Blocking Projector Beam

[mjw56]

hi everyone,
i am hanging a projector from an electric about 20' off the ground but have realized a few problems.
the projector supplied by the school wont tun off the light source but keep the rest of the projector on; therefore my blackouts will be dimly lit by the projector even when only projecting black. and powering on and off isn't an option because of the blue screen and menu that appears when doing so.
i was thinking of making some kind of shutter to put a few inches in front of the lens to physically block the light but was unsure of the best way to do this. the images im told will be videos imbeded into powerpoint and sent over VGA from a PC. i can supply dimmed or undimmed power and run any wires i want to the projector.any suggestions would be great
thanks

 

[Van]

What you want is referred to as a douser. There are several version of them from DMX controlled units to DIY analog systems. I posted a thread a year or two ago titled "Anyone Need a remote control douser ?". Search for the term "douser" and you'll find it along with a lot of other responses and solutions.

 

[mjw56]

Now why didn't i think of that
Absolutely awesome idea.
Thanks

 

[Sayen]

There is a blackout option in PowerPoint as well, although I don't recall the command for it. It's not perfect, but unless you have a perfect blackout anyway, it might work for you. I use it frequently as a workaround to not having a douser at the moment.

 

[mjw56]

Well the show goes off tonight and my CD-ROM douser works perfectly. well at least the 2nd one did. i am very happy with the results if i remember to take a few photos of it tonight ill post them up with an explanation of how i did it

 

[bluetoooth]

In last month we have finished own Porjector shutter- on request specially for the Sanyo 18cm optics . Now it's ready to action:

..:: S.R.S Light Design ::..

 

[shiben]

We have one at my theater that we inherited from the AV department, really jenky thing but it does the job...

 

[Van]

Now why didn't i think of that
Absolutely awesome idea.
Thanks

You're welcome/

Well the show goes off tonight and my CD-ROM douser works perfectly. well at least the 2nd one did. i am very happy with the results if i remember to take a few photos of it tonight ill post them up with an explanation of how i did it

Excellent!

 

[MarshallPope]

Hope this isn't too off-topic, but has anyone tried to do a multiple-step douser using neutral-density gels so that the beam would sort of fade out? We are using three projectors together for our current show, and keep noticing the little jagged wave that happens when the three dousers come down at the same time.

 

[ruinexplorer]

There is a blackout option in PowerPoint as well, although I don't recall the command for it. It's not perfect, but unless you have a perfect blackout anyway, it might work for you. I use it frequently as a workaround to not having a douser at the moment.

That should be B. Pressing it a second time would resume presentation. However, this would not hide "video black" which, depending on the contrast of the unit can be quite bright.

 

[mrtrudeau23]

I replied to a thread similar to this awhile ago.
At my school we use a color scroller with a gray scale roll in it mounted in front of the projector and the scroller runs off the light board.

 

[mjw56]

well i forgot to take the pictures but hopefully ill remember tonight
here's the explanation though.

Materials:
CD-ROM with operating CD tray
L bracket
5 min Epoxy
Aluminum coil stock or equal
small TEK screws
18-6 wire
momentary push button
4 inline splices
Power supply plug for CD-ROM
Black Spray paint
computer

Tools:
Screwgun
Small Screwdriver (eyeglasses size)
Electrical hand tools (dykes, tester etc.)
Tin Snips
soldering iron,solder,flux

ok this method worked for my douser but very likely the mount wont work for everyone.

1. begin by opening the CD_ROM and removing the laser/cd rotator assebly
2. connect the cd-rom to a computer and test to ensure that the tray still opens and closes. if it does ur ok. if not replace the assembly and disable the mechanism that lifts the assembly into the tray and imibilize the asebly so it cannot fall into the tray and jam it.
3. solder 2 leads from the eject switch on the front of the cd-rom and route the wires to the back of the case. be sure to test for the correct tabs on the circuit board. my switch had 3 common tabs and one not.
4. put the case back together
5. epoxy the terminal strip near or on the back of the CD-rom, remember to rough up the surfaces first
6. mount the angle bracket to the bottom of the CD-rom. i used a tek screw and epoxy but there was a convenient hole in the circuit board for the screw to run through. u may not be so lucky

to be continued

 

[mjw56]

Continued...
6.5 mark a CD sized circle onto the coil stock and cut out. epoxy this to the tray and paint black
7. connect the CD-Rom power plug to the cd-rom and to the terminal strip. also connect the wires from the eject button to the terminal strip. all on the same side.
8. once again test that it still opens and closes easily while it is accessible
9. pull the 18 wire from the computer to the location u intend to put the douser. keeping it away from power lines is not critical as it will only be carrying power (no data stream).
10.with the computer off and unplugged open the case and locate a power supply cable that doesn't have much on it. maybe a floppy drive. i would stay away from the hard drive just because the hard drive will basically always be running and u don't want power draw issues.
11. get ur 18 wire neatly into the case and use the splices to connect the wires together. remember what colors went together, ull need it to connect to the douser properly.
12. find a convenient place to mount ur momentary push button and solder the remaining 2 18 wires to it.
13. close up the computer and move on to the terminal strip on the dowser.
14.strip and insert the wires into the terminal strip to match the order u spliced them into the computer. the yellow wire and the black wire next to it should carry 12volts and the red and black wire next to it should cary 5 volts. don't screw that up. check the diagram or tech specs for ur player to be sure.
15. turn on the computer and hit the momentary button. if it works ur golden. mount it in front of the projector and touch up any paint if necessary. if it doesnt work.. curse under ur breath then trouble shoot


i found that the first mount i made, which attached to the sides of the case squoze the sides together and fouled up the trays ease of motion. i initially thought i was having severe voltage drop issues due to the 140' run of 18 wire but later found that the tray not opening was due to the mount.

the location and orientation of the mount on the CD-rom case will be determined by the location and orientation of ur projector.


this is what worked for me. lets see if someone can improve on it.

 

[mjw56]

here are the photos it took. didn't get a chance to take pictures while i was making the douser. i think im going to make another one and mount it to sweep down. if anyone is interested ill take progress photos when i do it.

 

[firewater88]

I have two projectors double stacked and merged for one image. I had the same issue as video black is not true black. So I looked around the shop and thought about an I-cue that I had that the mirror had fallen off. I re-engineered the unit to one stepper motor with a piece of matte board mounted to it and placed it between the two on the stacker mount. at 0 DMX it is parallel, at 35 DMX it is vertical, blocking both projectors at once. I just run it on a fader on the console and even put it into cues. Works great.

 

[museav]

I re-engineered the unit to one stepper motor with a piece of matte board mounted to it and placed it between the two on the stacker mount. at 0 DMX it is parallel, at 35 DMX it is vertical, blocking both projectors at once.

You might want something a bit more heat resistant if the dowser is close to the lenses, if somebody engages it while a bright image is being projected you might end up with with the matte board burning.

 

[Dionysus]

Another solution (costs some money) is the DMX controlled Projector Douser by City Theatrical. It works fantastically, and since it is DMX controlled you can build it directly into your Lighting Cues.

They have an instructional video on YouTube if you are interested. YouTube - City Theatrical Projector Dowser

A good solution if you care to spend the money, don't want to make something yourself, or want a clean out-of-the-box solution. Also makes it easier to work for other projectors and if someone else wants to use it in the future.

It can also be used for other tasks.

Cheers.

 

[mjw56]

Yeah. definitely didn't want to spend the money. and its a permanent install, at least for the foreseeable future. i admit its not the cleanest looking install. the whole thing looks pretty clunky IMO. but i finished it at 1:30 AM the day of the first performance. i didnt want to be on that scaffold any longer than i had too. once the holiday events are over im going to have to go up there and stare at it for a while to figure out how to clean it up a bit. im thinking of pulling it up closer to the electric but i have a speaker cluster hanging 15' towards stage and 1.5' down from that electric, that i have to clear.