The most popular light source is the common household lamp, the incandescent
lamp. Though they are the most common, they are also the most inefficient source
of light available and have the shortest life. The lamp consists of a resistive
tungsten filament that heats up and glows. Tungsten evaporates, gradually weakening
the filament, and leaving a blackened inner surface on the bulb.
An improvement in this lamp type is the tungsten halogen lamp. The halogen
gas helps redeposit the evaporated tungsten onto the filament leading to
a life span 2-3 times longer. The color of the light output is better, it
is whiter at full brightness and when dimmed passes through shades of yellow
and orange. Both of the above types operate at mains voltage and can be dimmed.
Low Voltage Tungsten Halogen
Low voltage lamps are used domestically for spotlights, down lighters and modern
table lamps. They are available in different sizes, beam angles and wattage's
from 5w to 50w. They are all categorized by requiring a 12v supply that is
derived by using a transformer of the correct wattage for the lamp.
The input to the transformer is the mains supply (or channel output from a
dimmer) the output of the transformer is a (dimmed) 12v supply to the lamp.
These lamps give a more complete crisper light with better color rendering.
They are more efficient and last up to 5 times longer than tungsten lamps.
Comes in a variety of sizes, but most common is the tube and compact fluorescent
types. The latter is used domestically in the form of a low energy replacement
for a normal lamp.
They operate by creating a UV arc that excites a phosphor coating which fluoresces
creating the light and hence the name. Interrupting the supply to a choke also
known as ballast starts the UV arc. Fluorescent's are much more efficient than
incandescent lamps and are available in different colour temperatures. Domestic
compact fluorescents are not dimmable but instead can be switched as part of
a scene or program. However, tube fluorescents can be dimmed with a high frequency
dimmable ballast. These have a live supply and a control supply commonly 1-10v.
Most Intelligent lighting controllers have an interface card which provide
a control signal for telling the ballast what level to dim to. Typically fluorescents
can be dimmed down to 5 to 10% depending on the ballast manufacturer. Energy
saving through dimming is proportional to the dimmed level on a 1.1 ratio.
Neon - Cold Cathode
Used most often in signage and to light ceiling recesses in buildings. They
are usually custom made, with different gases and tube coatings for different
colors. They are powered by a high voltage transformer that operates from
1 - 6KV. These transformers can be dimmed on the mains supply side by some
controllers. The minimum dimming level, typically, is 10% dependent on the
lamp and transformer characteristics. Energy is saved when dimming though
lamp life is not extended.
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