Types of LEDs

In earlier times the use of LED was restricted, and it was only available in a small number of designs. Technology has progressed a long way in recent years, and LED is now made in a variety of forms — tubes, reflectors, GLS lamps and spotlights — with a range of fittings such as bayonet and screw caps, and in powers comparable to incandescent bulbs.

Compared with other light bulbs the price is manageable, and it offers a considerable saving on monthly electricity bills. In its most basic form, a light-emitting diode (LED) is a semiconductor device that emits light through electroluminescence: a forward-biased PN junction that gives off light when current flows. Every industry makes use of it, from cars to streetlights, office and home lighting, smartphones and televisions.

Types of LEDs

LED's cutting-edge properties — compact size, sturdiness, durability, long life, low power consumption and fast on/off switching — have led to its widespread use, and brought it to the attention of a very large audience. LEDs are also a popular component in projects by students, engineers and electronics enthusiasts.

1. Dimmable LEDs

Like other bulbs, LEDs can be used with dimmer switches. A dimmer designed for incandescent bulbs does not always work as well with LEDs, so it is best to replace standard bulbs with dimmable LED bulbs, which use far less power.

2. Colour temperatures

LED lights come in three main colours — cool white, warm white and daylight — and each has its place. Warm white, like a halogen lamp, is often used indoors. Daylight LED is meant to emphasise true colour, and consists mostly of a stark white with a hint of blue.

3. LED tubes

LED tubes replace fluorescent tubes, and in some situations are the only option offered. Some designs need rewiring and a new ballast. They are available in every standard size and work by running a string of small LEDs down the length of the tube.

4. SMD LEDs

Surface-mounted diode (SMD) LEDs are widely used in lighting and can be attached to any flat surface. The SMD chips in a bulb provide increased light output and suit both commercial and household use.

5. COB LEDs

Another generation of LEDs, chip-on-board (COB), provides more light than SMD and gives more control over the beam. Measured in lumens per watt it performs well, indicating a high level of efficiency.

6. Graphene LEDs

In late 2015 the BBC reported on LED filaments coated with graphene, which were expected to cut energy costs by around 10% while costing less to make than conventional bulbs. Graphene's practical uses were first discovered by researchers at the University of Manchester, and work on new and durable applications for the material continues.

7. Traditional and inorganic LEDs

The classic LED is made from inorganic materials and takes the familiar form of a diode. Compound semiconductors such as gallium arsenide phosphide and aluminium gallium arsenide are used to make the most common LEDs, and the materials determine the colour of the light.

Inorganic LEDs are the small indicator lights that appear on control panels, and they come in many formats: surface-mounted LEDs, flashing LEDs, multicolour and bicolour LEDs driven by varying voltages, single-colour 5 mm LEDs and alphanumeric LED displays. Ever larger numbers of these inorganic LEDs are expected to become available.

8. High-brightness LEDs

High-intensity and high-brightness inorganic LEDs have begun appearing in domestic lighting and decorative settings. Because they produce light so efficiently, they are quickly gaining widespread use. Getting maximum light output from an LED requires power and current levels within sensible limits, and to reduce the heat given off the LED may be mounted on a heat sink.

In terms of energy saving, the LED is a significant alternative to many conventional light sources, and automatic lamps in the home are becoming widespread. LEDs are superior to CFLs, compact fluorescent bulbs and incandescent lamps in environmental impact and energy efficiency. High-brightness LEDs cope well with being switched on and off repeatedly and last for a long time — though their lifetime still has a limit that cannot be overlooked.

9. Organic LEDs

The organic LED (OLED) uses the same principle as a traditional LED, but, as the name suggests, is constructed from organic substances. Where a basic LED emits light from a PN junction made of doped inorganic semiconductors, an OLED uses thin sheets of organic material, which is what gives a display its diffused, even light.

Mostly it is a thin film printed on a glass substrate, with a semiconductor circuit delivering the electrical charge that makes each pixel light up. LED technology keeps getting better, and it can be used in almost any field.

The wattage of a bulb indicates how bright it is, just as with incandescent bulbs — but LEDs use a small fraction of the power other lights need to produce the same amount of light, which is why they are popular and useful in every industry. They now come in many styles and colours, which helps them keep pace in the very competitive world of electronics.