Automotive Electronics


Basic Description

Headlights illuminate the road when the ambient light is insufficient for safe driving. Typically, these lights are mounted near the front bumper of the car and have both low- and high-beam settings that control where the light is aimed. The low-beam setting aims the light down at the road in front of the vehicle to avoid blinding the drivers of vehicles in oncoming traffic. The high-beam setting aims the light straight ahead and is used when the low beam setting does not give enough visibility or when driving on rural roads when there is no oncoming traffic. Headlights normally have a range of about 1000 ft over an area of about 10 to 15 degrees out from each front corner of the vehicle. There are various types of headlights employing different bulb technologies. These different bulb technologies are described below:

Incandescent bulbs: The oldest electric light source, incandescent bulbs consist of a wire filament that heats up and glows when current passes through it. The bulb contains a gas that displaces all the oxygen surrounding the filament and prevents it from burning up (at least for some time). Most incandescent bulbs have a filament made of tungsten and employ argon gas. Incandescent bulbs operate at relatively low efficiency compared to competing lighting technologies. There is also a trade-off between efficiency and the expected life of the bulb. For the first 60 years of automotive history, virtually all electric lights in an automobile were incandescent bulbs. Today, incandescent bulbs have been largely replaced by other lighting technologies.

Halogen Lamps:  Halogen lamps generate high levels of luminous power from relatively modest amounts of electrical power compared to incandescent bulbs. Like an incandescent bulb, they have a tungsten filament surrounded by a gas. However, the halogen gas in a halogen lamp allows the tungsten to be heated to much higher temperatures without burning up. The higher temperature causes the filament to emit much more light for a given amount of current passing through it.

Gas-Discharge Lamps: Gas-discharge lamps do not employ a filament. Instead, the light is created by an arc that forms in a gas between two electrodes. As electricity flows through the gas, the gas is energized and light is emitted. The most common gas used in these type of automotive headlamps is xenon. These lamps are often referred to as High Intensity Discharge (HID) lamps or Xenon lamps. They employ a ballast to generate the very high voltages required to make the lamps work and often require a warm-up time to reach full output. HID lamps use less power and put out more light than their halogen counterparts. HID lamps tend to be expensive and are mostly found on higher end automobiles. However, aftermarket HID conversion kits are available to retrofit older cars with these high output headlights.

Light Emitting Diodes: LEDs are semiconductor devices that emit light. They do not employ filaments or gas. They are highly efficient, durable and relatively compact. Permanent degradation of LEDs can take place if operated above the maximum junction temperature for a long period. Arrays of white LEDs have recently been introduced for use as automotive headlights, however the extensive amount of heat sinking required to keep the LEDs cool enough to function reliably makes the cost of LED headlights high relative to other options.

Lasers: Laser headlights bounce blue laser light off a set of reflectors through a lens containing yellow phosphorous creating an intense diffused white light with twice the range of LED headlights. Laser headlights have the potential to be about 30% more energy efficient than LED headlights. Audi and BMW were the first OEMs to offer this technology in production vehicles. BMW offers laser headlights on the i8 plug-in hybrid. Audi employs this technology on a special-edition R8 LMX for European markets. Currently, NHTSA regulations restricting headlight design effectively prevent laser headlights from being offered on cars sold in the U.S.

Auxiliary Headlights

Pencil Beam: These lights are usually purchased and installed aftermarket and are illegal for on-road use in some jurisdictions. These lights usually employ Halogen or HID bulb technology and have a discharge pattern that is very focused. This allows the beam to have an effective range much longer (up to 2000 ft) than that of the standard headlights and allows the driver to see objects much further down the road. This can be an advantage when racing on- or off-road at night.

Flood Beam: These lights, like the pencil beams are purchased and installed aftermarket. These lamps can also employ Halogen or HID bulb technology. These lights have a very wide illumination pattern and are used to 'flood' the area near to the car with light to improve visibility. These lights have a similar range and function to normal headlights and are used to backup the regular headlights or to provide light in addition to the regular headlights.

Fog Lights: These lights can be offered as a dealer option when one buys the car or can be added to a vehicle aftermarket. These lamps can use different bulb technologies and can be different colors such as yellow or blue. Yellow light is used because it can aid visibility in fog. Blue light is used because it can help increase visibility in rain. Fog lamps are located in the front of the car low to the ground and are aimed slightly towards the ground to improve visibility in foggy, rainy or snowy driving conditions.

Bosch, GE Lighting, Hella, Ichikoh, Koito, Magneti Marelli, North American Lighting, PIAA, Philips, Stanley Electric Co., SL America, Sylvania
For More Information
[1] Head Lamp, Wikipedia.
[2] Car Headlights, May 7, 2006.
[3] 2010 Audi R8 LED Headlights - Tech Dept., Car and Driver, Sept. 2009.
[4] Xenon vs. Halogen, YouTube, Apr. 16, 2009.
[5] BMW’s Laser Headlights, MotorTrend, Oct. 14, 2011.
[6] BMW i8 with Laser Lights, YouTube, Apr. 27, 2014.
[7] 470project, YouTube, Apr. 23, 2015.