How Fluorescent Lights work Leave a comment

Fluorescent Lamps (Tubes):

A Fluorescent Lamp is a type of electric light which uses ultraviolet rays emitted by mercury vapor to excite a phosphor, which emits visible light. This process is also called Fluorescence.

Fluorescent Lamps work by ionizing mercury vapor in a glass tube. This causes the electrons in the gas to emit photons at UV frequencies. The UV light is then converted into a standard visible light by using a phosphor coating on the inside of the tube.

A fluorescent Lamp converts electrical energy into useful light much more efficiently than Incandescent Lamps.

History of Fluorescent Tubes: 

In 1852, an Irish scientist, Sir George Stokes named the phenomenon “fluorescence” after Fluorite. Later, in 1856, German glassblower Geissler invented the first gas-discharge lamp, the Geissler Tube.

Popular scientists such as  Edison and Tesla experimented with fluorescent lamps in the 1890s but could not produce them commercially. 

In 1901, Peter Cooper Hewitt developed the first commercial mercury vapor lamp. An electric arc through mercury vapor is the basis for the modern fluorescent lamp.

Basic Construction:

A fluorescent tube light consists of

1.      Lime Glass Tube

2.      Drop of Mercury

3.      Argon Gas

4.      Phosphor Coating

5.      Electrode Coils

6.      Mounting Assemblies

7.      Aluminum Cap

Types of Fluorescent Lamps:

There are three common types of Fluorescent Lamps. They are T12, T8, and T5 lamps.

The “T” in T5 indicates that the bulb is tubular shaped, while the “5” denotes that it is five-eighths of an inch in diameter. It is the same for T8 (eight eighths inch = 1″) and T12 (twelve eights inch = 1½” tubes). 

Fluorescent light bulbs typically have a rated lifespan of 7,000 to 15,000 hours.

The Ballast:

All Fluorescent type lights require a ballast to start/run the light. The ballast’s purpose is to  prevent regulate the amount of electricity being provided to the tube. It causes the lamp to start with a high voltage for a split second when it is switched on. There are two types of ballasts. They are magnetic and electronic ballasts.

Magnetic ballasts are the original ballast, and very common in T12 type systems but have fallen out of use. They are less efficient than electronic ballasts and provide lower quality light due to flickering.

Electronic ballasts provide the same function, but do so more efficiently than Magnetic ballasts While also reducing flickering. Common in most T8 and T5 Tube Systems.

Compact Fluorescent Lamp (CFL):

CFL is another type of fluorescent lamp generally designed as a replacement for incandescent or halogen lamps. The lamps use a tube which is curved or folded to fit into the space of an incandescent bulb, and a compact electronic ballast is fitted into the base of the lamp.

Like their tubular counterparts an electric current is driven through a tube containing argon and a small amount of mercury vapor. This generates invisible ultraviolet light which excites a fluorescent coating (phosphor) on the inside of the tube, which then emits visible light.

There are two major types of compact fluorescent lamp, screw-in, and plug-in. The most common type being screw in.

CFLs come in a wide variety of wattages, sizes, color temperatures, and base types, and they are known primarily for their efficiency, long life, low cost, and ease of upgrading. One downside of CFL use is the negative effects of improper disposal – Because they contain mercury they must be disposed of properly. 

History:

The modern CFL was invented by Edward E. Hammer in 1976, However high production costs prevented the bulb from becoming commercially viable. Later in 1980, Philips became the first mass-producer of CFLs which significantly increased their popularity. 

Basic Construction:

Energy Efficiency of CFLs:

The luminous efficiency of a typical CFL is 50–70 lumens per watt (lm/W). Compared to that of a typical incandescent lamp (10–17 lm/W), CFL has very high efficiency. Compared to a theoretical 100%-efficient lamp (680 lm/W), CFL lamps have lighting efficiency ranges of 7–10%.

CFLs have a rated lifespan of 6000-15000 hours. However, the actual lifespan of a bulb depends on many factors such as cycling, operating voltage, temperature, mechanical shock, etc.

Advantages of CFL:

–          Up to four times more efficient than incandescent bulbs.

–          Eco-friendly when properly disposed of.

–          While, initially, they cost more, CFLs are less expensive in the long run because they last much longer than incandescent bulbs.

–          Highly versatile.

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