Facts about LEDs

Lights of the future
LEDs are the light sources of the future, and more and more people are using them for lighting – both indoors and outdoors.

Even today, LEDs for professional lighting are 5 times as energy efficient as conventional incandescent bulbs, and colour rendering is on a par with fluorescent tubes. As a rule, LEDs have a lifetime of between 25,000 and 50,000 hours – depending on how they are managed. Moreover, LEDs are more robust than ordinary light sources because they do not contain any filament or glass.

The use of LEDs for lighting has been limited up to now, mostly because LEDs have not been sufficiently energy efficient and did not emit enough light. Also, colour rendering has not been good enough. However, there have been significant improvements in recent years.

LEDS are interesting as light sources because they:

• Light in a forward direction
• Have a long lifetime
• Provide full strength immediately
• Can be dimmed without change in colour (however, dimming requires suitable electronics in the driver)
• Do not radiate any infrared (IR) or ultraviolet (UV)
• Are energy efficient
• Are mechanically robust
• Are small
• Tolerate very low temperatures
• Can provide very saturated colours
• Do not contain mercury
• Can provide energy savings

Energy efficiency
Commercially available LEDs are 5 times as efficient as incandescent bulbs, 3 times as efficient as halogen bulbs, and equal to energy saving bulbs – with an efficiency of typically 50-60 lm/W.

Energy efficiency of a light source is calculated by looking at the quantity of light emitted by the light source (the lumen package), and the energy consumption of the light source (in Watts). Energy efficiency is stated in lumen per watt (lm/W). When calculating the energy efficiency of a light source, you should remember that the energy consumption of a light source includes the power loss in the transformer, electronic ballast unit or driver.

Switch on instantly
LEDs switch on instantly and provide their full strength immediately. In the long term, the small components in LEDs are suitable for dimming the lights, and the light doesn’t change colour when dimmed, which is what happens with incandescent and halogen lights. Nevertheless, LED bulbs sold on the market today are not capable of being dimmed, because they do not yet contain the necessary electronics.

Colours
The colour properties of a light source are relevant to white light, and are described as colour temperature (expressed in Kelvins, abbreviated as K) and the colour rendering index (CRI) or Ra index. The CRI ranges between 0 and 100 and indicates how good a light source is at reproducing a number of reference colours. A CRI of 100 is the best.

The light from LED sources is either warm (typically 2,700-3,000 K), neutral (3,500-4,500 K) or cold (4,500-10,000 K). A comprehensive selection of LEDs is available with a CRI of over 80. The best LEDs have a CRI of over 90.

Lifetime
LED lifetimes vary considerably but as a rule are between 25,000 and 50,000 hours. The lifetime depends to a large extent on how they are managed. High temperatures and high current loads can quickly take their toll on an LED, which in many ways resembles an ordinary electronic component.

LED light transmission
LEDs project all their light forwards, whereas the most common light sources emit light in all directions. This is why LED bulbs are best suited to lamps that project light in one direction, such as spot and pendant lamps that solely light downwards. LEDs will not usually be suitable for fittings which have a transparent shade or which in some other way are designed for light sources that emit light in all directions.

The forward directed light from LEDs makes them suitable for lighting in signs. LEDs are also suitable for special lighting, for example lights integrated into railings, balustrades or buried in the ground. LEDs also make it possible to design very small and flat fittings.

Safety
The concentrated light from LEDs means that the light can be very powerful. Today, LEDs belong to the same category as lasers in terms of safety. In the EU, products must be CE marked and need to conform to the EN 60825-1 standard (Safety of laser products). This means that you should be aware of the risk of eye injuries. This is particularly relevant as LEDs become more powerful.

You can risk damaging your eyes by using LEDs in equipment with optics and lenses. You should therefore not look directly into an LED at close range.