ROANOKE TIMES
Copyright (c) 1996, Roanoke Times
DATE: Tuesday, December 3, 1996 TAG: 9612030034
SECTION: EXTRA PAGE: 3 EDITION: METRO
COLUMN: At Home With Technology
SOURCE: DAVID BUTLER
Q: Street lights obviously have a built-in sensor that causes them to turn on at dusk and off at dawn. Are light sensors available for regular household lights?
A: Light sensors, also known as photoelectric diodes, are available for a wide variety of lighting controls and fixtures. Perhaps the most familiar is the motion-activated security floodlight. Most models include a photo-diode, which prevents the light from coming on during the day.
Several companies make decorative fixtures with built-in light sensors. You can choose from several styles including globe lights, coach lights, carriage lights and lanterns. Most models are available in antique brass, polished brass, white or black. Some also have built-in motion detectors; others simply turn on at dusk, off at dawn.
Transformers supplied with most landscape lighting systems have a built-in light sensor that works in conjunction with a time clock. In this case, the lights turn on a dusk and off at the time you select.
The most flexible photoelectric lighting controls aren't built into a fixture but can be used with existing fixtures - both indoors and out.
The simplest type inserts between the lamp and the socket (screw-in), an ideal way to automate a living room lamp or front porch sconce. Some models have an integral delay timer that turns off the light after six hours.
Plug-in and wall-switch photoelectric controls are also available. One model turns the fixture off after a random delay, giving your home a lived-in look while you're away. Other models combine a light sensor with a motion detector. These usually have adjustable delay and light level sensitivity.
One unique wall switch combines a photo-diode with a sound sensor. Whenever the switch detects sound (such as someone entering a room), it turns on the lights if it's dark. Sound sometimes works better than motion for occupancy detection - for example, if the switch is around a corner from the entrance path. The sound switch, also available in a plug-in version, has a sensitivity adjustment.
For some applications, you may need a stand-alone photo control that can be permanently connected to the electrical circuit away from the wall switch or fixture. One company sells a full line of wire-in photoelectric switches with appropriately sized pigtails (wires) and various mounting configurations.
Power line carrier (PLC) home control systems can also use light level to trigger events. A four-channel mini-controller is available with built-in photo-diode. It can operate any light connected to a PLC module or switch. One company makes a wired-in light sensor that transmits PLC signals in response to light levels. The unit has an adjustable timer that turns the lights off before dawn.
Some commercial lighting controls use strategically placed light sensors to balance light levels with sunlight. The system adjusts light levels accordingly, as the sun's angle changes throughout the day or if clouds block the sun. Some high-end residential lighting control systems now offer this feature.
LENGTH: Medium: 60 linesby CNB