(Passive InfraRed sensor) A device used to detect motion by receiving infrared radiation. When a person walks past the sensor, it detects a rapid change of infrared energy and sends a signal. PIR ...

When a mouse is just 4.5 m from the detector, only the short-range PIR sensor reacts. A human intruder that close to the detector would reflect a large area to the microwave sensor, so when only the ...

The BOM on [Jeremy S Cook]’s build is extremely short – just a PIR sensor and an optoisolator, with a battery, a plug for the camera’s remote jack, and a 3D-printed bracket.