LED Lighting

LED lighting uses solid state (electronic) devices to produce light, rather than by heating a thin wire (incandescent) or creating an arc in a tube (fluorescent). The technology has been around for many years, but light output, cost and colour has always been the thing that has prevented its widespread adoption for general purpose lighting. While things are gradually improving in these areas, there is still a long way to go and it is as well to understand what is and is not possible with LED on a realistic budget.

What is LED really good at?

LED is a fantastic solution for accent/highlight applications where a small light source is needed to illuminate a feature in a room. It is also very good at colour washing over larger areas and, as LEDs can be arranged in spotlights, in linear strips or even in circles and irregular shapes, large areas can be washed in this way.

LED is not currently effective for general lighting applications for the following reasons:

• The white light does not have good colour rendering. Even the warm white LEDs have a peculiar quality of light which, while attractive for specific highlights, is not good for general illumination.
   
• The efficiency of LED at higher power levels is currently not dramatically better than normal halogen, which they would tend to be replacing in this application. LED manufacturers often specify efficiency figures that only apply when the LED is running at low power and low light output. As the light increases, the efficiency drops. This is beacuse the LED does not like to get hot, and keeping the temperature under control in a restricted space is difficult. Additionally, the size of the LED itself makes dissipating the the heat very difficult. Be aware that the light outputs and efficiencies for white LED are normally quoted for the cool white, while the warm white (more desirable for general lighting) has lower efficiencies.
   
• The best commercial products are around the equivalent of a 35W low voltage halogen lamp (20W high efficiency halogen such as Philips ES or Osram IRC), yet consume only 7.8W, plus a bit for the driver. Certainly a worthwhile saving, if the light quality is acceptable and the costs (£80 for the lamp, plus the driver costs which average about £30 per lamp) are not an issue. Contact JCL if you would like to use this type of LED in your project, and we can advise on suitability and costs and the correct drivers, wiring scheme and control equipment.

Types of LED

There is not really a [non-technical] standard for LED, in the same way as for 12V halogens (for example) where a lamp from Osram will work with a transformer from any of hundreds of manufacturers. For this reason, it is usual to obtain the power supply, or driver, for the LED from the same place as the fitting itself. It takes a good level of technical understanding to be able to mix and match across manufacturers with any level of certainty.

One common type is the 350mA constant current device, often referred to as 1Watt, 350mA, Luxeon or LumiLED which are used in a wide range of products. These are wired in a specific way and are fully dimmable with special drivers. They are often combined in Red,Green, Blue sets allowing colour changing (by varying the proportion of each colour into the mix). There are higher power 700mA, 1000mA and 1500mA types.

Several manufacturers offer complete solutions of lamps and drivers, but with an industry standard control connection such as DMX or 1-10V. Again, these are dimmable with the correct equipment and are commonly available in single colour and colour changing.

Mains powered LED are the simplest to install, simply replacing a normal mains lamp. Other than the ease of connection, there is not often much to recommend these type of LED. They rely on internal power supplies, to convert from mains (240V AC) to the few volts DC that an LED needs. This small, cheaply produced power supply is normally the weak part of the design and is prone to regular failure.

Here are some links to LED suppiers that we think have interesting products.