Design Controlling House Curtain Via DMX

[creamers]

I just saw this thread. http://www.controlbooth.com/forums/scenery-props-rigging/27822-grand-curtain-motorization.html

When I was thinking that my schools main curtain is motorized as is. There used to be a open and close button running up the the lighting booth. (Now that wiring is for a closed circut phone system) The curtain control has three buttons a Open, Close, and Stop. Is there any way I could use dmx addressing to issue a event. Basically a press of the button but with dmx. I have seen similar solutions that can trigger key on a keyboard using a decoder. Could the same principle be applied to this. If can someone point me in the right direction for accomplishing this.


The reasoning for this is that we only have a Sound (Me), and Light Operator. Full time and finding someone to open a curtain a few times during a show is a big deal.

~Wesley K.

 

[DuckJordan]

The safe answer is NO. DMX is not very safe system to be using to control motors period. Now if you had those open and close buttons up in the booth, it would be fine to have an operator with their hand on it such as you or the light op. Running Motors off of DMX is just as bad as running Pyro of DMX. too many things to go wrong and there is not error check in DMX.

 

[chausman]

Hopefully there is some room in some conduit for you to possibly pull a line to add motor controls in the booth again. But you don't want a curtain to be DMX. To many weird circumstances to have to be right. Things like, what if a small DMX hiccup causes your main to start closing? What if your board crashes and or there is a DMX death gasp when you power down the console? If you start using DMX, what will happen with the onstage controls? How can a light op see behind a curtain (assuming no video monitoring system) to make sure nothing is going to snag and cause very expensive damage?

If finding a person who you can trust is an issue, maybe this thread can help.


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[mozsey]

I would say that you would need to know code. IF you were, and only IF you were, going to do this I'd suggest at getting an arduino and building the DMX shield for it. When compiling the code for it, you'd have to add redundancy safety features. If you lose connection from DMX, you can either build a home value or say to just hold where it is until it gets the DMX data chain back.

Basically, you'd have to build the DMX shield. You'd need to know code. Like everyone else says though, there are a LOT of safety problems involved. That would fall under stage automation and triggering stage automation with DMX is very difficult.

 

[tayklor]

I would say that you would need to know code. IF you were, and only IF you were, going to do this I'd suggest at getting an arduino and building the DMX shield for it. When compiling the code for it, you'd have to add redundancy safety features. If you lose connection from DMX, you can either build a home value or say to just hold where it is until it gets the DMX data chain back.

Basically, you'd have to build the DMX shield. You'd need to know code. Like everyone else says though, there are a LOT of safety problems involved. That would fall under stage automation and triggering stage automation with DMX is very difficult.

Having just worked with an Arduino-based controller for some LEDs embedded in a set piece that we needed DMX control over, I would have to disagree with this idea. I would never trust a DIY device with homebrew code to control something with the potential to do as much damage as a flying curtain. I agree with what others have said—DMX is too flaky to trust with something so potentially dangerous. Leave it to the already installed control system—it's backed by its manufacturer and installer.

 

[chausman]

I agree, arduino is too finicky to be reliable in my opinion. I also just used one and it would require frequent restarts and changes to the code to run reliably. We also faced a lot of issues with the arduino app itself not running reliably.


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[Chris15]

I'm sorry to be grumpy, but if you don't understand the technical reasons behind why we harp on about not controlling anything that can cause injury with DMX then you are not competent to consider building this.

The fundamental issue with using DMX for this sort of thing is there is no error checking. If for whatever reason the device receices (or decodes) a corrupted DMX packet it does not know this and proceeds to change based on it. In the old days of dimmers no one got hurt if this happened, and even with moving lights or fog machines, nothing unsafe happens. But with automation or pyro or anything like that, one pulse is more than enough to inflict some serious damage...

 

[FMEng]

If there was curtain control in the booth before, conceivably it would not be hard to put it back because the wire and conduit is already there. If you still need the phone in the booth, pull some cable for that. The telephone can be run on practically any twisted pair cable and it doesn't have to be in conduit. (The exception to that is a plenum space.)

 

[creamers]

Pulling wire isnt really any issue. It just involves me on a ladder for an hour or two. Heck we have some contracters at school that could do it for me. In there free time. Or send in a maintenance request. The existing wiring isnt in a conduit, it is just laying in the ceiling.

As far as checking stuff backstage. We can either wire a temporary video feed or get a permanent one installed to check for anything behind the curtain. Though most of the time for shows we would used this in. It is a set time or the curtain cue is an act.

I really do like the arduino idea, I dont code but I have a cousin that does. It it would need to do is decode dmx and short out 3 sets of pins which is what the existing curtain control does. To add them in all I should need to do is solder a few wires together.

Why the hate for dmx on anything that isn't a conventional light fixture. Most fixtures are still built on it except for anything which is ethernet based, as far as I can tell.

 

[icewolf08]

Why the hate for dmx on anything that isn't a conventional light fixture. Most fixtures are still built on it except for anything which is ethernet based, as far as I can tell.

The fundamental issue with using DMX for this sort of thing is there is no error checking. If for whatever reason the device receices (or decodes) a corrupted DMX packet it does not know this and proceeds to change based on it. In the old days of dimmers no one got hurt if this happened, and even with moving lights or fog machines, nothing unsafe happens. But with automation or pyro or anything like that, one pulse is more than enough to inflict some serious damage...

Let me start by saying: "What he said!"

There is a reason that even on shows where the entire show is automated (lights, sound, pyro, motion control, etc.) that there are individual systems for each department. They are usually linked using something like SMPTE or MIDI, not DMX. Using DMX to fire a sound cue or a projections cue isn't a big deal because it won't hurt anyone if the sound or image goes at the wrong time. As Chris15 said, if an automation cue is triggered at the wrong time, people can be seriously injured or killed.

Yes, we are talking about a curtain, a piece of soft good in this particular instance, but if that curtain is piped or chained to keep it hanging nicely, it could really hurt someone if it came in on top of them.

Recently I have been discussing installing a new architectural control system in my theatre. The idea would be to replace the current analog relay controls for things like house lights, work lights, cue lights, lobby bells, and grand drape with something like an ETC Paradigm processor and button stations. Even with a setup like this, we would program the system so that the grand drape can only be operated after keying an unlock code on the button station so that it is not bumped, bashed, or otherwise triggered inadvertently.

There is no "hate" for DMX being used to control things that are not conventional fixtures. You can control many things with DMX, and do so safely. However, by nature, DMX is very finiky, and as mentioned, it has no error checking. You may see a moving light twitch when it gets a bad packet, you won't even notice if an incandescent on a dimmer gets a bad packet, but if you were controlling your pyro with DMX and a bad packet came in and it triggered an effect while an actor was standing on top of it, well, it would be bad. If your grand drape got a bad packet and started coming in during the big second act production number, there would be a lot of unhappy people.

There are safe ways that you could link an automation control system to your lighting desk, but DMX control is not one of them. In the end, is it really so bad to have the SM or light board operator or an ASM backstage run the curtain? That is what we do, and we are a large professional theatre. An time we use the grand drape, one of the ASMs backstage runs the cue.

 

[josh88]

Chris has already explained it pretty clearly why you don't want to use dmx for much more than lights or fog:

The fundamental issue with using DMX for this sort of thing is there is no error checking. If for whatever reason the device receices (or decodes) a corrupted DMX packet it does not know this and proceeds to change based on it. In the old days of dimmers no one got hurt if this happened, and even with moving lights or fog machines, nothing unsafe happens. But with automation or pyro or anything like that, one pulse is more than enough to inflict some serious damage...

Edit: Icewolf beat me to the same quote.

 

[DuckJordan]

No its a lighting control not a scenery/automation control this will end badly and you will probably lose your job. There is a reason tours use a seperate device not just because they want to. Trust me less crap in the truck the better.

 

[creamers]

OK thanks for the help on this. I will look inside the curtain control and see what we can do with it. I will probably end up running an Ethernet cable upstairs and terminate it at a keystone jack. There will be a little control box that can be unplugged when it isn't in use.

As far as losing my job. All this is volunteer work at my high school. There is no way for me to lose my job if something goes wrong we can blame it on the Auditorium.

 

[josh88]

As far as losing my job. All this is volunteer work at my high school. There is no way for me to lose my job if something goes wrong we can blame it on the Auditorium.

that's not so much true though. If someone were to get injured and since it's volunteer work you could very easily end up in a lawsuit. You can't just blame it on the auditorium if you were the one who made the environment for something to go wrong.

 

[creamers]

that's not so much true though. If someone were to get injured and since it's volunteer work you could very easily end up in a lawsuit. You can't just blame it on the auditorium if you were the one who made the environment for something to go wrong.

Well using common sense and not being stupid. The only enviroments im ever involved in is setting up a acc lighting system and sound. Never anything structural.

 

[65535]

As far as losing my job. All this is volunteer work at my high school. There is no way for me to lose my job if something goes wrong we can blame it on the Auditorium.

That's not a healthy attitude for someone working in a theatre at any capacity.

 

[Les]

Has it been established that the curtain flies, or is it a traveler? Not that it matters much - even a tame 'ol traveler can snag on a set piece or lighting boom and bring it to the ground.

As the TD at UT Austin said during a UIL State convention: "If your actor is on this line when the curtain flies in, you'd better have his understudy ready!"

 

[josh88]

Well using common sense and not being stupid. The only enviroments im ever involved in is setting up a acc lighting system and sound. Never anything structural.

Automating a curtain through dmx is certainly a way for people to get injured, and if you're the one who made it possible and ran the wires etc and it pulls a boom or something over as Les mentioned, the first question they will ask is who was responsible for running it and who was the person who installed it. In any aspect of theatre, whether you are involved in doing it yourself or you know of/see somebody doing something unsafe you should stop it. It's always better to assume you will ALWAYS be the person held responsible (even if that's not the case) and not allow unsafe practices. If I saw someone hanging from a batten as people tried to fly it out I wouldn't turn around and say I didn't work on that so if something happens we'll just blame the other people. Common sense goes a long way, but also helping others who might not have as much common sense as you, is a good responsibility to take on as well.

 

[chausman]

Has it been established that the curtain flies, or is it a traveler? Not that it matters much - even a tame 'ol traveler can snag on a set piece or lighting boom and bring it to the ground.

I've seen travelers knock quite a bit over at once. If this was[/i a flying curtain, this is an even worse idea.

OK thanks for the help on this. I will look inside the curtain control and see what we can do with it. I will probably end up running an Ethernet cable upstairs and terminate it at a keystone jack. There will be a little control box that can be unplugged when it isn't in use.

As far as losing my job. All this is volunteer work at my high school. There is no way for me to lose my job if something goes wrong we can blame it on the Auditorium.

But it would still be using DMX while that was connected.

Well, you may not loose a paying job, but lawsuits are an issue as was stated, and lawyers WILL find someone and anyone who could be even remotely related. Also remember, this is a VERY SMALL industry, and word travels fast. You may not loose a job at that high school, but it would affect job opportunities later.

 

[Chris15]

I think we've reached the point in this discussion where we might need to collectively take a step back...
I hope it's become reasonably clear why using DMX as the control protocol would be a poor choice.

But if we return to the original problem we're trying to solve...
As I understand it, there is a lack of available (semi?) skilled labour to operate the curtain and the envisaged solution would have returned that capacity to the control room, right?
So that same functionality, albeit with less integration and "cool factor" but with an appreciably larger safety factor could be achieved with 3 buttons on a box or a wall plate in the control room, being open, close and stop (which by the way ought be a mushroom headed button...)

I think the best way of getting a safe and long term solution is the one suggested all the way back in post #8. Pull a Cat5 and swap your phone system over to that and reinstate the curtain controls as they previously were.
Pull extra Cat5 because it's always useful to have around and cable is much cheaper than labour...