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C&G LED FAQ - Q20-Q28

Article Index
C&G LED FAQ
Q4-Q9
Q10-Q14
Q15-Q19
Q20-Q28
All Pages

 


Q20. How LED works?


An LED consists of a chip of semiconducting material treated to create a structure called a p-n (positive-negative) junction. When connected to a power source, current flows from the p-side or anode to the n-side, or cathode, but not in the reverse direction. Charge-carriers (electrons and electron holes) flow into the junction from electrodes. When an electron meets a hole, it falls into a lower energy level, and releases energy in the form of a photon (light).



Q21. When LED was invented?


LEDs were first developed in the 1960s but were used only in indicator applications until recently.
The electronics industry has used LED technology for several decades as indicator lights for various electronic devices. In more recent years, LED technology has progressed to the point where it is viable for general lighting applications.



Q22. Why LED's?


As a rule, LED bulbs use 90% less electricity than standard bulbs. They have an unparalleled even spectrum of light and have a lifespan beyond ten years. LED's provide us the most efficient way to save energy and conserve our natural resources. If LED's were implemented right now universally, we would not need to build another power plant. LEDs would actually eliminate the need for over 30 existing power plants!



Q23. How LED emit different color?


The specific wavelength or color emitted by the LED depends on the materials used to make the diode. Red LEDs are based on aluminum gallium arsenide (AlGaAs). Blue LEDs are made from indium gallium nitride (InGaN) and green from aluminum gallium phosphide (AlGaP). "White" light is created by combining the light from red, green, and blue (RGB) LEDs or by coating a blue LED with yellow phosphor. See "Color Quality" section for more information.

 



Q24. What’s Low Power LEDs?


Low power LEDs commonly come in 5 mm size, although they are also available in 3 mm and 8 mm sizes. These are fractional wattage devices, typically 0.1 watt, operate at low current (~20 milliamps) and low voltage (3.2 volts DC), and produce a small amount of light, perhaps 2 to 4 lumens.



Q25. What’s High Power LEDs?


High power LEDs come in 1-3 watt packages. They are driven at much higher current, typically 350, 700, or 1000 mA, and—with current technology—can produce 40-80 lumens per 1-watt package.

 


Q26. Why have past attempts to create general illumination LEDs failed?


Conventional approaches to developing general illumination LEDs often involved retrofitting existing fixtures to house the new LED technology.

Instead of investigating the benefits and challenges of LEDs, many early attempts simply used traditional lighting standards and housings.

The problem was that LED technology breaks all traditional rules, and it quickly became apparent that old thinking couldn't be applied to this new technology.



Q27. Why don't LEDs function as efficiently in a traditional fixture housing?


An LED module may physically fit into an existing housing, but that housing doesn't leverage the inherent qualities of the LEDs. Standard housings can't handle the challenges of LED thermal management, which is vastly

different than thermal management for traditional incandescent or fluorescent lighting. Also, the optical design used in most traditional fixtures doesn't maximize the LED's efficiency.

 


Q28. Do I have to replace LED diodes?


An LED does not burn out like a standard lamp, so individual diodes do not need to be replaced. Instead, the diodes gradually produce lower output levels over a very long period of time. If one LED fails, it does not produce a complete fixture outage.