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HID Light Bulbs

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In HID light bulbs, or High Intensity Discharge light bulbs, there is a capsule of gas in place of the filament. Ballasts are required for these bulbs to operate. A ballast is a device used to stabilize the current in a circuit and supply proper voltage. An arc discharge between two electrodes that are closely spaced emits the light in HID bulbs. All of this takes place inside a small quartz glass tubular capsule. HID bulbs produce more light than regular halogen bulbs, and they also consume less power. HID bulbs come very close to the true color temperature of natural daylight.

Light is produced in High Intensity Discharge bulbs by a current that passes through a metal vapor. Electrons bump into atoms in the vapor, and this action causes the electrons to go into a higher orbit of the atom for a short period of time. When an electron returns to its normal level of orbit, a quantum of radiation is discharged. The wavelength of radiation depends not only on the energy zone of that particular electron, but also on what type of metal vapor is used in the tube.

A HID light bulb produces five percent of its output when it is first lit; the rest of the light takes about 15-20 seconds to respond. Also, if the light is turned off or the power is somehow lost, the arc tube has to cool to a specific temperature before it can be turned back on. Luckily, this cooling period is usually only about 15-30 seconds.

When compared to halogen bulbs, HID bulbs have many advantages. Some are following:

• More light output. An 18 watt HID bulb can produce the same amount of light as a 55 watt halogen bulb at three to five times the halogen bulb's efficiency. One reason for this is that the HID bulb boasts true 6000K color temperature, making its light appear almost as bright as a 55 watt halogen bulb. Also, the HID bulb is six to eight times more efficient than an incandescent bulb.
• Whiter light. The color temperature of a HID bulb is much closer to the color temperature of natural daylight than a halogen bulb's light, which is usually yellowish in comparison. For this reason, a HID bulb will appear brighter and more pleasing to the eye than a halogen bulb.
• Longer service life. On the average, HID bulbs last three to five times as long as halogen bulbs. Usually, HID light bulbs will last for over one thousand ignitions.

HID bulbs are often used in areas where energy efficiency and long bulb life are important, most often where high levels of light are needed to illuminate large areas. Examples include gymnasiums, large public areas, warehouses, outdoor activity areas, roadways, parking lots, and paths. Sometimes HID bulbs are used in retail and residential environments. These bulbs have also made indoor gardening more practical, since they emit light that is so similar to natural daylight.

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