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Theme: lighting and electrics

A new generation of light-emitting diode technology is building on its recognised reliability and long life, increasingly becoming the lighting of choice for discerning designers and architects in need of both high performance and aesthetics What is an LED?

A light-emitting diode (LED) is a special type of semiconductor device consisting of a chip of semi-conducting material impregnated or doped with impurities to create a structure called a 'pn junction'.

As current passes through the LED, the materials that make up the junction react and light is emitted. The wavelength of the light, and therefore its colour, depends upon the band-gap energy of the materials forming the pn junction.

Basically, it is a solid-state component that uses electricity to make light. LEDs do not have a fi lament that will burn out and do not get especially hot.

Applications Early LEDs were only bright enough to be used as indicators, for instance in the displays of calculators or digital watches.

LEDs have been used successfully as industrial indicators for the past three decades, and electronic designers have long understood their basic appeal.

New-found LED performance levels have resulted in a whole new range of LED applications, and our world is now bristling with LEDs. On our roads, 50 per cent of European cars have LED panel illumination, many have LED brake lights, some have LED headlights, and traffic lights are being converted. Our mobile phones use LEDs for LCD illumination, and LEDs are also being used in an increasing number of advertising/ POS (point of sale) and signage situations.

Now we have the visible spectrum and increasing brightness levels (LEDS are becoming approximately twice as bright every 18 months or so). We can now therefore use LEDs in a wide variety of applications including cinemas, theatres, hotels, bars and clubs.

Exterior applications Before we begin, it is useful to clarify 'Lumileds' and 'Luxeon' as references because these crop up frequently. Lumileds Lighting is one of the leading manufacturers of high-power LEDs. The company's patented Luxeon Power Light Sources are the fi rst to combine the brightness of conventional lighting with a small footprint, long life and other advantages of LEDs.

(Lumileds is a joint venture between Agilent Technologies and Philips Lighting. ) Lumileds Luxeon LEDs played a significant role in the lighting of three of Glasgow's bridges over the Clyde. Philips' LEDline, using high-power LEDs, was selected for its ability to create intense effects, with the advantages of extra long life, cool running and simple maintenance.

The bridges are lit by LEDline 1.2m linear floodlights, each containing four modules of 12 high-brightness Luxeon Star 1W LEDs.

Unlike ordinary LEDs, Lumileds Luxeon LEDs contain heat sinks to increase powerhandling capability and therefore light output. Because the light-emitting area of an LED is small (typically 1mm 2), precise optical control is possible. Although lens systems can be designed as part of the LED module to focus the light, in the case of the LEDline fl oodlights, an optical system has been built around the LED.

The LEDline has a unique optical collimator (lens), designed to capture efficiently the light emitted by the Luxeon LED and focus it into an intensive tight 2 x 3° beam.

Spacing and light distribution are designed so that the floodlight appears to project a continuous linear sheet of light. The result is a beam that has the power to wash concave curved surfaces up to 20m away. This enables the LEDline to create a blanket lighting effect on the under-arches of the bridge, grazing the surface to reveal the form and texture in a way that would be impossible with any other luminaire/light source combination currently available.

Similar to Philip's LEDline is Crescent's CL, which uses Luxeon Star LEDs.

This linear LED colour-change system can be surface-mounted or concealed to provide bold washes of coloured light. The system is resin-fi led to achieve an ingress protection of IP68, so it can be used outside to wash coloured light over building exteriors, facades and gardens.

Cube Lighting's Portal is an IP 54 wall-mounted floor washer housing a single Luxeon LED, either 1W warm white at 3,200K or Luxeon III (700ma), which is equivalent to 2W.

This is a perfect example of how LEDs are taking over from fi bre optics. This product can only really be used for effect and, as fi bre is an expensive, though impressive feature product, this offers a viable alternative.

The costs of Lumileds can be high, depending on the luminaire and LED confi gurations. Lighting control can also be complex. Simpler LEDs that are less expensive and easy to control are available in a range of saturated colours (currently about 16). These are available from a number of sources, one of the biggest being Nuchia in Japan. These LEDs have a good output and look like the small domed LEDs of old. A number of luminaire suppliers use such LEDs in their products.

The Light Projects Group has launched a unique LED colour-change floodlight - the CFL Colour Changer. The innovative 266 x 152mm floodlight works in a similar way to a television set, where combinations of red, green and blue from high-power LEDs are mixed to produce virtually any colour.

The new-generation LEDs used in the CFL Colour Changer are extremely powerful (approximately 40 times more light than that of conventional LEDs), and have an extremely long life (50,000 hours) and low lumen depreciation. In addition, they contain no glass or mercury, and are both shock and vibration resistant. The integral driver unit mixes light output from each LED, creating strong saturated colours without the losses associated with conventional fi ered light. Full DMX Control provides huge flexibility including 0-100 per cent dimming, switch-on at any level and pulse switching.

Light output from each LED is concentrated using a newly developed 'columator' device. This is a small prism of PMMA plastic, which is placed over individual LEDs to focus the beam into a 10 ° spread.

The CFL LED colour-change floodlight now lights the domes of Whiteleys shopping centre in London's Bayswater, (original concept by Speirs and Major, Lighting Architects Group, with design development by consultants Rybka).

Interior applications LEDs are highly suitable for interior applications including domestic, retail and leisure. ACDC Lighting, Lutron and Vos Solutions created the first fully dimmable and chromatically controlled RGB LED lighting apartment, the Vos Pad in Chelsea Harbour. This used several ACDC architectural lighting products based around the high-brightness Luxeon LED.

Atlantis was used in-ground throughout the apartment to bathe the walls in coloured light. The micro aluminium fitting Minicubeus was used in the bedroom and living areas, to create a stunning visual effect that utilised the powerful light output from the single Luxeon source.

LEDs are also perfect for leisure spaces - Light Engine recently lit the Lonsdale Bar, Notting Hill, London.

The products used included bespoke colour-mixing LEDs in the banquet seating area - individual red, blue, green, chromaled diodes are operated via an analogue dimming system that allows accurate control of the intensity of each colour.

Hoare Lea Lighting specified colourchanging LEDs in the Gibo clothing store on London's Conduit Street. Supplied by NJO Technology, these light the skylight at night. The LED strips can be set on any colour, thereby distracting the visitor from the 'black hole' effect of the skylight at night while also creating a dynamic feature that gives interest to the casual viewer.

Hoare Lea Lighting also used NJO's Aurora linear LED arrangement within the main street/atrium area of the new mathematics and statistics building at the University of Warwick. These units were positioned alongside structural elements to add gentle touches of interest into the space.

RGB LEDs have been used, allowing colours to change during the course of the week.

Emergency lighting LEDs are also suitable for emergency lighting. ETAP Lighting's K9 is one of the slimmest emergency-exit signs on the market. It incorporates the latest LED technology, and the LEDs are available with a choice of three or 10 years' life. K9 has a choice of surface, suspended and recessed mounting options.

Automatic self test comes as standard, or it can be linked into ETAP Safety Manager, a central management and control system.

Cube Lighting's Exodus range of emergency fittings also use LED sources. Instead of depending on short fluorescent tubes or halogen lamps maintained by NiCd batteries, Exodus uses high-output LEDs operated via advanced electronic control by NiMH batteries.

Exodus benefi ts from the reliability and long life of the light source, coupled with the environmental and performance benefits of the batteries.

A motherboard containing selfdiagnostics checks the operation of the LED array, battery pack and charging circuit. In normal operating conditions, a central bi-colour LED provides a green signal for easy visual checks, confirming that all components are operating normally.

If a fault is detected, this LED flashes red to indicate that attention is required. The circuitry also contains a switched power supply for maintained operation, providing practical security lighting.

Eness Lighting Systems, in conjunction with Fagerhult, has developed the emLED.

This is based on the use of a high-intensity LED, which has advantages for life span, size and personal safety.

EmLED increases personal safety because the emergency light is created from a light source with an extremely long life - the risk of the emergency light failing due to a burnt-out light source is virtually non-existent. EmLED also provides a signifi cantly improved lightinglevel balance compared with conventional emergency lighting systems. Additionally, new emergency lighting possibilities using emLED are available for luminaires that cannot normally be equipped with emergency lighting, either via a centralised or decentralised system. This includes luminaires containing light sources that do not instantly re-strike, and also where heat or available space may be prohibitive.

EmLED can offer a small, discreet means of allowing emergency lighting to be housed within a luminaire or surface-mounted/ recessed on a ceiling.

That's entertainment Of course, LEDs are great for entertainment purposes, possessing the ability to turn ordinary spaces into mesmerising environments. The range of visual effects that can be created makes LEDs suitable for a variety of applications - from shows to concert tours to architectural installations.

The iColor Tile FX from Color Kinetics is a 60 x 60 cm 'tile' that applies custom Chromasic technology to individually controlled 144 tri-colour LED nodes for effects and installations in decorative wall and ceiling applications.

Element Lab's Versa Tile received the Debuting Product/Promising Prototype of the Year award at the Entertainment Technology Shows-LDI 2004. Each tile is edge-lit by LEDs to give smooth light output. Like building blocks, tiles can be placed together in any configuration. LED video display technology enables Versa Tile to produce a broad spectrum of rich, saturated colours - as well as flesh tones, browns and greys.

Advantages of LEDs

l Flexibility and improved aesthetic design advantages;

l Size - their high intensity, low weight and volume enable designers to make maximum use of tight spaces;

l Accurate colours (although 'white' is still elusive, both in colour rendering and temperature);

l Monochromatic light - less chromatic aberration in the lens compared to white light sources;

l Long life - up to 100,000 hours (that's 11.4 years! ) of continuous use;

l Low operating temperature, cool, safe to touch;

l Safe, low-voltage power consumption;

l Ten to 50 times more energy efficient than tungsten, reducing operating costs by up to 90 per cent;

l Allow dimming to zero output;

l Almost nfinitely switchable with instantaneous 100 per cent output;

l Fast response time, no flicker, just pure dramatic light;

l Quality light output, minimum ultraviolet and infra-red radiation;

l More durable than conventional bulbs, good resistance to temperature extremes, shock and vibration;

l Can be pulsed or flashed;

l Excellent colour-mixing possibilities - over 16.5 million colours by combining red, green and blue;

l Maintenance-free, just 'fit and forget';

l Exciting new possibilities in an ever-increasing range of lighting applications.

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