DMX Controlled Projection Screen (do they exist?)

[Hilary Watts]

stevefez' suggestion of a motorised roller screen seems the most appropriate and this is what we have in a local theatre which has a 'cinema screen' across the whole width of the stage. Control is by two sets of 'Up' / 'Down' wired buttons, one by the Stage Manager's desk and the other in the control room at the back of the auditorium. We regularly show cinema-style adverts during the interval and it's an easy matter to raise or lower the screen from either control position. I wouldn't want to see it controlled by DMX - there are too many occasions when there is somebody or something in the way and the fact that the control is operated manually makes it more likely that appropriate action is taken to clear the screen path before lowering it!

[timsabre]

Can you really get roller back-project screens? I tried to find one some time ago and came to the conclusion they don't exist - I presumed because of the requirement to tension the RP surface.

[ben-collins]

So to clarify, do you or do you not have the grid or space to fly it out? If not, really the only solution is a motorised roll screen, controlled by one of the various methods described above.

 

oh, no sorry I ment just motorised roll up and down. (fly up and down) :)

 

Can you really get roller back-project screens? I tried to find one some time ago and came to the conclusion they don't exist - I presumed because of the requirement to tension the RP surface.

 

I think so, but not too sure come to think of it? :P

[dwright2104]

theretically, it could be acheived by a DMX Switch pack feeding a 240v Double Throw Relay.

By switching the mains to the relay on and off, the relay will switch beetween up and down. So When relay is powered makes live for screen to go down. and when relay isnt powered will make live for screen to go up.

 

http://cpc.farnell.com/productimages/farnell/standard/1655527.gif

 

You would have to be extremly carefull as to make this safe, and have a very competent person to do this. under no circumstances I suggest trying this without knowing what you are doing.

[Matthew Robinson]

While all of this discussion is interesting and the ideas are commendable, moving stuff is one of the things that you shouldn't use DMX for. DMX has no error detection: if you get interference, then your screen may fly in when you don't want it to (or worse, when it isn't safe for it to do so).

[Bryson]

Indeed: DMX isn't the right protocol for controlling stuff like this. (Would you want the Blackout button on the console to retract the screen?* :() But a box fitted next to the console would work fine.

 

 

* = Yes, I suppose you could patch it as an attribute of some kind that doesn't respond to intensity commands, but that relies on the patch being correct, no-one ever loading a different show, and it's totally non-standard....

[TomHoward]

We have a motorized DaLite screen which is wired to a MK two-way retractive switch on the trunking next to the desk - no need for DMX control, and no chance of being powered up & down simultaneously.

 

http://img269.imageshack.us/img269/4172/30104281.jpg

 

We also have a trailing controller for it if we want to use it outside of the main venue - using two SPDT switches, you can easily make sure it doesn\'t get powered both ways by running the live feed for the second switch from the NC of the first. Same principle could easily be applied with relays.

[ben-collins]

Indeed: DMX isn't the right protocol for controlling stuff like this. (Would you want the Blackout button on the console to retract the screen?

 

Yeah, good point! :(

 

We have a motorized DaLite screen which is wired to a MK two-way retractive switch on the trunking next to the desk - no need for DMX control, and no chance of being powered up & down simultaneously.

 

http://img269.imageshack.us/img269/4172/30104281.jpg

 

We also have a trailing controller for it if we want to use it outside of the main venue - using two SPDT switches, you can easily make sure it doesn\'t get powered both ways by running the live feed for the second switch from the NC of the first. Same principle could easily be applied with relays.

 

 

Maybe this is the way to go then, mounting a up/down switch close to the desk or pc? :)

[Ashley R]

Can you really get roller back-project screens? I tried to find one some time ago and came to the conclusion they don't exist - I presumed because of the requirement to tension the RP surface.

 

I think so, but not too sure come to think of it? :(

 

 

I'm such an idiot :)

 

I have seen exactly what you are looking for (well everything except the DMX Part) don't know why I didn't bring this up earlier.

 

At school we had installed earlier this year a roll down projection screen with a Rear projector mounted on the back wall.

 

The screen along with everything else is controlled by a what I can describe as a touch screen the size of a Australian double 10A GPO, so at the press of a button the screen rolls down and the projector fires up, there are two locations that there is a control panel, one backstage and one on the lectern although if you turn the whole system off at the backstage panel you cant turn it back on via the lectern one.

 

So simply they do exist.

 

And they also hooked the audio system up to it, but I've got a feeling the way its set up now something is going to burn out, as there is one outlet that all the audio gear is plugged into and when you push the button 'audio on' it fires up everything at exactly the same time, (Desk, Amps, digital graphic)

 

Edited for spelling

[mac.calder]

And they also hooked the audio system up to it, but I've got a feeling the way its set up now something is going to burn out, as there is one outlet that all the audio gear is plugged into and when you push the button 'audio on' it fires up everything at exactly the same time, (Desk, Amps, digital graphic)

 

Edited for spelling

 

 

The touch panel stuff is Crestron or AMX or one of a number of other room control systems - their control over the screen would be via relay contacts most likely.

 

As for getting an RP roll down screen, they are not off the shelf. They are generally by special order only. AVStumpfl or ScreenTechnics should be able to supply. Expect long lead time and to pay a lot of money. Looking at that venue, the ceiling would be very open to a long-drop pantograph projector dropper. So a projector could be snugged up in the ceiling and dropped down with the screen making most arguments about switching to front project nearly redundant. Definitely work out cheaper and get a better result, methinks.

[Ashley R]

And they also hooked the audio system up to it, but I've got a feeling the way its set up now something is going to burn out, as there is one outlet that all the audio gear is plugged into and when you push the button 'audio on' it fires up everything at exactly the same time, (Desk, Amps, digital graphic)

 

Edited for spelling

 

 

The touch panel stuff is Crestron or AMX or one of a number of other room control systems - their control over the screen would be via relay contacts most likely.

 

 

Yep sounds about right, It was installed by DIB Australia - Audio Visual Systems.

 

Just wondering is this bad for the Audio gear to be switched on all at the same time? As I've seen threads about having automated ways of fireing stuff up in a certin sequence so something dosent blow up.

[Matthew Robinson]

Just wondering is this bad for the Audio gear to be switched on all at the same time? As I've seen threads about having automated ways of fireing stuff up in a certin sequence so something dosent blow up.

 

No, it's just that when you turn on some equipment (such as arc lamps), there is a large transient current as it turns on. After a period of time (which depends on exactly what it is) this transient stops and there is a much smaller power draw. The point of staggering the devices turning on is so that this larger current draw is spread out over a period of time, and thus you are less likely to overload (and thus trip) the breaker.

[Ashley R]

Just wondering is this bad for the Audio gear to be switched on all at the same time? As I've seen threads about having automated ways of fireing stuff up in a certin sequence so something dosent blow up.

 

No, it's just that when you turn on some equipment (such as arc lamps), there is a large transient current as it turns on. After a period of time (which depends on exactly what it is) this transient stops and there is a much smaller power draw. The point of staggering the devices turning on is so that this larger current draw is spread out over a period of time, and thus you are less likely to overload (and thus trip) the breaker.

 

Ah ok. already knew about the enormous amounts that arc lamps use when they first fire up. but was unsure about audio gear, thanks for clearing that up for me.

[Andrew C]

Just wondering is this bad for the Audio gear to be switched on all at the same time? As I've seen threads about having automated ways of fireing stuff up in a certin sequence so something dosent blow up.

It may be that they wanted all the ancillary kit powered up and stable before switching the amps on. You can avoid some nasty thumps this way (if your amps don't have delays on the outputs).