[ladyada] has a freshly-published and amazingly thorough tutorial on passive infrared (PIR) motion sensors. Most often seen in security floodlights and automatic doors, in creative hands these sensors ...

If you’re looking for something to do this weekend, consider this PIR (passive infrared) Sensor Alarm project. Not only will the motion-sensing alarm protect your gear from animals and zombies alike, ...

Passive InfraRed sensors (PIRs) are electronic devices which are used in some security alarm systems to detect motion of an infrared emitting source, usually a human body. All objects, living or not, ...