# Dousing a Projector with a Scroller



## metti (Feb 4, 2011)

I want to be able to remotely douse a pair of small LCD computer projectors. I don't have one of those projector dousers and there is not really a budget to rent a pair for this show. I do have a couple extra SmartColor Pros that I can use. Is there a way for me to make a custom scroll with one frame of clear and then some sort of opaque material for the second frame. I can probably figure out some sort of mounting device to hold the scroller in front of the projector.


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## Kelite (Feb 4, 2011)

metti said:


> I want to be able to remotely douse a pair of small LCD computer projectors. I don't have one of those projector dousers and there is not really a budget to rent a pair for this show. I do have a couple extra SmartColor Pros that I can use. Is there a way for me to make a custom scroll with one frame of clear and then some sort of opaque material for the second frame. I can probably figure out some sort of mounting device to hold the scroller in front of the projector.


 
Hi Metti-

We have made gel strings with Mylar to reflect and effectively block projector light. Are you able to absorb this reflected light with some type of flat black box placed behind the projector?


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## metti (Feb 4, 2011)

Kelite said:


> Are you able to absorb this reflected light with some type of flat black box placed behind the projector?


 
Definitely. I might be able to do this with some extra black Commando I have lying around too. I'll call my local dealer about pricing on a two frame custom gel scroll. Do you guys have the mylar in stock or will the minimum number of scrolls for non-Apollo colors apply to this situation?


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## Kelite (Feb 4, 2011)

Metti-

Are you able to construct a string consisting of a single wide frame of clear and a single wide frame of Mylar? (Sheets and short rolls of Mylar are easily found at Hobby Lobby or other local craft shop.) Tape your custom string onto the existing take-up reels located within the scroller.

Knowing the scroller really wants to 'read' the total string length of 16 frames- you may still be able to get by on the cheap by setting a command of 5% for your clear frame and a command of 95% for your Mylar frame...


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## metti (Feb 4, 2011)

Kelite said:


> Metti-
> 
> Are you able to construct a string consisting of a single wide frame of clear and a single wide frame of Mylar? (Sheets and short rolls of Mylar are easily found at Hobby Lobby or other local craft shop.) Tape your custom string onto the existing take-up reels located within the scroller.
> 
> Knowing the scroller really wants to 'read' the total string length of 16 frames- you may still be able to get by on the cheap by setting a command of 5% for your clear frame and a command of 95% for your Mylar frame...


 
I could probably go DIY on this. As long as there isn't a risk of damaging the scroller with a string that short. I have gel tape so I can order some clear gel and give it a shot.


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## sk8rsdad (Feb 4, 2011)

There's no harm in using a short scroll. The first thing scrollers do is figure out how long the string is. 

I did the mylar thing but had the scroll rip apart because the tape didn't bind well to the mylar. I redid it with an R26 gel and found it blocked most of the visible light. An R382 would probably work better but I needed the red for our low-light camera.


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## Kelite (Feb 4, 2011)

And since the string is so short Metti, you could/should certainly tape each side of the string to ensure a strong bond between said frames...


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## MPowers (Feb 4, 2011)

Talk about re-inventing the wheel. When I was in grad school, we had a multimedia production that needed to douse several projectors, 20, in tight sequence for a total of 5,000 slides during the performance, Yeah, I said "SLIDES", you know, those celluloid things with a cardboard or plastic frame.... 'bout 2"x 2 1/4"??? Now, because this was in the Jurassic period, the projectors were Kodak Carousels, rotating tray, 80 slides each. Our problem was that no projector could change slides fast enough for the scenes and the available technology at the time could only fade or change from one projector to another on the same screen, in about 1.5 seconds. No such thing as "click - click - click". So we build a dedicated, analogue, computer. It could only do one job, run only one program, "The Slide Show"! The next thing we developed was the douser. A rotary solenoid with a 1/4" rod attached. The rod had two sheet metal "vanes" braised on at 60 degrees apart. The Carousels were stacked with the lenses as close as possible and the rod ran up and the vanes were in front of each lens in turn as the solenoid rotated the rod. each projector changed it's slide while the douser was in front of the lens. Thus the change on the screen when the solenoid flipped, was instant, no fade up or down or dark time while the next slide dropped. The "computer" control was one button, every push and the program advanced a step. Ten Screens, ten solenoids, twenty projectors, 5000 slides. It took us, roughly 6 grad students, 2 faculty, about 8 months to work it out and construct. Some time in the future I'll tell you how we made slides in the days before computers and photo shop and digital photography.


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## metti (Feb 4, 2011)

MPowers said:


> Talk about re-inventing the wheel.


 
I'm well aware that there are superior, existing ways to do this. I have worked with the City Theatrical dousers many times but this show has a tiny budget and I already own the scrollers. I am just trying to work with what I have.


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## Repeater (Feb 5, 2011)

I assume you may have thought of a hand at each projector with a piece of black cloth or foamcore, dropping said light-blocking device on cue.


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## metti (Feb 5, 2011)

Repeater said:


> I assume you may have thought of a hand at each projector with a piece of black cloth or foamcore, dropping said light-blocking device on cue.


 
They are both 15' up on the pipe grid which sorta rules that out as a possibility.


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## joeb (Feb 5, 2011)

metti said:


> They are both 15' up on the pipe grid which sorta rules that out as a possibility.


 
In the past, I've rigged up a simple system with tie line, pulleys and small hinged pieces of wood or hung pieces of fabric. With some scrap lumber and less than an hour, you could get a pretty simple system set up that avoids custom gel strings. Of course this system is not dmx controlled (unless you want to go through the fun of hooking it up to a dmx relay with a few more steps), but it's effective.


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## gafftapegreenia (Feb 5, 2011)

Wheres the link to the build it yourself CD-ROM tray douser?


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## joeb (Feb 5, 2011)

gafftapegreenia said:


> Wheres the link to the build it yourself CD-ROM tray douser?


 
Could this be what you're looking for?

http://www.controlbooth.com/forums/multimedia-projection-show-control/6801-need-remote-douser.html


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## MPowers (Feb 5, 2011)

Metti,

Didn't mean to disparage your efforts, merely remarking on the fact that after forty years we (theatre technicians) are still trying to achieve some of the same things. I was also poking fun at the somewhat caveman technology and tactics we went through to get to the end result. Today, with computers and the other technology available, one or two people with 4 weeks time could easily duplicate our months of effort. In addition, their program would be changeable and adjustable with a few moments and a little keyboard data entry. With the system I described, any change would mean hours of un-soldering connections on rotary switches, re-wiring and re soldering for each step. Each step change would cascade down each succeeding step until a check point was reached and each step in the cascade would need the same reworking. A check point was an intentional "end point step" inserted every so often, so that everything from that point on started new and earlier changes did not affect them. If there had been such things as DMX and scrollers then, we might well have used that method and saved our selves a lot of time and effort.


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## dramatech (Feb 6, 2011)

joeb said:


> Could this be what you're looking for?
> 
> http://www.controlbooth.com/forums/multimedia-projection-show-control/6801-need-remote-douser.html



I built several projector dousers, using Northlight DMX to servo circuit boards. I thought that we had thee ultimate douser. After reading the various posts on the using a CD drive for a douser, I made one of those little guys. It quickly became our first choice.
The primary reason for it's popularity is that it can be controlled by the person that is running the visual program on a computer or DVD player. When using the DMX controlled douser, the light cues or lighting board operator had to control the douser. In almost all of our productions, the program on the projector is conrolled backstage at the Assistant Stage Manager's podium, while the lighting board is in the booth. After loaning our CD tray douser to several other theatres, I ended up building quite a few more for those theatres, and several more for our theatre, for when we do multiple projections.
The DMX to servo boards ended up being removed from their dousers and being used insted to build DMX controlled irises.

Tom Johnson
Florida's Most Honored Community Theatre


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## shiben (Feb 6, 2011)

Could you use some sort of RC car servo motor and a foamcore flag? Wire them all to switches? Probably could do the entire thing for pretty cheap, could even use XLR connectors if you really wanted.


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