LED Lighting General

Light Emitting Diodes: What are they?

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light emitting diode

9 percent perspiration

We all know stories of Thomas Edison, toiling in his New Jersey laboratory trying out metal after metal to see which ones heated the brightest and lasted the longest in a vacuum tube. He had tried at least 1,000 metals. When he decided, in 1879, on tungsten extracted from wolframite, a compound of iron, manganese tungstate, he had invented the incandescent light bulb. 

It took a lot of trial, error, and chemistry. Edison said, "I didn't fail 1,000 times. The light bulb was an invention with 1,000 steps."

Chemistry

It was different with electronic lighting. The invention of the LED was really what we now call "open source." In 1907, a British experimenter, Henry Joseph Round, with the English Marconi laboratory happened to notice that when 10 volts of direct current (DC) was applied to a crystal of silicon carbide (the stuff in sandpaper), it emitted a yellowish light.

It took 20 years for a Russian, Oleg Vladimirovich Losev to publish a note about how the yellow light works. It has to do with the oscillation of crystal molecules. It took another 30 years, until 1955 for an American researcher, Rubin Braunstein, working at the RCA laboratory (also in New Jersey) to make a working light emitting diode (LED) that emitted infrared light when connected to a current.

Then there was the search for which crystals worked best for what kind of light. In 1961, Gary Pittman and Bob Biard at Texas Instruments found that crystals of gallium-arsenide worked best for infrared light and received a patent for the infrared LED. In 1962, the first visible light (a red light) was developed in the GE laboratory.

In 1972, different crystals were tried and the yellow LED was invented as well as a brighter red LED. A high brightness LED was invented in 1976 to be used in fiber optics telecommunication. A different crystal was used by a Japanese inventor to create the first blue LED in 1979. But, the LED was too expensive for commercial use until 1994.

Practicality

The first practical LED were costly, around $200 per piece, and were only used in professional laboratory equipment. It took a manufacturer of computer chips, Fairchild Semiconductors, to make LED chips for LEDs. Innovative packaging methods and a planar manufacturing process to reduce the price of LEDs to about 5 cents by the 1970s. Fairchild Semiconductors made LEDs into a commercial product with a variety of uses.

The LED systems that Fairchild and others turned out in the 1970s were small, brightly colored lights for use in electronic consumer devices like displays, remote controls, and other wireless control devices. These were not yet the LED lights that are now competing with incandescent bulbs for light bulb dominance.

In the 1970s and 1980s, LED competed with tiny incandescent bulbs that were then used to make lighting displays.

LEDs generate more light per watt of electricity, they are much smaller than incandescent lights, they light much more quickly (which is very important for signaling in remote controls), they are much more difficult to damage because the crystals can be embedded in thick glass, and they last a lot longer than incandescent lights whose metal filaments disintegrate quickly. Price was still a factor which impeded the marketing of LEDs.

Modern Lighting

The fluorescent lamp was invented in the early 1900s by Peter Cooper Hewitt. Mercury vapor fills a tube and electric current shoots through the vapor. The action electrons passing through the mercury causes excitation which generates ultraviolet light.

To make the light visible a phosphorescent powder is introduces as a coating on the glass. The ultraviolet light causes the powder to glow in visible light. This kind of lighting is also less expensive, perhaps half as expensive per watt than incandescent light.

The system is more expensive though because the fluorescent lamp requires a "ballast" to regulate the flow of electrons to keep the light even. It also relies on dangerous mercury vapor which can't be legally disposed of.

LED lamps last 10 to 20 times longer than fluorescent lamps and can be backed by 5 to 10 year warranties.

Modern LED fixtures are based on small crystals mounted in a glass container and connected to a DC power converter. Their size, lack of major heat generation, color flexibility, and simplicity makes them ideal for designing useful and beautiful commercial light fixtures and lamps.

MultiSite LED are experts in multi-location/multi-site LED conversion projects, a full service, national provider of professional, turnkey LED lighting solutions. Please contact us to learn more.