Light Emitting Diode

A Light Emitting Diode or LED is an electronic component that converts electric current into visible light through compound semiconductors. LEDs are low-maintenance, robust and have a very long lifespan. They are extremely small, consume very little energy and produce high light output. On top of this, they do not emit any IR or UV radiation.

Like a normal diode, the LED consists of a chip of semiconductors to create a p-n junction. Current flows easily from the p-side (anode) to the n-side (cathode) but not in the reverse direction. Normally it is used with constant current or constant voltage including series resistance.

LED lighting is the future. Significantly reduced power consumption and longer maintenance cycles make for considerable cost savings in the long run. Added to this, they are far more durable and versatile than glass bulbs and tubes, opening up many new lighting opportunities.

Henry Joseph Round first discovered the effect of electro luminescence in 1907.

In 1962, the first practical visible spectrum red LED (GaAsP) was developed and launched.

More colours of LEDs were developed in the 1970s and efficiency and performance continued to be improved.

The first white LED was produced in 1991 and it was launched two years later.

In 2003, warm white (>2.800K) and neutral white (>3.300K) LEDs entered the market.

The “T” stands for “tube” and the number represents the diameter of the tube in inches. A T2 miniature fluorescent lamp has a diameter of 2 inches or 7mm, a T5 fluorescent lamp has a diameter of 5 inches or 16mm and a T8 has a diameter of 8 inches or 26 mm. The T4 fluorescent lamp with a diameter of 13 mm is relatively new, but it is not standardised, meaning that some lamps of the same wattage are offered in different lengths by different manufacturers.

A Lux (lx) is a unit of measurement for light output. It indicates how much light reaches a specific area.

A Lumen (lm) is a measure of the perceived power of light. Lumen is defined in relation to the candela.

1lm = 1cd*sr

e.g. a 25W incandescent lamp = 230lm. A 20W fluorescent lamp = 1.250lm

Lumens per watt (lm/W) is a ratio of light emitted from a light source to the electric power consumed by the source and thus describes how efficiently the source provides visible light from a given amount of electricity.

Color Rendering Index (CRI) is a measure of the ability of a light source to reproduce the colors of objects faithfully in comparison with a natural light source.

Beam angle refers to the width of the light beam produced by a light source. Smaller beam angles (25 degrees or less) are best used as spot lights while larger beam angles (45 degrees and above) are better suited to downlights and ceiling lights as they can cover a larger amount of space.

The color temperature of a light determines the color of its light. Warm color temperatures (2700K-3000K) appear to have a yellow hue while lights with high color temperatures (5000K) have a blue tint.

Each color temperature has its own unique qualities and uses:

Soft White (2700K)

Soft white lights provide a wonderful warm glow. These color temperature is perfect for living areas or any other place you like to kick back and relax

Bright White (3500K)

Bright white lighting is ideal for any space where detailed work is done. This includes the kitchen, hobby rooms, the garage, and the basement.

Daylight (5000K)

The blue hue of daylight lights is great at encouraging productivity and is tailor made for reading. In addition, the bright light closely imitates natural daylight to create a lively atmosphere.

The average rated life is the average life expectancy of individual lamps operated under normal conditions.  At this point 50% of the lamps have failed. Some will have failed sooner, others much later.

We assume that 10% of ballasts will fail after 30,000 hours when they are operated between 40-50°C. Their lifespan can be doubled by operating them at just 10°C lower e.g a device with an imprint of ta 40°C is operated at 20°C = 10% loss after 120,000 hrs.

If no temperature or safety class is specified, then a maximum temperature of ta 25°C IP 20 applies.

Yes, with the dimmer switch approved for the transformer being used i.e. a leading edge or a trailing edge phase dimmer.

Yes, some heat is generated by the LED diodes, but the light is designed to dissipate this heat very quickly to protect the electronics. It doesn’t feel hot under the light beam of an LED.

LEDs consume significantly less power than incandescent bulbs or halogen lamps. Up to 90% of the energy used is converted into visible light. Even so-called “energy efficient lights” are much less efficient than LEDs. LED lights have the world’s lowest power consumption and longest service life -a combination that could not be more economical.

Yes, LEDs can be used to illuminate any room just as brightly as conventional bulbs.

There are large differences in the energy efficiency, light output, lifespan and ability to recycle. An energy saving bulb uses mercury and must be disposed of carefully. Furthermore, energy-saving lamps generally have a light output of only 10 percent, and a burning time of 12,000 hours compared to an LED with an output of 30 percent and a lifetime of 35,000 hours.

No, definitely not. Unlike some bulbs, which can take over a minute to build up to full brightness, LED lights shine at full brightness as soon as they are switched on.

The lifetime of an LED depends on the ambient temperature. At room temperature LEDs can operate for up to 50,000 hours lifespan. Usually the light output degrades slowly until it reaches 50% of its original output. This is considered the end of the LED’s lifetime.

Watts are used to measure energy consumption. Lumens are used to measure light output. Historically, incandescent bulbs have been categorized by their wattage. However, modern lighting devices such as LEDs and CFLs are able to produce more light with far less energy. To regulate which bulbs are truly the brightest, government regulations now mandate each lighting product provides its light output measured in lumens.