounding circuits to integrate into an amplifier circuit with a band-pass filter function. It separates the thermoelectric signal and amplifies it by thousands of times; and through the optimized design of the parameters, cooperates with the comparator circuit to further eliminate the interference caused by the flowing hot air, and analyzes and judges the thermoelectric signal separated by the two-stage amplification. Set the judgment standard to judge whether it is an alarm. If it is judged as an alarm, it will output a switch alarm signal.