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Incandescent Bulb:
The invention of the incandescent bulb is often attributed to Thomas Alva Edison. However, there were other individuals who contributed to the development of a method to generate light with electricity. In 1801, Humphry Davy experimented with a glowing platinum wire, which immediately burnt out. In 1854, Heinrich Göbel successfully created the first true incandescent bulb. His bulb consisted of a carbonized bamboo filament inside a vacuum-sealed eau-de-cologne bottle.
He could create a vacuum by filling the bottle with mercury and then allowing it to drain out. The vacuum prevented the bamboo filament from burning. Göbel’s lamp burned for 400 hours. Edison applied for a patent on a similar lamp 25 years later. Göbel filed a lawsuit and in 1893 was vindicated. However, he passed away in the same year.
An incandescent bulb is a glass lamp in which light is produced by means of a glowing filament. When voltage is applied, a current flows through the filament, causing it to heat up and emit light. Historically, filaments were made of carbon, but today they are made of tungsten. The glass of an incandescent bulb is quite strong, even though it is thinner than a sheet of paper. This strength comes from the shape into which the glass is blown. The electrical resistance of a tungsten filament is only a few dozen Ohms when cold and, influenced by the developed heat, it rises to several hundred to thousands of Ohms right after the voltage is applied. Therefore, when an incandescent bulb is switched on, a current surge occurs, often causing the filament to burn out if it already has a thin spot.
The filament doesn’t just burn out during glowing because the glass bulb housing the filament contains little to no oxygen, being filled with argon or another noble gas instead. In open air, the filament of an average lamp would burn out within seconds of connecting to a power source. In a burning incandescent bulb, the filament material evaporates gradually due to the heat and deposits on the inside of the glass bulb. This can be recognized by the dark color that older bulbs develop on the inside of the glass. As soon as a dark haze is present inside, the bulb should be replaced immediately. When replacing one bulb, it is best to also check the condition of the other bulbs.
Halogen Lamp:
A halogen lamp gets extremely hot. Temperatures can reach up to 250 degrees Celsius. Therefore, the lamp is made with heat-resistant glass. A small amount of halogen (e.g., iodine, bromine, chlorine, or fluorine) is added under high pressure inside the lamp, becoming gaseous due to the heat. The halogen forms a compound with the evaporated material of the filament in colder parts of the lamp. This gaseous compound breaks down into halogen and metal when it comes close to the very hot filament. The metal then redeposits on the filament, extending its lifespan.
The advantages of this lamp include small size and ease of focusing the light into a beam.
More information about the headlight and the beam can be found on the headlight page.
Xenon Lamp:
A xenon lamp (also known as a gas discharge lamp) produces more light output than a standard halogen lamp. This lighting technology has been used for some time, not in the automotive industry but for lighting football stadiums. Xenon lighting allows the intensity and color of daylight to be closely approximated.
Advantages of xenon:
- Xenon lighting in the car is brighter and spreads better than standard halogen lighting.
- Due to the enormous light output of xenon lighting, it is possible to mount the headlights in a smaller housing. Even with a smaller surface area, the same or greater light output can be achieved. This provides an advantage for car manufacturers to optimize aerodynamics and offers more freedom in design.
- Consumes 30% less energy.
Disadvantage of xenon: - It blinds oncoming traffic more than halogen lighting, especially if the headlight does not have a suitable lens for xenon lighting.
As previously mentioned, the higher light output makes it possible to use a smaller reflector and headlight. Because xenon lamps convert electrical energy to light more efficiently, much less heat is generated compared to standard halogen lighting.
The lifespan of xenon lamps is also longer than that of halogen lamps. The average lifespan of a xenon lamp is generally about 2000 hours. This corresponds with the average lifespan of a car.
The ECE regulation states that vehicles equipped with xenon lighting must also have a level adjustment system. The level adjustment (automatic height adjustment) prevents blinding of oncoming traffic. An angle rotation sensor is mounted on the rear axle, registering the vehicle’s tilting. This collected data is processed in a control unit, which in turn adjusts the headlight unit upward or downward.
To minimize the formation of stray light, which is light that falls outside the intended beam, it is essential to keep the headlight lenses clean. Therefore, a cleaning system for the headlight lenses is mandatory for cars with xenon lighting. A pump builds up water pressure of approximately 3.5 bar, after which two arms extend from the bodywork to clean the headlight lenses. After spraying, the arms are retracted back into the bodywork.
More information about the headlight can be found on the headlight page.
Xenon lamps do not have filaments like halogen lamps do. Instead, a discharge tube enclosed by quartz glass is used. The lamp is filled with noble gases and metal halides and is ignited using two electrodes between which an arc is formed. The arc is created by applying a short ignition impulse between 20,000 and 30,000 volts. Then a constant voltage of approximately 85 volts ensures the lamp stays lit.
To generate and limit these high voltages, an electronic ballast is used: the igniter. The igniter provides the high initial voltage. The ballast (shown separately from the igniter in the illustration) is often housed with the igniter in one casing. The ballast regulates the maximum current through the lamp. Without the ballast, too much current would flow to the lamp, causing it to fail.
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