Motion or presence detectors automatically switch on lights in response to objects or bodies moving within their monitoring zone. They are available in a variety of technical designs: with passive infrared (PIR), radar or ultrasound sensors. Activation time is controlled by a timer and can be varied.

Motion detectors can be installed both outdoors – e.g. in the garden or in parking facilities – and indoors – e.g. in hallway or offices. Outdoors, they double as protection from crime, indoors they are effective energy savers. To prevent lights being switched on and off in daylight, motion detectors should be combined with a light sensor.