Adding DMX devices before distribution box

H

hhslights

Member
For our upcoming musical we have decided to use position some intels up in the booth near the light board. No problem right? Wrong. Having the low budget we do, we can only afford to use intels that use 3 pin dmx.

There is only one spot for us to plug a three pin dmx line into the board. That line is running from the booth to a backstage distribution box. We need these lights to be up in the booth for the show and buying or renting anything additional to make this idea happen is out of the question.

My initial thought was to run another line back from the box to one of two fixtures in the booth and then daisy chain over to the other fixture. But I don't know if we have enough cabling for that and plus I would much rather save the time and cable and not do that.

Then an idea struck me. What if we were to daisy chain the fixtures in so they came before the distribution box?

I tried asking the "tech (actually pit) director" if this would work and of course he had no clue so I asked the director who also had no clue.

I want to know two things, 1) will this work, 2) will it screw up other fixtures currently depending on the line coming from the board to the distribution box and then to their position on the electrics.

I drew something up on my computer real quick to illustrate my idea. It is not to any scale and just to show what I am generally thinking.
 

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What you're proposing is the way I would do this. Light board -> fixtures in booth -> backstage distribution. Does you're light board have a 3-pin XLR DMX output? What brand and model is it? Most boards, except the cheap ones, have 5-pin XLR outputs.
 
Yes, this will work, although I really don't recommend it you do it.

You lose any isolation protection the splitter is providing. If the light fails in an interesting but sadly not that unusual a manner, you could have current flowing along the DMX line to your lighting board, and your lighting board will NOT like it. Current could also go in the opposite direction and take out the splitter. And you won't be having a show that night.

If you absolutely must do it, make sure your lights have a passive DMX through connector, or this layout has another problem. If it's an active through, and the light craps out, you lose distribution to everything after it.

Given that cable is relatively cheap, and the DMX gods are capricious, I strongly suggest you go from the board to the splitter and then back to the lamps.

Plus there're some esoteric but very real ground loop issues you could encounter.

Robert Armstrong
Technical Sales
Pathway Connectivity
 
Theorectically your idea should work.

The quality of the DMX512 signal will be degraded before it gets to the to the DMX splitter.
Whether it is is degraded to much you won't findout to you try it.

Since these units use 3 Pin XLR fittings will you be using proper DMX rated cable or will you be using microphone leads. If you use microphone leads this will degrade the signal.

Idealy you should hire another splitter to have in the control booth.
This will help minimise any potential problems.

If you are hiring any gear you will find a DMX splitter won't cost much to hire, they may even throw it in free.

Brent
 
pathsupport said:
Yes, this will work, although I really don't recommend it you do it.

You lose any isolation protection the splitter is providing. If the light fails in an interesting but sadly not that unusual a manner, you could have current flowing along the DMX line to your lighting board, and your lighting board will NOT like it. Current could also go in the opposite direction and take out the splitter. And you won't be having a show that night.

If you absolutely must do it, make sure your lights have a passive DMX through connector, or this layout has another problem. If it's an active through, and the light craps out, you lose distribution to everything after it.

Given that cable is relatively cheap, and the DMX gods are capricious, I strongly suggest you go from the board to the splitter and then back to the lamps.

Plus there're some esoteric but very real ground loop issues you could encounter.

Robert Armstrong
Technical Sales
Pathway Connectivity
Click to expand...

The Problem with this analysis is that basically you are telling folks that everyone needs a splitter before their light board, for opto isolation. Obviously this is not the case, as many folks simply run a single dmx line.

Not knowing what DMX board it is it may or may not have Isolation.

I would argue that the signal degrade due to adding a few movers USING PROPER DMX CABLE at the booth and then feeding the splitter, would probably not cause signal degradation, and at the moving light connection there probably would be a cleaner signal than one coming from a cable running from the last fixture post splitter then to a long dmx line back to the booth.

I would say, get proper 3 pin dmx cables, and you should be fine.


Sharyn
 
epimetheus said:
What you're proposing is the way I would do this. Light board -> fixtures in booth -> backstage distribution. Does you're light board have a 3-pin XLR DMX output? What brand and model is it? Most boards, except the cheap ones, have 5-pin XLR outputs.
Click to expand...

Just got a new Ion. One DMX port is for the dimmers and the other has a five pin to three pin transformer. I know, its horrible but I don't have that much purchase influence.

I would love to either buy or rent more cables but we are several years over budget with the purchase of these used intels. I am still surprised we got the money for them in the first place.

I do hesitate about putting them first because I also have the fear that one will go wrong and screw everything up but I am also fearful of what will happen to the DMX signal being broadcast over such a long line.
 
If you're renting the fixtures, then ask the rental company if they have a splitter. Most do. You can probably get one for about $10 a week. Or just buy an Elation one for about $150. Then you can go out of the booth, split to the movers, then another line split to the stage and you're done.
 
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Personally, as long as you test the setup before you're in a critical situation, I think you're fine without a splitter in the booth. You'll want to test out the setup as much as possible to do the best you can to see if there will be any issues. For instance, my church has a Unique 2.1 hazer that just does not get along with our Mac500's. Some of our other intelligents (I know, bad term) get along with it just fine, but the Mac's just don't like it. You want to discover issues like while you still have some time to find a solution.

As I said, I think you're fine without a splitter in the booth, but try to use proper DMX cable if possible, and, as always, terminate your DMX runs. Just beware though, when using mic cable for DMX, or doing anything else less than ideal, you always increase the risk of something going wrong. YMMV.
 
hhslights said:
Just got a new Ion. One DMX port is for the dimmers and the other has a five pin to three pin transformer. I know, its horrible but I don't have that much purchase influence. ...

I do hesitate about putting them first because I also have the fear that one will go wrong and screw everything up but I am also fearful of what will happen to the DMX signal being broadcast over such a long line.
Click to expand...


The conversion from 5 pin to 3 pin does not require any transformer at all, it is simply that on the 5 pin two of the pins are not used so basically there is NOTHING different about 3 pin or 5 pin, and most 5 pin dmx cables only have 3 connections.

Wherever did you get the idea that three pin conversion was Horrible????????????

A Martin MAC600 which I think most would consider to be quite Professional uses 3 pin xlr

Get proper DMX Cables and IF you do get a splitter, make sure you Terminate the feed to the "Intels"

3 pin devices or 5 pin really don't matter, I am assuming that for some reason you think that 3 pin has as you said a transformer and that is going to cause some problem.

The ION'S outputs are all going to be opto isolated and protected.

Sharyn
 
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I would of course test the setup out. I was actually planning on doing it tomorrow. I put the fixtures up there today and shouldn't take more than five minutes to test out. We are using Elation powerspots and powerwashes. I wouldn't even dream of ending a line without terminating. Enough goes wrong when things are perfect, I try to keep as much as I can under control.

I did mean adapter, could not remember the word for some reason.

I remember reading somewhere that changing the cable that the signal is carried down deteriorates it. Going down from five to three or vice versa. Please correct me if I am wrong in this thinking, this is the first show that we have ever had any form of intelligent lighting.
 
DMX only uses 3 pins for data transmission. Converting from a 3 to 5 pin connector only degrades the signal as much as it being another connection in the line. 2 25' cables in series will have a slightly more degraded signal than 1 50' cable. That's a very extreme example with minimal degredation, however, when looking at a large touring setup, these types of things can end up compounding and making your life hell.
 
While Elation Power spot and power Washes are not the top of the line they certainly are not low end junk. I would have NO problem running proper dmx cable thru them placing them before the splitter. As stated above there is no problem with 3-5-3 pin setups, it all depends on length and quality of the cable

Quite a bit of higher end equip is using 3 pin (martin as I showed)

Putting the Spots/washes first will also reduce the chance that you could have problems controlling them, the "Intels" typically are a lot more sensitive to long cable runs etc than dimmers

Sorry I misinterpreted your comments calling it a transformer. I have seen folks think that 3 pin vs 5 pin is like balanced unbalanced audio

Sharyn
 
One quick and slightly off topic question. Does your booth have adequate ventilation? It occurs to me that it might get a bit warm in there what with at least one person, a board, 2 monitors, 3 MLs, and anything else up there. Not really sure how big the MLs are, but even an amp can make a booth uncomfortably hot if on for too long.
 
Whats happening with the existing 2 DMX ports on the Ion ?. I would assume that the house system would only be using Port 1.

Is port 2 used ?, and if not, then run data from the Ion to the booth fixtures, using 5 to 3 adapters as needed as well as appropriate data cable with 3 pin XLT cables as daisy'ing between fixtures.
 
Regarding "active vs passive" connections on the three booth fixtures, almost all fixtures are passive. If you want to assure that these are, simply unplug the power cords on the 3 booth fixtures and see if the rest of the system continues to work. If it does, then they are passive. As said before, 3 vs 5 pin connectors will not make any difference, and will not degrade the signal as long as the cable used is DMX cable. (Not mic cable.) The DMX protocol was written around 5 pin connectors but never fulfilled the use of the second pair. The best practical advantage it has is that you can sort them out from mic cords, and that everyone (kind of) agrees on the format.
 
SHARYNF said:
I originally thought that, but then the further points seem to highlight a fear of 3 pin and the fact that it is "horrible"

Sharyn
Click to expand...

Well, I wouldn't say it's "Horrible"... a good chunk of my gear is three pin... And I'm not 'affraid' of using it...

I am, however, aware that every time I use a 3-Pin connector, or cable, I'm not following the DMX Spec (USITT DMX 512 1990). And I lose any and all complaining rights if and when something goes horrendously horribly wrong. (Like someone using a Mic Cable because it wound up in the 3-Pin DMX bin, or a DMX line somehow ending up in an Audio snake)

We all do what we need to... Convert 5-Pin down to 3, skip a terminator on an opto-line because we're short, and the equipment seems to work... Run 5 Scrollers on an output designed for 4... :lol:

But there's nothing wrong with saying "You shouldn't, and here's why."
 
Lotos said:
Well, I wouldn't say it's "Horrible"... a good chunk of my gear is three pin... And I'm not 'affraid' of using it...

I am, however, aware that every time I use a 3-Pin connector, or cable, I'm not following the DMX Spec (USITT DMX 512 1990). And I lose any and all complaining rights if and when something goes horrendously horribly wrong. (Like someone using a Mic Cable because it wound up in the 3-Pin DMX bin, or a DMX line somehow ending up in an Audio snake)

We all do what we need to... Convert 5-Pin down to 3, skip a terminator on an opto-line because we're short, and the equipment seems to work... Run 5 Scrollers on an output designed for 4... :lol:

But there's nothing wrong with saying "You shouldn't, and here's why."
Click to expand...

There are several issues here;

The DMX SPEC attempted to get all manufacturers to use 5 pin. This has not been successful, IF the other 2 lines had been used in the protocol it might have been more successful

Using 5 pin has no guarantee that the cable being used (since THIS IS WHAT MATTERS NOT THE CONNECTOR) is proper spec dmx cable.

I agree it can help to relieve confusion but the fact is that there are a lot of 3 pin dmx devices out there so it is usually a case of needing converters away

Most folks dealing with 3 pin in an audio environment choose a different color jacket to reduce confusion


Sorry to be picky but the connector is not the factor it is the cable, and simply using 3 pin connectors is not going to lose "any and all complaining rights" Using the wrong spec cable or not terminating will

Sharyn
 
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