Aug 07

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Common Lamp Types

Incandescent Lamps
The incandescent lamp dates back over one hundred years to Thomas Edison’s original invention. Essentially, an incandescent lamp produces light when its filament is heated by an electric current, causing it to glow or “incandesce.” Normally, the filament is made of a coiled or doubly-coiled tungsten wire.

The advantages of incandescent lamps include a low initial cost, high color rendering ability and general ease of operation; dimming is easy and a variety of wattages can be used in the same socket.

There are hundreds of variations of wattages, sizes, shapes, and colors. The everyday incandescent lamp is called a “general service” lamp or an “A” lamp.

Tungsten halogen lamps are basically incandescent lamps that operate at higher pressure and temperature than standard incandescent lamps, producing a whiter light and longer life. The “tungsten” part of the name comes from the filament material – tungsten. The halogen part refers to the type of chemical additive that bestows the lamp with its special properties.
Another way halogen is an improvement over standard incandescent is in light output. Incandescent lamps have a tendency as they burn to slowly deposit their allotment of tungsten onto the glass bulb, turning the bulb black. This black coating blocks some of the light from coming out of the bulb. Eventually, the filament gets thinner, breaks, and the lamp fails.

The halogen gas in the lamp significantly reduces the deposition of evaporated tungsten onto the glass bulb. No bulb blackening = more light!

Fluorescent Lamps
Fluorescent lamps produce light by passing an electric arc through a mixture of an inert gas (argon or argon / krypton) and mercury (a tiny amount). The mercury radiates ultraviolet energy that is transformed to visible light by the PHOSPHOR coating on the bulb.
Fluorescent lamps are more efficient at producing light compared to standard incandescent or even halogen. In fact, their efficacy is 4-8 times that of the filament sources. Fluorescent lamps have life ratings from 7,500 hours to 24,000 hours, with a few even beyond that. Life is dependent on many variables such as lamp type, ballast type, operating environment and how often they are switched on and off.

There are two general categories of fluorescent lamp:
Linear Fluorescent
Linear fluorescent lamps come in a range of wattages and sizes – 4 and 8 foot lamps are most common for commercial uses such as office buildings and warehouses.

Compact Fluorescent (CFL)
COMPACT FLUORESCENT LAMPS (CFLS) operate on the same principle as regular fluorescent, but are more “compact.” CFLs became popular in the mid-to-late 1980′s. The original concept was to provide an energy efficient replacement for incandescent lamps.

An integrated type of CFL combines the lamp and ballast in one unit, which can be screwed into a standard incandescent lamp socket.

Other Fluorescent lamps
Some fluorescent lamps are circular, and use designation of “FC”, and others are bent into a U-shape. These use a designation of “FB” for bent.
High Intensity Discharge Lamps
HID lamps produce light a different way than the previous lamp types examined. HID light is produced directly from the arc itself. Due to the high pressure under which these types operate, the arc becomes extremely intense. Once turned off, it must cool down to reduce the arc tube pressure before the arc can restrike.
This arc is relatively short (compared to a fluorescent lamp) and therefore it is considered a point source.
Since these sources use an arc, they need a piece of auxiliary equipment called a BALLAST.

There are three basic types of HID lamps, all operating on the same general principle but producing dramatically different results:

Mercury Lamps
Metal Halide
High Pressure Sodium (HPS)

LEDs, or light-emitting diodes, are electronic light sources. An LED is a semiconductor device that emits visible light of a certain color. LED lighting is fundamentally different from conventional light sources such as incandescent, fluorescent, and gas-discharge lamps. An LED uses no mercury, no lead, no gas or filament, it has no fragile glass bulb, and it has no failure-prone moving parts.

An LED is a type of solid-state diode that emits light when voltage is applied. LEDs become illuminated by the movement of electrons through a semiconductor material.

LED Facts

Up to 50,000 hours or more.
Light output remains constant over time, only decreasing towards the end of the rated lifetime.
The shade of white light appears clear and consistent over time.
Light comes on instantly when turned on.
when dimmed with approved, tested dimmers for LED use.

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