12 September 2016
n WITH TIM BROWN
• Enlightenment on Modern Lighting
• Is “Green Energy” Really Green?
Enlightenment on Modern Lighting
QI see a lot of ads for LED and CFL lighting advertised as a replacement for incandescent lights. Which is better? Joshua Peeples
Battle Creek, MI
ACompact Fluorescent Lamps (CFL) and Light Emitting Diode (LED) lamps were designed as a low energy consuming alternative to residential standard base screw-in incandescent lamps.
Figure 1 shows the internal components of an
incandescent lamp. The incandescent lamp consists of a
Tungsten filament enclosed in a glass bulb which is filled
with inert nitrogen or argon gases. When the filament
conducts electricity, it heats to approximately 3,100 to
5,500 degrees Fahrenheit, where it glows and converts
approximately two percent of the electrical power input
into visible light and 98 percent into heat with a trace of
ultraviolet (UV) light.
Incandescent lamps are very efficient generators
of heat (a.k.a., great wasters of electricity), but not too
efficient as light emitters. [Our instrument shop used
several 100 watt incandescent bulbs wired in parallel as a
dummy load for testing DC motor controllers.] A 60 watt
incandescent lamp radiates around 800 lumens of visible
light, which is approximately 13. 33 lumens per watt of
input electrical power. A 60 watt incandescent lamp costs
approximately $0.50 and will last approximately 1,200
Figure 2 shows the internal construction of a CFL. The
CFL is essentially a tube type fluorescent lamp twisted into
a helical package. As such, it requires a ballast to produce
a sufficient voltage to cause the lamp to fluoresce and to
regulate current to the lamp after the fluorescence starts.
The process of fluorescence uses mercury ( 3 to 5
milligrams per lamp of an extremely toxic substance)
vapor in argon gas. When an electrical voltage is placed
across the lamp, the mercury atoms ionize and when the
electrons recombine with the atom, UV light is emitted.
This UV light energizes a phosphor coating on the inside
of the CFL’s glass tube which emits visible light. My
experience with CFLs is that they sometimes take a while
to reach the full light output and proper color — especially
in cold ambient conditions — and they sometimes generate
Q & A
In this column, Tim answers questions about
all aspects of electronics, including computer
hardware, software, circuits, electronic theory,
troubleshooting, and anything else of interest
to the hobbyist. Feel free to participate with
your questions, comments, or suggestions.
Send all questions and comments to: Q&A@
n FIGURE 1.
n FIGURE 2.