조명 시스템

조명 시스템

LED 조명 기본

2008-08-23 15:18
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Altman Lighting’s Spectra Cyc, a 48 or 96W cyclorama/wall wash luminaire utilizing red, green, blue, and amber LEDs. The Spectra Cyc blends colors via a patent-pending LED lens which reduces pixellization from direct view. The on board power supply allows for direct power and data input which can be daisy chained thru 12 units. The Spectra Cyc comes complete with a library of pre-programmed single colors to various color mixes.  

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The Impression from Elation Lighting. It is a moving head fixture with 90 K2 Luxeon LEDs for its source. It comes available as an RGB version with 30 LEDs per color and also comes in a white LED version featuring white and amber LEDs allowing color temperature control from daylight to tungsten. The movement range is 660 degrees of pan and 300 degrees of tilt.  

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The AC Lighting Chroma-Q Color Punch provides 1,250 lumens output in an IP65 rated, machined aluminum and high impact plastic casing. The fixture features convection cooling for silent operation.  

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For photographers and videographers, the Element Lab’s Kelvin TILE is an LED-based lighting system that provides variable color temperature. Kelvin TILEs have a unique mix of LEDs, resulting in full spectrum white light specifically developed for film and video applications. And, unlike traditional lighting products, color temperature reportedly remains consistent throughout the full range of intensity variation.  

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The ColorReach Powercore from Philips Solid-State Lighting was launched at Lightfair. With more than 4,000 lumens of output and 400-foot projection, the product is designed for long throws such as washing the side of a building.  

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The Selador X7 Paletta, a 40 2.5W LED color changing fixture product line comes in 11-inch, 22-inch, 44-inch, and 66-inch lengths. As with all Selador fixtures, the Paletta accepts a full line of secondary horizontal and vertical beam shaping lenses from 20 degrees to 80 degrees.  

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PixelRange’s PixelArt, a modular LED video product, allows designers to build their own custom display surface. Each batten consists of 6 x 72 tri-colored SMD LED pixels, each pixel being individually controllable. It is designed to handle low resolution video and can serve either as a video display or as a lighting device.  

Light Emitting Diodes (LEDs). You hear a lot about them. While LEDs are definitely here to stay, there are still many myths about what they can do. In addition, there needs to be some education about when and how to incorporate LEDs into your lighting systems. With the costs of energy rising daily and the need to reduce our impact on the environment, LEDs certainly will play a much larger role in the lighting systems of houses of worship, both in theatrical and architectural applications.

As for architectural applications, I recently attended the Lightfair International (LFI) 2008 tradeshow in Las Vegas, Nevada, one of the largest architectural lighting shows in the world. With almost every lamp, luminaire, and control manufacturer represented, I lost count at 160 companies that had something to do with LEDs. It is becoming apparent that LEDs are the light source of choice and even fluorescent technology is starting to wane, mostly due to its environmental impact issues. While a number of states have mandated that no more incandescents will be available and that you must use only compact fluorescents, many people are pointing out the mercury in fluorescents as doing more harm than good.

I have found a number of examples of LED technology that are being incorporated into luminaire design for everyday task lighting and general illumination duties. White LEDs are coming into their own and becoming the source of choice for many lighting fixture designers. I have long maintained that the company that produced a usable white LED for general commercial and residential application would become the Edison A-lamp of this century. The potential of this technology is virtually limitless.

In this article, I will give you some of the core concepts of LED technology so that you have a basic understanding of the technology. I want to point out some of the myths of LEDs and some of the new products that are pushing the application of LEDs forward. As always, I hope that this article makes you think and helps to start some good conversations—and gives you a background on the information so you can make the best choices for your applications.

Lighting Technology Made Simple
LEDs have several advantages over incandescent lamps. They don’t have a filament that will burn out since they produce light by the movement of electrons in a semiconductor material. LEDs last a lot longer by not having this delicate filament that can break. In addition, the plastic covering of the LEDs makes them more rugged than a glass bulb. The biggest advantage of LEDs, though, is that the way they produce light is a lot more efficient. In an incandescent lamp, the filament is heated up to produce light, which generates a lot of heat. A large percentage of electricity goes to heating the filament, which is wasted, because it’s not producing usable light. LEDs directly use a higher percentage of power to generate actual light and produce much less heat.

Myth: there is no heat produced. Myth Buster Note: Heat is still produced and must be shed away from the LED to maintain its life.

There are some basic areas where LEDs are being used in house-of-worship applications. The most common one at the moment is as a color mixing fixture. Generally, these have been red, green, and blue (RGB) LEDs that are great sources for color washes, but that do not produce an adequate white. Some manufacturers are now adding in amber and white LEDs to the RGB mix for more color choices; and some are producing all-white LED fixtures. The Color Rendering Index (CRI) of the white LEDs is getting better and is in the 80 (out of 100) range, which means they reproduce colors fairly accurately.

The next area that LEDs are being used in is video applications. Element Labs, Barco, G-Lec, PixelLine, and others are producing LED products that can make video screens for image magnification or to display videos. These range in resolution and form factors. Some now come in a scrim-like form so you can light behind them for contrast or effect.

As always, you need to do your research. Get demonstrations of LED products; many of which can be rented. Go to tradeshows such as Worship Facilities Conference & Expo (WFX) and LDI and see them in use; attend seminars on LEDs, and speak with the manufacturers. Now is the time to start planning how your lighting needs impact the environment as well as your electrical bills.

Myth Busting
Here are some myths about LEDs and some information debunking them. The myths are dying as people get better educated on the technology. In the early days of LED fixtures, now about 10 years ago, people would often wave their hands like a cheap magician and say “LED,” as if it would solve any lighting challenge and that was all you needed to know. However, a bit more knowledge is needed than knowing what LED stands for, so here are some myths and realities of LEDs.

Myth: LEDs Last Forever
When LED lighting became popular there were a lot of claims that “they last forever” or “LEDs last for more than 100,000 hours.” LEDs have a long life more in the neighborhood of 50,000, which is what a lot of the manufacturers are now stating for life. Also, one should note that LEDs don’t abruptly burn out or stop working at the end of this time, but rather the usable light begins to fade. Most companies now say that after 50,000 hours the light output will be about 70% of the initial lumen output. If you do the math, 50,000 hours equates to just shy of six years using the LED continuously 24 hours a day, seven days a week. Most of us do turn them on for a few hours and off after a service, so they will last awhile longer under standard usage.

Myth: LEDs Produce No Heat
When producing light, LEDs do not produce infrared heat, only visible light, but like any light source, heat is produced. It is especially important for the manufacturer of the light to tie the secondary package to a heat sink to shed the heat away from the die. Well-engineered heat sinks will help conduct the heat away from the die and the circuit boards. The larger the heat sink, the better. Also, you need to look to see that the dies are actually attached to the heat sink; surprisingly, I have found a few lights where there was a large heat sink but no connection to the actual die. This is not as effective a heat shedding system as one would want to see. Heat does affect the life of an LED.

Myth: LEDs Are Expensive
Amber and red LEDs were the first colored LEDs widely available and have been used as indicator lights for years, so they are among the cheapest. A few years ago, blue and white LEDs were very expensive to manufacture. Over time, the prices for production of these LEDs have dropped significantly. While LEDs in general are more expensive initially, when you calculate the savings in energy drawn, they even out over time. In color effect applications you get rid of a dimmer and a color changer and all of their attendant cabling and accessories, then LEDs are more in line with traditional color creation. If you are using them for general illumination, LED lighting systems offer a typical payback of around three to four years over a traditional lighting method, such as fluorescent. Also be sure to speak with your local utility to see if they can offer any rebates for the purchase of LED lighting. Many around the country are starting such programs.

Myth: LEDs Aren’t Bright Enough
This is one that even I believed for a long time. LED manufacturers are producing brighter and brighter LEDs in smaller and smaller packages. It is much the same as Moore’s Law is for computer processors that get faster and faster over time. Look at many applications where LEDs are used outdoors, especially in video panels; they look pretty good even in bright sunlight.

Today, there are quite a few LED applications that are more efficient and put more light where you need it vs. many traditional technologies, including incandescent and fluorescent. Also, the punch of many of the theatrical LED lighting units is well in line with what one needs to fulfill most design requirements.

Myth: The Higher the Wattage, the Brighter the Light
For years, we have looked at lights and known that 1,000W is brighter than 500W. That stopped being true when the ETC Source Four Ellipsoidal came on the scene in the early 1990s and proved that better fixture design coupled with a more efficient lamp would mean that a 575W is brighter than 1,000W. With LEDs, you have to look at the efficiency of the package design as well as the fixture design. A 3W LED may not be brighter than a 1W LED; you have to look at the whole system. Light output and efficacy are the key factors in judging an LED source, rather than wattage. Efficacy is the amount of light in lumens to the power used in watts or lumens per watt. Two different LEDs can be the same wattage but have different light output. When selecting LEDs and LED fixtures, you should use light output rather than power.

LED Glossary
Common terms relating to LEDs:

Primary Package: This is the actual diode or die itself. It is mounted onto a circuit board then mounted into the lighting fixture.

Secondary Package: This is the circuit board that the die are mounted to then installed into the light. It is best if this secondary package has some metal in it to mount to the heat sink and help shed the heat away from the junction of the die and the circuit board. Heat management is crucial in the life of the LEDs.

Binning: This is the term used for the selection of the LEDs after they are produced. In the production of LEDs there are inherent variance and inconsistencies of color. Tight binning means that the color should be consistent from one LED to another. It costs more to keep tight binning, which results in the colors remaining consistent across different fixtures. In lower cost units, there are times when colors are not close to each other. With white LEDs, tighter binning is used to keep the color temperature more consistent.

Through Hole: This is the method where the LEDs are mounted separately next to each other. Most of the LED lighting products available today use this method. You will see a group of red, green, and blue LEDs. By having separate sources of each color—when you go to mix to a color—you will get the odd, multiple colored shadows.

Surface Mount Device (SMD): As the die packages became smaller, manufacturers put multiple die into one very small package, usually square. These packages would have a white diffuser over the die to help blend the colors into a usable image. The diffusing layer also cuts down on the brightness of the die, which is useful for direct view products. This method is used a great deal for LED video products.

Eyeballs or Lenses: These are plastic lenses that sit on top of an array of LEDs to change the spread of the light. They are often used to concentrate the light into a tighter beam. Eyeballs usually are mounted on individual LEDs or in a one-to-one relationship. There are also lenses that are more like a sheet of plastic, usually with micro-etchings to spread and conduct the light into different directions. Some lights have multiple lenses to change the beam angle of the light output.

Pitch: The distance between LEDs, which are often referred to as pixels. This is measured in millimeters. It is used more with LED video products to measure the resolution of the image. Currently, low resolution is in the 20mm and higher range and high resolution is 6mm to 10mm. There are some products out now that are 4mm and look like a high definition TV. Of course, as the resolution increases, so does the cost.

Organic LEDs : There is a new technology, called organic light emitting diodes (OLEDs), that is still in the early stages of development. These are solid-state devices composed of thin films of organic molecules that create light with the application of electricity. OLEDs can provide brighter, crisper displays on electronic devices and use less power than the conventional LEDs of today. There is still a long way to go to make this technology viable.

Did You Know?
LEDs don’t have a filament. They produce light by the movement of electrons in a semiconductor material. Therefore, LEDs last a lot longer by not having this delicate filament that can break—50,000 hours in many cases. In addition, the plastic covering of the LEDs makes them more rugged than a glass bulb. The biggest advantage of LEDs, though, is that the way they produce light is a lot more efficient.

Michael S. Eddy writes about design and technology. He can be reached at mseddy2900@hotmail.com.  EMAIL MICHAEL S.

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