Page 259 - Electromechanical Devices and Components Illustrated Sourcebook

Chapter 12 Lighting 221

Trigger Plate
Tube
Electrodes

Terminal Terminal

Straight Tube
Trigger

Trigger Plate
Electrodes
Tube
Terminal

Trigger

Terminal

U-Tube
Figure 12-38 Commercial Xenon Flash Tubes

operation voltage is maintained during operation. Because of
the extreme heat that these bulbs generate, most units are
Trigger
water cooled.

FT 1 C Carbon Arc Lighting
250–400 VDC C 1 2
Carbon arc lighting has all but disappeared in modern appli-
cations. It has been principally replaced by short arc xenon
lamps. In the early 1800s, the first street lighting was carbon
T 1 R 1 arc. Probably the most noteworthy application of carbon arc
lighting was the spotlights used during World War II to spot
enemy planes flying over England at night. Figure 12-41
Figure 12-39 Xenon Flash Tube Circuit
shows a schematic representation of a carbon arc spotlight
with a high-voltage ignition starter.
Short arc xenon lamps are intended to operate in a steady
state fashion and are deployed for applications that require an
extremely high-intensity output and daylight color balance. Light Emitting Diodes (LED)
The most noteworthy application of short arc xenon lamps is
in motion picture projectors found at local movie theaters. Light emitting diodes (LED’s) have permeated our lives over
Figure 12-40 shows a typical short arc xenon lamp. A high- the years. The little indicator lamp that shows your hard drive
voltage pulse is applied to start the bulb and then a lower is working, the infrared source in your TV remote controller,
and the red power indicator on your stereo, are all LED’s.
Light emitting diodes are diodes that generate light emis-
Quartz Bulb Electrodes
sions when they are energized. They are commonly supplied
in two basic sizes—5 millimeter and 3 millimeter —as shown
in Figure 12-42. Light emitting diodes are available in red,
yellow, green, and white. There are super bright versions that
Terminals are appropriate for lower level lighting applications. These
super bright LED’s are commonly found arrayed for traffic
signals and automotive tail lights. They are also used for small
inspection lights, being no bigger then a pen or can be hung
Figure 12-40 Short Arc Xenon Lamp on a key chain.