Film-Tech Forum ARCHIVE: Need Zipper unit with longest stroke

This is topic Need Zipper unit with longest stroke in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Frank Angel (Member # 248) on 12-17-2006, 03:08 PM:

I need to jerry-rig a "change-over" dowser that I can sit in front of the lens of an EIKI video projector. The thing puts out and unacceptable amount of residual light even when no signal is fed to it and it's supposed to be "off." Eiki calls it a "theatrical" 3XLCD projector, yet they didn't build a mechanical shutter to block the residual light.

So when we are running a mixed show with film and video, I can go from video to film and have the solenoid unit drop a shutter plate in front of the video projector lens to block the residual light output.

Thing is, the shutter plate has to move at least 5 inches to clear the projector lens. Zipper units must come in a variety of stokes, some longer than others. With a proper fulcrum design, I suppose I could make any stroke length work, except the shorter the stroke, the larger the physical contraption has to be. The longer the stroke, it can be less of a "thing" that looks like something out of Jules Vern sitting in front of the projector. Any suggestions on which change-over solenoid units would have the longer stroke?

BTW, video projector manufactures are salavating to get into the theatrical market, they should think theatrical and build this stuff into their products -- like how about an exhaust duct for the EIKI's 4 lamps? And how about an LCD menu window or even an output so a menu monitor could be hooked up so that config menus NEVER EVER need to be projected onto the screen (where you can't read them anyway). Excuse the rant.

I was also thinking of an alternative to a solenoid, should that prove too clumsy -- how about a geared, reversible mini robotic motor that would simply wind a cord onto a small drum and pull the shutter up and down, guillotine style. Since this is not a change-over in the sense that it needs to be instantanious, this design would serve the purpose, even if it takes a few seconds to raise or lower the shutter.

Posted by Peter Mork (Member # 1336) on 12-17-2006, 06:06 PM:

I did this once for a temporary setup by sticking a black card on a crossing gate from a Lionel train set, and mounting it in front of the lens.

Posted by Adam Martin (Member # 641) on 12-17-2006, 06:17 PM:

Brad has installed changeover dowsers on video projectors in several locations and wired them into the automation to be a seamless part of the show. Maybe he can post a photo.

Posted by Ron Curran (Member # 3631) on 12-17-2006, 06:20 PM:

Frank, till we organised an RGB1 to RGB2 changeover in our automation, we rigged up a drop on our porthole shutter, just a simple string and pulley arrangement. That is assuming your video projector is inside the booth.

Posted by Scott Norwood (Member # 30) on 12-17-2006, 07:55 PM:

Sell the Eiki and get a Panasonic 7700. It has a built-in changeover douser and the on-screen menus can be turned off and yet still used (if you know the exact keystroke sequence) during the show. It gives a great picture, too.

Alternatively, get a junked CD-ROM drive, tape a piece of cardboard in the "tray" area, and wire it up to "eject" and "load" the tray on remote command. Put it next to the video projector so that the tray (with cardboard in the center) covers the lens when it is "ejected." This will be far cheaper than a zipper-type changeover and is just as effective.

Posted by David Graham Rose (Member # 1450) on 12-18-2006, 03:47 AM:

Greetings

Why not use a Dolby ScreenTalk dowser? This would be ideal for the purpose.

David

Posted by Richard Fowler (Member # 893) on 12-18-2006, 08:26 AM:

Navitar sells a Light shutter device that is a set of double doors on a motorized frame that open and close.

Posted by Frank Angel (Member # 248) on 12-18-2006, 08:57 AM:

Great ideas guys, thanks. Scott, your's gave me quite a chuckle....I love it, and it's environmentally green (what to do with all that old computer junk!).

Everyone....have a happy and safe holiday and let's hope for a New Year where Peace On Earth becomes a reality.

Posted by Andy Frodsham (Member # 4061) on 12-18-2006, 01:45 PM:

I have already researched this topic well, Frank, having recently installed a video projector in our projection booth.

I have heard of several DIY sollutions including one which uses an adapted CD ROM drawer to obscure the projection lens!

There are companies out there which make such devices - some which may interface with computer controlled lighting panels and some which are free standing. One device, called 'the flapper' may be found on the following link:

http://www.response-box.com/store.shtml

I agree with all your comments about the ability to pre-view the output from the projector and need to switch-off the various on-screen menus - early days perhaps!

Posted by Tim Reed (Member # 137) on 12-18-2006, 06:27 PM:

quote:
Zipper unit with longest stroke

You naughty boy! [Razz]

Posted by Scott Norwood (Member # 30) on 12-18-2006, 10:36 PM:

Frank--I was actually serious about the CD drive thing. If you want it to look nice, buy a Sun 411 external SCSI box on Ebay, remove and throw away the 4mm tape drive that probably came in it, and install your junk CD drive (which doesn't need to be SCSI) inside it instead. Just hook up the power cable to the power supply in the 411 box and solder wires to the open/close terminals on the bottom PC board of the drive (may need to remove bottom cover of drive). Then, you can open/close the "changeover" with a contact closure.

The downsides are that a) there's a bit of a delay before the open/close cycle stards and b) the open/close state is toggled with only one contact closure, rather than separate contacts for the open and close cycles. But, for a total cost of $0-10, it's hard to beat.

Posted by Frank Angel (Member # 248) on 12-19-2006, 01:00 AM:

Scott my man....I know you were totally serious as was I -- it's a terrific solution -- ingenious, actually. The delay is no problem, as I said, it's not for the kind of instantanious change-over between dual projectors. And the pulsing is fine -- nothing is automated and the change-over pushbutton switches actually have an extra pole so I don't even have to futz with sticking in an extra relay.

BUT....I can't have it pulse OPEN and CLOSE every time I make a change-over at the 35mm projectors -- every time the OPEN button is pressed on either 35mm change-over, it would either OPEN or CLOSE the CD Dowser/draw, depending on what state it's in. That's no good. To prevent that, I'll add a microswitch that at the draw/dowser which will open when the draw is opened, that way, after the first activation by the 35mm projector change-over push, the CD unit will no longer respond to any further pulses from the projector change-overs. The only time the CD draw will activate again (to close -- i.e.,the OPEN position for the video projector) would be from the switch at the video projector which would by-pass the micro-switch and pulse the CD draw again. That closes the micro and makes the CD unit ready for another pulse from either 35mm change-over switch.

OR....I can just get them to buy that Mini Flapper that Andy found for $200 and change and be done with it -- but what fun is there in that?. What's more of a kick than getting the problem solved for the price of a length of wire and a microswitch?....hehe

Posted by Louis Bornwasser (Member # 3063) on 12-19-2006, 06:03 AM:

I have used a broomstick and a cardboard flap mounted in stacks of drive in speaker magnets in an emergency. "Wipes" were excellent in a 2 machine booth. It almost wasn't worth repairing the zippers.

Cinerama used automated dousers....I have a few around here somewhere. 4-5" hole with a solenoid to operate a spring mounted light duty paddle. Perhaps I should copy this and bring to market? Louis

Posted by Gordon McLeod (Member # 33) on 12-19-2006, 09:46 AM:

In the UK there used to be a porthole mounted changeover system

Posted by Adam Martin (Member # 641) on 12-19-2006, 12:56 PM:

These manual changeover dowsers need to become popular again. [Big Grin]

Posted by Floyd Justin Newton (Member # 1316) on 12-19-2006, 01:58 PM:

Good idea Adam. But have you priced an iris lately? [Confused]

Posted by Joel N. Weber II (Member # 3530) on 01-22-2007, 01:46 AM:

While the pushbutton on the drive itself does both open and close, I believe a computer attached to a CD drive can send open and close as distinct commands. (Notice how NetBSD's ``eject'' command has a ``-l'' flag to load the media; it seems to work correctly on at least one drive I have.) Presumably this doesn't really help Frank, but it might be useful in an installation that already has a computer controlling things.

I have an Asus DVD reader in one of my computers at home that automatically closes itself after some length of time being left open, so a little bit of care in selecting the right drive may be needed; on the other hand, I don't remember ever encountering that ``feature'' on any other drive.