Light emitting diodes (LEDs) are found everywhere today, from simple indicator lights on electronic equipment to traffic signals to the LED backlights found in LCD televisions. They form the individual pixels on giant outdoor video screens and the light source in the optical mice used with computers. In spite of the wide variety of uses to which LEDs are put, the technology behind them is relatively simple.
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What is an LED?
Diodes are semiconductor devices, just like the familiar transistors. Made of nonconductive material, they are doped with substances to add a charge, often phosphorus or arsenic for a negative charge and gallium or boron for a positive one.
When a diode is doped with negative material on one end and positive material on the other, the free electrons near the junction migrate from the negative part to the positive part, creating an inert area that serves as an insulator. This means that no further current flows through the diode, unless something else happens.
If that something is an electric potential, or voltage difference, applied so that the negative end of the circuit is toward the negative material and the two positive ends are also together, current will flow through the diode.
When the electrons move to produce a current, they either absorb or release photons of light. When the doping is such that excess photons are released in the visible spectrum, the result is a light emitting diode. Sealed in the familiar torpedo shaped epoxy case, the resulting LEDs are ready to use in technology of all sorts.
Advantages of LEDs
As improvements are made in LED technology, it becomes more and more advantageous to use a light emitting diode where an incandescent or fluorescent light might once have been used. LEDs have no filament, so they do not burn out or release waste heat, meaning they run cool and last far longer than incandescent bulbs. Being diodes, they integrate seamlessly into digital devices and are easily programmable. Since LEDs require relatively little power, they are impressively portable, able to run off small batteries or even a portable solar array.
Disadvantages of LED Technology
By varying the materials used to make LEDs, manufacturers can produce almost any color in the spectrum, but they cannot directly produce pure white. Various methods are used to approximate white, but a white emitting LED remains something of a Holy Grail. In addition, the initial cost of LED technology can be high, and the devices are very demanding about both the magnitude and the polarity of the voltages they will accept. Also, like most digital devices, LEDs function best in a temperature controlled environment.
LEDs have spread far beyond their initial uses in electronic equipment. Now found in applications ranging from aviation lighting to mass transit destination signs, LED technology is developing at a rapid pace and expanding into new areas every day.
Thomas Jay is an article writer for i-Adapters.com. He loves doing research and blogging on various technology related topics.