LED Light Fixtures

LED Light Fixtures

LED Drivers

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.

LED Valuable Information

Like all light sources (e.g., incandescent, halogen, xenon, fluorescent, metal halide, high pressure sodium) LEDs manifest both positive and negative characteristics and here is a list of some of those pluses and minuses.

COLOR TEMPERATURE

No White LEDs – Presently, there are no white LEDs, per se. In reality, a white LED is a blue LED that has a yellow phosphor coating. White light can also be produced through color mixing of red, blue and green LEDs that are in close proximity. This latter method of producing white light with LEDs is sometimes used with LED signs (e.g., jumbotrons).

A Variety of Color Temperatures – LED technology enables a fairly wide range of available color temperatures for white LEDs (e.g., warm white, neutral white, cool white, daylight). Because the “warmer” color temperature white LEDs need more yellow phosphor coating than the “cooler” color temperature white LEDs, warm white LEDs are always less bright than cool white LEDs assuming all other variables remain constant.

Color Variation – You may see some variation and color inconsistency among white LEDs. Check the color temperature of the LED light fixture you want to try. The temperature has 4 digits, and the higher the number, the bluer the light will look. Incandescent light is normally around 2700K-3000K and this is what you should look for if you want to emulate the “warm” look of incandescent light.

Provide Very Saturated (Pure) Colors – LEDs are available in a range of colors, including red, blue, green, and amber. 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. Several manufacturers offer track, theatrical, underwater, outdoor, and other LED 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 a proprietary controller to generate effects including fixed color, color washing, cross fading, random color changing, strobing, and variable strobing.

COST

Relatively Expensive – LEDs are relatively expensive when compared to standard incandescent light bulbs or even CFLs because the manufacturing technology used to create LEDs is still very new and quite complicated. Over time, prices for most LED light fixtures will come down just as they did for other electronic products like calculators, cell phones, and flat-panel TVs. Despite the relatively high cost of manufacturing LEDs, there are some LED light fixtures on the market now that are very reasonably priced such as barbecue lights, cabinet lights, exit signs, flashlights, night lights, step lights, and under cabinet lights.

DIMMABILITY

Limited Dimmability – Although some LEDs available now are dimmable, this is a technology that is still evolving and has not yet been completely refined. It could be that a dimmable LED light fixture needs a special dimmer or it may be incompatible with the dimmer that you currently have. If your present dimmer is incompatible with your new LED light fixture, it is not considered dangerous situation. In all likelihood, your LED light fixture will flicker when you try to dim it. You will simply need to change the dimmer to an on/off switch or use the right dimmer.

ENERGY EFFICIENCY

Energy Efficient – Good LED bulbs consume extremely little power for the same light output of other sources. A good 5-watt LED light bulb produces about the same light output as a 25-watt standard incandescent light bulb. An 11-watt LED PAR reflector light bulb produces light equivalent to a 50W PAR halogen light bulb. In traffic signal lights, for example, a red traffic signal head that contains about 200 LEDs and draws only about 10 watts of power versus its incandescent counterpart that draws somewhere between 60 and 170 watts. It is estimated that replacing the incandescent lamps in all of this country’s approximately 260,000 traffic signals (red, green, and yellow) could reduce energy consumption by nearly 2.5 billion kWh (kilowatt-hours). In short, the energy savings associated with using LEDs can be substantial.

Can be Battery Operated – Because LEDs use very little power, in some cases, they can receive their power from standard alkaline batteries.

Can be Powered by Solar Cells – Likewise, LEDs can easily be powered by solar cells as well.

ENVIRONMENTAL IMPACT

No Toxic Mercury – Mercury is not used in LEDs, freeing you from the environmental hazard that can be associated with disposing of burnt-out fluorescent, metal halide, and high pressure sodium light bulbs.

FIXTURE DESIGN

Back Heat Requires Good Engineering – Contrary to some popular opinion LEDs do generate some heat but this heat comes out of the rear of the LED and not the front. This heat needs to be carefully taken away from the LEDs and dissipated by using a well-designed heat sink of some sort. A well-engineered LED light fixture must have a working heat sink that ensures that the LEDs will not become too hot. The existence of heat sink “fins” does not ensure that the LED light fixture has a good heat management system. The “fins” may have been added simply for aesthetic reasons in order to make the light fixture look contemporary or “cool-looking”. Remember, it is imperative that good heat management techniques maximize the life of the LEDs in the light fixture. If not, the life of the LEDs will be dramatically reduced if this heat is not managed properly.

Limited Brightness – Presently a single white LED cannot equal the light output of a 100W, 75W, or even a 60W standard incandescent light bulb. Since today’s LEDs are just not yet powerful enough to do that job, it usually takes multiple LEDs to produce the amount of light that’s needed.

Focused Light – The optical makeup of the standard LED package focuses the light without the need for additional optical components, making them more efficient and cost-effective at utilizing the light produced. On the other hand, the nature of incandescent or fluorescent light bulbs requires external optics to collect the emitted light and direct it in a usable fashion.

Design Flexibility – A single LED is very small and produces little light overall. However, this weakness is actually its strength. LEDs can be combined into 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 LED’s integral 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.

INFRARED RADIATION

No Beam Heat – White LEDs do not emit infrared radiation; so, the beam of light produced by a white LED does not contain any heat. This makes LEDs ideal for shallow ceiling downlighting and display lighting.

OPERATION

No Warm-Up Time – LEDs do not have the long warm-up time many people find annoying about CFLs. Instead, the light from LEDs shines at full brilliance as soon as the switch is turned on.

Mechanically Durable – Unlike other light bulbs that use fragile filaments (especially incandescent light bulbs) LEDs tolerate vibration exceptionally well because they do not use filaments. Vibration or shock easily breaks the fragile filament in an incandescent bulb and the glass tubing of a fluorescent lamp. LEDs, on the other hand, are completely solid-state technology and are virtually indestructible under normal circumstances.

PHYSIOLOGICAL EFFECTS OF LEDS

Better Vehicle Headlights – LED headlights offer a safety advantage to drivers for purely physiological reasons. The higher color temperature of LED headlights compared to halogen and xenon headlight systems improves driver vision in low-light conditions (twilight and darkness). Also, our peripheral vision is improved with the use of LED headlights. The high blue share of LEDs leads to higher sensitivity to potentially hazardous objects appearing in the lateral field of vision.

RATED LIFE

Long Life – Good LEDs will last a very long time. Conventional incandescent light bulbs last around 1000 hours. Normal screw-in compact fluorescent lamps (CFLs) last around 8000-10,000 hours. White LEDs for everyday use in a well-designed light fixture should last around 35,000-60,000 hours.

Reduced Maintenance Costs – The long life of LEDs can translate into substantially reduced maintenance costs, especially for hard-to-reach light fixtures (e.g., traffic lights).

Life Span Unaffected by Rapid On/Off Cycling – Unlike with fluorescent light bulbs the life span of LEDs is not affected by turning the LEDs on and off in rapid succession.

They Don’t Burn Out – LEDs will not burn out like conventional light bulbs. Instead, over their lifetime LEDs simply get progressively dimmer until they do not emit enough light to be useful.

Longer Life in Open Fixtures – Since the buildup of heat is so detrimental to the life of LEDs it naturally follows that LED replacement light bulbs would probably last longer in open fixtures like simple track fixtures that allow the air to circulate freely around the LED reflector light bulb. Conversely, when LED replacement light bulbs are used in enclosed recessed downlights their life will be diminished.

ULTRAVIOLET RADIATION

Limited Fabric Fading – Amazingly, white LEDs do not produce any ultraviolet (UV) light even though all other natural and artificial light sources do. Thus, when using white LED light fixtures, there will be minimal fading and deterioration of fabrics, documents, or artwork due to exposure to the white light from LEDs.

Better for Fruits & Vegetables – Unlike light sources like metal halide, LEDs do not radiate high levels of UV rays. While it is common knowledge that heat can speed up food’s spoilage rate, it is lesser known that high UV levels can actually decrease the nutrient levels in food. Thus, using LEDs to light the produce in a super market, for example, may not only be energy efficient, it may also help the produce to maintain higher nutrient levels.

Do Not Attract Bugs – Since white LEDs do not emit ultraviolet light (the invisible portion of the spectrum just beyond visible violet) light fixtures using white LEDs do not attract bugs.