White LED
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#1
21-09-2008, 10:36 AM


Until recently, though, the price of an LED lighting system was too high for most residential use. With sales rising and prices steadily decreasing, it's been said that whoever makes the best white LED will open a goldmine.
White LED lighting has been used for years by the RV and boating crowd, running off direct current (DC) battery systems. It then got popular in off-the-grid houses, powered by photovoltaic cells. It used to be that white LED was possible only by "rainbow" groups of three LEDs -- red, green, and blue -- and controlling the current to each to yield an overall white light. Now a blue indium gallium chip with a phosphor coating is used to create the wave shift necessary to emit white light from a single diode. This process is much less expensive for the amount of light generated.

Each diode is about 1/4 inch and consumes about ten milliamps (a tenth of a watt). Lamps come in various arrangements of diodes on a circuit board. Standard arrays are three, six, 12, or 18 diodes, or custom sizes -- factories can incorporate these into custom-built down lights, sconces and surface-mounted fixtures. With an inexpensive transformer, they run on standard 120-volt alternating current (AC), albeit with a slight (about 15% to 20%) power loss. They are also available as screw-in lamps to replace incandescent. A 1.2 watt white LED light cluster is as bright as a 20-watt incandescent lamp.
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