A driveway motion detector is an electronic device that detects movement within a set area. Usually installed above garage doors and aimed at a surveillance area in a driveway, hence the name, it typically activates floodlights that illuminate the surveillance area. A driveway motion detector is useful both for home security and for the convenience of the homeowner and any guests using the driveway after dark.
A motion detector acts much like sonar; it transmits signals throughout the surveillance area that bounce back to the detector, which analyzes them. Any change in the returned signal is interpreted as movement. The detection of movement typically activates one or more security responses like floodlights or alarms. Another technology employed by motion detectors detects body heat and responds accordingly. Some motion detectors employ more than one technology, enhancing their reliability and reducing the possibility of false alarms.
Motion detectors began as high-tech security devices in commercial spaces and the residences of the very affluent. As is common with new technology, they were sometimes unreliable or hyper-reliable; a motion detector would fail without warning, or would be so sensitive that it would set off an alarm if an insect or rodent moved through the surveillance area. The technology became more sophisticated and the devices became more reliable, and became common security devices in commercial establishments, as well as in some residences.
Motion detectors are efficient security devices inside commercial spaces because they can be calibrated to activate only when movement is detected in the surveillance area when it's vacant. Since motion detectors cannot be calibrated to recognize legitimate targets in the surveillance area, though, their use as residential security devices is limited. They can be useful in residences whose owners are frequently absent, or in little-used areas of large residences, but for most middle-class homes they're more of a nuisance, activating whenever they detect movement, even if the target is a legitimate resident.
As an external security device, though, a driveway motion detector provides a number of valuable functions. First, it detects movement within the surveillance area and illuminates it with floodlights, generally frightening off intruders. Second, when legitimate people enter the surveillance area, the floodlights are activated, illuminating the area for their convenience. A driveway motion detector can be effectively used in areas other than driveways, such as decks, back doors, and lawns — anywhere people might need lighting after dark. Of course, a driveway motion detector can also be installed in any location where it might enhance a residence's security, such as around outbuildings and inside basements.
Driveway motion detectors are a green approach to security and convenience, automatically activating only as programmed, and then turning off automatically without human intervention. In addition to being efficient security and convenience devices for residences, they also serve the same dual purpose for commercial buildings and are being used in some mall parking lots as well.