Basics & Background

A light-emitting diode (LED) is a semiconductor device which converts electricity into light. This application of LED in illumination is referred to as Solid State Lighting (SSL). It is traditionally used in signs, signals and displays, and now it is rapidly evolves to provide light sources for general illumination. LED lighting starts with a tiny chip comprising layers of semi-conducting material. LED packages may contain just one chip or multiple chips, mounted on heat-conducting material and usually enclosed in a lens or encapsulant. The resulting device, typically around 7 to 9 mm on a side, can produce 30 to 150 lumens each, and can be used separately or in arrays. LED devices are mounted on a circuit board and attached to a lighting fixture, architectural structure, or even a “light bulb” package.

Unlike incandescent or fluorescent lamps which create light with filaments and gases encased in a glass bulb, solid-state lighting consists of semiconductors that convert electricity into light. LEDs are grouped together for higher intensity applications. The fixtures normally require a driver which is analogous to the ballast in fluorescent fixtures. The drivers are typically built into the fixture or they are a plug transformer for portable fixtures.

The uniqueness of LEDs is it placed light in a single direction better than incandescent or fluorescent bulbs. Due to the directional output, LEDs have unique design features that can be exploited by clever designs. Now, different types of LED lightings are applied in various places, no matter indoor or outdoor. LED strip lights can be installed under counters, in hallways, and in staircases; concentrated arrays can be used for room lighting. Waterproof and outdoor fixtures are also available. It is more rugged and damage-resistant than compact fluorescent and incandescent bulbs.

The performance of LED lightings in terms of light output, color, luminous efficacy and life will vary depending on how they are implemented into the lighting application. Under perfect conditions, LEDs may operate 50,000 to 100,000 hours. But in reality, LEDs can have drastically shortened lives and substandard lighting quality as a result of poor fixture design or installation. The most common threat to LED lighting quality and life is heat.