File puptcrit/puptcrit.0803, message 89


Date: Tue, 4 Mar 2008 12:24:33 -0500
To: puptcrit-AT-puptcrit.org
Subject: Re: [Puptcrit] two overheads projectors ganged together


A single 3-way household wall switch can be wired to flip between two 
lights.  It has been perhaps 20 years since I did that, so I don't 
recall the details.  An electrician might be able to help.

But, I am not so sure this is a good idea. Many projectors have fans 
that stay on for a while after the bulb is turned off. Also, 
regarding dimming, some projectors (many nowdays), have an electronic 
powersupply that doesn't like to be dimmed, and will actually fight 
to keep the bulb at the same brightness.

Mechanical dowsing sounds like the best option.  I know that in the 
theater maillist I am on, several people have talked about adapting a 
CD-Rom drive to do this.  They connect to the electric motor that 
moves the tray in and out... but I don't know the details.  Another 
option for electrical control of the douser is to use Radio Control 
servos.  There are electronic kits (about $40 to $50) to give you 
direct-wire control over a servo.  You can then connect the servo to 
an opaque disk of material in front of the lens so that it moves in 
and out of the beam.

Let me know if you want to know  more about the electrical control of 
dousers, and I can do more research.

Joe Dunfee
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