(PIR) Passive infrared sensor

A Passive Infrared (PIR) sensor is a device that detects changes in the infrared (heat) radiation levels in its field of view. It is commonly used for motion detection in security systems, lighting controls, HVAC systems, and other applications that require sensing of motion in a specific area.

PIR sensors work by measuring the difference in the amount of infrared radiation emitted by the surrounding environment and the amount of radiation reflected off objects within the sensor's field of view. When a person or object moves within the field of view, the amount of infrared radiation they emit causes a change in the overall infrared radiation levels, which the PIR sensor detects and converts into an electrical signal.

The sensor consists of a pyroelectric material, which generates an electrical charge in response to changes in infrared radiation levels, and a lens that focuses the incoming infrared radiation onto the pyroelectric material. The output of the PIR sensor is a series of electrical pulses, which can be processed by an electronic control system to trigger an event, such as turning on a light or sounding an alarm.

Overall, PIR sensors are cost-effective, reliable, and widely used for motion detection in a variety of applications.