In the past, the only places in the home that you saw light-emitting diodes, or LED, were on the digital alarm clock display and the indicator lights on electronic devices. With technology advances, however, LED has found its way into more and more applications, from traffic lights to TV screens--and now, increasingly, general room lighting.
Function
A light-emitting diode is made of semiconducting material that has been treated to create an imbalance of electrons--one side of the diode has more electrons than its atoms can accommodate, while the other has a lot of atoms with "holes" where electrons should be. When current runs through the LED, electrons travel from the "oversupplied" side to the "undersupplied" side. When an electron finds a hole, it drops down to a lower energy level and emits a photon, the basic unit of light.
Types
The wavelength of the emitted light determines its color, and the wavelength is determined by the materials used to create the semiconductor. The first LED, made with aluminum gallium arsenide, produced red light. Indium gallium nitride LEDs produce blue light. And LEDs made with aluminum gallium phosphide give off green light. Since these are the three primary colors of light, they can be combined to produce the full color spectrum. If the only color you need is white, such as for room lighting, you could combine red, blue and green in equal amounts, but there's a cheaper alternative: using blue LED coated with a special phosphor.
White Lighting Benefits
LED is considerably more energy-efficient than other light sources, using about one-tenth the energy of incandescent lights and half that of compact fluorescents, the main alternatives for home lighting. A traditional incandescent lamp uses electric current to heat up a tungsten filament enough that it glows--so as much as 90 percent of the energy in an incandescent bulb goes to generate heat. LED, by contrast, uses 90 percent of the supplied energy to produce light, with very little heat buildup. Since it is a solid-state product, with no filament or thin glass that can break, it is more rugged than either incandescent bulbs or fluorescent lamps. It lasts longer, too: up to 50,000 hours, compared with 2,000 hours for incandescent bulbs and 10,000 for compact fluorescent lights.
Colored Lighting Benefits
The ability of LED to produce colored light gives it another advantage. To get colored light from incandescent or fluorescent lamps, you need to use filters. Filtering, by definition, means some of the light won't be used, which means the energy to produce it has been wasted. In applications, such as traffic lights and colored ambient light, this can make a significant difference.
Consideration
For all its advantages, LED has long had one big strike against it: cost. Incandescent and fluorescent light bulbs are cheap to produce, LEDs are not. However, the relatively recent innovation of using phosphor-coated blue LEDs to produce white light has brought the price down enough to make LED a viable option for residential lighting.
Member Comments