Basic (something I should know) DMX hardwiring questions

[Aaron Clarke]

I'm now working in an old vaudeville/movie theatre and the light booth is the old projector booth. The only (okay, there are many more than one) problem is from booth I can't even see the bottom of the cyc since it so high above the balcony. This makes it a real PITA to program the show. I either have to guess and then try making changes via the RFU from the main floor or just take notes and guess at later time and repeat.

They have a ETC senor rack, Expression III with the standard ETC DMX input panel in the booth (DMX 1,2,3 in, RFU and ETC link ports). This is the only input panel.

I'd like to have the ability to pull the board to the main house level for tech and programming shows. Several other venues I've worked in would have a 2nd or even third input panel in various locations and I'm curious what it would take to do the same here. I really could just run some longer DMX cables down the balcony and drop to the floor but I'm curious what would be involved in adding a second input panel on the main level. I really only need the DMX universes.

So here is the question I need an answer to:
Would that additional input just be wired in a series the current one or are all the inputs routed to some type of DMX combiner for each universe?

If it just in a series it maybe something I'll ask/help the theatre to do. It's easy access to run the cable and place a floor pocket. If its going to involve more equipment, then probably just keep running and taping down those extensions for my shows.

 

[Mac Hosehead]

Generally, multiple DMX inputs on the same universe are wired in a daisy-chain fashion. It is true that plugging in at the mid location will create a "stub" of cable that is not used. However, if the system has proper termination this stub will usually not affect the DMX signal. Some consultants are of the opinion that all DMX inputs should have separate lines and be able to be mergered with different consoles.

 

[John Palmer]

Sensor CEM's will take an input from two different DMX sources. So, instead of worrying about stubbing off the existing data run, you can have a new DMX input panel installed where you need it.
I would suggest you contact your local ETC dealer to get their help in getting the correct panels for the installation. You will probably need an electrical contractor to run the conduit and pull wire unless your dealer can provide this service. If you are going to all of this effort, run network wiring as well! You could also look at a back plane upgrade to CEM3 on your Sensor dimmer racks. My understanding is that this will re-warranty your racks when done by an ETC service provider.
Hope that helps.
John

 

[SteveB]

ETC's own install spec's allow for a 2nd DMX port on an existing line.

Reality though is and with a single console being moved around, I'd just run a few DMX lines as well as some cat 5 in conduit as necessary, back to the booth and terminate in a wall jack, then just plug the "floor" connection into the existing connections that goes to the dimmer rack and onstage.

Cat 5 is useful down the road if you upgrade the console and need to do designers remote at the floor level via a network.

 

[Aaron Clarke]

Reality though is and with a single console being moved around, I'd just run a few DMX lines as well as some cat 5 in conduit as necessary, back to the booth and terminate in a wall jack, then just plug the "floor" connection into the existing connections that goes to the dimmer rack and onstage.

I was just thinking of a doing a very similar thing just last night. It's real easy access under the booth & "inside" the balcony framing to run a couple lines to the nose of the balcony that can just be dropped to where I would have the board on the main floor. Given it's a community theatre and I most likely will pay for it the long run that's probably what we will do. If other designers/users turn out to like the idea then I can float a more permanent upgrade with the board. Could merge that and running DMX lines for future LED at the same time.

 

[RickR]

Look really hard for that seating panel! They can hide; half behind seats, buried under tape/junk/carpet and who knows what. I can't tell you how many times I've heard "So that's what that is!"

Be very careful changing the existing wiring. I've seen some pretty odd things done in older systems. The first step would be to map out the entire wiring and verify that you aren't assuming connection paths. Pull cover plates, do continuity checks, trace everything!

Doing a general DMX upgrade at the same time is a great idea.

 

[JD]

How about just looping an extension run down from the booth? When it's not in use, it's dead cable. When you need to use it, just plug the booth end into your stage run and move your board down to the location you want. If the house isn't open when you need to do it, you could simply throw the cable out the booth window. (make SURE no one is below!!) Probably a lot easier than pulling a new line all the way from your dimmers.

 

[DavidJones]

If you do have to do this at your own expense, consider just pulling a run of install grade cat5e and terminating it with a 5-pin XLR. It meets the spec for DMX, and is very cheap. Even if like posted above you just run it out the window and over the seats. I used to get free 100' pieces of install grade network cable when that was all that was left on a 1000' roll; the installers would just throw it away because it was too short. You could even piece some together. It's not elegant or long term, nor would I use it to run a show, but as a temporary line for programming, the price is right.

 

[Jay Ashworth]

David: do *you* have a spec for an A5M that expects 24AWG solid wire?

 

[DavidJones]

Nope. Just read it somewhere in a report or specification on the internet, and you can find many commercially available products that use DMX over Cat5e/6, like the TMB sneak snake. Also, I have Done it and it works, given the caveats I listed above.

 

[JD]

David: do *you* have a spec for an A5M that expects 24AWG solid wire?

ETC had them. Wall mount with punch-down for cat5 / cat6

 

[Jay Ashworth]

ETC had them. Wall mount with punch-down for cat5 / cat6

I *did* say A5M.

I know you can do it as a wall-jack...

 

[JD]

I *did* say A5M.

I know you can do it as a wall-jack...

yea, don't know of any inlines (for good reason), although I must admit to making one. The real problem is not soldering the pins, it's just that solid conductors will likely break near the connector strain relief after awhile from flexing. The one I made was about 10 years back. Still works. Has about 8 inches of heat-shrink on it, with a second layer about 3 inches going into the connector. As long as it has a "guardian" (someone who looks after its handling) it will last. in the regular Rock-n-Roll world, I would expect it to have a lifespan of 1 to 3 gigs