Shed Some Light

Looking on the Bright Side


You are driving your car down a lonely country road at 11:00 pm. The road is winding back and forth but you cruise along at a comfortable and steady 45 mph. You probably have the stereo on playing some personal selection from your iPod, or perhaps you are listening to some off the wall talk radio show about aliens from outer space. Either way your drive is no problem. Even when a deer jumps out in front of you, the animal is easy to spot, so you just slow down a little and the thing gets out of the way.

The thing that makes this leisurely drive possible is the headlights of your car. These lights are usually taken for granted despite the fact that without them your car becomes completely useless literally half of the time. Imagine making the same drive with no headlights. How long would you be able to drive before your car is in the ditch? With these two simple electrical devices on the front of your car you can see just about everything that you need to in order to keep the situation under control.
Headlights are almost as old as the automobile itself. They were applied to some of the very first cars in the form of kerosene burning lamps. Over the years headlights have changed substantially but on the other hand they have stayed the same. They always come in pairs and they are always in about the same place on the front of the car. They have high beam and low beam modes in which they operate, and they actually add something to the overall looks of the exterior of the vehicle in a way that not many other features do.

Let’s have a look at some of the different headlight designs, and some other features that are becoming more and more common each year.

Sealed Beam

These are the old style headlights that were essentially the same from the 1930’s to the 1970’s. The filament is tungsten like most other bulbs, and in later sealed beam head lights the filament was surrounded by halogen gas to make the light brighter, and help the filament last longer.
Seal beam headlamps

These headlights incorporate the filament, reflector, lens, and housing all into one unit. Some of them have the high beam and low beam filaments together in the same housing as well. This means that the entire assembly must be changed if the filament burns out. The angle of the beam is adjusted by moving the position of the entire assembly.

These lights are cheap to replace even if everything is combined into one unit because for years and years the design of the seal beam headlight didn’t change. They were all round pretty much from the time they were invented until engineers at GM came up with the revolutionary idea of making them square. Once the square ones caught on then all of them were square. Considering all of the many different designs that were found on various makes and models between the 1930’s and the 1980’s, it’s funny to think that the headlight shape hardly changed at all.

Composite Halogen

The composite headlamps that are found on 90% of cars today use a halogen bulb similar to the sealed beam headlights, except the lens, reflector, and housing are a separate assembly from the bulb. This means that the bulb alone gets replaced when it burns out. This is also the reason that so many different headlight designs exist today. These separate bulbs are easy to replace, and only a few different bulb designs can suit the needs of the many different shapes and styles headlight assemblies.
Composite headlight assembly.

The bulbs are just halogen bulbs but the reflectors vary substantially. Some halogen bulbs use a projector beam reflector and lens to concentrate the light from the bulb. These are the headlights that actually appear to have a small, dark, round lens behind the main outer lens when the headlights are not on. Sometimes these are confused with HID headlights but they are not the same. HID or Xenon headlights are explained below.

The bulbs in the composite headlight assemblies are easy to replace but caution should be taken when servicing these bulbs. If you touch the glass part of a halogen bulb, the bulb will burn out very easily. Oils from your skin, no matter how clean your hands are, will cause the glass the get even hotter than it already does under normal circumstances. This will actually melt the glass and cause the bulb to pop.

Sometimes the regular halogen bulbs that are car uses are not bright enough. The aftermarket has a few products that can actually make the headlights brighter. One of them is the Sylvania Silver Star bulbs. These bulbs are not cheap considering that a pair of them will set you back about $50. They are very bright and will help you to see better at night.
Two headlights are shining on this door form the same vehicle. The one
on the right is a conventional halogen bulb and the one on the left is a Sylvania
Silver Star halogen bulb. This is not a paid endorsement but a photo actually
taken by the author of this article.

HID/Xenon

These are those headlights that appear different than other headlights when you see them from a distance. They will usually have a blue tint to them that is bluer, the farther away the vehicle is. As the car gets closer the light becomes whiter. These lights will always use a projector beam reflector and lens to direct the light from the bulb.

An HID headlight. The one on the left is the HID used for low beam. The one on the right is halogen used for
high beam. This configuration is sometimes referred to a bi-xenon.

The bulb does not contain a filament like the sealed beam or the halogen bulbs. The HID bulbs actually produce light by arcing electricity from one electrode to another within the bulb. The light is literally emanating from the electric arc rather than from a glowing piece of wire. In order to make this work a ballast is used to step up the 12 volts from the vehicle’s electrical system to a level high enough to make the jump. These types of bulbs take a second to actually come on because it takes a moment to build the necessary voltage within the ballast. An igniter is used to make the initial ionization of the air molecules between the electrodes in the bulb. Once the arc has jumped the ballast provides the increased voltage to maintain the arc. The bulb is filled with xenon gas that helps the arc to be even brighter. These bulbs are about $200 to $300 a piece, but they last much longer than a regular halogen bulb.


HID headlights are somewhat controversial because they are brighter than halogen bulbs. Some people complain that when they approach another car with HID headlights, they are blinded by the extra brightness coming from these lights. Because of this many vehicle with HID’s will have a self-leveling mechanism that corrects the angle of the reflector when needed. If something heavy is placed in the trunk, or if you are hauling around your 300 pound sister, the back end of the car will sag. This makes the headlights tilt up which makes the headlights more blinding to oncoming traffic no matter what kind of headlights you have. Most HID headlights will have a sensor that can determines when the headlights are not level or pointing in an upward direction and a small motor will activate to tilt them back down.
Fake xenon lights are lame.

A very popular thing right now is fake xenon lights. These are halogen bulbs that are tinted blue and give off blue light to simulate HID’s. Many times the package will call them HID or xenon, but they are not. These bulbs can be spotted easily because they appear blue but are not really all that bright. They also appear blue from a distance but don’t turn white as you get close to them. These bulbs are for the silly kids that like to think they’re cool.



Light Emitting Diodes

Of all lights sources that exist in this world, the one that is quickly becoming more common in every area of lighting is the light emitting diode (LED). Everything from flash lights, to TV screens, are now using LED’s instead of incandescent or other types of bulbs. The biggest reason for this is that LED’s use a tiny amount of energy compared to standard bulbs, and they last much longer. LED bulbs also don’t suffer from a decrease in output and intensity over time, in the way that incandescent bulbs do.
LED headlights on a Lexus LS600h.

LED bulbs are very efficient because more of the energy that they use gets converted to light rather than getting converted to heat. Standard incandescent bulbs and halogen bulbs can produce a lot of light but they actually produce more heat than anything else.

Because LED bulbs are the latest, they are also the most expensive. Like everything else the cost will come down with a little time. Right now only the most high-end luxury or sports cars have them. People who buy these cars are usually willing to pay anything for a gadget that nobody else has.

Other Headlight Features

Some other headlight features are becoming more common. Most of these things are made possible by the fact that headlights are now computer controlled on most vehicles, in some way or another. Putting computers in charge facilitates many features that people come to rely on, and eventually cannot do without.

Headlight Washer Systems

In Europe, automotive lighting standards dictate that any vehicle with headlights that discharge a high level of lumens must have a system for washing the headlights. This system will consist of wiper arms that look like tiny windshield wipers, and/or a system that sprays the headlights with washer fluid. These sprayers might be hidden and only pop up to spray the lights. These light washer systems are meant to clean the headlights which in turn reduces glare from the headlights when viewed by drivers in other cars approaching at night.
Headlight wiper on a euro spec Mercedes.
In the U.S. such headlight washing systems are not required but are permitted. Because of this many European cars and few Asian cars sold in the U.S. may have these systems. Since manufacturers put these systems on models sold in Europe, they don’t bother to remove them from the U.S. versions.

To activate the headlight washer, the driver can usually just clean the windshield with the headlights turned on, and the headlights will be washed as well.

Automatic Dimming

Automatic headlights, the kind that can turn themselves on and off, are very common on cars and trucks today. These have been around for some time, but new ways to automate headlights are now starting to appear. Things such as automatic headlight dimming are now common on most high-end cars. This feature is not just there to switch between high beam and low beam, it actually requires some processing to determine how the lights should be controlled and when.

A digital camera is found somewhere in the front of the car to face forward and look at any light in the distance as the car is moving down the road. The computer uses these images to determine if the light ahead of the car is light from another vehicle, such as headlights or tail lights, or if it is something like a street light. If the light is determined to be coming from another vehicle then computer will determine how far away the light is.
camera on the rear view mirror for automatic dimming.
The computer uses high-side drivers to feed power to the headlights at a varying duty cycle to control the brightness of the lights. This means that the computer turns the headlights off and on so fast that you can’t see them flicker, however, the longer they are on the brighter they appear, and the shorter the time they are on the dimmer they appear. So rather than just having high beams and low beams, the brightness of the headlights is infinitely variable within a given range. Maximum brightness when no other cars are around, rather dim when other cars are close, and somewhere in the middle when cars are ahead but maybe a little ways off.

Cornering Lights

Cornering lights have traditionally been the lights that are located on the sides of the front corners of the car, and come on when turn signals are turned on while the headlights are on. The light shines to the side of the car helping to illuminate the turn. Some of these systems still exist but cornering lights are generally much different today. They still help drivers to see better in a turn but now the cornering lights use a system that actually rotates the bulb and the reflector in the headlight assembly as the car goes through a turn.

The computer that controls this system is watching a steering angle sensor that’s attached to the steering column. As the wheel is turned while the headlights are on, the computer activates small actuators in the reflector assembly to steer the lights in the direction that the wheel are turning. This system shares some components with the automatic leveling system that was discussed previously.

Driving/Fog Lights

Real fog lights are yellow.
Fog lights are yellow, driving lights are not. Most cars that have extra lights lighting a path for the vehicle, other than the regular headlights, have driving lights. Driving lights are white, the same color as the headlights. These are just meant to provide extra light on the front of the vehicle and are not intended to be used alone, or in conjunction with the marker lights only.

Fog lights are yellow and always mounted very low on the front of the vehicle. Yellow light will not reflect off of fog, or falling snow and it makes driving in such conditions much easier. Driving in a blizzard or heavy fog at night can be especially nerve racking but real fog lights make a difference that is amazing. Most real fog lights are after market since auto manufacturers don’t install yellow lights on their cars from the factory.

Shed Some Light

Take care of your headlights. Nothing is worse than driving a car at night that has headlight problems. Keep them clean and properly aimed. Also, remember that your headlights really can be a problem for other drivers. Don’t drive with your brights on in city limits, if you have a lifted 4X4, make sure to adjust your headlights accordingly. Good headlights help you and help other drivers, especially on the winding canyon road in the middle of the night.

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