@ruger |
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Fluorescent Tubes A while back I looked into how fluorescent tubes work and found that the principles were really quite simple, then recently it came up in conversation and I had forgotten it all, so I thought I better make myself a permanent reminder and give a simple explanation for any one else who wants to know. Typically a fluorescent tube consists of sealed glass phosphor coated tube containing a small amount of mercury and an inert gas usually argon with an electrode filament at each end. When a high voltage is applied to the electrodes, electrons migrate through the gas ionizing it causing the mercury to vaporise, this produces ultraviolet light which is then converted into visible light by the phosphor coating on the inside of the tube. The electrical circuit consists of a starter and a ballast. The ballast is a large coil with an iron core connected in series with the fluorescent tube and provides the initial starting kick, it also works as a current limiter. The starter which initiates the starting kick is connected in parallel to the electrodes on the fluorescent tube, see diagram below.
The most common type of starter is the glow starter, which consists of a bi‑metallic switch, neon and suppression capacitor. When power is applied current follows through the ballast and because of the neon in the starter through both the filaments, allowing them to warm up. The neon heats the bi‑metallic strip of the open switch causing the switch to close thus shorting out the neon allowing the bi‑metallic strip to cool, when the contacts subsequently open it creates an inductive kick via the ballast that causes the main discharge in the fluorescent tube. The main flow of current is now through the tube via the ionized gas which stops the neon in the starter from warming up again. This simple experiment demonstrates how a starter works.
Quick Note: Further Reading: How Stuff Works |
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Last Update 30/6/2017 |
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