Automotive LED Lighting Explained
The old and faithful incandescent light bulbs are being forced out of automotive lighting, to be replaced by LED lights. LED is short for Light Emitting Diodes. This is a form of transistor, doped with a substrate that emits light when current is applied. The LEDs have a number of advantages over incandescent lighting that are very attractive for automotive use:
- They are very insensitive to vibrations
- They last for the life of the vehicle (does not apply to headlight LEDs yet)
- They can be baked into moisture proof casings to be installed in all kinds of harsh environments
- They light up much quicker than incandescent bulbs
- They are extremely compact
- They can be made to emit different colors
- They run cool
- They give more light per supplied watt than incandescent light bulbs
There is now LED lighting technology available for every conventional automotive lighting purpose. The LEDs are also creating new light features for automotive purposes, as the LEDs can be installed in ways and in locations that are impossible with incandescent and fluorescent lighting.
Corvette brake lights were first
The first automotive use of LEDs was on the 1984 Corvette, which had a LED center high mount stop lamp. The LEDs are better for stop lamps than anything else, as they light up instantaneously. This gives the drivers behind more time to react to avoid an accident if a car makes a sudden stop. It might seem insignificant that a LED lights up 0.2 seconds faster than an incandescent bulb, but at 75 mph this translates to 21' extra braking distance for the cars behind. This can literally make the difference between life and death.
Changing from incandescent light bulbs to LEDs in the brake light thus is not only a question of styling. It is also an important safety measure.LED brake lights are more or less standard on modern cars. The LEDs also make for development of better brake lights. Some cars now have brake lights that become brighter with increased pressure in the braking system, or LEDs that start flashing rapidly when the car is braking really hard. This gives the drivers behind even better warnings, helping them to avoid accidents.
High cost holds LEDs back
LEDs are also quickly becoming standard technology for rear lights and turn indicators. The only factor that makes car manufacturers hold back on LEDs is that LED lighting still is more expensive than fixtures for incandescent lighting. But their compact format and long life are strong arguments for installing LEDs. After all, it is important to safety that rear lights and turn signals work when they are needed. The long life of LEDs is also a strong argument for replacing incandescent light bulbs in rear lights and turn signals with aftermarket LEDs.
The LEDs that replace conventional light bulbs are made as assemblies of a number of LEDs. There are two reasons for this: The individual LEDs still don't have the same light intensity as an incandescent bulb, and LEDs emit the light in a very narrow angle. Thus, to make the LED light visible from all angles or to make LED fixtures for ambient lighting, several LEDs must be used, emitting light in different directions. One feature of the LEDs that is beginning to transform the design of automotive lighting is their ability to emit light of different colors.
All colors from one light
The RGB LEDs have a design that allows them to emit any color light from the same LED unit. They are either built with three different LEDs combined into one unit, with one emitting red, one green and one blue light, or they are constructed as one LED doped with three different substances that emit red, green and blue light when current is applied. By varying the voltage applied, these LEDs can be made to emit any combination of the three colors. Red, green and blue mixed together at equal brightness is perceived by the human eye as white light, and the eye will perceive other mixes as all kinds of different colors (this is also used in printing, where red, green and blue are used to create all colors in the visible spectrum). The multicolor feature of LEDs makes it possible to make one single strip of LEDs that can perform several functions: to display a red rear driving light, to display a bright, or even pulsating, intense red light on braking, to blink amber on turns and to light up in white for backing up. The LEDs can be made to light up simultaneously as a single unit, or sequentially, to create "running turn signals", all depending on the configuration of the circuitry governing the LEDs. Examples of how this LED feature can be used for practical purposes are the Tailgate LED Light Bar and the Fire and Ice Light Bar by Putco lighting.
LEDs can hide away
The small size of LEDs also makes it possible to make thin strips of lights that can be twisted and turned and placed in locations where there is no room for conventional lighting. The most prominent use of this is in running lights, which can be made not only to make the vehicle visible by emitting light, but also to do this in a shape that provides a unique character to the vehicle. The best known example of this is Audi, whose LED "whiskers" have become part of their trademark. LEDs are ideal for running lights, as they don't burn out, consume very little energy and are maintenance free. Installing aftermarket LED running lights can actually save you money if your vehicle uses the low beams as automatic running lights. With LED running lights installed, you can turn off the expensive incandescent bulbs in your low beams and thus prolong their lifespan considerably. LED strips can even be made so thin that they are virtually invisible when they are not lighted up. The PLASMAGLOW® - Lightning Eyes Headlight Kit is one example. This strip can be mounted in the small space between the headlight and the body and is hardly noticeable when the car is parked. The LED strips are widely used by both vehicle and aftermarket manufacturers for under dash lighting, door lights and foot well lights. They are used as side markers and contour lights on emergency vehicles, trucks and custom builds.
Headlights are next
LEDs are also beginning to substitute headlights, with the 2007 Lexus LS600 hybrid being the first vehicle to use LEDs this way. The brightness of LEDs has now reached levels that make it possible to use them for this most demanding of automotive lighting fixtures. As the prices of LEDs go down, more LED headlights are certain to be installed, substituting incandescent bulbs. There are however many problems to be solved before LEDs becomes the preferred source of light in headlights. Even though LEDs run cooler than incandescent bulbs, they emit less light when the temperature goes up. As even LEDs get pretty hot when you apply the power needed to emit the lumens necessary for headlights, it is an uphill battle for developers to make LEDs that emit a lot of light. The other obstacle is that without manipulation an LED emits light through a very narrow angle.
The LED headlights made today combine advanced LED design with advanced optical design and intricate cooling devices to perform adequately. This gets very expensive. However, with the rapid development taking place in the field, there is no doubt that we will see new and more efficient LED headlight designs very shortly.
The future belongs to LEDs
The incandescent bulbs haven't really developed that much in the 140 years they have existed, while the development rate of LEDs is very rapid, with LED performance being doubled every 36 months, a development rate that is similar to the fast pace of computer development. There is no doubt that the future of automotive lighting belongs to the LEDs.
by Justin Gazzara on