Today's incandescent is a direct descendent of the original concept. It typically consists of a base with electrical contacts, a glass enclosure or bulb and a filament wire, typically tungsten, that is suspended inside the bulb. Incandescents can have one or multiple filaments in the same bulb.
The filament is part of the electrical circuit. As current passes through it, the wire heats up due to the resistance in the tungsten. When the current reaches a certain level, the filament begins to glow a dull color. Add enough current, and it will glow "white hot." Unfortunately, in order to operate, incandescent bulbs waste 95 percent of the energy flowing through them as heat.
If used in an atmosphere containing oxygen, the filament would quickly begin to combine with the oxygen and deteriorate. The result of that combination, the corrosion, would promptly cause the lamp to fail. To prevent or slow the process, the bulbs are filled with an inactive or inert gas that doesn't combine with the filament.
Filaments used as part of incandescent vehicle lighting are typically found in three styles. It may be a straight wire, a single strand that reaches directly from one support across to another. Another style is the coiled filament, which has a conductor that is coiled and reaches across from one support to another. The coils provide a means of increasing the amount of filament surface area to produce more light, while concentrating the light. It also provides a spring-like action to help cushion the filament from vibration. The coiled filament is the most common type found in vehicle lamps.
A variation on the coiled filament is the coiled coil. With it, the filament wire is tightly coiled and is then wrapped again into the normal coiled shape.
Incandescent lamps have been around for many decades. They still have attributes that make them a good choice. They are relatively inexpensive to acquire and use. They are also readily available from a myriad of sources including, in some cases, grocery stores. Incandescents are available in a wide variety of sizes and styles.
On the other hand, they have a short life when compared to newer technologies. Vibration has a damaging effect on them. And, over time, in many incandescents, the inside of the glass bulb becomes blackened by an aging filament, cutting down the light output.
Incandescent lamps are particularly sensitive to voltage that varies even slightly above the norm. Operating an incandescent light at just 5% over design voltage reduces the life of the bulb by 44%. At 10% over design voltage bulb life is reduced by 68%.
About Light Emitting Diode Lamps (LED)
The most important improvement in non-forward lighting has been the advent of lightemitting diode (LED) lamps. LED's are semiconductors, which means that they allow current to pass through in only one direction. As the current passes through a crystal chip, it jumps from a negative plate to a positive plate, and as it does so, a "photon" of light is generated. Light emitted by an LED is directly proportional to current passing through it. LED's can produce light in many colors, for example red, green and amber. A recent development was the advent of the clear or colorless LED.
LEDs make very efficient use of the electrical energy that powers them, significantly better than the traditional incandescents they replace and they run much cooler and do not fail due to heat buildup. They start producing light the instant they are switched on. LED have builtin color and don't require a separate color lens. They are very vibration resistant, which also helps extend the life of LEDs devices. They often last the lifetime of the vehicle.
The most susceptible component of an LED lamp to corrosion is the circuit board. For protection, each Grote board is sealed with a special "potting" compound to protect it from the worst that Mother Nature and the vehicle wash rack can offer. Grote engineering has further enhanced the life of LEDs with specially formulated potting that draws heat away from the LED.
The diode design offers high efficiency resulting in relatively low current draw compared to incandescent while providing light equivalent to a typical incandescent. Grote engineering continues to develop more and more effective LED solutions for vehicle applications.
LED vs. Incandescent Lighting Quick Comparison
Amperage Draw LED's draw 1/10th the amps of incandescents and a typical semi-trailer truck uses up to 15 fewer amps. The lower draw saves wear on the alternators and batteries and leaves more power available for equipment such as onboard electronics.
Instant-On An LED turns on in 0.00006 mSec. An incandescent lights up in 250 mSec. At 65 MPH, that extra time provides an additional 24 feet of stopping distance for following vehicles.
Efficiency LED's run cooler because they don't have to heat a filament. Incandescents waste 95% of their current draw generating heat not light.
Ruggedness LED's are much less susceptible to vibration than incandescents and color doesn't fade over time.
This documentation was provided by Grote Industires, Inc.