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<big>I had gotten a lot of emails after my short article, "A Bright
Color Mixer", appeared in the Trick of the Trade column of The Physics
Teacher magazine, Vol. 40. In this column I described how to turn an
old three-panel video projector into a bright, three-color mixer. Many
of the people who emailed me were looking for advice on how to go about
finding a surplussed projector that still worked. Repairing a broken
projector can be cost-prohibitive, and even just replacing a bad bulb
may cost hundreds of dollars.<br>
<br>
This week, the bulb in my Sharp XG-E1100U projector finally went out,
so I decided to try an alternate lighting method. I removed almost all
the electronics from the projector. I then installed a small
transformer to power the two 12V DC fans. I wired these directly to
the supply so that the fans run continuously when the projector is
plugged in. I removed the high-voltage lamp from its reflector, then
had our machinist install an electrical attachment through the base of
the reflector. The attachment is two female clips in a ceramic disc,
designed to fit a 600W, 120V BHC projector lamp. We buy these for
$5.95. I then rewired the projector for the 120V bulb. I placed the
power switch and other safety switches in series with a relay. When
power is on and all safety switches are closed, the relay engages to
power the bulb. In series with with the relay and bulb are two
resettable heat fuses that were already in position, and also a 10A
fuse that I installed.<br>
<br>
The new projector works very well, though to my eye it is not quite as
bright. But since it is easier to find a broken projector than a
working one, a little extra labor makes this demonstration more widely
available, and also less expensive.<br>
<br>
To view the original Physics Teacher column article, follow this link:<br>
<br>
<a class="moz-txt-link-abbreviated" href="http://www.phys.appstate.edu/demos/mixer/lightmixer.htm";>www.phys.appstate.edu/demos/mixer/lightmixer.htm</a><br>
<br>
John Cockman<br>
Lecture Demonstration Manager<br>
Phsics and Astronomy<br>
Appalachian State University<br>
<a class="moz-txt-link-abbreviated" href="mailto:cockmanje@appstate.edu";>cockmanje@appstate.edu</a><br>
828-262-7089<br>
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