The most recent addition to the array of residential lighting options is LED-based lighting. An LED, or light emitting diode, is a semiconductor-based device that emits light due to the change in energy of electrons in the semiconductor material as a result of an input voltage.
The two key advantages of LED lighting are energy efficiency and lifetime. While lighting efficiencies of incandescent bulbs are around 3%, LED bulbs are much more efficient, emitting much more light per watt. A 12 watt LED emits more light than a 60 watt incandescent. Recent LED-based bulbs have efficiencies similar to those seen in fluorescents, without the environmental issue of mercury that is a concern with compact fluorescent bulbs.
One of the biggest advantages of LEDs is their lifetime, which typically approaches 20,000 hours. LED bulbs also have a quicker start time than compact fluorescents, which have a delay between when they are switched on and when they actually begin to produce light.
LED lighting systems consist of a light source (the LED), a driver circuit, and a luminaire. The luminaire consists of the containment structure, which usually incorporates a phosphor material to control the output light color and intensity, and a thermal management scheme. Unlike incandescent bulbs, which release heat as radiation, LED bulbs are “cool” lights, and require a heat sink in the containment structure.
One aspect of future LED lighting that will be quite different from existing lighting is that LED light sources will consist of arrays of several smaller lights, as opposed to the 2 to 4 bulbs per conventional incandescent light source.
Because of the complexity of LED lighting, components that support different manufacturer’s products are generally not interchangeable. The ballast/driver circuit should be matched to the specific LED bulb or array.
Dimmer switches are available for LED lights, but they should also be matched to the specific product for which they were designed. Dimming of LED lighting is done through pulse-width modulation, which is a different modulation approach than that used for conventional lighting. This approach eliminates flickering of the lights, which was a problem with earlier dimmer technology. Some newer bulbs even have a remote control option for adjusting color and brightness.
When installing LED lighting, it is important to avoid placing them in an area that is susceptible to large temperature swings. In general, LED lights work best at cooler temperatures and degrade rapidly if exposed to heat. Some of the best applications for LED lighting include task lighting (at a distance of about 12”) and outdoor focal point lighting.
Figure 1 Source: Sharp Press Release sharp-world.comLog in to post comments