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LED Light Source - An Education

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The following article will give you a little education on the ins and outs of efficient LED Lights and how they work.

Sustainable lighting

Efficient lighting is needed for sustainable architecture. A 7 watt LED lamp produces 450 to 650 lumens, which is equivalent to a standard 40 watt incandescent bulb. A standard 40 W incandescent bulb has an expected lifespan of 1,000 hours while an LED can continue to operate with reduced efficiency for more than 50,000 hours, 50 times longer than the incandescent bulb

LED Output Power

When high-power LED light fittings first became available, it was common to refer to the different powers available in terms of 'watts'. For example, the first generation of general lighting LED's are referred to as "1W" LED's, the second generation referred to as "3W". This was primarily done in order to provide a comparison to conventional halogen or incandescent bulbs. However using watts is a misleading way of describing LED output, as the present generation of LEDs demonstrates; you can have an LED that uses 2W but puts out more light than a "3W" LED! The most accurate form of comparison is to describe LED's in terms of overall efficiency, or Lumens per Watt. This allows for accurate comparison to other light sources and between different generations of LEDs. LED

LED Efficiency

LED Lamp Lifetime

Stated LED lifetime is usually in the realm of 50,000 hours. This represents (in the case of CREE LED's) the period of operation before the output is reduced to approximately 50% of its original level.

Colour Rendering Index (CRI)

Colour Rendering Index (or CRI) is a representative measure of how accurately a certain light source represents the colours and objects it illuminates. A burning filament, such as an incandescent bulb, has a high CRI of nearly 100. A monochromatic source, such as the orange sodium-vapour street lights, has a low CRI of almost 0! You can imagine the difference of how a photograph might appear under those varied light sources! LED's have traditionally had quite low CRI's of around 50, however the latest generation of LED's, including those from CREE, have much higher CRI's of around 89, close to that of a halogen bulb.


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