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.