What is a PIR Motion Sensor?

All objects emit invisible infrared radiation. A Passive Infrared (PIR) sensor detects changes in infrared energy within its field of view—such as when a warm-bodied animal passes in front.

The term “passive” refers to the fact that the sensor does not emit any radiation itself—it simply monitors the infrared radiation naturally emitted by objects in its surroundings. This makes PIR sensors extremely energy-efficient and reliable for long-term use in the field.

In a camera-trap setup, the PIR sensor’s role is to detect an animal’s presence and automatically trigger the connected photographic equipment, such as a DSLR or mirrorless camera. This enables the capture of high-quality photographs and video footage of wildlife with minimal human disturbance.