LED Light Fixtures

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LED Light Fixtures

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LED FAQ

Advantages
Q) What are the advantages of LEDs?

A) LEDs are very energy-efficient, they have very long rated lives, they are very small in size, they do not have any restrike time, they are dimmable, they generate relatively less heat, slow failure rate, they are shock resistant, work well in low temperatures, their light can be easily focused, and they contain no toxic mercury.

Q) Do LEDs contain any mercury like many other light sources (e.g., fluorescent, metal halide, and high pressure sodium)?

A) No, LEDs do not contain any mercury, which makes them less toxic and, therefore, a safer light source to dispose of.

Basic Information
Q) What do the letters, L-E-D, stand for?

A) Light Emitting Diode

Q) What is an LED?
A) An LED is a small electronic device (a semiconductor diode) that emits light when electricity passes through it.

Q) What colors do LEDs come in?

A) LEDs can be red, green, blue, or amber. Presently, a white LED is created by covering a blue LED with a yellow phosphorus coating.

Q) Are there any other ways of producing white LED light?

A) Yes, white LED light can also be created by using a red, blue, and green LED in close proximity to each other.

Q) Are there any LEDs that emit white light?

A) No, not yet but this is considered to be the “holy grail” of LED light research.  

Q) Why do different LEDs emit different colors of light?

A) The color emitted by an LED depends on the materials used to make that LED. For example, a red LED is made from the chemical elements of aluminum, gallium, and arsenic.

Brightness
Q) How bright is a high power LED?

A) A single high power LED can produce up to about 80 lumens of light.

Q) How does the brightness of LEDs compare with incandescent light sources?

A) Since a standard 60W incandescent light bulb can produce about 900 lumens a single high power LED is only about 1/11th as bright.

Q) How can LEDs be used successfully in lighting fixtures?

A) For most LED lighting fixtures to provide adequate lighting the fixture must contain groups of LEDs.

Q) Will LEDs become even brighter in the future?

A) Almost certainly. The lumen output of LEDs has almost doubled in the last two years.

Color Rendering
Q) How is the color rendering ability of white LEDs measured?

A) A measure of any light source’s ability to render colors accurately is called color rendering index. The scale ranges from 1 (low pressure sodium) to 100 (the sun). A CRI of 75 is considered to be good, a CRI of 85 is considered to be very good, a CRI of 95 is considered to be excellent, and a CRI of 100 is considered to be perfect.

Q) How well do white LEDs render colors?

A) Warm white LEDs are now available with a CRI of 80.

Color Temperature
Q) What is the color temperature of a light source?

A) Color temperature is a measure of the color appearance of a light source which helps describe the apparent "warmth" (reddish) or "coolness" (bluish) of that light source. Generally, light sources below 3200K are considered "warm;" while those above 4000K are considered "cool" light sources. The color temperature of a light source has nothing to do with how hot the light source will get or how much heat is given off by the light source. The letter, K, stands for Kelvin, a type of temperature scale.

Q) What is the color temperature of white LEDs?

A) White LEDs can and do vary in color temperature. Some white LEDs can be as "warm" in appearance as 2600K but most white LEDs are slightly "cool" in appearance since most white LEDs are created by putting yellow phosphors over blue LEDs.

Cost
Q) Are LEDs and LED light fixtures more expensive than some other fixtures?

A) Yes for some LED light fixtures but like all new electronic products (e.g., computers and TVs) the cost of LEDs and LED light fixtures has been coming down in price and will continue to come down in price.

Q) Are some LED light fixtures now “reasonably priced”?

A) Absolutely.

Drivers, LED
Q) What is an LED driver?

A) Fluorescent light bulbs cannot function without a ballast, which provides a starting voltage and limits electrical current to the lamp. LEDs also require a similar electronic power source, usually called a driver. The driver converts line power to the appropriate voltage (typically between 2 and 4 volts DC for high-brightness LEDs) and current (generally 200-1000 milliamps or mA), and may also include dimming and/or color correction controls.

Q) How efficient are LED drivers?

A) LED drivers are typically about 80%-85% efficient. So LED efficacy should be discounted by 15%-20% to account for the driver.

Efficacy
Q) How is the efficacy of LEDs measured?

A) Like all light sources LED efficacy is measured in lumens/watt, that is, the amount of light produced by one unit of power.

Q) How efficient are white LEDs in the real world?

A) Warm white LEDs produce 25-44 lumens/watt while cool white LEDs are more efficacious by producing 47-64 lumens/watt. In comparison, incandescent light bulbs produce 10-18 lumens/watt, line voltage halogen light bulbs produce 15-20 lumens/watt, compact fluorescent lamps or CFLs (including the ballast) produce 35-60 lumens/watt, metal halide lamps (including the ballast) produce 50-90 lumens/watt, and linear fluorescent light bulbs (including the ballast) produce 50-100 lumens/watt.

Heat Generation
Q) Is it true that LEDs generate no heat?

A) Definitely not. All light sources generate heat, including LEDs.

Q) How does heat affect an LED?

A) Yes, all lighting sources generate heat including LEDs. However, they do not get very hot, especially if the LEDs and the light fixture are well-designed with "heat sinks" to help dissipate the heat.

Infrared Radiation
Q) Do white LEDs emit infrared radiation (heat radiation) like incandescent light sources?

A) No, they do not.

Life, Rated

Q) Do LEDs ever burn out like incandescent light bulbs?

A) No, instead over their lifetime LEDs simply get progressively dimmer until they do not emit enough light to be useful.

Q) When is the amount of light being emitted by an LED considered to be no longer useful.

A) Generally speaking, an LED is considered to be no longer useful when it is emitting only 70% of the amount of light that it originally emitted. The time that this takes is considered to be the "rated life" of an LED.

Q) Do some LEDs have a rated life of 100,000 hours?

A) Some LEDs may have a rated life of 100,000 hours but only under perfect conditions in the laboratory. Under real-world conditions when operating in a light fixture LEDs might last up to 60,000 hours. The rated life of an LED in a light fixture is often much less than the rated life of the same LED operating outside a light fixture.

Q) What is the rated life of an LED in a light fixture?

A) The typical LED may have a rated life of about 30,000 to 60,000 hours while operating in a light fixture.

OLEDs
Q) What is an OLED?

A) An OLED is an organic light emitting diode, that is, an LED that also contains the element of carbon.

Q) How does an OLED differ from an LED?

A) OLEDs generally are manufactured as flexible lightweight sheets.  Today, OLEDs operate at substantially lower efficiency than inorganic (crystalline) LEDs.  OLEDs typically emit less light per area than inorganic solid state LEDs, which are usually designed for use as point-light sources.

UV Radiation
Q) Do white LEDs emit ultraviolet radiation (UV rays)?

A) No, they do not emit UV light..

Q) Are insects attracted to the light produced by white LEDs?

A) No. Insects are not attracted to the white light produced by LEDs because what they are attracted to is UV light and white LEDs emit no UV radiation.

Caution

Although there has been a lot of media attention given to LEDs, far too many LEDs are not well-manufactured and too many LED light fixtures are not well-designed. In short, the LED lighting market is still maturing. Research continues to improve the brightness, the efficacy, and the life span of LEDs at a remarkable pace. However, Pegasus Associates Lighting continues to be cautious about which LEDs and LED fixtures it brings to the market place because we want our customers to be pleased with our LED lighting products both today and tomorrow. We suggest that you be cautious as well.