How They (LED Christmas Lights) Work
We use Light Emitting Diodes, L.E.D.s, now considered "the greatest invention in lighting since Edison's light bulb in 1879." L.E.D.s are rapidly replacing light bulbs in a variety of high reliability applications including traffic lights, brake lights, and emergency exit signs.
L.E.D.s are constructed from tiny solid-state chips similar to those used in computers. These chips directly convert electricity to light without the use of a filament or glass bulb. Instead, the chips are encapsulated in solid plastic that can be made into a variety of shapes and sizes.
Since L.E.D.s have no filament, there is nothing to burn out and no need for a breakable bulb. Without the burning filament, very little heat is produced.
L.E.D.s are constructed from tiny solid-state chips similar to those used in computers. These chips directly convert electricity to light without the use of a filament or glass bulb. Instead, the chips are encapsulated in solid plastic that can be made into a variety of shapes and sizes.
The principle behind L.E.D.s can be made easy to understand. An L.E.D. is a special type of diode and is similar to a transistor. Diodes and transistors are "solid state" devices that are made from semiconductors such as silicon. The semiconductor is made to contain two types of special impurities. The first type of impurity, calL.E.D. "N" for negative, is a material with an excess of electrons. The other type of impurity, calL.E.D. "P" for positive, has a deficiency of electrons in "holes." These two kinds of impurities are dispersed into the semiconductor at different regions, so that a "P-N junction," or active layer, is created at the border.
Semiconductors do not freely conduct electricity like materials such as copper. Instead, they can be made to conduct electricity under certain conditions. For diodes and transistors, these amount to connecting electric power across the junction to make the "P" side more positive and the "N" side more negative. When this happens, electricity flows freely across the "P-N junction" and the electrons fill up the holes. The laws of physics describe the energy between electrons and holes and show that this energy is a fixed amount depending on the materials. L.E.D.s differ from ordinary diodes in that the "P" and "N" materials take this energy and convert it to photons, or light. Since the energy involved is a fixed amount, the light that results has only a single wavelength, or color. Using different materials for the "P" and "N" impurities enables the light to be manufactured in different colors.
General Electric introduced the first L.E.D.s in 1962. These L.E.D.s came only in red, the lowest energy of all visible light colors. In the 1970s, yellow and green were introduced, along with intermediate colors such as orange. However, then the materials used were inefficient - very little light was produced for each Watt of electric power used. Conventional light bulbs are also very inefficient yielding at best only about 6% of their electric power used in the form of light. The rest of this power turns into heat, as one finds out quickly when touching a lighted bulb. Over the years, L.E.D. efficiency, brightness, and lowered cost have exploded in parallel with computer components. Today, L.E.D. power efficiency surpasses that of a fluorescent and is increasing with 75% efficiency on the horizon.
Costs have plummeted such that bright red, yellow, green and intermediate colors are now pennies apiece. With the introduction of blue in the 1990s, L.E.D.s now come in a full palette of colors, including pure white. Blue and white are presently too expensive for most applications, costing dimes instead of pennies each, but this should change within a few years.
L.E.D.s have also evolved to last much longer. Today, L.E.D. lifetimes are not specified by a time to burnout because it simply takes too long to measure. Instead, L.E.D. lifetime is specified at time when a barely noticeable loss of light occurs. This lifetime is about 100,000 hours, or more than eleven years of time. If the L.E.D. is off for any portion of time, then this lifetime increases. Conventional light bulbs are typically rated at about 1000-2000 hours or so before they burn out. But even this rating assumes that the light bulbs are not turned off and on and that they are not jarred in any fashion. Anyone familiar with Christmas light strings is experienced with burnout.
Our lights are built with patented circuitry to maximize efficiency of their L.E.D.s. This revolutionary design concept eliminates the use of traditional components that add to cost and generate heat. While details are proprietary, in essence the circuitry allows the L.E.D.s to flash on and off with AC power. Like a television set, the flashing occurs sixty times per second and is invisible to the eye. By flashing the L.E.D.s on and off this way, the circuit can be made at least twice as efficient as is possible with traditional L.E.D. circuitry. In addition, the overall L.E.D. lifetime is more than twice as long, since the L.E.D.s are off more than half of the time. Unlike conventional light bulbs, particularly fluorescent bulbs, switching L.E.D.s off and on does not affect their longevity. The result is a cheaper, safer, and longer lasting product with less power consumption than could otherwise be designed. Lifetime is predicted to be over twenty years of continuous use, and much longer if just used seasonally.
How They (L.E.D.) Work | Forever LED Christmas Lights Home Page | Copyright Forever LED, L.E.D. Lites, Inc 2003-2010
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