LED lighting


A light-emitting diode (LED) is a semiconductor device that emits incoherent narrow-spectrum light when electrically biased in the forward direction. The color of the emitted light depends on the chemical composition of the semiconducting material used, and can be near-ultraviolet, visible or infrared. It consists of a chip of semiconducting material doped with impurities to create a structure called a p-n junction. Charge-carriers - electrons and holes flow into the junction from electrodes with different voltages. When an electron meets a hole, it falls into a lower energy level, and releases energy in the form of a photon as it does so.

LEDs now are available in various colours such as red, infra red, green, orange, yellow, emerald, blue, white, etc. Yellow LED lights are a good choice to meet these special requirements because the human eye is more sensitive to yellow light.

Unlike incandescent light bulbs, which light up regardless of the electrical polarity, LEDs will only light with positive electrical polarity. If the voltage is of the wrong polarity, no light is emitted. LED lighting only works on DC supply. On AC supply with change in polarity it switches on and off. Thus LED lighting comes with a DC converter circuit.

LED lighting is a replacement for incandescent and fluorescent bulbs. Solid State Lighting (SSL) is the application of LEDs in lighting. Small spotlights made of many individual LEDs are used for lighting. SSL LEDs are packaged as a cluster of white LEDs grouped together to form a light source.

The advantages of using LED lighting are that LEDs are capable of emitting light of an intended color without the use of color filters. Secondly the shape of the LED package allows light to be focused. Incandescent and fluorescent sources often require an external reflector to collect light and direct it in a useable manner. LEDs are insensitive to vibration and shocks, unlike incandescent and discharge sources. LEDs have an extremely long life span: typically ten years, twice as long as the best fluorescent bulbs and twenty times longer than the best incandescent bulbs. Further, LEDs fail by dimming over time, rather than the abrupt burn-out of incandescent bulbs. LEDs give off less heat than incandescent light bulbs with similar light output. LEDs light up very quickly. An LED will achieve full brightness in approximately 0.01 seconds, 10 times faster than an incandescent light bulb.

LED lighting thus has a lot of advantages and looks to be the future of lighting.

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