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Ten Things You Should Know About LED

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Ten Things You Should Know About LED Ten things you should know about LED LED Light source of the future LED terminology LED: Light source of the future LED: Light Emitting Diode. LED is without doubt the most talked-about issue in the lighting industry these days. What makes LED so interesting? LED MODULE: An assembly of one or more LEDs on a The LED technology is in rapid development, and LED has many printed circuit board. applications. Because of the robustness of the diodes, LED is fast LED DRIVER: The power becoming the preferred light source in cold environments such as control used to manage cold rooms and freezer rooms, and for demanding use, such as the light output of the LED on board ships, rigs, and moving machinery. The longevity of the module. diodes makes them popular in inaccessible areas on top of windmills, telecommunication towers and chimney stacks, while the size makes TOTAL LUMINOUS FLUX: them particularly suitable in really small spaces. The amount of light com- ing from a light source or Other applications are emergency lighting, task lights, downlights, luminaire. spotlights and other general lighting products, and as replacement TOTAL POWER CONSUMP- for conventional light sources wherever possible. TION: The power con-sump- tion of the whole luminaire At Glamox, we aim to produce LED luminaires with single LEDs, LED or system, including losses. modules and LED drivers of the best possible quality. We always LM/W: Lumen per watt. Lu- use the best quality components for our purposes, from the best men out of the light source manufacturers. or luminaire, divided by the total power consumption. Ten things you should know about LED Also known as efficacy. On the following pages we are presenting ten aspects of LED technology that we believe are essential for the understanding of CCT: Correlated Colour advantages and challenges related to the use of LED. Temperature. Whether the Glamox Technology Team light is perceived as warm-, neutral- or cool white. MACADAM’S ELLIPSE/STEPS: A measure of colour toler- ance. CRI: Colour Rendering In- dex. A measure on how well a light source renders colours. Also known as Ra. L70: The time elapsed to a LED emits 70% of its origi- nal light output. A typical lifetime is L70 minimum 50.000 hours. T amb: Ambient temperature. FRONT PAGE ILLUSTRATION: THE BUTTERFLY EFFECT LED is a small and powerful light source that is changing the world of lighting. The butterfly is a sym- bol of the “butterfly effect”: that a small change at one place in a model (e.g. a weather system) may lead to big changes at another place. 2 1 LED is a small and powerful light source that is changing the world of lighting. A Light Emitting Diode (LED) is an electronic component that generates light in a semi-conductor material. Using the right materials, a diode may produce visible light of various wavelengths. White light is created by either using a i.e. LEDs operating at powers of around blue diode or “chip” and adding yellow 1 W, have reached a level of cost and phosphor on top of it or mixing light from performance that make them attractive to one red, green and blue diode (RGB). The the general lighting industry. use of phosphor conversion is the most used method in the lighting industry, due Market studies forecast that in 2020, 400 500 600 700 nm to its high efficacy and flexible production close to 50 % of all new and replacement The spectral power distribution (how much light that is emit- method. The phosphor can be added light source unit sales will be based on ted at each wavelength) of the LED mirrors the blue light directly onto each diode or as a remote LEDs. Since LEDs are more expensive than from the chip and the yellow phosphor. phosphor plate on top of a mixing chamber. conventional lighting, the value of the LED Both methods create a particular colour sales will be even higher. spectrum, or spectral power distribution for LED chip the LED depending on the phosphor layer. The efficacy of the LED is measured in lumen per watt. The LED itself is expected PCB LED is not a new invention and most of us to yield around 200 lm/W within the next LED are used to LED`s being red or green signal decade. The LED luminaire, however, may Heat sink markers on your Hi-Fi or television set. These reach an efficacy of above 160 lm/W due are so called – low-power LEDs. During the to system losses. last couple of years “high power” LEDs, Standard light sources LED 170 LED Metal halide 150 Schematic overview of a LED mounted on a printed circuit board (PCB). Heat is removed from the LED chip to ambient Fluorescent via the heat sink (grey). 100 CFL Mercury 50 Light source efficacy (lumen/Watt) Halogen Incandescent 1950 1990 2010 2020 Time This figure shows the development in efficacy (lm/W) over time for conventional and LED light sources. Whereas fluorescent tubes are expected to reach a maximum of 120 lm/W, LEDs may reach above 200 lm/W in 2020. Note that luminaire ef- ficacy is lower due to losses in the driver, optics, etc. (Source: Osram) 3 LEDs are more efficient than many conventional light sources. Conventional luminaire One of the advantages of LED is that all the light is emitted in one “Light output”:2 Watt direction. This entails fewer reflections inside the luminaire since we Efficiency: Light Output Ratio normally want the light to go downwards only. If we need a light distribution that goes both up and down, the LED is less suitable compared to e.g. a fluorescent lamp. Ballast The performance of a LED is often measured The rated lumen value from a LED module Optics in terms of lumen per watt or luminous may give an inaccurate picture of how FL tube efficacy. The efficiency of luminaires with many lumen you actually get from the fluorescent tubes is explained using the LOR luminaire. When you calculate the lumen or Light Output Ratio. The LOR indicates output from a luminaire with fluorescent light how efficient the optic is. For these sources you must take the rated lumen from luminaires, the installed power in watt is the lamps and multiply with the Light Output often used as a measure on the luminaire’s Ratio (LOR) of the luminaire. One should light output. LED luminaires, however, only pay special attention to the difference use the total luminous flux. between the total luminous flux of the LED- luminaire and the rated lumen output of the LED luminaire LED module itself. Light output: Lumen Efficacy: Lumen per watt OUR SOLUTION: When documenting a LED luminaire, we always list the total luminous flux of the luminaire. LED driver LED Lost light Optics For luminaires with fluorescent tubes, the wattage is often enough to understand their light output. With LED luminaires the total luminous flux is the correct measure. The same applies for luminous efficacy. Lumen per watt is the measure for the efficacy of a LED luminaire, whereas LOR is of- Conventional light sources cast a lot of light backwards, which may be lost in the optics design of a luminaire. The LED, on ten used for luminaires with fluorescent tubes. the other hand, emits all light in one direction. 4 t LED The typical lumen maintenance curve of 110 % LEDs according to most manufacturers. After 50.000 hours, the remaining light 100 % output is 70% of the original output. Life- time data can be given in terms of B50 90 % (normal case), where 50% of the diodes 80 % are better than the given lifetime value, or B10 (worst case), where 90% of the 70 % diodes are better than the given value. 10k 20k 30k 40k 50k 60k 70k t T8 110 % 110 % 110 % 110 % 110 % 1 2 3 1 2 1 2 3 4 5 1 2 3 4 100 % 100 % 100 % 100 % 100 % LEDs last90 % longer and do not 90 % 90 % 90 % 90 % need to be replaced as often as many80 % conventional light 80 % 80 % 80 % 80 % sources.70 % 70 % 70 % 70 % 70 % One of the benefits10k of20k the30k LED40k is its50k long60k lifetime.70k 10k 20k 30k 40k 50k 60k 70k 10k 20k 30k 40k 50k 60k 70k 10k 20k 30k 40k 50k 60k 70k 10k 20k 30k 40k 50k 60k 70k Because it has no movable parts or filaments 3 t Compact fluorescent 110 % 110 % that may break,110 % LED’s can have long lifetimes. 110 % 110 % That makes them particularly well suited where 1 2 3 1 2 1 2 3 4 5 1 2 3 4 100 % 100 % installation heights100 % are large or when the luminaires 100 % 100 % 90 % 90 % are not easily90 accessible % for lamp replacements. 90 % 90 % We normally define the lifetime but its light output will drop 80 % 80 % 80 % 80 % 80 % of a LED as the time expected 30% over its lifetime. 70 % 70 % for it to drop to70 70 % % of its 70 % 70 % initial light output. This measure Sometimes, the LED driver is called L70. A typical L70 lifetime is the bottle neck of 10k 20k 30k 40k 50k 60k 70k 10k 20k 30k 40k 50k lifetime60k 70kis 50.000 hours. 10kFor 20kthe 30ksystem40k design.50k If60k e.g.70k the 10k 20k 30k 40k 50k 60k 70k 10k 20k 30k 40k 50k 60k 70k Glamox the stated lifetime is driver lifetime is limited to related to L70 at the stated 50.000 hours at the rated t Metal halide 110 % 110 % 110 % 110 % 110 % ambient temperature (Tamb) of ambient temperature, and the 1 2 3 1 2 1 2 3 4 5 1 2 3 4 100 % 100 % 100 % the luminaire.
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