Light Emitting Diodes, or LEDs, have been used for some time in various automotive applications such as warning indicators and alphanumeric displays. More recent developments in LED technology have seen the production of a wider range of colors, and LEDs that are brighter than previous types.
It is now possible to get bright red, green, blue, yellow and clear or white light LEDs. This has made it possible to use LEDs for many new applications, such as more general lighting applications. For example LEDs can now be used for stoplights, indicators and interior lighting on vehicles.
One of the advantages of LEDs is that they turn on instantly. This is particularly useful in brake lights as they can reduce the braking response time by 2/10th of a second. This translates to an extra 16 feet or 5 meters of stopping distance at highway speeds. LEDs also have better visibility in poor weather and they can last up to 100 times longer, reducing the cost of servicing.
LEDs can be specifically designed for LED lighting and also as LED replacement bulbs for more traditional bulb holders.
For automotive applications a number of LEDs are grouped together to provide the amount of light required for the application. Additionally LED light lenses are specifically designed to get the most out of the available light.
An LED is like a normal diode and only passes current flow in one direction. This means they are polarity conscious. When an LED is forward biased, current flows through it and it emits light. So it is essential that when the LED is coupled to an electricity supply, it must be done in the correct polarity in order for the lights to work. A typical LED has a voltage drop of 1.2 volts across it when it is forward biased and emitting light.
When used in automotive lighting, many LEDs are required to give off the required amount of light. To do this they are usually connected in groups called series strings. A number of series strings are then connected in parallel until the necessary number of LEDs are connected to give off the required amount of light.
LEDs work best when the voltage to them and the current flow through remains constant at a preset level. There are two main ways to achieve this; the first is via a resistor. The second and more preferred way is through the use of a voltage regulation circuit.
Some LED lights are multi-voltage, this means they can work on both 12 and 24-volt systems. These are normally used in aftermarket products, which are able to be fitted to a wide range of vehicles.
