(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.

While PIR sensors are inexpensive, radar technologies are decreasing in cost and becoming more compact and simple to design. Radar solutions can range from simple motion detection to complex imaging ...

this DIY motion trigger for a DSLR is a quick and easy build, and probably loads more fun. The BOM on [Jeremy S Cook]’s build is extremely short – just a PIR sensor and an optoisolator ...