[Design Application]
Cost-Effective LEDs Fit Snugly In Today's Energy-Conscious World
Know the basic concepts of LEDs and their benefits, and learn how to maximize their use in various applications.
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 LEDs.
Although recent advances in LED technology have dramatically broadened the applications for these rugged little light sources, it wasn't so long ago that red was the only "daylight-visible" LED color. This wasn't the only characteristic limiting their use, either.
Unlike incandescent bulbs, which 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 and in a variety of angles. For many applications, such as indicators or switch illuminators, this isn't a problem. But it took the development of multichip arrays and high-flux LED chips to begin to achieve the effect of an incandescent filament.
Major advances in LED technology have taken place in recent years. For example, look at the new "doping" technologies that increase LED light output by as much as 20 times over earlier generations while allowing 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 impossible to achieve, is now available in three different LED shades (see "What Can White-Light LEDs Illuminate And How Can They Be Used?," p. 94).
The efficiency of LEDs is most apparent in applications that require color. Light from a typical incandescent bulb must be filtered so that only light from a particular part of the spectrum (for example, red, amber, or green) is visible. While LEDs deliver 100% of their energy as colored light, incandescent bulbs waste 90% or more of their energy in light blocked by the colored lens or filter they use. Incandescent bulbs also waste 80% to 90% of their energy on heat generation to reach the intensity (Kelvin scale) for which they are designed.
LEDs are able to provide a more color-controlled intense light. For instance, observe the color difference in the center brake light on many modern cars. One third of all center brake lights are red LED clusters. Many automobile manufacturers frequently use LEDs because the center light is often inaccessible, and replacement is essentially impossible. The next time you're in traffic, look around and notice how much more vivid the red is on this light than it is on standard, filtered incandescent taillights.
Once considered a fairly marginal light source, LEDs aren't marginal anymore. In many applications, LEDs exceed the energy available from incandescent bulbs and offer significant additional benefits. Consequently, LED clusters and lamps are as friendly to the environment as they are to the operating budget.
LED Options Abound LEDs with standard light bases used to be the only competition for tiny miniature and subminiature bulbs, called the T1 or 3-mm "grain of wheat" bulbs. Today, LED lamps come in a wide variety of standard light bases, in sizes ranging from the grain of wheat T1 3-mm to medium-screw 25-mm bulbs and larger. LED lamps are rugged, durable, and daylight-visible. As a blessing to overworked maintenance personnel, they also have a life span far exceeding that available from current incandescent technology.
Previously, the cost of the incandescent bulb itself was inconsequential. The real cost came in lost production and wasted labor and energy. More significantly, a failed light can bring an entire machine down, or even idle an entire line of skilled workers. Also, consider the labor costs associated with maintenance workers who could spend time on more productive projects than changing light bulbs.
Depending on what it costs you to have a machine down and pay an operator and maintenance worker—even if it's just for a quarter of an hour—the real cost of relamping incandescent bulbs can be astronomical.
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