licht.wissen no. 17 "led: the light of the future"

licht.wissen 17LED: The Light of the Future

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licht.wissen 17_ LED: The Light of the Future

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The LED heralds a new age of lighting – it beats every other option hands down. Its widescope for application, its flexibility in terms of shape and colour dynamics, its outstanding ef-ficiency and longevity make it the lighting tool of the future.

LEDs address both indoor and outdoor applications, making for a new quality of lighting inoffices, foyers and homes, on facades and fabrics, in streets and automobiles. The possibilityof fine-tuning colour and light temperature to suit the time of day and meet particular require-ments makes LED light an everyday tool in hotels and shops, museums and theatres, indus-try and trade, and at the workplace. Variable LED light is used by doctors to optimise a widerange of examinations, sets a dramatic and brilliantly colourful stage for concerts and TVshows and permits problem-free presentation of sensitive merchandise in infrared- and UV-free light.

All these fascinating applications are addressed with extremely high efficiency and longevity.Anyone who opts for LEDs gets green technology that is easy on the budget. Containing nomercury, economical on power and virtually maintenance free, every LED makes a contribu-tion to environmental protection. Where conventional lighting is replaced by LEDs with intelli-gent lighting management, the energy required for lighting is reduced by around 70 percent.This makes for massive carbon savings and provides an incentive for all sides to help vigor-ously drive forward the further development and implementation of LED technology.

In Germany, the Federal Ministry of Education and Research (BMBF) promotes LED technol-ogy in a variety of ways as part of the country’s “High-Tech Strategy”. Alongside basic re-search projects, it has launched an LED lead market initiative and introduced a competitionunder the banner “Municipalities in New Light”. The lead market initiative, which draws on theexpertise of the leading actors of the lighting industry, is designed to bring together partnersto establish LED in general lighting and carry forward the new business models required. Theaim of the competition is to promote the use of LED by paying tribute to the top ten munici-pal demonstration projects.

People do not buy what they do not know, so it is essential to get more information aboutthe new technology into the public domain. This booklet will help do just that. Highlightingthe unique advantages and applications of LEDs, it shows the scope for design and presentsideas for improving our “light climate”.

The spectrum of information is rounded off by articles looking at the way LEDs work, thelighting management options they offer and the technical applications they can address – aswell as real-life examples of LEDs in use. These insights into the new technology will broadenour perspective of the world of lighting and pave the way for new and original ideas for thelight of the future.

Read this booklet and discover new worlds of light!

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Editorial

Andreas KletschkeAssistant Ministerial CounsellorFederal Ministry of Education and Research


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Introduction LED: The Light of the Future 06

LED Applications City and Street 10

Facade and Advertising 12

Office and Administration 14

Hotel and Hospitality 26

Art and Culture 30

Shops and Presentation 32

Hospital and Surgery 36

House and Home 42

Industry and Trade 46

Emergency and Safety Lighting 48

Auto and Mobility 52

LED Special The LED Light Source 18

Modules, Systems, Quality Features 22

Operating Devices and Ballasts 40

Safety, Marks of Conformity, Standards 50

OLED – Technology of the Future 54

FAQs about the Light-Emitting Diode 56

licht.de Series of publications 58

Imprint 59

Contents

[02] LED spots set the stage for the organiccurves of the concrete walls. With a lightingmanagement system, mood images can beproduced in RGB colours.

Whether indoors or out, decorative or func-tional – LEDs (light-emitting diodes) permitsolutions today that would have been in-conceivable even a few years ago. Startingout as a coloured signal indicator, the en-ergy-efficient semiconductors advancedrapidly to become one of the principal lightsources for accent and orientation lighting.With white light and intelligent manage-ment, LEDs now ensure a high quality oflighting right across the range of outdoorand indoor applications.

LED technology is regarded as the mostimportant invention in the history of lightingsince Edison’s development of the “lightbulb” over a hundred years ago. Never be-fore has so much light come from such asmall fitting; never before have light sourcesworked so reliably for so many years andconsumed so little electricity. Even recently,

attention still focused on the richness ofcolour achieved by LEDs; today, high-per-formance LEDs are transfiguring generallighting.

The many positive characteristics of thelight-emitting diode include: > extremely long life and virtual freedomfrom maintenance > high efficiency > white and coloured light with good colourrendering properties> insensitivity to vibration> light with almost no heat generation, noIR or UV radiation, no interference with nocturnal insects > instant, flicker-free lighting that is infinitelydimmable> very compact design> no mercury content and no end-of-lifedisposal problems.


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LED: The Light of the Future Light-emitting diodes are the shooting stars of lighting. Tiny and extremely efficient, they are revolutionizing theworld of light – delivering a whole new quality of lighting, addressing an ever growing number of applications andsaving a great deal of energy. LEDs are the light of the future and are conquering the realm of general lighting.

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LEDs are long-lived and efficient

LEDs have an operating life of 50,000 hoursor more. That amounts to six years of main-tained operation or 45 years of light forthree hours a day. So they can be installed,connected and then forgotten – becauseno matter how intensively they are used, itwill be a long time before any maintenancework is required.

LEDs burn fifty times longer than incandes-cent lamps. And are far more efficient than many conventional light sources: theirluminous efficacy is much higher and theirdirectional light can be easily and efficientlybundled. An 8W LED lamp, for example,delivers the same amount of light as a 60Wincandescent lamp. Today, LED systemscan even stand comparison with fluores-cent lamps. And their potential is far fromexhausted yet: LED luminous efficacy in thepast has doubled about every two years.

LEDs for a “green future”

Even today, the longevity, efficiency andhigh lighting quality of LEDs literally makeconventional lamps look old by comparison.The days of “energy-guzzling” light sourceslike the incandescent lamp – generating

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[05] Street lighting is an area with high po-tential for savings. Local authorities could re-duce their energy consumption by as muchas 70 percent. With LED luminaires, it is evenpossible to achieve a saving of 80 percent.At present, however, LEDs are not yet an op-timal alternative for every lighting application.

[03] The city at night: highly focused LEDlight is ideal for highlighting architectural details.

[04] Innovative LED technology enhancesthe gastronomic experience. Discreet spotsprovide glare-free light at the table.

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[06] LEDs are the light source of the future.The table below shows the lighting industry’sten-year forecast for lamps and their applica-tions.


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cent of global energy consumption for light-ing could be saved through the use of LEDs.And that is a great deal of energy – becauseno less than a fifth of the electricity gener-ated in the world is used for artificial lighting.

The German government is also focusingon the tiny diodes as a source of sustain-able solutions. It has sponsored many LEDresearch projects in recent years under thebanner of Germany’s “High-Tech Strategy”.Now, its sights are set on harnessing thewealth of expertise in the German lightingindustry to translate LED solutions swiftlyinto practical products. At the beginning of2009, the Federal Ministry of Education andResearch teamed up with partners in indus-try and science to launch the “LED LeadMarket Initiative”. Its purpose is to acceler-ate the introduction of LED technology on a broad front.

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95 percent heat and just 5 percent light –are finally over.

Climate change, scarce resources and rising energy prices make a re-think essen-tial. And policymakers are acting: The Ger-man Energy Saving Ordinance (EnEV) 2009and the EU Eco-Design Directive for Energy-related Products effective as of November2009 – transposed into German law as theEnergy Using Products Act (EBPG) – set thedirection; inefficient products are being re-moved from the market. The old Edisonlamp is one of the light sources set to bephased out across the European Union; thelist also includes a number of inefficienthalogen lamps, fluorescent lamps and high-pressure mercury lamps.

The solution for the future is LED. Eventoday, experts estimate that up to 30 per-

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Solutions tailored to needs and good for the environment

LEDs are highly efficient light sources. Butthey offer even greater savings potentialwhen used in combination with “intelligent”lighting management systems designed fordaylight- and presence-dependent regula-tion. The dynamic duo achieves savings ofup to 80 percent in offices, shops andstreet lighting – with a corresponding re-duction of carbon emissions.

But LED solutions are more than just easyon the environment and the pocket. Noother light source has ever offered so muchscope for design in terms of form andcolour. LEDs can be integrated practicallyanywhere. Their rich colours add an emo-tional dimension and offer maximum lightingquality for human needs: LED lighting con-cepts allow light to be optimally tailored tomeet human biological requirements – fromcool bright light for concentration to asoothing lighting atmosphere that facilitatesrelaxation in the evening.

So LEDs are not just an increasingly popu-lar option for accent and event lighting; they are also advancing on the generallighting front. But for LED systems to playout their many advantages, the qualityneeds to be right. The development andmanufacture of efficient LEDs require agreat deal of expertise – something whichdoes not go into every product found onthe market. Consumers are well advised torely on the experience of reputable manu-facturers.

Even today, the cost of a quality system isquickly recouped through high efficiency,longevity and convincing lighting quality.And system performance is improving fast.LED development is advancing just as rap-idly as computer and flat-screen technology.

High performers: LEDs in corridor lighting

High lighting quality and efficient technology are compelling arguments in favour of LED solutions forgeneral lighting. As the example here shows, higher capital outlay is quickly recouped. The comparison isbased on downlights in a 20 metre long corridor, fitted with 2x26W fluorescent lamps in one case and 26WLEDs in the other. The calculation is based on 10 years of operation with a burning time of 12 hours a day,250 days a year, and an electricity price of 21 ct/kWh.

LED Fluorescent lamp

Downlights installed 4 4

Total price of luminaires 800.– € 400.– €

Total wattage 104 W 244 W

Maintenance costs – 200.– €

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Germany’s lawmakers have given local authorities a new responsibility; they wantthem to set a good example in terms of energy conservation. At the same time, theidea is to sharpen city profiles in globalcompetition. Lighting and the face of thecity at night play a significant role in this.They heighten appeal, shape image, pro-vide security – and offer massive potentialfor savings. The German Electrical andElectronic Manufacturers’ Association(ZVEI) estimates that a switch to efficientsolutions could save around € 400 million a year in street lighting alone.

After all, more than a third of street lightingis over 30 years old. Obsolete technology isresponsible for low coefficients of utilisation:inefficient lamps such as high-pressuremercury vapour lamps – which will bebanned in the EU in 2015 – consume toomuch energy. LED luminaires are not justmore efficient; they also have other winningfeatures:> homogeneous light> long life and low maintenance > precise optical control, preventing unde-sirable stray light

> simple dimming and lighting manage-ment.

Tailored white light

White light is now available in just about anyhue required and can be selected to suitthe type of street in question: warm whitelight with a colour temperature in the2,700–3,000 kelvin range is right for the at-mosphere of a historical town centre, parkor residential area; LED luminaires produc-ing neutral white light are appropriate forbusy roads and business parks – and veryefficient at 70 lumen/watt.

Many municipalities are already switching toLED luminaires. In the Lower Saxon town ofSoltau, for example, old twin-lamp mush-room luminaires fitted with 80W high-pres-sure mercury vapour lamps were replacedby LED street lights with single 59W LEDmodules. The result: the LED solution re-duces the energy required by 60 percent.This is due not just to its higher efficiencybut also to integrated lenses permitting pre-cise light control even without secondaryoptics.

[10] Ground-breaking: flat recessed spotsand a narrow recessed ground luminaire withblue LED light guide visitors safely to thebuilding.

[11] The light of the recessed ground lumi-naires with LEDs sets distinctive accents inthe pedestrian precinct.

[12] The LED luminaires cast agreeablywhite light evenly over footpath and road.The power required for each light point is just34W and the LED modules can simply be replaced as required.


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LEDs for City and Street LEDs have been used in decorative outdoor lighting for years. With white light, they now also make for optimalvisual conditions on roads and paths. No other lighting technology couples so much freedom for lighting designwith such low energy and maintenance requirements.

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Light that meets needs

Electronic regulators integrated in the lumi-naires themselves make for very high effi-ciency: they ensure that light output is auto-matically kept constant throughout the LEDluminaire’s life of around 50,000 hours andthat illuminance never falls below the mini-mum level required. These regulators alonecut energy requirements and costs by 15percent.

Lighting control also enables LEDs to beautomatically dimmed in the event that noor only little light is required. When the sen-sors register the presence of pedestrians,cyclists or automobiles, the lighting can bespecifically powered up again to illuminate aparticular street section. LED systems caneasily be incorporated in lighting or tele-management systems. Modular conceptsfacilitate system maintenance and make iteasier to replace LED modules at the end oftheir service life.

Even though it may be tempting, switchingfrom old luminaires to LED solutions or re-placing defective lamps with LED retrofitsystems is still problematical. Lighting andelectrical values need to be checked andapproved by manufacturers and operators.

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[13] High-impact facade lighting: NarrowLED light strip is used here as an indirect lightsource to accentuate the sheet aluminium fa-cade.

[14] The lettering and the globe on the roofof Hamburg’s Atlantic Hotel are visible from agreat distance. The colour of the LED lightcan easily be varied as required. The light-emitting diode’s long life saves energy andexpensive maintenance work in placeswhere access is difficult.

[15] An attention-grabber: The multimediafacade of Vienna’s Stadion Center shoppingmall can be used to display static or movingimages. The entire facade is enveloped in aflexible, 80-metre long LED net offering at-tractive possibilities for outdoor advertising.Each of the 37,620 LEDs is individually con-trolled by a video management system.

[16] LED spots with a highly focused beamdirect the eye to historical details.

Their light seems to come from nowhere yet has a remarkable presence: in compactdesigns and with RGB colour controllers,LEDs provide striking accents on any scale.

They also offer huge scope for lighting de-sign: narrow LED strip winds around bendsand corners, lends emphasis to window reveals and arches. Up- and downlightsflood facades with homogeneous glancinglight that picks out structures in sharp relief. Powerful floodlights with over a hun-dred high-performance LEDs effortlesslycast light to the tops of spires 240 metresabove the ground. And extremely preciselighting effects are achieved by minimalistspots with extremely sharp contours.

LED systems combine scope for designwith high efficiency and a long service life.Today, the large-scale floodlighting that waspopular in the past is also being increas-ingly replaced by low-key lighting accentsrealised by LEDs positioned directly on orclose to the facade. This saves even moreenergy and reduces unwanted light emis-sions that might disturb local residents.

Light advertising and “talking walls”

Intense colours and robust design long agowon LEDs a place in light advertising andcorporate colour branding. Flexible, com-pact LED modules can easily be deployedto illuminate individual characters or entirelogos – whether they are three metres highor just a few centimetres. Thanks to theirlow design height, LEDs integrate harmo-niously into the architecture and are a rec-ommended solution for backlightingtranslucent surfaces.

With the necessary controllers, LEDs create“talking walls”. Media facades are in vogue;they permit moving images at the push of a button and attract lots of attention. Adver-tising messages, news, light art or even

video recordings of events can thus be pro-jected onto facades and walls.

In contrast to fluorescent lamps, specialLED modules make maintained, ignition-problem-free operation possible down totemperatures of minus 20° C – withoutcompromising on constant light, brilliantcolour saturation and low power consump-tion. Another advantage: the longevity ofLEDs eliminates the need for regular lampreplacement and expensive maintenancework, especially at height, where luminairesare difficult to reach.

LEDs for Facades From discreet integrated light strip to large-scale illumination, white orcoloured LED light heightens the visual impact of architecture and grabsattention.

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[17– 21] Lighting atmosphere based on requirements and time of day: the hybrid luminaire for the conference room combinesdirect LED light with energy-efficient T5 fluo-rescent lamps for indirect lighting. Separateswitching and dimming for the two lightsources offers high lighting comfort.

[19] Recessed LED modules make for afriendly reception in the lobby.

A uniform lighting level of 500 lux through-out the office? Those days are gone. Light-ing concepts today are no longer static but flexibly adaptable to personal needs:they ensure balanced, tailored lighting ateach workplace, they adjust to suit the timeof day and they send the right signals to the human biological clock. This promotesa sense of wellbeing in employees and enhances their peformance.

LED systems not only achieve a betterquality of lighting. Their high efficiency andlong life also make them a long term“green” solution. And scope for improve-ment in that respect is still present in abun-dance in small and large offices: anyonewho refurbishes inefficient old installationsand switches to innovative technology withlighting management can save up to 75percent of the cost of electricity required forlighting. And since lighting accounts fornearly 40 percent of all the electricity costsin an office building today, the initial invest-ment is generally recouped within just a few years through lower energy consump-tion.

LEDs at the workplace

Workplace lighting needs to meet high ergonomic and economic requirements.Quality office luminaires offer glare-free

lighting for optimal visual comfort even atcomputer workstations. They conform tothe relevant standards and are energy effi-cient.

New hybrid luminaires offer the best of bothworlds in one system: they combine ad-vanced LED technology, for example, withenergy-efficient T5 fluorescent lamps (16mm lamp diameter) – a mix that makes forextremely efficient direct/indirect luminaires.They ensure that the punctual light of theLEDs is focused and directed onto the worksurface while the light of the fluorescentlamps radiates widely and evenly over theceiling.

Hybrid luminaires thus offer cool direct LEDlight for optimal colour rendering – and witha high blue content for biological stimulation– as well as warm indirect light for a senseof harmony. The possibility to switch anddim the LEDs and fluorescent lamps sepa-rately makes for tailored lighting comfort. A wide variety of lighting atmospheres canthus be created – finely tuned to suit per-sonal preferences and the nature of thework tasks performed. The combinationalso ensures excellent quality of lighting inconference rooms.

Apart from hybrid luminaires, there are alsopendant, recessed and standalone lumi-


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LEDs for Office and Administration Good workplace lighting motivates, promotes health and boosts performance. Intelligent LED solutions meet these high requirements, fulfil statutory energy-saving regulations and make for a sustainable reduction of costs.

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naires on the market that work exclusivelywith LEDs. And companies are starting toswitch over entirely to diode technology,using high-performance LEDs to provide allthe lighting required for workplaces andmeeting rooms, foyers and corridors. Em-ployees’ and visitors’ footsteps are guidedby extremely flat modules that fit seamlesslyinto the architecture. At workplaces, stand-alone or pendant luminaires with both directand indirect lighting components deliver the glare-free 500 lux required.

Better lighting, lower costs

The use of innovative LED solutions raiseslighting quality while at the same time permitting a sustainable reduction of light-ing costs. Savings potential is maximisedby “intelligent” luminaire management,whereby the brightness of each luminaire isadjusted automatically in response to pres-ence and daylight sensors. So the artificiallighting provided is no more than is actuallyneeded. This is not only a practical solutionfor offices. The combination of LED lumi-

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[22] LEDs provide all the lighting requiredfor this modern office building in Hamburg’sHafencity. General and accent lighting on six floors is delivered by a total of 3,000 LEDluminaires.

[23] High intensity and high efficiency: LED ceiling luminaires with acrylic glass diffu-sor for the aisle zone. The recessed lumi-naires are only a few millimetres high and radiate light downwards in a wide uniformbeam.

[24] At the workplace, standalone lumi-naires with direct and indirect lighting com-ponents guarantee glare-free, standard-compliant lighting. Integrated presence- anddaylight-dependent control makes for maximum efficiency.

[25] LED downlights lead the way to the lift.

[26] The suspended hybrid luminaires eachfeature twelve 3W LED modules and two54W T16 fluorescent lamps. Their reduceddesign harmonizes perfectly with the officefurnishings.

naires and lighting management also savesa great deal of lighting energy – and thuscosts – in corridors, seminar rooms, toiletfacilities and technical rooms.

LED luminaires producing coloured orcolour-changing light set striking accents inreception areas, corridors and stairwells.Colour and dynamism emphasize areaswith a prestigious character and also en-liven meetings. With a wide spectrum ofcolour temperatures, LEDs can even recre-ate the natural progression of daylight in-doors and thus promote relaxation and acti-vation in line with biological rhythms. Andmaintenance? With LED solutions, that isnot an issue for many, many years.

LEDs produce light – but that is about the only thing they have in common with halogen or energy-saving lamps. Unlikeconventional lamps that work by heating afilament or by gas discharge, LEDs are tinyelectronic chips of special semiconductorcrystals.

When a current is passed through the solidcrystal, it induces electroluminescence: thediode glows, emitting what is sometimesreferred to as “cold light”. This is because,unlike the light of an incandescent lamp,LED light is not heat driven.

With edges only around a millimetre long,LEDs are among the smallest light sourcesavailable – not much larger than a pencildot. To protect them from environmental in-fluences, the semiconductor crystals areembedded in a plastic case, which helpsproduce higher light densities and makes

beam spreads of 15 to 180 degrees possi-ble.

Light-emitting diodes always produce nar-row-band (=monochromatic) radiation. Thedominant wavelength and thus the colourof the light emitted – red, green, yellow orblue – is determined by the semiconductormaterial used.

White LEDs and colour rendering

White LED light can be produced by vari-ous manufacturing methods. The methodthat is most widely used at present isbased on the luminescence conversionprinciple used for fluorescent lamps: a verythin film of yellow phosphor material is ap-plied to a blue LED chip, which changespart of its blue light into white. To achievethe light colour required, the concentrationand chemical composition of the phosphor

LED Special: The LED Light Source The advent of the LED brings a totally new light fitting onto the market. In contrast to conventional lamps, LEDs are electrical components – tiny electronic chips of semiconductor crystals.


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[27] LEDs do not require colour filters. Thecolour tone of the light is determined by thesemiconductor material used and the domi-nant wavelength.

[28] White light is generally produced by luminescence conversion: a very thin layer ofyellow phosphor material is applied to a blueLED chip and turns the blue light it emits intowhite light.

[29] LED luminous efficacy is rising. Valuesof 200 lumen/watt are already achieved inthe laboratory. 27

material needs to be very precisely con-trolled. Today, a variety of white tones arepossible, from warm white (colour tempera-ture � 2,700 kelvin, K) through neutralwhite (�3,300 K) to daylight white (�5,300

K). Other advantages of this method in-clude relatively high luminous fluxes andgood colour rendering up to Ra � 90.

White LED light can also be produced byadditive colour mixing, i.e. using multi-LEDs or coloured LED modules to mixcoloured light of different wavelengths (red,green and blue). This method has the ad-vantage of permitting controlled changes oflight colour, allowing not just white but alsocoloured light to be produced. So RGB so-lutions are good for dynamic coloured light-ing applications. Realising white light bythis method also calls for a great deal of

expertise because precise control is difficultto achieve with coloured LEDs of differentbrightness and results in white light with apoorer colour rendering property – Ra � 70to 80 – than that produced by lumines-cence conversion.

Where white light is required to permit aswitch from warm white to cool white foroffice applications, for example, new tech-nologies combine coloured chips withwhite LEDs. The result is dynamicallychanging white light with a good colourrendering property.

Efficiency and luminous efficacy

LEDs are extremely efficient light sources.The first LED, produced in 1962, achieveda luminous efficacy of 0.1 lumen/watt(lm/W). Today, ratings in the region of 50l/W are standard and high-power LEDsreach an average of 90 lm/W. By compari-son, incandescent lamps achieve around10 lm/W, halogen lamps around 20 lm/W.

And development continues apace: someLED chips already deliver 200 lm/W. However, such efficiency is achieved only in the laboratory; in practical operation –mounted on a board and integrated in a

Colours straight from the semiconductor

LEDs do not require colour filters: their light comesin different colours produced directly by differentsemiconductor materials. Secondary colours arealso possible. The major semiconductors are:

Semiconductor Abbre- Colour(s)material viation

Indium gallium green, nitride InGaN blue

(white)

Aluminium indium red, gallium phosphide AlInGaP orange,

yellow

Aluminium- redgallium arsenide AlGaAs

Gallium arsenide red, phosphide GaASP orange,

yellow

LEDs are based on compound semiconductors.Very little energy is needed to induce them to emitlight. Light-emitting diodes consist of a n-typebase semiconductor with a surplus of electrons.This is “doped” with a thin layer of p type semi-conductor material that has a deficit of electrons,called “holes”. When current is applied, thesurplus electrons and “holes” migrate towards oneanother and recombine in what is known as the p-n junction or depletion layer. The energy thusreleased is converted into radiation in the semi-conductor crystal.

To simplify the electrical contacts and protect theLED from environmental influences, it is encasedin a housing. Reflectors ensure that the light radi-ates upwards at angles up to 180°. The light isdirected by lenses.

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fluorescent layerLED-chip

blue light

white light

conversion layer

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© licht.de28

cathode

epoxy lens

LED-chip

wire bond

How LEDs work

© licht.de

luminaire – the LEDs cannot match thatlevel of performance. LED manufacturers’data sheet specifications are based onideal laboratory conditions and extrapola-tions for the raw LED chip. The values donot correspond to the actual luminous fluxof an operational LED luminaire or retrofitlamp. What matters in practice is the effi-ciency of the entire LED system, i.e. theway LED chips, optics and operating de-vices interact (see also page 57).

Extremely long life

LEDs have an extremely long service life.While an incandescent lamp burns foraround 1,000 hours and a fluorescent lampfor around 18,000 hours, high-performanceLEDs have a life of 50,000 hours or more.This means that an LED luminaire in opera-tion for 11 hours a day, 250 days a year,will last for around 18 years.

However, the length of an LED’s life depends very much on operating and ambient tem-perature. The colder the location, the moreefficiently LEDs work. They do not like highambient temperatures; their luminous fluxdiminishes and their life can be significantlyshortened. So effective heat dissipation is aparticularly important consideration in thedevelopment of efficient LED systems.

Unlike conventional lamps, LEDs practicallynever fail. However, the intensity of their

light decreases over time as a result of in-creasing imperfections in the semiconduc-tor crystal. This characteristic is known asdegradation and means that the end of thelife of LEDs needs to be defined for a par-ticular application. It is normally reachedwhen the luminous flux emitted by theLEDs decreases to 70 percent (or 50 per-cent) of the original luminous flux (see Fig.31).

Because of their longevity, LEDs are virtu-ally maintenance-free in practice. There isno need for lamp replacement or servicingoperations.

Luminous flux and brightness

Light-emitting diodes have an exponentiallyincreasing current-voltage characteristic,i.e. minor fluctuations in voltage causemajor changes in current. So LED chipsneed to be operated on constant current.They should not be connected directly to avoltage source. The more power a diodeconsumes, the brighter it shines. The catchis that higher operating currents heat thesemiconductor – and thus reduce effi-ciency. So high-intensity LEDs need goodthermal management to remove the heatfrom the LED chip. Thanks to larger LEDchips and new designs for optimal heatdissipation, modern high-power LEDs (1W– 5W) can be operated on higher currentsabove 100 milliampere (mA). They emit a


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[31] LEDs do not fail but the intensity of the light they produce diminishes over time.The lifespan (L) of an LED thus needs to bedefined for different applications. For emer-gency lighting, for example, ratings up to L80or more are required; this means that theLED reaches the end of its service life whenthe luminous flux falls to 80 percent of theoriginal flux measured. For general lighting,values of L50 or L70 are defined. The lifes-pan of an LED depends to a large extent onambient and operating temperature. Wherean LED is operated at a high temperature(Tc1) or with poor thermal management, itslife is shortened.

[32] Highly flexible LED module in SMDtechnology. 31

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1907 … English experimenter Henry Joseph Rounddiscovers that inorganic substances can emit lightwhen an electric current is passed through them. Hereports his findings the very same year in the journal“Electrical World”. However, because his primaryfocus is the development of a new radiolocationprocess for shipping, his discovery initially sinks intooblivion. 1921 … The Russian physicist Oleg VladimirovichLosev observes electroluminescence again. Becausehe believes it to be the converse of Einstein’s photo-electric effect, he studies the phenomenon moreclosely through to 1942. 1935 … George Destriau reports on light producedby passing an electric current through zinc sulphidepowders and calls it “Losev light” in honour of theRussian physicist.

1951 … The development of the transistor brings a scientific breakthrough for semiconductor physics.The emission of light can now also be explained. At first, scientists keep on experimenting with zincsulphide. It is not until 1959 that light generationresearch focuses on semiconductors; particularlyimportant here is the visible light emission producedby a mixed crystal of gallium arsenide (GaAs) andgallium phosphide (GaP). 1962 … The first red luminescent diode (GaAsP)appears on the market, developed by the Americanscientist Nick Holonyak. It marks the birth of industri-ally manufactured LEDs. 1971 … Owing to the development of new improvedsemiconductor materials, light-emitting diodes arenow also available in other colours: green, orange,yellow. At the same time, steady progress is made onimproving LED performance and efficiency. 1980s through to the early 1990s … The new semiconductor material gallium nitride (GaN) permitsgreen tones through to ultraviolet and paves the

History of the LED: A long road to market

way, in 1993, for Shuji Nakamura’s invention of thefirst commercially successful brilliant blue LED inJapan. Blue LEDs prior to that were based on theindirect semiconductor silicon carbide, which is notvery efficient. As well as the blue GaN LED, Naka-mura develops the very efficient green indiumgallium nitride diode (InGaN-LED) and later also awhite LED. 1995 … The first LED using phosphor material toproduce white light by luminescence conversion ispresented. Two years later, these white light-emittingdiodes are on the market. 2006 … The first 100 lm/W LEDs are available. Interms of efficiency, they are surpassed only by gasdischarge lamps.

In the recent past, the efficiency of LEDs hasdoubled every two years. They are conquering moreand more applications and their development showsno signs of coming to a halt …

great deal more light than earlier versionsand are already breaking records in termsof luminous efficacy: up to 200 lumen on1A operating current. Simple standardLEDs, by comparison, deliver 1-2 lumenfrom 20 mA.

Low-power LEDs

Low-power LEDs – also referred to as ra-dial LEDs – include the classical 3 or 5 mmdesigns, usually with two “legs” and a nar-row beam spread of 15° to 30°. The 5 mmLED launched the triumphant career of the light-emitting diode; today, high-per-form ance diodes are in much more wide-spread use. Low power LEDs operate oncurrents from 20 mA to a maximum of 100 mA.

Superflux or high flux LEDs (also called spi-der or piranha LEDs) have four pins. Theygenerally operate on 70 mA and have ahigher light output. The housing of theseLEDs can also accommodate severalchips, which can be separately controlled.Their design permits a wider beam spreadof 90° to 130°. Superflux LEDs are usedmostly in automotive engineering.

High-power LEDs

High-power LEDs – also referred to ashigh-performance LEDs – deliver the

most light of all. They initiallycame onto the

market as efficient 1W pack-ages operated at 350 mA. Shortly after-wards, 3W and 5W high-power LEDs ap-peared on the scene. At the same time,LEDs were further miniaturised. The small-est high-power LED available is little largerthan a matchstick head and achieves 100lumen/watt efficiency.

Types of LED

Wired LEDs (radial LEDs) date back to theearly days of LED technology. The internalLED chip is encased in a plastic housingthat protects it from damage. Today, be-cause of their generally low light output,these low-power LEDs are predominantlyused for simple signal indicators.

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COB LEDs (= chip onboard) are used for tightlypacked high-power LED modules.With COB technology, the LED chipsare placed directly on a printed-circuitboard (PCB) and wire-bonded tothe contact surface. An

epoxy lens, or“bubble”, defines the beam

spread, which can be narrow or wide-an-gled.

SMD LEDs (= surface mounted devices)are very small mass-produced products.They are placed directly on a PCB andelectrically contacted by soldering. Likewired LEDs, they are encapsulated. SMDLEDs are the type most widely used inmodules or luminaires.

SMD models are fitted both with low-powerLEDs and with high-power LEDs. They permit the industrial production of high-per-formance modules of extremely shallowand narrow construction.

[33] LEDs are generally used as modules,which are either custom-designed or stan-dardised. These modules offer optimal scopefor fine-tuning to the relevant application andcan be used directly as encapsulated mod-ules even without a luminaire housing. Thetwo LED retrofit lamps on the right replace incandescent lamps with a screw base (top)and halogen reflector lamps with a pin base(bottom).

The tiny semiconductor diode has pre-sented a new light source for lighting: theLED module. Basically, it consists of one ormore light-emitting diodes mounted on aPCB. The PCB provides the electrical con-nection for the diodes, dissipates heat andenables the LEDs to be controlled. The flatmodules permit flexible and efficient use ofLED technology. They are fitted with differ-ent types of LED, depending on application.

LED modules

LED modules are a versatile light sourcepermitting totally new design solutions. Asencapsulated modules, they require nohousing and can be directly recessed, forinstance, in floor or ceiling ducts. As indi-vidual modules, they are integrated in mini-malist LED luminaires and, with an appro-

priate base, serve as replacements formany conventional lamps.

Linear LED modules are particularly suitablefor wallwashing effects and for architecturallighting. They give depth to facades and arches and fit into narrow outlet ducting. They can also be used to realise long lines of light.

Flexible LED modules are particularly goodat negotiating curves and corners. They aremostly fitted with SMD LEDs. The flat mod-ules are the right solution where curved sur-faces need to be illuminated or back-lit, e.g.lettering or handrails.

Planar LED modules are normally availableas ready-to-use LED panels with diffuseglass or plastic surfaces. They are used aslight tiles or complete luminous ceilings.


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LED Special: Modules, Systems – and Quality FeaturesLight-emitting diodes can only be used for lighting tasks when assembled as a module on a printed circuit board (PCB). The production of high-performance modules, lamps and complete LED luminaires calls for specialmanufacturing processes and a great deal of technological expertise is needed to meet the relevant quality requirements.

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Where a number of modules are connected– and an appropriate control system in-stalled – large-area displays can be realised.

LED chains are used where surfaces needto be back-lit or under-lit, e.g. in light adver-tising.

Retrofit lamps: LEDs with base

LEDs with pin or screw base are a specialmodule variant. With an E14 or E27 screwbase and a classical “bulb” design, they re-place conventional incandescent lamps;with pin bases, they replace the correspon-ding halogen lamps. Delivering warm whiteor coloured light, retrofit LED lamps are anenergy-saving alternative for home or smalloffice use. They can simply be inserted intoexisting luminaires. However, they do notmatch the performance of a complete LEDluminaire. Even so, they are a good alterna-tive: an 8W warm white LED light bulb, forexample, has a life of around 25,000 oper-ating hours – which is nearly 25 years at almost three hours a day.

LED luminaires and LED systems

One of the prime requirements for an effi-cient LED solution is optimal synchroniza-

tion of module and luminaire housing; thetwo always form a complete system. Theirproduction calls not only for a great deal ofdevelopment and manufacturing expertisebut also for the use of high-grade materi-als. Among the distinguishing features of aquality luminaire are good – and compact –solutions for lighting control, thermal man-agement and optical design.

LED luminaires or LED systems for re-cessed and surface-mounted fittings arealways made in four stages (see Fig. 34):Their manufacture starts with an LED chip,which is encased in plastic to protect itfrom environmental influences and defineits emittance characteristics and thenplaced in a housing.

This diode (stage 2) is mounted on a PCB,which provides the electronics, control andthermal management. In the third stage,the LED-PCB is then fitted with secondaryoptics such as lenses, reflectors or dif-fusers.

In stage 4, the LED module is integrated in the LED luminaire. In this productionphase, a great deal of attention is paid tothe rear of the luminaire, where thermalmanagement is a major issue. This ensures

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[34] The production of efficient LED sys-tems calls for a great deal of technologicalexpertise. The quality of the components andthe standard of manufacturing are crucial forthe efficiency and performance of an LED luminaire.

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that heat is conducted away from thediode and is crucial for the efficiency andlifespan of the system as a whole.

Quality features and maintenance factor

LEDs are in vogue – and the market is flood-ed with products that do not always meetthe necessary requirements. In many cases,poor systems do not reveal their weaknessuntil they are in operation. Quality products> offer balanced luminance that cannotharm the human eye,> have minimal early failures (approx. twoper million LEDs) and carry a manufac-turer’s warranty,> offer the prospect of future replacementin the same lighting quality despite the rapiddevelopment of LED technology, > feature good thermal management, en-suring that luminaires do not get too hotand can be touched without risk,> offer a good maintenance factor.

The maintenance factor (MF) of a lighting in-stallation is the ratio of the luminous flux atthe time of maintenance to the original lumi-nous flux when the system is installed. Ittakes account of > the reduction of luminous flux due to thefailure and ageing of lamps,> the possible soiling of a luminaire in thecourse of time,> room or outdoor conditions that maycontribute to soiling and ageing.

For example: Where MF = 0.5, a lighting in-stallation needs to produce twice as muchluminous flux at the outset so that it will stillprovide the illuminance required for standardcompliance by the end of the first mainte-nance interval. Generally speaking, the qual-ity of LED luminaires is reflected in uniformlight colours and homogeneous brightnessas well as in the rated life of the system as awhole. Important issues in this context arethermal management and binning.


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[35] Agreeably uniform, glare-free light isprovided in the office by the extremely flatsuspended task area luminaire with direct/in-direct light distribution and integrated lightingmanagement system. Another advantage isits long life, which saves maintenance costs.

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Thermal management

Even though the light radiated by an LED isnot hot, it is wrong to assume that LEDs do not give off heat. Just like other lamps,LEDs convert only part of the incoming en-ergy into light – the rest generates heat in-side the semiconductor. To ensure a longlife and high efficiency, it is imperative thatthis heat should be transferred. This appliesparticularly to high luminous flux LEDs.

Reliable manufacturers thus always quotean LED ambient temperature in which theluminous flux and lifespan of their luminairesand modules are reached.

Binning

In the industrial production of LEDs, thereare always differences within batches:diodes vary, for example, in their colourand luminous intensity. To guarantee con-

stant lighting quality with the same bright-ness level and uniform light colour, LEDsneed to be sorted within each batch. Thisis called binning. Major selection criteriahere are:> luminous flux, measured in lumens (lm)> colour temperature, measured in kel-vins (K)> forward voltage, measured in volts (V).

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[36] ] Uniform LED light colours are guaranteed by ANSI binning.

The colours of LEDs are subject to natural fluctuations. To guarantee a uniformlight colour, they need to be categorised. The process of sorting LEDs by colour isknown as binning.

The red triangle in the chromaticity diagram (left) of the International LightingCommission CIE indicates the space in which a chromatic locus could theoreti-cally be plotted by mixing the colours of three LEDs. If the binning group is on theblack curve of the Planckian locus, it is classed as “pure white”. If the bin is abovethe line, the LED has a greenish tint. Today, LEDs are sorted on the basis of the ANSI bin standard (ANSI = AmericanNational Standards Institute). This defines colour variations in xy space with thehelp of a MacAdam ellipse and recommends that colour values should be withinan ellipse with four threshold units. LEDs in these tightly defined bins guaranteeuniform light colours, e.g. 2,700 K for warm white.

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Definition of white LED colours

spectral locus

line of purples

theoretical colours

blackbody radiation curve

© licht.de

ANSI colour codes

Lighting plays an important role in hotels,restaurants and wellness centres. It con-tributes crucially to a guest’s sense of well-being and desire to return. Here, light playsout its emotional qualities, underlining acomfortable and agreeable atmosphere.

At the same time, lighting facilitates orienta-tion, e.g. on parking decks, in corridors andpassageways. In conference rooms, hotelrooms and service areas, lighting alsoneeds to cater for different room uses –while keeping costs as low as possible.

High-power LED systems meet the com-plex requirements of restaurants and hospi-tality venues at the highest level: They

> can be flexibly controlled and offer dy-namic scene-setting lighting in rich colours, > provide different white tones to underlinea homely or fresh ambience, > have a service life of 50,000 hours ormore, > are very efficient, > are small and discreet and accentuate ar-chitecture,> save maintenance costs and have a lowenvironmental impact.

The tiny power packs not only ensure first-rate lighting quality; they are also extremelyeconomical on energy. LED solutions andintelligent lighting control can cut lightingcosts by as much as 75 percent. Another


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LEDs for Hotels and Hospitality From traditional hotel to trendy bistro, country inn to wellness oasis – successful “hosts” cosset their customers,offering pleasure and wellbeing. The right light is just as important here as impeccable service.

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advantage: their longevity saves mainte-nance costs by eliminating the need for fre-quent lamp replacement in difficult placeslike high stairwells. What is more, the lowheat gain of LEDs reduces air-conditioningcosts.

First impressions count

With a broad spectrum of colours andcolour temperatures, LEDs ensure a friendlyreception. They provide guidance for visi-tors and facilitate communication betweenguests and staff. Planar light conveys gen-erosity and makes for good general lighting.Such solutions can be realised with floodingLED light from cornices or with a full diffuseopal “skylight ceiling” of back-lit glass.Warm white light or cheerful bright colourtones are the most suitable options.

Walk-over recessed floor lights or discreetlight panels in the wall guide the visitor tothe reception. There, the glare free warmwhite light of elegant LED luminaires facili-tates work at the computer. Good colourrendering with Ra � 90 guarantees thatcolours, faces and objects look natural.

In lobby, bar and corridor, directional LEDspots set striking accents as energy-effi-cient replacements for halogen lamps. Theirbig advantage: they emit neither ultravioletnor infrared light. So even old masters sus-tain no damage and eye-catching creationson the dessert buffet are cast in an appetis-ing light with no risk of them drying out.

Colour and dynamism for lighting comfort

Coloured lighting for selected surfaces anddynamic light hold a special fascination. Experienced hoteliers are not the only ones

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[37] The slate wall is an eye-catcher in thelounge, lent depth by cubic recessed lumi-naires with single 1.2W LEDs radiating light inthree different white tones.

[38] The right lighting helps us unwind.Here, a homogeneous “light wall” providesagreeably diffuse light at the bed. 38


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who realise this; the positive impact onhuman beings has been confirmed by nu-merous studies. With LED solutions, it isparticularly easy to harness the beneficialeffects of colour and dynamic light. Andthere is no need for colour filters: given anappropriate module, a single LED luminairecan produce more than 16 million differentcolours as well as a range of white tones.

LED lighting with dynamic colour manage-ment has various uses. In a hotel room, itenables the guest to set “his” lighting to suit his biorhythms – fresh white tones witha high blue content in the morning to helphim wake up, more red content in theevening to help him unwind. In conferencerooms, the lighting can be switched as required from concentration-boosting whitetones through gently soothing mood light to inspiring colour changes for creativebrainstorming.

Intelligent, sensitive colour managementalso makes for great effects in wellnesscentres – effects that customers appreciate.

Green tones are soothing for a relaxingmassage, a delicate violet is good for therest zone of the sauna and turquoise blueconveys a sense of cleanliness and fresh-ness in the whirlpool. To ensure safety inswimming pools, plunge pools and show-ers, however, any LED luminaires usedthere need to be designed to appropriatedegrees of protection.

High-quality LED systems can be infinitelydimmed. They can thus provide subduedlighting for guests in rest zones and brightlight for cleaning.

Video-capable LED systems add a highlightto lounge and bar areas. They let ceilings tell stories. Programmed to create differentshapes and slowly changing colours, theymake for a subtle cosy atmosphere; loadedwith images, they set trends. The planar lu-minaires can be installed on ceilings or walls.

Lighting management for comfort

Tailoring lighting to preferences and needs

calls for lighting control and appropriatemanagement systems. They should be easyto use and convenient for guests and staff.Simple control is offered by multifunctionaloperator interfaces where a single panel re-places a cluster of switches and dimmers.

Clearly identified programmed lighting at-mospheres can be activated at the push of a button or by remote control – a wel-come convenience in any hotel or confer-ence room. At the same time, lighting andblinds can be adjusted to suit daylight and weather. Where time of day and humanpresence are taken into account, lightingmanagement permits a further sustainablereduction of energy consumption. This alsomakes good financial sense in toilet facilitiesand on parking decks.

Long-life low-consumption LED luminairescombined with lighting management thusmeet the requirements for efficient, top-quality lighting for every part of a building.Depending on configuration, all areas canbe centrally monitored and controlled –from hotel room to car park.

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[39] Downlights and cornice lighting overthe entrance mark the route to the reception.

[40] LEDs create an attractive lighting at-mosphere in the restaurant: the back-litcounter is a prominent design feature. Slim-line LED modules also set the scene forglasses on the shelves on the rear wall.

[41] LED solutions with dynamic colourmanagement are a good choice for wellnessfacilities. They pamper guests with stimulat-ing or relaxing light, depending on the time of day. 41


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[42] Modern LED spots are perfect for themuseum because of their versatility. Colourtemperatures and colours can easily be mod-ified to cast the relevant exhibits in exactlythe right light. LED light contains no UV or IRradiation, so sensitive materials are pro-tected.

[43] Energy-efficient LED spots on a slen-der track system illuminate sculptures per-fectly from a height of five to six metres.

[44] The old manuscripts in the showcasesare gently and evenly illuminated with LEDlight.

Any lighting design for a museum or artgallery needs to focus on the exhibits. Anattractive dramatic lighting installation takesaccount of this: while effectively showcas-ing architecture and exhibitions, the lightsources themselves remain discreetly in thebackground. Because of very compact di-mensions and extremely shallow design,this presents no problem for LED modules.

Luminous ceilings open up rooms

Especially in modern museums and gal-leries, there is a marked trend towards theuse of large diffuse light panels. The advan-tage: their soft flooding light blurs theboundaries of the room and softens hardcontours. So large back-lit ceilings or pan-els are ideally suited for general lighting.With long-life LED light tiles, light lines orspecial module strings, such luminous ceil-ings can easily be realised for a virtuallymaintenance-free solution.

The contrast between the diffuse light of an LED light panel and the highly focuseddirectional beam of LED spots holds a par-ticular allure. It focuses attention on the exhibits while at the same time structuringthe room and facilitating orientation. WithLED spots on power track or gimbal-mounted – i.e. rotatable – downlights, theaccent lighting remains flexible for revolvingpresentations.

Changing light

LED solutions coupled with dynamic light-ing management provide the full range ofRGB colours and a broad spectrum of pas-tel and mixed colours for individual lighting“productions”. With no need for colour filters and at the push of a button, the lightchanges from stimulating cool blue throughwarm white to glowing red. The lighting can thus be perfectly tuned to suit differentperiods in history and different exhibition

themes. Bright glossy materials such asphotographs, for instance, acquire a specialbrilliance at high colour temperaturesaround 5,000 kelvin: historical costumes orfurnishings show all their facets at a warm3,000 kelvin. Additional accents can thenbe set by adjustments in brightness be-tween 10 and 100 percent.

LED light is gentle on old masters

Museum lighting also needs to take account of conservationist requirements. Oil paint-ings, old documents and fabrics are sensi-tive and must not be exposed to harmfullight or heat. LEDs rise to the challenge withease: they emit neither ultraviolet (UV) norinfrared (IR) radiation and the light they radi-ate remains cool. They thus protect sensi-tive exhibits from degradation and preservetheir colours.

Dramatic effects on stage

At rock concerts, in the theatre or for TVshows – where attention-grabbing produc-tions are presented, rich colours andchanges in lighting are a must. Moderncontrol systems with digital interfaces en-sure successful effects. With large numbersof LED points, for example, large panelscan not only be activated, deactivated ordimmed; each light point can even be sep-arately controlled to produce changes incolour and intensity. With video-capableLED luminaires, which can play back im-ages and film sequences, light itself be-comes the star of the show.

LEDs for Art and Culture Modern art, sculpture or old manuscripts: exhibition lighting requires a very sensitive touch and gentle light. With dynamic light, LEDs also introduce colour and movement into the scene.

In an exclusive brand outlet or supermarketdeli department, modern lighting sets thestage for the merchandise on offer and cre-ates an ever-changing backdrop of excitingenvironments. Flexible coloured LED lightgives the presentation the right pizzazz. Itguides and informs, dramatises and differ-entiates...

Light-emitting diodes have an outstandingtrack record as more than just sales pro-moters. Extremely efficient, each one ofthem helps reduce energy costs for 50,000working hours – which makes a noticeabledifference. Lighting accounts for around 25percent of the electricity consumed in retail-ing, so it is well worth paying special atten-tion to it and to intelligent options for man-aging the energy it consumes.

LEDs make light move

Modern LED technology introduces a totallynew tone to the exciting dialogue between

lighting and merchandise. Particularlytrendy at present are luminous ceilings,which gently flood an interior with light. Inlarge malls especially, they make for a posi-tive lighting atmosphere and blur theboundaries of the retail space. Video-capa-ble LED media luminaires can display im-ages and messages on the ceiling at thepush of a button – or reproduce the skyover the course of the day. If required, theycan also be used to present moving orstatic images without compromising onimage quality or uniformity of colour. Dy-namic colour and light management setsthe scene for product presentations andwindow displays. With electronic controlsystems, any lighting combination and at-mosphere can be programmed for activa-tion in the sequence required.

Coloured light for any collection

Coloured light is a major issue in retailing:discreetly illuminated coving between walls

[45+46] LED light turns this shop into aplace of delight and discovery – and dis-penses with visually obtrusive luminaire hous-ings. Gentle flooding light is provided by largelight walls, while fine light strips illuminate theshowcases.

[47] The eye-catcher of the mall: an LEDmedia ceiling that can be programmed todisplay moving or static images.


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LEDs for Shops und PresentationSaturday shopping in the city or at an outlying retail park: flexible LED light makes shopping an emotional experience, helps staff serve customers better and contributes substantially to the success of the business.

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Solution for difficult locations

The longevity of LEDs saves maintenance,which is particularly welcome where lampreplacement is difficult or expensive, suchas on escalators or in rooms with very highceilings.

LEDs are also good for freezer cabinets,where they can simply be used in place offluorescent lamps. The big advantage isthat whereas fluorescent lamps provide lesslight at minus 20° Celsius, LEDs literally finda new lease of life at sub-zero tempera-tures. They are also unaffected by vibra-tions caused by slammed doors – and theygenerally enjoy a longer life than the freezeritself.

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[48] Elegant lighting solution for thecounter: white LED light floods out of the cor-nice beneath the ceiling, emphasizing thecurves of the counter.

[49+50] Coloured light directs attention andcan be adapted to suit any collection.

[51] With functional white light and colouredspecial-effect lighting, the lighting concept forthe bank helps create an agreeable atmos-phere and conveys a sense of security in theevening. Providing warm to cool white light,variable colour temperature LEDs enable thelighting to give the right prompts for humanbiological rhythms during the course of theday.

[52] During the day, the shopping mall isflooded with daylight; in the evening, efficientLEDs take over. Coloured light accentuatesthe architecture.

[53] LEDs are perfectly happy at sub-zerotemperatures. Bathing the frozen foods inuniform light, they are economical on energyand vibration-resistant.

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and ceiling blur boundaries, recessed floorlights identify different zones, directional spots direct the eye to product presentations. With LEDs it is easy to combine agreeablewhite general light with coloured accents.

For example, lighting can change with eachnew collection: fresh yellow and greentones for summer, warm orange and redsfor autumn and cool white and blue for win-ter. It also works in a delicatessen depart-ment. Cool colours underline the freshnessof fruit, meat and fish; spots switching be-tween red and green provide charminglighting for fine wines.

LED light for sensitive merchandise

Projected light directed straight at an objectproduces high luminance. That attracts at-tention. With LEDs, spotlighting even sensi-tive merchandise – cosmetics, foodstuffs,sensitive fabrics or leather – is problem-free. The light they emit contains no harmfulinfrared or ultraviolet rays; supplementaryfilters are no longer necessary.

As a result, spots and LED luminaires canbe installed directly in shelving systems, sothe energy needed to illuminate merchan-dise is less than where conventional accentlighting is used.

[54] Warm colours and warm white LEDlight help mothers-to-be feel at home atNuremberg Hospital.

[55+56] Creating a bright and cheerful at-mosphere, the lighting concept for the sur-gery is based entirely on LED luminaires. Thesimple elegance of the light fittings is a per-fect match for the furnishings.

Even the Ancient Egyptians were aware ofthe power of colour: they immersed theirsickrooms in warm red light. The beneficialeffect that colour and dynamic lighting haveon human beings is confirmed by modernscience. While the focus in the past was onoptimal lighting for diagnosis and therapy,the emphasis in hospitals, surgeries andcare facilities today is increasingly on mak-ing use of the psychological and aestheticimpact of light.

Such concepts can be easily and efficientlyrealised with LED systems. Colour adds anemotion dimension to light – and impactsdirectly on a patient’s sense of wellbeing.Efficient and flexible LED solutions invitecreative use of light – facilitating orientationas recessed wall and floor luminaires, lend-

ing structure to long windowless corridorsas wallwashers in combination with brilliantaccent lights, receiving patients in the re-covery room and reassuring parents-to-bein the delivery suite as diffuse luminaires.

The right “medicine”: LED light

Gentle coloured light is not only the right“medicine” for fear and anxiety in a waitingarea. It is also found increasingly useful inplaces where surroundings are predomi-nantly defined by medical equipment. ForCT (computer tomography) scans or digitalmammography, an ambience shaped bycoloured light significantly helps patientsrelax. And because less anxiety means lessstress, examination error rates are also low-ered.


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LEDs in Hospital and Surgery The healthcare system is changing. Hospitals, doctors’ surgeries and care facilities are becoming modern health-care centres and need to be competitive. Tailored lighting concepts help patients feel well looked after.

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RGB control enables light to be tailored toany requirements: white or coloured, brightor gently dimmed, static or programmed fordynamic change. So an agreeable lightingatmosphere can also be realised in a pa-tient’s room to take account of human bio-logical rhythms: cool daylight white for thedoctor’s round in the morning, warm whitelight for relaxation in the afternoon, dimmedgeneral lighting supplemented by accentlighting in the evening.

LEDs in the doctor’s surgery

Combining high performance with puristdesign, efficient maintenance-free LEDsalso ensure optimal lighting at a doctor’ssurgery. Diffuse light tiles or recessed spotsfacilitate orientation, luminaires with directand indirect components provide glare-freelighting for waiting areas and for placeswhere work is performed at computers andelectronic equipment. Spots put pictures,sculptures and plants in the limelight.

In treatment rooms, doctors and nursingstaff need good general lighting of around500 lux and flexible lighting for examina-tions. With intelligent management systems,

lighting can easily be switched and dimmed. This ensures comfort and adds to energysavings.

Lighting for examinations and surgery

High-intensity high-power diodes are alsoincreasingly used for examination lumi-naires. The advantages are not only a longlife, which keeps maintenance to a mini-mum, but also their hemispherical radianceand the ample scope for using optical con-trol elements to direct the beam of the“punctual light sources”. Also, in contrast toconventional lamps, LED light contains nei-ther ultraviolet nor infrared radiation, whichis good for skin and bodily tissue.

The use of different coloured LEDs in a lu-minaire facilitates assessment of the condi-tion of skin and wounds. This is basicallydue to a “shortcoming” – because thecolour rendering properties of neutral whiteLEDs (Ra � 90) at present are often notgood enough for the demanding visualtasks performed in an operating theatre. Sountil diodes with optimised phosphor coat-ings for a higher colour rendering index areavailable, neutral white chips are combined

with other light colours. This smoothes outthe spectral profile of the luminaire andguarantees optimal colour rendering.

Colour mixing also offers physicians the option to vary the white LED light for a particular examination at the push of a but-ton or through use of a remote control de-vice. For example: neutral white for generalexaminations, warm white light for examin-ing skin, cold white light for vascular identi-fication.


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[57] Art in the surgery corridor. The filigreealuminium wall luminaires are fitted with 8WLEDs, which is equivalent to a 30W halogenlamp. The 2W LED wall luminaires at kneeheight mark the route through the surgery.

[58] Operating theatre lights with high-in-tensity LEDs facilitate the demanding visualtasks performed by surgeons. Light colourand brightness can be changed in seconds.

[59] Lighting atmosphere with a twofold ef-fect: dynamic LED lighting helps quell anyanxiety that the patient might feel and thusalso reduces the risk of false readings. Morethan 60,000 different light colours can becreated in the MRT (magnetic resonance to-mography) treatment room at Saint Mary’sHospital in Hamburg. Positive side-effects in-clude lower energy costs and a zero mainte-nance requirement.

[60] Different coloured LEDs in the exami-nation luminaire help doctors assess the con-dition of skin and wounds.

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The kind of operating gear selected is de-termined by the type and application of theLED luminaire. Luminaires can be supplieddirectly with mains voltage – if the operat-ing gear is integrated in the luminaires – orthey can work on a safety extra-low voltage delivered by external operating devices.LED modules are dimmed by separate con-trol inputs (e.g. DALI, DMX) or by pulsewidth modulation.

Basically, operating devices for LED mod-ules or LED luminaires guarantee:> the right power supply for the type of fit-ting: normally safety extra-low voltage(SELV),> reliable operation even where ambientconditions are difficult,> LED control, depending on type, and in-terfaces for management systems, > a long life tailored to the light source sothat LEDs can be used effectively.

Operating devices are either integrated di-rectly in the printed circuit board (PCB) as-sembly of the LED modules – as in the caseof LED modules in capped designs (retrofitlamps) – or designed as separate compo-nents.

A distinction is made between operatingdevices that form an integral part of a lumi-naire, devices that are incorporated in a lu-minaire and devices that are independent.Integral operating devices cannot be re-moved from a luminaire intact, incorporatedoperating devices can be removed or re-placed with the help of tools. Where incor-porated or independent operating devicesare used, luminaires need to meet safety-relevant requirements.

Separate operating devices meet the safety-relevant requirements of international stan-

dards by virtue of their design and can thusbe installed outside luminaires or equivalentfittings.

Apart from the constructive design of oper-ating devices, the supply voltage of the LEDmodules is a matter of major significance.

Reducing mains voltage

There are two types of operating device fortransforming mains voltage for LEDs:> operating devices with constant outputvoltage reduce the mains voltage from230V to a stabilised low voltage such as10, 12 or 24V. These operating devices arenormally used for LED modules with cur-rent-limiting devices on the PCB.

LED modules that are operated on a con-stant low voltage need to be voltage con-trolled. They permit only simple regulationof light intensity by pulsing (i.e. turning onand off) the voltage. This operating moderequires a current limiting device in LEDmodules because some LEDs have a wideforward voltage spread. If the current limitersettings are wrong, diodes and operatingdevices may be destroyed. So only operat-ing devices that are specifically designed forthe LEDs in question should be used. As a general rule, LED luminaires with a powerrating of less than 0.5W are voltage-con-trolled.

> operating devices with constant outputcurrent produce a stabilised output currentfrom the 230V mains voltage. The constantoutput currents realised are typically 350milliampere (mA), 700 mA or 1,050 mA.With this variant, LED modules can be operated direct and the LEDs switched “inseries” – up to the maximum no load volt-age of the operating device. The devices

are also typically limited to a safety extra-low voltage.

Current-regulated control of LED modulesoffers more advantages in constant opera-tion and scores points for efficiency(lumen/watt) because there are no powerlosses due to current-limiting devices.Thanks to a stable operating current, thereis also no risk of the diodes being over-loaded; fluctuating forward voltages are notan issue here. Current-regulated control isparticularly suitable for high-performancehigh-current diodes.

It is worth noting that all operating deviceson the market that meet the relevant safetyrequirements and have a safety extra-lowvoltage (SELV) output ensure safe supplyline isolation. They have an internal trans-former. So even non insulated LED modulescan be safely accessed.

Lighting management

LEDs permit virtually limitless combinationsof brightness and colour. Lighting manage-ment ensures the right light at the rightplace and the right time. “Intelligent” man-agement systems offer four major advan-tages:> simple adjustment of lighting to suit differ-ent tasks or times of day,> high cost and energy savings,> dynamic lighting control,> high flexibility.

Depending on the assignment, solutionscan be realised for specific luminaires, indi-vidual rooms, entire buildings or outdoor installations – with control ranging from individual light points to programmed light-ing scenes. LEDs thus offer efficient solu-tions for standard-compliant general lighting

LED Special: Operating Devices and Ballasts The way LED modules work in luminaires is crucially influenced by current and voltage supply. Electronic operating devices ensure optimal luminous efficacy and longevity by precisely defining electrical parameters. “Intelligent” management can significantly enhance efficiency and comfort even more.

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as well as for customised accent lightingand lighting scenarios.

Dimming and colour control

As a general rule, lighting control is possibleonly if luminaires are designed for switchingor dimming – either manually or by timer,computer or sensor. Light intensity is regu-lated by appropriate sensors: depending on time, human presence or daylight. LEDluminaires are normally dimmed by the veryefficient, low-loss method of pulse widthmodulation. Here, the lighting is digitally activated and deactivated at such a highfrequency that the flicker is imperceptible to the human eye.

Coloured lighting scenarios are also possi-ble – e.g. through the use of RGB systemscontrolling identical or different colouredLED modules in three- or multi-channel operation. With additive colour mixing andprecisely controlled brightness control ofred, green and blue, up to 16.7 millioncolours can be produced. From delicatelilac through orange to midnight blue – LEDlight harnesses pale and bold colours insharply contoured or subtly blurredarrangements to create fascinating atmos-pheres with a soothing or stimulating effect.Dynamic colour sequences are particularlyappealing. Depending on how the controlunit is programmed, they can change al-most imperceptibly at predefined intervalsof seconds, minutes or hours.

Control system interfaces

Appropriate interfaces enable LED lumi-naires to be easily incorporated into mod-ern control systems. The simplest systemsfrom a technological viewpoint are analogueinterfaces such as the 1-10 V interface for dimming LEDs. Combined with a se-quencer, this also permits dynamic coloursequences. In many cases, signal receiverscan also be installed in existing LED lumi-naires or junction boxes. Multifunctionswitches or remote control devices canthen be used to adjust the lighting as re-quired. Digital control systems offer a great dealmore performance. They integrate lightingmanagement into modern BUS control systems that meet the rising standards of

comfort and efficiency required in buildingservices and facility management. Forroom-related applications or relatively smallbuilding solutions, systems that work withthe DALI digital interface (the acronymstands for Digital Addressable Lighting Interface) are a suitable choice. DALI cancontrol a large number of control circuits individually via a small number of lines evenover long distances. With the help of a cen-tral control element, programmed coloursequences and brightnesses can thus berealised as required without difficulty; evenenergy saving presence and daylight de-pendent regulation is possible with the rightcontrol equipment.

Among the more expensive systems avail-able is the multiplex transmission systemDMX. Developed in the United States, itwas initially used mainly for stage lighting.Today, DMX is also often used by architectsand lighting designers who wish to harnessthe opportunity it offers to control as manyas 512 channels with rapid signal se-quences from a single central control unit,realise colour mixes and automate fadesand cross-fades. For large-scale applica-tions, DMX units can be linked together.Both DALI and DMX can be integrated inhigher-level building management systemssuch as KNX. These systems network alltechnical components and control heating,lighting, blinds, ventilation and security sys-tems as required. They thus offer a high de-gree of comfort and convenience in con-junction with maximum efficiency.

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[61] A marriage of art and technology: six-metre-high stelae used for revolving art in-stallations in Munich. The stelae are fittedwith the latest LED lighting technology anddigital control systems. They can be pro-grammed to display static or moving images.


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62

“Here I am Man, here dare it to be”. Goethe’s words read as if they were written about theprivacy of the home – because whether welive in a rented apartment or a privatelyowned house, what matters in the domesticenvironment is a sense of security and sur-roundings shaped by personal style. Per-fect, then, that modern LEDs offer the rightsolution for every kind of home and everytaste. The tiny diodes enhance every atmos-phere – from minimalist Bauhaus to cosycountry cottage – as well as offering maxi-mum flexibility and low power consumption.

LEDs for every kind of home

Purists delight in the fact that LEDs, em-bracing the maxim “form follows function”,make life easier while discreetly emphasizingarchitecture and furnishings. Slender lightingstrip allows light to flood from suspendedceilings or narrow wall outlets, minimalistLED downlights brightly illuminate the entiredining table, flush-mounted recessed spots

direct light onto staircase treads and drawattention to pictures and sculptures.

Colour lovers enjoy the feel-good partner-ship of “light and colour” and the range ofmore than 16 million possibilities offered byLEDs. They know that coloured lightprompts the human body to secrete mood-brightening substances. A second with theremote is all it takes to change living roomlighting from meditative blue to rousing red.

Anyone wishing to bathe whole ceilings orwalls in a favourite colour needs high-inten-sity RGB floods. Mobile LED luminaires are a practical alternative to permanently installed systems. They enable pools orsplashes of colour to be added as andwhere required.

Robust, efficient and with a long life

Environmentalists are not the only ones de-lighted with the many “green” qualities of

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[62] An elegant solution for this outdoorarea is provided by translucent surface-mounted ceiling luminaires of extremely shal-low design with spraywater protection to IP44. Each unit has a power rating of just 9Wand easily replaces a 50W halogen lamp.

[63] LED solution for the hallway: the sur-face-mounted luminaires on the ceiling radi-ate their energy-efficient light directly down-wards and use a secondary indirect beam tobrighten the ceiling and walls. Wall luminairesset close to the floor provide additionalbrightness.

[64] Mobile LED luminaires are a flexible op-tion that can bathe rooms in coloured light.

[65] The LED desktop luminaire providesenergy-efficient light for working.

LEDs for House and Home Great lighting and major energy and electricity savings – LEDs make it possible. They are a star turn in the home – not just as mood lights for special accents but also in kitchens and bathrooms or as end-to-end energy-saving solutions for high comfort and convenience.

63 64 65

sustainable LED solutions: compared to in-candescent lamps, they make for an energysaving of 80 percent. That eases the pres-sure on both the environment and thehousehold budget. For ultra-low-energy“passive” houses, LEDs’ low heat gain is animportant advantage. As for lamp replace-ment and disposal, these are hardly anissue with LEDs because they have a ser-vice life of 50,000 hours or more. Switchedon for three hours a day, they have a life ex-pectance of no less than 45 years. An in-candescent lamp, by comparison, lasts foraround one year. Another environmental ad-vantage is that, unlike energy-saving lamps,diodes contain no mercury. So they do notneed to be disposed of as special waste atthe end of their life.

LEDs are also convincing in terms of light-ing quality. With warm white light colour andgood to very good colour rendering, theyproduce a fresh, natural light. Diodes alsogive a 100 percent performance from themoment they are switched on. And frequentswitching – e.g. under the control of a mo-tion detector – does not shorten the robust

light source’s life, which is not the case withenergy-saving and fluorescent lamps.

LEDs in and around the home

In new buildings, lighting installations incor-porating LED and lighting control systemsoffer maximum efficiency, convenience andcomfort. With a building management sys-tem, for example, a variety of lighting at-mospheres can be defined for the entirebuilding. From “bright” in the morning to“cosy” in the evening, the different atmos-pheres can be selected by residents at anytime and for any area at the push of a re-mote control button.

However, LED solutions can also be inte-grated in an existing home without majorrefurbishment work. One option is to usecompact surface-mounted and recessedluminaires, which are available for both in-door and outdoor use; another is to installmobile luminaires, which have no difficultywhatsoever finding a place in the home.Kitchens and wardrobes can be bathed inlight and colour by flexible LED modules.

It is also easy to replace old “light bulbs” inexisting luminaires with power-saving LEDs:LED lamps are available today with a screwor pin base and in a whole range of whitetones, colours and even colour-changingdesigns. A 60W incandescent lamp canthus be replaced in seconds by an LEDlamp that delivers the same radiant flux butrequires only 8 watts of electricity to do so.


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66

[66] Agreeable uniform light is provided inthe bathroom by LED wall luminaires with in-tegrated converter. The slender luminairehead can be swung forward and positionedat any angle.

[67] The compact design of LEDs paves theway for totally new, slimline luminaires. Theheight-adjustable pendant luminaire over thedining table is only five centimetres wide butemits extremely intense light and consumesvery little electricity.

[68] Recessed floor luminaires set thescene in the entrance area and guide visitorsinto the home.

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67

68

Energy cost comparison for a three-room apartmentIn domestic lighting, efficient LEDs score points not only because of the lighting quality they deliver but alsobecause they save a great deal of energy and therefore electricity costs. The example shows the lighting costsfor a 58 sqm three-room apartment over four years. (assuming an electricity price of 0.21 €/kWh and 1,460 luminaire operating hours a year)

Room LED solution Conventional solution

Kitchen 32 W 194 W

Bathroom 20 W 90 W

Hall 24 W 150 W

Living room 48 W 210 W

Bedroom 44 W 235 W

Children’s room / home office 23 W 102 W

Balcony 16 W 60 W

Converter/ballast 31 W 104 W

Total wattage 238 W 1,145 W

Approx. electricity costs over 4 years € 292.– € 1,404.–

Saving € 1,112.–

For global player and regional dental labora-tory alike, competition demands precision-made quality products at reasonable market prices. Manufacturing structuresneed to be optimised down to the last de-tail, which means that lighting is constantlyreappraised. Correct lighting has beenshown to help lower error and sick rates. Italso boosts the performance of every em-ployee.

LED solutions for general lighting are still ararity in industry but they are an increasinglypopular choice for workplace oriented light-ing. The tiny diodes score points for theirextremely long life of 50,000 hours or more,

their low power consumption and the con-stant high lighting quality they deliver. Theirstrengths save both maintenance and oper-ating costs.

Another important point is that LEDs arenot sensitive to vibration or shock, so theyare optimally suitable for workplace lightingin a manufacturing environment. What ismore, they project no beam heat – an im-portant advantage especially inside largemachines, where the use of LEDs helpsprevent coolants and lubricants beingbaked onto surfaces.

High-intensity point lighting

High-frequency operation means that LEDsproduce uniform flicker-free workplace lightand thus prevent potentially dangerousstroboscopic effects. This reduces the riskof accidents during the installation andmaintenance of machines. Glare free andproducing a very intense beam of light,LEDs also facilitate work wherever minutedetails need to be reliably recognised andthe highest visual performance is required,e.g. in jewellery making or prosthetic dentistry.

New LED luminaires permit precise adjust-ment to the requirements of trade and in-dustry. Flexible luminaire head joints ensurethat light is directed exactly where it isneeded; robust articulated rod and headassemblies are the right choice for large-scale facilities. High degrees of luminaireprotection (see also page 51) prevent theLEDs being damaged during grinding, engraving or sawing operations.

With sophisticated electronics, LED lumi-naires can also be connected directly to a24 V d.c. or a.c. power source. In compari-son to conventional light sources, thismeans fast and flawless installation with low maintenance requirements.


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LEDs in Industry and TradeLighting for workplaces in industry and trade needs to meet the highest requirements in terms of quality and reliability. At the same time, workplace lighting should be energy efficient and have low maintenance requirementsbecause downtimes are something that no company can afford any more.

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LED spot Halogen spot

Purchase price € 300,– € 200,–

Wattage (w) 3 x 3 W 20 W

Light source lifespan 50,000 hrs 2,000 hrs

Maintenance costs/lamp replacement

– 25 x € 45.– = € 1,125,–

Total cost over 50,000 € 381,– € 1.505,–

operating hours at 0.18 €/kWh

Saving € 1,124.–

Cost comparison

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71 73

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70

[69] A direct cost comparison over 50,000operating hours shows that an LED spotsaves more than € 1,000 compared to a halogen spot. LEDs lower both energyconsumption and carbon emissions.

[70] The minimal dimensions of LED lumi-naires are an advantage especially in machin-ery and plant engineering. Other plus points,in addition to high lighting quality, are shockresistance, IR- and UV-free light and no projected beam heat.

[71] High-power LEDs beat conventionallight sources hands down in terms of lumi-nous efficacy and longevity. The light of anLED spot is five times more intense than thatof a halogen lamp.

[72] Slimline hybrid solution for industry.The wall luminaire incorporates a fluorescentlamp for planar lighting and LEDs for direc-tional point lighting.

[73] The 6-LED magnifying luminaire focuses light precisely on the inspectionplane.


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74

Wherever people are present in large num-bers, safety lighting is a must. Its momentcomes when mains voltage fails. In thatevent, it needs to be activated immediatelyby a standby power source. Routes out ofthe building are marked by escape signs;supplementary safety lighting helps avoidpanic, facilitates orientation and lessensthe risk of accident.

Escape sign and emergency luminaires are often in operation 24/7. So it is not sur-prising that long-life solutions like LEDs areincreasingly the option of choice for suchapplications. Provided that thermal man-agement is effective and high-quality oper-ating devices are used, LED systems havea lifespan of 50,000 hours or more. Inpractice, this means lower maintenancecosts, optimised lighting and a reduced energy bill.

Escape signs

The small dimensions of LEDs permit vi-sually discreet escape sign luminaires offormally reduced design. At the sametime, manufacturers face the challengeof transforming the punctual luminanceof LEDs into a uniformly bright luminoussurface while also ensuring compliancewith the relevant standards. Escapesigns need to be clearly identifiableeven when general lighting is switchedon; the required average luminanceneeds to be at least 200 cd/m² – and500 cd/m² for the white parts of thesign. So luminous flux should decreaseas little as possible over the life of theLEDs. In quality lighting systems, thisage-related fall in LED luminous flux istaken into account by allowing an extramargin for degradation. Alternatively,

many systems work with what is knownas a maintenance function: they makeup for the decrease in LED luminous fluxby dimming the diodes at the outset toaround 70 percent of their capacity andthen raising it gradually to 100 percentover the course of their operating life.

Emergency luminaires

In emergency lighting, LED solutions helpsave energy. LED luminaires with a low con-nected load permit efficient, eco-friendly in-stallations. To achieve the optimal efficiencyof LED luminaires, additional optics and re-flectors may be needed so that the numberof luminaires installed can be reduced –without prejudicing compliance with norma-tive and statutory emergency lighting re-quirements.

Thanks to their small dimensions, LEDemergency luminaires keep a low profile.They thus offer the designer greater free-dom.

More information and planning tips can befound in booklet 10 “Emergency Lighting,Safety lighting” of the licht.de series of pub-lications. It is available for download atwww.licht.de/licht.wissen.

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[74] The formally reduced design of theLED escape sign luminaire blends seamlesslywith the modern architecture.

[75] Energy-efficient LEDs are increasinglythe solution of choice for emergency andsafety lighting. Their longevity cuts mainte-nance bills.

LEDs for Emergency and Safety Lighting Safety and accident prevention are important lighting tasks. With diminutive dimensions and a long lifespan, LEDs provide more scope for luminaire design and reduce operating costs.

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It is worth paying attention to quality whenselecting lighting equipment, especially for LED applications. Many of the LEDproducts now on the market do not meetstatutory requirements and, in some cases,are seriously flawed. But modules with in-sufficient insulation, badly designed lumi-naires or poorly made operating devices domore than just impair LED longevity andlight output; they can actually constitute areal hazard, present a health risk or evencause a fire.

LED modules, luminaires and operating de-vices need to conform to the relevant stan-dards of the IEC (International Electrotech-nical Commission). Marks of conformity andinformation about classes and degrees ofprotection need to be displayed on theproduct label. They are listed and describedbelow:

ENEC/VDE test mark

The ENEC mark (ENEC = European NormElectrical Certification) shows that lumi-naires and built-in operating devices complywith current standards. The number afterthe mark identifies the testing agency re-sponsible. In Germany, this is VDE (VerbandDeutscher Elektrotechniker), which com-bines its mark with the ENEC symbol. VDEnot only tests products in Germany; it alsomonitors their production.

GS mark

The GS mark (= Geprüfte Sicherheit) mayonly be used in conjunction with the markof an authorised testing agency. In Ger-many, for example, this could be VDE orTÜV. The GS mark is used to confirm thatthe product tested conforms to the Ger-man Equipment and Product Safety Act(GPSG).

EMV mark

The EMV mark guarantees the electromag-netic compatibility of luminaires and operat-ing devices. To be eligible to display it, adevice must not emit any electrical or elec-tromagnetic noise or signals that coulddamage or inferfere with other appliances.

CE mark

The CE mark is not a test mark but is es-sential for products marketed within theEU. It is applied by manufacturers and im-porters to certify that their products meetthe “fundamental requirements” of certainEU directives. These include, for example,the Eco-design Directive and the EMC Di-rective. Manufacturers and importers needto present evidence of conformity to therelevant government agencies on request.

Classes of protection

Luminaires and operating devices are electrical products, which need to be ade-quately insulated to ensure safe operation.DIN EN 61140 divides them into threeclasses of protection.

Class I

Luminaires for connection to the line-sidePE conductor. Live parts can be touchedeven if the basic insulation fails. They do notcarry dangerous voltages. The symbol isshown at the point of connection.


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LED Special: Safety, Marks of Approval and StandardsLED lighting really only plays out its advantages where light sources, modules, luminaires and operating devices are of impeccable quality. Standard-compliant products and professional installation prevent malfunction and guardagainst health risks.

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[76+77] Danger arises where water andelectricity meet. So luminaires for use inbathrooms or outdoors need to be suitablywell protected. Pointers for safe operationare provided by IP degrees of protection.

Class II

Luminaires in which live parts are furnishedwith additional or enhanced insulation. Theyhave no PE conductor terminal.

Class III

Luminaires operated on a safety extra-lowvoltage (SELV). The supply voltage down-stream of the operating device must be nohigher than 50 V.

Fire protection symbols

Where LED modules or luminaires are in-stalled in or on furniture, they need to meetcertain thermal requirements and be labelledaccordingly. The following table shows whatthe individual symbols stand for.

To eliminate fire risk, a stipulated minimumdistance from other components needs tobe observed.

Degrees of protection

Not all LED luminaires can be used in abathroom or garden. Pointers for safe op-eration are provided by IP degrees of pro-tection. The first numeral indicates the de-gree of protection against solid bodies andcontact, the second attests to the degreeof waterproofness.

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Standards

Standards set out the requirements thatproducts and services need to meet. LEDluminaires and operative devices, for exam-ple, need to satisfy certain requirements interms of radiation safety. Various standardsneed to be observed both in the productionand in the application of LED solutions:

Luminaires: DIN EN 60598. Luminaires –Part 1: General requirements and tests;Part 2: Particular requirements.

LED modules: DIN VDE 0715-100. LEDmodules for general lighting – Safety re-quirements.

Sockets: DIN IEC 60838-2-2. Part 2: Par-ticular requirements. Section 2: Connectorsfor LED modules.

Operating devices: DIN EN 61347-1.Lamp controlgear – Part 1: General andsafety requirements.

DIN EN 61347-2-13. Lamp controlgear –Part 2-13: Particular requirements for d.c.or a.c. supplied electronic controlgear forLED modules.

EMV-relevant standards: DIN EN 55015.Limits and methods of measurement ofradio disturbance characteristics of electri-cal lighting and similar equipment DIN EN 61547. Equipment for general light-ing purposes – EMC immunity require-ments.

DIN EN 61000. Electromagnetic compatibil-ity (EMC) – Part 3-2: Limits – Limits for har-monic current emissions. Part 3-3: Limits –Limitation of voltage changes, voltage fluc-tuations and flicker in public low-voltagesupply systems for equipment with ratedcurrent � 16A per phase and not subject toconditional connection.

For more information and links about stan-dards and marks of conformity, go to thewww.licht.de website.

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Pole position for the LED. Used for years toilluminate displays, switches and buttons,light-emitting diodes now provide signallight in indicators and brake lights and arealso starting to take off as a light source foroutdoor luminaires. The first vehicles withefficient multichip headlights are already onthe roads.

Agreeable light, optimal visibility

With a colour temperature of around 6,000kelvin, LEDs emit a very bright light thatmotorists find very agreeable. It enablesthem to make out the road ahead, the edgeof the carriageway and any upcoming ob-stacles better at night and is less likely tocause visual fatigue. Studies show that seri-ous accidents at night can be significantlyreduced by the use of higher-temperatureheadlights.

LEDs also set safety standards in rearlights, providing immediate bright light onbraking. The motorist behind thus receivesthe early warning needed for a swift re-sponse. Valuable seconds are saved.

Saving fuel and servicing

Light-emitting diodes have a lifespan ofthousands of hours and save the motoristexpensive servicing and replacementlamps.

Their compact dimensions also permit styl-ish new luminaire designs – from pixelatedlook to luminous front line. Because LEDslend themselves well to dimming, it is possi-ble to integrate a number of functions in a single LED module. Depending on variantand requirements, the range of achievableluminance extends from 125 lumen for single chip modules to 1,000 lumen for five-chip models. With an intelligent control system, brightness can be regulated and is

optimally suitable for all main headlightfunctions from high beam to fog light. Day-light running light can be realised, for exam-ple, by dimming the low beam in the mainheadlight. That makes additional compo-nents unnecessary and saves space in theengine compartment.

One very important point is that efficientLEDs consume a great deal less energythan conventional lamps. This makes aconsiderable difference where daytime run-ning lights (DRLs) are concerned. For safetyreasons, the use of DRLs has been recom-mended in Germany since 2005; as of2011, they are required to be a standardfeature of all new vehicles in the EU. Any-one using special LED luminaires for day-time running light has a lower environmentalimpact and smaller fuel bills than a motoristusing conventional lamps.

Experts anticipate further major improve-ments in the efficiency of LEDs for automo-tive lighting. They already achieve a lumi-nosity of 80 lumen/watt (lm/W) and areexpected to reach 200 lm/W in a few years’time. To give this perspective: a conven-tional halogen lamp produces 23 lumenfrom a single watt of electricity, a xenonburner produces 83 lumen.

“Intelligent” headlights

LEDs will increasingly blaze a trail for intelli-gent front lighting systems capable ofadapting flexibly to motoring needs. Once installed, the light-emitting diodes will permit the realisation of not only high beam, lowbeam and daylight running light but alsosupplementary curve lighting that dispenseswith the complex mechanics and servomo-tors required by conventional systems.

It will be possible in future to drive on highbeam at all times outside built-up areas –


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LEDs for Automobile Lighting Seeing and being seen clearly – optimal lighting is a safety factor at least as important to motorists as effectivebrakes and good tyres. LEDs are rapidly conquering the realm of automotive lighting – as brake lights, daytimerunning lights and in headlights.

even in the presence of oncoming vehiclesor other motorists ahead. This is becauseLED pixels are activated and deactivated in-dividually as required. So we are on thethreshold of having access to the first glare-free high beam that illuminates only the areaof the carriageway where it is actuallyneeded.

Vehicles ahead can thus be simply “maskedout” while the motorist himself enjoys opti-mal visibility to left and right and, thanks tothe bright LED light, is able to recogniseobstacles far more quickly than with con-

ventional low beam light. Such a system re-quires a camera pointed in the direction oftravel and modern electronics networkingthe navigation system with the curve light-ing function and processing the informationfrom light-based driver assistance systems.

In the future, LED technology could thusoffer a standard of safety never achieved inthe past.

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[78] Stylish design and economical on en-ergy: an efficient LED headlight.

[79] High-performance modules permit newapplications, such as daylight running oreven low beam systems based on LED tech-nology.

[80] Customised interior: the LED lightingsuits the style of the vehicle. The colouredlight can be easily changed to meet the per-sonal preferences of the driver.

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80

Light = lamp + luminaire? Not for muchlonger: in a few years’ time, ceilings will radiate colour, transparent glass windowswill spread a subtle warm white light in theevening, office or kitchen wallpaper will turn into a display screen at the push of abutton – and the television set will roll up to fit into a handbag.

What sound like items on a props list for a science fiction film are already a reality for scientists at universities and corpora-tions. OLEDs unlock the door to excitingnew dimensions of display technology andlighting.

OLEDs are the first truly planar light source.Unlike the point light sources realised withinorganic LEDs, they use organic semicon-ductors to produce light. And they offermany advantages:

> They are extremely thin – the entire device is currently around 1.8 mm thick –and thus also lightweight and aestheticallypleasing.> They produce uniform, largely glare-freelight with a high colour rendering index.> They deliver their full light output in-stantly, can be easily and infinitely dimmedby adjusting the operating current and per-mit extremely flexible colour control. > They can easily be incorporated intoother materials, appear transparent or dif-fuse during the day and gleam as bright asday in the evening.> They can be placed close to sensitivematerials and touched without risk ofburns. The light they produce can be con-trolled by a hand movement.> They are environmentally friendly; theycontain neither mercury nor other toxicsubstances and are recyclable.

With these characteristics, OLEDs will notonly transform the design and atmosphereof interiors and outdoor space; they willalso make a significant contribution to envi-ronmental protection.

How OLEDs work

In contrast to conventional lamps, wherecurrent is passed through a wire or gas,the current that flows in OLEDs is con-ducted through ultra-fine layers of organicmaterial – a hundred times thinner than ahuman hair. As a general rule,OLEDs today are basedon small mole-cules

(smOLED);in future, long-chain

polymers (pOLEDs) will be anincreasingly widespread alternative.


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LED Special: OLED – Technology of the FutureSubtle lighting from living room windows, satnav information displayed on the car windscreen: organic light- emitting diodes (OLEDs) open up whole new realms of opportunity for harnessing light – in the home and at work,on wallpaper and fabrics.

81

As Fig. 81 shows, the structure of an OLED resembles a sandwich. The organiclayers are always embedded between twoplanar electrodes: a negatively chargedlayer of aluminium (= cathode) and a posi-tively charged, transparent layer of indiumtin oxide (= anode). The material used forthe substrate at present is generally glass.When a voltage is applied, electrons andelectron “holes” – positive charge carriers –migrate to the middle of the device, recom-bine and excite the embedded molecules,causing them to emit light. As with LEDs,the colour of the light produced dependson the molecular structure of the semicon-ductor used.

Because OLEDs respond very sensi-tively to oxygen and moisture,they are encapsu-lated. On

the rearof the device is

a cushion-like “getter”,which intercepts the moisture be-

fore it can reach the particularly rust-sus-ceptible cathode.

On the way to market

Organic diodes are already usedfor lights in mobile phonesand gameboys. They alsohave a promising future asultra-flat displays for tel-evision – because un-

55

like LCD displays with conventional back-lighting, self-illuminating OLEDs save agreat deal of space and energy. The firstOLED screens came onto the market inearly 2009.

In three to five years’ time, experts reckonthe luminescent plastics will also start theirtriumphant march through the world oflighting. Individual prototypes have alreadybeen presented but more developmentwork still needs to be done.

Major challenges include extend-ing OLED life and im-proving the

gossamer-thinfilms’ sensitivity tooxygen and water.Suitable plasticsneed to be found to protect the sensi-

tive organic layersthroughout their long

life – because as soon asthey come into contact

with water or oxygen, theyrapidly disintegrate.

The development of transparentplastics that provide the necessary

protection will pave the way for flexibleOLED panels – large, uniformly luminous

surfaces delivering light tailored to colourand brightness requirements and capable

of being applied to nearly any surface in vir-tually any shape.

In companies and in national and Europeanresearch projects – such as OLED100.eu –lighting technologists and scientists areworking to drive OLED technology forwardfast. Prototypes today achieve 25 lumenper watt (lm/W) efficiency; in cur-rent research projectsthey even reach

65 lm/W.The second goal

is to increase longevity sig-nificantly beyond the 10,000 hours

achieved today.

84

82 83

[81] Organic LEDs today are generallybased on small molecules. Their structure resembles a sandwich.

[82] A rare sight (for the moment) of OLEDsin action. Organic diodes are the first trulyplanar light source. They will open up a worldof opportunity in lighting design.

[83] Lighting technologists and scientistsare working on OLED development.

[85] LED fashion: Diodes woven into fabriclight up a winter outfit.

Why should LEDs be used for generallighting? Old incandescent lamps cansurely be replaced by energy savinglamps.Energy-saving lamps are still certainly agood alternative to the incandescent lampat present. Eventually, however, they will besuperseded by high-performance diodes,which offer a whole range of advantages:> LEDs will soon be a great deal more effi-cient; in the recent past, the light output ra-tios they achieve have doubled every twoyears, > the lifespan of LEDs today is already fivetimes long than that of energy-savinglamps,> LEDs can produce different light coloursand coloured light and can be both effi-ciently dimmed and dynamically controlled,> LEDs permit directional lighting whereasenergy-saving lamps have a diffuse radia-tion characteristic. With LED luminaires,light is delivered exactly where it is needed.So less light is needed to achieve the re-quired brightness – which saves energy.

Is it true that LED colour rendering is notvery good and that LEDs are only suitablefor general lighting up to a point?No, that is a mistaken belief stemming fromthe early days of LED. LEDs today achievea good colour rendering index (Ra/CRI) inthe 80–90 range. Even values as high as Ra

98 are now attained – which is very close tothe maximum (100) delivered by sunlight.So in that respect, LEDs already outperformenergy-saving and fluorescent lamps.

Isn’t white LED light cold and uncomfortable?Again, this is a common misconception thathas persisted since the infancy of LEDtechnology. Indeed, the opposite is true:LEDs today are available in colour tempera-tures ranging from 2,700 (= warm white) to6,500 kelvin (= cold white).

With special modules, the white light colourcan even be varied at will: from cool whitelight for better concentration in the morningto warm white light for a cosy atmospherein the evening. This flexibility makes the effi-cient long-life LED a particularly goodchoice for general lighting in professionalapplications.

Do LEDs emit IR and UV rays?No, LED light contains no infrared or ultravi-olet radiation. Heat is generated at printedcircuit board (PCB) level but is not radiatedin the direction of the illuminated object. Sosensitive and precious objects in museumsor shops can be strikingly illuminated withno risk of radiation damage.

It is important to note, however, that all visi-ble light is radiation. So even where IR orUV content is zero, it would be wrong toassume that illuminance can be raised toany level. Having said that, however, LEDlight is a great deal gentler than the widelyused light of low-voltage halogen lamps.


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LED Special:FAQs about the Light-Emitting DiodeAre LEDs really at the stage where they can be used for general lighting? And is their colour rendering goodenough? Here are some answers to frequently asked questions about innovative LED technology.

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How long is the lifespan of LEDs? LED luminaires have a very long life – up to50,000 hours or more.

And unlike conventional lamps, LEDs donot fail at the end of it. But even they age.Their light output slowly declines withoutany noticeable change in the subjective im-pression of brightness. However, at the endof their rated life, performance is still around70 or 50 percent. So the LED failure rate issignificantly lower, for example, than that ofcompact fluorescent lamps.

One prerequisite for a long life is preciseobservance of the installation conditions setout in mounting instructions. Economy-priced LED products often fail to deliver thepromised performance because they do nothave sufficient heat removal capacity.

LED solutions are more expensive thanconventional lamps. So is the higheracquisition price recouped, e.g. throughenergy savings? LED solutions work very efficiently and are agood alternative to established systems.However, comparison should not be basedsolely on energy costs. Savings potential isalso offered, for example, by LED longevity:this ensures that light sources need to bereplaced far less frequently and mainte-nance costs can be reduced. What is more,LED solutions offer lots of advantages thatgive them a high added value for particularapplications. Those advantages include reli-ability, dynamic colour and colour tempera-ture management as well as the fact thatLEDs emit neither infrared nor ultraviolet ra-diation.

The use of modern LED technology is in-creasingly promoted by statutory energy re-quirements for buildings and the power con-sumption ceilings they need to observe. Thevalidity of basing appraisals solely on energycost savings is also called into question.

Can LEDs fail completely? Total failure is very unlikely. The statisticalfailure rate is around two in a millionmounted LEDs.

What happens when an LED is defective?Does the luminaire need to be replaced? If an individual LED does fail or an entire lu-

minaire is defective, the maintenance workneeds to be carried out by an authorisedprofessional. In the case of any faults thatoccur during the statutory warranty period,consumers have a right of remedy. Evenafter the warranty period expires, an over-haul should also be possible. This mattershould be clarified when the luminaire ispurchased. Where a component needs tobe replaced, account should be taken ofthe light colour and brightness of the otherLEDs in the system.

Do new LED products differ in terms oflighting performance? What needs to betaken into account? LED development is a process of constantoptimisation, analogous to the rapid ad-vance of the microchip industry. Perform-ance and efficiency are steadily improvingas a result of continuous further develop-ment. Manufacturers pass on these im-provements to the consumer by always fit-ting luminaires with the latest generation ofLEDs. LED luminaire specifications can thuschange. So the rule to remember is: useonly the luminaire manufacturer’s currentdata records.

Do the luminous flux figures given in LEDmanufacturers’ data sheets also apply toluminaires and LED lamps? No, a distinction needs to be made be-tween the luminous flux figures that appearin specifications and the actual available lu-minous flux of an LED luminaire or retrofitlamp ready for use.

The background to this is that the luminousflux figures in data sheets refer to valuesachieved in the LED itself at a temperatureof 25° Celsius. The LED tested is in a “raw”state; it is not mounted on a printed circuitboard and not installed in a luminaire orlamp. For specification testing, LEDs areoperated on currents considerably lowerthan the customary 350 mA or 700 mA –and only for a very short time. The resultsare then extrapolated, which produces val-ues of more than 110 lm/W. Depending onLED type and light colour, temperatures ofmore than 80° Celsius are permitted toreach the lifespan given. In practical opera-tion, these ceilings need to be observedthrough the use of efficient thermal man-agement.

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In practice, therefore, care must always betaken to distinguish between LED manufac-turers’ data sheet specifications and the ac-tual luminous flux of a complete luminaire orretrofit lamp. Reputable suppliers providethese figures; less reputable ones may notdisclose them at all.

Is it harmful to the eye to look into anLED luminaire? No, LED luminaires spread the light gener-ated by a light-emitting diode and presentno problems for the eye. LEDs with a lowpower rating of less than 1W generally fallinto the most harmless LED category (ClassI) and have been classed alongside classi-cal light sources since mid-2008. Becauseof the high luminance, however, it is not ad-visable to stare directly at an LED lightsource for any length of time. Having saidthat, the same advice essentially applies toother, conventional lamps.


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24 Jens Küsters

53 Michael Sazel, Wien

54, 55, 56 Wolfgang Schmidt

66 René Müller

78, 80 Audi AG, Ingolstadt

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licht.wissen 17LED: The Light of the Future

licht.wissen no. 17 "led: the light of the future"

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