The presented schematic shows how to build a simple PIR motion sensor. PIR sensors allow motion sensing, it is almost always used to detect whether someone has moved in or out of the sensors range.

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, ...

An Infrared close object sensor installed on an industrial vehicle detects objects or pedestrians located in a hazardous area. When it detects a problem an audio/visual indicator makes an alert, that ...