Once limited to simple status indicators, Light Emitting Diodes (LEDs) now play prominent

roles in back lighting, panel indication, decorative illumination, emergency lighting, animated

signage, etc.... The emergence of LEDs as a viable alternative to incandescent lighting can be

attributed to new manufacturing technologies, packaging innovations and an increasing

number of colors. These factors along with the growing awareness of the advantages of LEDs

(e.g., a life span measured in years not hours, vivid sunlight-visible colors and low power

requirements) have engineers, product designers, purchasing agents and component vendors

viewing LEDs in a whole new light.

For many applications LED lamps are superior to incandescent lighting. So why is it that in

tens of millions of switches, indicators, control panels, signs, annunciators, displays, decor

lights and dozens of other applications, design engineers still specify incandescent

technology? It might be that they’re just a few years behind what’s really happening in LED

illumination.

Although advances made in LED technology in the past few years have dramatically

broadened the applications for these rugged little light sources, it wasn’t that long ago that red

was the only “daylight-visible” colored LED. And that wasn’t the only thing limiting their use!

Unlike incandescent bulbs that give off the full spectrum of light in a spherical pattern, LEDs

emit a focused beam of a single wavelength (color) in only one direction, in a variety of angles.

For many applications, such as indicators or switch illuminators, this is not a problem, but it

took the development of multi-chip arrays and high-flux LED chips to begin to achieve the

effect of an incandescent filament.

Major advancements in LED technology have taken place in recent years such as

development of new “doping” technologies that increase LED light output by as much as 20

times over earlier generations, and allow the production of daylight-visible LEDs in virtually any

color of the spectrum. In addition to red, yellow, and amber/orange, LEDs are now available in

many colors from leaf green to ultra blue. Even white light, long thought to be an impossibility,

is now available in three different shades as a light-emitting diode.

The efficiency of LEDs is most apparent in applications requiring color. Light from a typical

incandescent bulb must be filtered so that only light from a particular part of the spectrum

(e.g., red, amber or green, etc...) for example—is visible. While LEDs deliver 100 percent of

their energy as colored light, incandescent bulbs waste 90 percent or more of their energy in

light blocked by the colored lens or filter. Incandescent bulbs also waste 80 percent to 90

percent of their energy on heat generation to reach the temperature for which (Kelvin scale)

they are designed.

The point is that what was once a fairly marginal light source isn’t marginal any more. In many

applications, LEDs exceed the energy available from incandescent bulbs and offer significant

additional benefits making LED clusters and lamps as friendly to the environment as they are

to the operating budget.