A motion sensor lamp is light-producing device that activates in response to motion. Sometimes, a motion sensor lamp is simply used as a convenience and will turn on when one enters a commonly-used room, such as a restroom. Upon activation, such a lamp will generally remain active until a certain amount of time has passed in which it has not detected motion. Such lamps are commonly used to reduce electricity costs as they automatically turn off when people aren't present rather than remaining constantly active. Motion-activated lamps are also commonly used outdoors for guidance and for burglar deterrence.
In most cases, a motion sensor lamp works through optical detection, meaning that sudden changes in external light or visual input generally trigger activation. Usually, this does not involve changes in visual light because such devices are often used in places that are subject to total darkness. They instead use lasers or infrared light; when a person or object passes into or through the laser or infrared light, the motion sensor lamp will activate. Continued motion in the detection area will cause the light to remain active, while a cessation of motion will cause the light to deactivate after a set period of time.
To ensure the light only activates when needed, it is important that the sensor is well placed and that the area of activation is well defined. If one wants a motion sensor lamp to activate when someone approaches his front door, for example, he should also try to make sure the light does not turn on every time someone walks past his house on the sidewalk. The light would probably irritate neighbors, frighten passers-by, and waste energy. To minimize accidental activations, a motion sensor lamp may have a time delay mechanism so that a moment of motion at the edge of the sensor area does not activate the light.
A motion sensor lamp can serve as a highly effective burglar or intruder deterrence system, as the sudden activation of a light reveals the intruder's activities and suggests to the intruder that he is being monitored. In some cases, a camera will be activated at the same time as a motion sensor lamp in order to record the activities of an individual passing through the sensor area. If the sudden activation of the light does not frighten the intruder away, the camera can help law enforcement officers to find the intruder and to verify his identity in court.
