A Passive Infrared (PIR) is an electronic device used to detect motion by measuring infrared (IR) radiation emitted by objects in its field of view. The sensor is made up of two slots, each sensitive to infrared radiation. When a warm object (like a person) enters the field of view, it creates a difference in the infrared levels between the two slots, causing the sensor to trigger. The PIR sensor doesn't detect specific objects but rather changes in infrared levels caused by movement. PIR sensor

How do motion sensor lights work? Those outdoor lamps that switch on when you walk by use passive infrared sensors. They detect tiny changes in infrared radiation when a warm body moves across their field of view. The sensor triggers a circuit that powers the light instantly. Engineers design them to ignore small fluctuations like wind or rain, so they only react to significant movement. A simple, brilliant mix of electronics and safety. | Electricalgram