What is a PIR motion sensor?

All objects emit energy in the form of invisible infrared radiation. A Passive Infrared (PIR) sensor detects changes in the levels of infrared radiation within its field of view. When a warm-bodied animal passes in front of the sensor, the amount of infrared energy detected shifts, allowing the sensor to register movement.

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 and flashes. This enables the capture of high-quality images of wildlife with minimal human disturbance.