DMX Jacks

[Anonymous067]

Our lighting system has a Leviton Innovator 600. The board has 3 universes of DMX outputs. There are two cables going from the board (A & B I would presume) to a wall jack under the counter. Then, all over the auditorium there is jacks labeled (DMX A, DMX B). I assume two of these exist at the rack of the dimmers (though I've never actually checked...).

Also, in various places we have those same DMX A/B Jacks. What I'm wondering is if I can also plug more devices (movers...) into those other open jacks. I'm not sure how they are wired...I guess in theory it doesn't matter, as long as pin 1 is pin 1 system wide and so on and so forth...but this should work? right? Thanks...

:]

 

[mstaylor]

If done correctly then it sounds like that should work. What question is whether it is wired as a passthrough or as a split. I would take something that is DMX addressable and see if it comes up in the same universe at each A point, then each B point. Let us know.

 

[JD]

"If Done Correctly...." Ah! That is the question! The way it should be wired is that the outputs on the board go into a pair of opto-splitters. From there they "star" out to all the DMX jacks with each one having a home run to the splitter. The real trick is to find and see-for-yourself the opto-splitters in question.

Are they Jacks or Jills ? (Female 5 pin)

 

[ship]

You have three universes of DMX but only two universes of A/B jacks. Simple question shouldn't it be ABC jacks?

 

[Anonymous067]

I know that DMX has to be terminated if not connected to anything...so I'm curious...what happens if these jacks are all daisy chained? Will that work if one of them has nothing plugged into it? Our system doesn't have a in and thru jack on the wall, just a single "DMX A".

My guess is they didn't wire DMX C because we don't have the need or capabilities for it, and on the board, universe C is for movers only. My plan currently is just to run a long DMX cable from the board to the flybar and not even mess with the wall jacks...

 

[mstaylor]

"If Done Correctly...." Ah! That is the question! The way it should be wired is that the outputs on the board go into a pair of opto-splitters. From there they "star" out to all the DMX jacks with each one having a home run to the splitter. The real trick is to find and see-for-yourself the opto-splitters in question.

Are they Jacks or Jills ? (Female 5 pin)

John:
I agree completely that it should go through a pair of opto splitters. I seriously doubt that happened and the plan to run a new wire is probably a good one. However, my question is hpw are the conventionals being run now? Do you have any issues with the DMX acting crazy now?
How many dimmers are you running and do you use more than one universe?

 

[Anonymous067]

I think it would be a fair assumption that we don't have any opto splitter dealios...then again, I'm the sound guy. I've seen the dimmer rack twice in my three years experience at this venue...

DMX Issues...rarely. Maybe a few per year, and many are due to people forgetting to lock out the idiot controls on the wall, and then it sends all sorts of weird signals to the dimmers, and the whole &^%$#@ system freezes...

Last show we had an issue with a few lights not powering on. After checking all patches replaces all lights cables and dimmers (switching) somebody (me) decided it might be a good idea to power cycle. That worked...haha.

To my knowledge, we don't even USE DMX B, and if that jack exists backstage, I will use that and run the movers from universe B.

Tomorrow sometime I'm going to run to school and drop the whole set of files (including setup files) from the board on a floppy and run it on the emulator program on my computer and see what I've got to work with. My backup plan is to run a nice long 300 foot DMX run from the booth to the 1st Electric...

We probably run 250 conventionals for the standard plot. This includes all stage lights, worklights, isle lights, house lights, and cyc boxes in back.

 

[mstaylor]

Try one of the B taps and see what you get. If it doesn't work then run your new homerun.

 

[epimetheus]

In my experience, DMX jacks located in the house are generally designed as inputs for relocating the light board in the house for tech/programming. If the jacks are male, I'd assume they were designed as inputs; if they are female, I'd assume they are outputs. If they are outputs, there should be opto-splitters somewhere in the system, as others have said above. If they are inputs, there are probably not opto-splitters as it was probably intended that only one input be used at any given time.

 

[len]

If indeed they are wired as labeled, it should work.

Remember, you can put multiple devices on the same dmx universe. The stipulations are a limit of 24 (I think it's 24, it might be 32) devices on a dmx run. Any more and you'd need a splitter, but they're fairly cheap for a decent Elation one. Or if you have the $$ get Fleenor, which are better, but more $$. And make sure that you have the addresses correct. If I were you, before I was to add more devices I would test the outputs near where you hope to mount whatever.

 

[Anonymous067]

So, one of my questions still remains unanswered...what happens if all the DMX wall ports (all Female if I remember correctly...) located around the whole space, are just "daisy chained" together? How else would they be connected if they aren't opto split?

 

[epimetheus]

So, one of my questions still remains unanswered...what happens if all the DMX wall ports (all Female if I remember correctly...) located around the whole space, are just "daisy chained" together? How else would they be connected if they aren't opto split?

Are the wall jacks male or female? My apologies if I missed the answer to this question above.

 

[Anonymous067]

Are the wall jacks male or female? My apologies if I missed the answer to this question above.

Female.
No worries.

 

[len]

If they are just daisy chained, then I'd drop a splitter in wherever I was planning to draw data from. If you're right at the dimmer rack, put it right in/on there. It'll stabilize your signal and you should be good to go.

 

[xander]

All this talk of optoes, I have to say something. Not a single small sized theater I have ever worked in owns an opto. While they are nice, if it is a small house they aren't necessary. If you have two male jacks where your board lives and they are labelled A and B then they are in all likelyhood inputs to receive DMX from the board and disperse it throughout the building. If you then have females (Jills) throughout the space labelled A and B, one can assume that they are corresponding outputs. You can test them if you want. What I am wondering is where are your dimmers? Are they A or B or something else completely? I highly doubt the the outputs are daisy chained. If there are multiple A outputs and then multiple B outputs then there is most likely an opto inline somewhere. What I do see most often is multiple inputs, A, B, C, whatever you want to call them, and then an output somewhere for each. Like A in FOH, B backstage, and C in the dimmer room. In this case no optos are necessary.

 

[Anonymous067]

Nobody has clarified how they would be wired if no optos are used?? Parallel? All tied together?

 

[Malabaristo]

Nobody has clarified how they would be wired if no optos are used?? Parallel? All tied together?

Just to make sure I'm understanding correctly: there are two male jacks in the booth Labled "A" and "B" and several female jacks scattered around the venue?

If that's the case, and there's no opto-splitter hidden away somewhere, then it's possible that all of those female jacks are daisy-chained together. This is generally a bad way to lay out a system, but there are plenty of badly-wired systems out there (as plenty of people here can attest).

Having multiple female connectors on the same DMX run makes it really likely that someone will plug in multiple devices and end up with branches of tens or hundreds of feet. DMX only allows for branches of 12-18" (I forget the exact number). It's the sort of thing that might work some of the time, but really doesn't make for a reliable system.

 

[len]

All this talk of optoes, I have to say something. Not a single small sized theater I have ever worked in owns an opto. While they are nice, if it is a small house they aren't necessary.

Necessary? No. But they do tend to minimize sins of improper cable, improper installation, etc. They also can minimize cable runs if going to multiple positions. My attitude is that technology is there to make life easier. And if I can find a box that does that, and does it economically, I'm using it.

 

[Anonymous067]

Just to make sure I'm understanding correctly: there are two male jacks in the booth Labled "A" and "B" and several female jacks scattered around the venue?

If that's the case, and there's no opto-splitter hidden away somewhere, then it's possible that all of those female jacks are daisy-chained together. This is generally a bad way to lay out a system, but there are plenty of badly-wired systems out there (as plenty of people here can attest).

Having multiple female connectors on the same DMX run makes it really likely that someone will plug in multiple devices and end up with branches of tens or hundreds of feet. DMX only allows for branches of 12-18" (I forget the exact number). It's the sort of thing that might work some of the time, but really doesn't make for a reliable system.

I don't know what gender the connectors are under the board, but I do know the jacks throughout the venue are Female 5 pin xlrs labeled A and B.

No C Universe jacks exist in the venue.

What do you mean you can only have 12-18" branches. The cable going from the wall to the dimmer rack is no doubt longer than 18", and how would the system know if it's going through a wall jack or not...its just seen as a long uninterupted cable...I'm confused.

 

[derekleffew]

...What do you mean you can only have 12-18" branches. The cable going from the wall to the dimmer rack is no doubt longer than 18", and how would the system know if it's going through a wall jack or not...its just seen as a long uninterupted cable...I'm confused.

DMX does not allow for "T" or "Y" splices. You are correct that the cable doesn't know it's going through a wall jack--until you plug a device into it, in the middle of the wire run. Then you have created a Y split, with one side going to your DMX device, and the other side running free and empty. This exposes you to signal reflection. As len said "If they are just daisy chained, then I'd drop an opto-splitter in wherever I was planning to draw data from." This will probably work, but is not recommended. Two terminators should be used, one at the last wall plate and the other at the end of the chain coming from the opto. Plan on running cable from your console direct to the device, just in case.