Light-emitting diodes (LEDs) are a relatively old technology (1970s) that has advanced from use in numeric displays and indicator lights to a range of new and potential new applications, including exit signs, accent lights, task lights, traffic lights, signage, cove lighting, wall sconces, outdoor lighting, downlighting and now all lighting for home, office and commercial applications.


LEDs offer benefits such as small size, long lamp life, low heat output, energy savings and durability. They also allow extraordinary design flexibility in color changing, dimming and distribution by combining these small units into desired shapes, colors, sizes and lumen packages. Notably promising current applications include retail display, colored lighting, tight spaces, areas that require low light levels, exterior lighting and applications where the integration of light sources and architectural elements is critical.


Characteristics
LEDs are solid state semiconductor devices. LED illumination is achieved when a semiconductor crystal is excited so that it directly produces visible light in a desired wavelength range (color). LED units are small, typically 5mm (T 1-3/4).

Method of Operation
When an LED unit is activated, a power supply converts AC voltage into sufficient DC voltage, which is applied across the diode semiconductor crystal. This results in electrons (negative charge carriers [N]) in the diode’s electron transport layer and holes (positive charge carriers [P]) in the diode’s hole transport layer combining at the P-N junction and converting their excess energy into light. The LED is sealed in a clear or diffuse plastic lens that can provide a range of angular distributions of the light.

Color
The color composition of the light being emitted by the LED is based on the chemical composition of the material being excited. LEDs are available that can produce colors including white, deep blue, blue, green, yellow, amber, orange, red, bright red and deep red.

Efficacy
LEDs are low-voltage, low-current devices and efficient light sources. For white, red, amber, yellow, green and blue LEDs, new materials have been developed that are more efficient than traditional materials, producing efficacies (lumens per watt) far greater than incandescent lamps and fluorescent lamps. 

White Light LEDs
The utilization of indium gallium nitride (InGaN) as a semiconductor material resulted in the brightest LEDs and enabled the development of the white light LED.

White light LEDs feature a phosphor added to a blue LED that converts some of the light emission into yellow, resulting in a bluish-white light. Further advances now allow for white LEDs to be a light source with a spectrum of correlated color temperatures in the range from warm to cool white- 2,600-11,000K. White light can also be achieved by color mixing the light produced by red, blue and green LEDs. 

Advantages of LED Lighting

LEDs offer numerous benefits due to their mode of operation:

Energy Efficiency
LEDs are highly efficient. In traffic signal lights, a strong market for LEDs, a red traffic signal head that contains 196 LEDs draws 10W versus its incandescent counterpart that draws 150W. Various estimates of potential energy savings range from 82% to 93%. With the red signal operating about 50% of the day, the complete traffic signal unit is estimated to save 35-40%. It is estimated that replacing incandescent lamps in all of America’s some 260,000 traffic signals (red, green and yellow) could reduce energy consumption by nearly 2.5 billion kWh. At the end of 1997, more than 150,000 signals were retrofitted, almost all of them red.

In architectural applications, the greatest penetration of LEDs has been in exit signs, both new signs and retrofits. LED retrofit products, which come in various forms including light bars, panels and screw in LED lamps, typically draw 2-5W per sign, resulting in significant savings versus incandescent lamps with the bonus benefit of much longer life, which in turn reduces maintenance requirements. Some of these products are designed specifically for either on-face or two-face exit signs. Many new LED exit signs are also available, including edge-lit designs. LED products currently make up about 50% of the exit sign market. A study conducted by the Lighting Research Center in 1998 found that about 80% of new exit signs being sold in the U.S. utilize LEDs. 

Long Life
Some LEDs are projected to produce a long service life of about 100,000 hours. For this reason LEDs are ideal for hard-to-reach/maintain fixtures such as exit sign lighting and, combined with its durability, pathway lighting. This service life can be affected by the application and environmental factors, including heat and if being overdriven by the power supply.

Range of Colors
LEDs are available in a range of colors (see above), including white light. White light can also be produced through color mixing of red, blue and green LEDs. In addition, through the innovative combination of various-colored LEDs, dramatic color-changing effects can be produced from a single fixture through dynamic activation of various sets of LEDs. There are track, theatrical, underwater, outdoor and other fixtures utilizing variable-intensity LEDs that can provide more than 16.7 million colors, including white light. These fixtures can be individually controlled via a PC, DMX controller or proprietary controller to generate effects including fixed color, color washing, cross fading, random color changing, strobing and variable strobing.

No UV Emissions/Little Infrared
LEDs produce no UV radiation and little heat, making them ideal for illuminating objects, such as works of art, that are sensitive to UV light.

Durable
LEDs are highly rugged. They feature no filament that can be damaged due to shock and vibrations. They are subject to heat, however, and being overdriven by the power supply.

Design Flexibility
LEDs can be combined in any shape to produce desired lumen packages as the design goals and economics permit. In addition, LEDs can be considered miniature light fixtures; distribution of light can be controlled by the LEDs’ epoxy lens, simplifying the construction of architectural fixtures designed to utilize LEDs. A controller can be connected to an LED fixture to selectively dim individual LEDs, resulting in the dynamic control of distribution, light output and color. Finally, DC power enables the unit to be easily adaptable to different power supplies.

Benefits

The benefits of LEDs include:
* Energy Savings (up to 90% over incandescent)
* Long Life (up to 50,000 hours and beyond)
* Reduced labor and maintenance costs
* Low heat
* No strobe flashing (constant steady light output)
* No UV
* Environmentally Friendly (contain no mercury, recyclable)
* Robust (shock and vibration resistant)
* Lights instantly
* Silent operation
* Low-voltage power supply (increased safety)
*Millions of color possibilities
* Flexibility of design.
*Easy Installation (use standard connections)

IMPORTANT NOTE ABOUT LED TUBES: Led tubes cannot be used in fixtures designed for fluorescent tubes without electrical modifications being made to the fixture. Please consult a professional electrician or purchase a fixture designed for led tubes.

2-5Phone:  202-580-8270