Light Emitting Diode (LED) is a semiconductor device which converts
electricity into light. LED lighting has been around since the 1960s, but is
just now beginning to appear in the residential market for space lighting.
At first white LEDs were only possible by "rainbow" groups of three LEDs --
red, green, and blue -- by controlling the current to each to yield an
overall white light.
Standard array 18
LED lighting diodesThis changed in 1993 when Nichia created a blue indium
gallium chip with a phosphor coating that is used to create the wave shift
necessary to emit white light from a single diode. This process is much less
expensive for the amount of light generated.

Each diode is about 1/4 inch in diameter and uses about ten milliamps to
operate at about a tenth of a watt. LEDs are small in size, but can be
grouped together for higher intensity applications. LED fixtures require a
driver which is analogous to the ballast in fluorescent fixtures. The
drivers are typically built into the fixture (like fluorescent ballasts) or
they are a plug transformer for portable (plug-in) fixtures. The plug-in
transformers allow the fixture to run on standard 120 volt alternating
current (AC), with a modest (about 15 to 20 percent) power loss.

The efficacy of a typical residential application LED is approximately 20
lumens per watt (LPW), though efficacies of up to 100 LPW have been created
in laboratory settings. Incandescent bulbs have an efficacy of about 15 LPW
and ENERGY STARR qualified compact fluorescents are about 60 LPW, depending
on the wattage and lamp type. Some manufacturers claim efficacies much
higher than 20 LPW; make sure to examine system efficacy, which accounts for
the power use of all components. In December 2006, the U.S. Department of
Energy studied the efficacy of four luminaries. All four fell short of the
manufacturers' claims; the study implies that manufacturers are relying on
measurements of how much light an isolated LED produces, rather than how
much light an LED luminaire actually delivers.

LEDs are better at placing light in a single direction than incandescent or
fluorescent bulbs. Because of their directional output, they have unique
design features that can be exploited by clever designs. LED strip lights
can be installed under counters, in hallways, and in staircases;
concentrated arrays can be used for room lighting. Waterproof, outdoor
fixtures are also available. Some manufacturers consider applications such
as gardens, walkways, and decorative fixtures outside garage doors to be the
most cost-efficient.

LED lights are more rugged and damage-resistant than compact fluorescents
and incandescent bulbs. LED lights don't flicker. They are very heat
sensitive; excessive heat or inappropriate applications dramatically reduce
both light output and lifetime. Uses include:

* Task and reading lamps
* Linear strip lighting (under kitchen cabinets)
* Recessed lighting/ceiling cans
* Porch/outdoor/landscaping lighting
* Art lighting
* Night lights
* Stair and walkway lighting
* Pendants and overhead
* Retrofit bulbs for lamps

Definitions and Terms


Term

Definition

Units

How to interpret


Color Temperature

Color of light

Kelvin (K)

Sunlight at sunrise is 1800K
100W Incandescent light bulb is 2850K
Overcast Sky is 6500K


Color Rendering Index (CRI)

Light's effect on color

Scale of 0 to 100 with sunlight at 100

The higher the number, the more "true" the color will look in that light


Brightness

The intensity of the light.

Lumens

The higher the lumens, the brighter the light


Power

Amount of electrical energy consumed

Watts

Lower the watts, the lower the energy consumed


Efficacy

The efficiency of the bulb to convert electricity into light

Lumens per Watt

More efficient bulbs provide more light using less energy





Mike Antheil

Mike Antheil

561.703.4345 Direct

mike@mikeantheil.com