[SML] Looking to build a dowser for an office projector, simple and cheap

[Ford Sellers]

Hi Chris,

I made such a beast about 10 years ago, at Cornell University.

Dick Archer, you may be able to find them (ask Fritz if he's seen them).

Basically, we took two CD Drawer mechanisms, and attached them to a piece of wood.  They were wired with a three position switch.
Position 1 closed the drawers (pulled them to a position where they were out of the past of light... so opened the shutter)
Center position killed the power
Position 3 reversed the polarity and opened the drawers (closed the shutter).

There is a trick to making this look good:
In order to not see a WIPE of the Projected Black, you need to make the fadeout happen over the whole beam.
The easiest way to accomplish this is by adding long pointy pieces of poster-board, or cardstock to the front edge of the doors.  This needs to be cut in a zig-zag pattern with long fingers.
As the fingers overlap, the light is blocked more uniformly than if the shutters simply close in from both sides.

For example... hold your hands up in front of your face, with the fingers spread slightly, and in slightly different planes.
Slide them together so that they overlap, and block your vision.
Now, imagine that your fingers are ling, pointy triangles (point at the fingertips, narrow base at your hand).
The more acute the angle, the longer the pointy strips are.
Depending on how closely they overlap, the image will be blocked in multiple planes, and your fadeout can look a lot more smooth.

It's difficult to explain, but if Dick can find these to send a picture, you will see it very easily.

I hope this wasn't too confusing.

-Ford


From: Stagecraft [mailto:stagecraft-bounces at theatrical.net] On Behalf Of Chris Clarke via Stagecraft
Sent: Monday, February 06, 2017 3:13 PM
To: stagecraft at theatrical.net
Cc: Chris Clarke
Subject: [SML] Looking to build a dowser for an office projector, simple and cheap

We especially need to block the annoying 'video black' rectangle for an upcoming show.

I've seen the DMX controlled dowser/flags like one offered by City Theatrical. Someone told me about a homebrew dowser made from the CD drawer mechanism of an old tower PC. Wireless control is nice, but wired would work just fine for our purposes this time out.

Does anyone here know where to find such a thing, or plans for one?

Thanks,

Chris Clarke
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