Can or should I not do this with a dmx cable.

Crisp image

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Jun 18, 2017
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Eastern Victoria Australia
I know I can but should or could I do this with a dmx cable.
The cable in question runs from the bio box to side stage. It is a 5 core shielded cable that currently delivers dmx to the stage.
Seeing as dmx only uses 3 cores (d- d+ gnd) will using a common ground and the other 2 cores to send a second universe to side stage be a problem. I seem to recall that the 5 pin dmx was designed to do just this but never took off.
This will give a little more flexibility at a low price point.
Regards
Geoff
 

RonHebbard

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Waterdown, ON, CA
I know I can but should or could I do this with a dmx cable.
The cable in question runs from the bio box to side stage. It is a 5 core shielded cable that currently delivers dmx to the stage.
Seeing as dmx only uses 3 cores (d- d+ gnd) will using a common ground and the other 2 cores to send a second universe to side stage be a problem. I seem to recall that the 5 pin dmx was designed to do just this but never took off.
This will give a little more flexibility at a low price point.
Regards
Geoff
@Crisp image Let's summon: @STEVETERRY and / or @jfleenor for a definitive answer. . .
Toodleoo!
Ron Hebbard
 

JD

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Jan 1, 2005
Location
North Wales PA
If the cable truly has two independent twisted pairs, then yes, it would work. I do that myself. HOWEVER, I have seen a lot of DMX cable that has four wires twisted together in a "twisted quad", so to speak. That would not work.
Example of "Twisted Quad":
SOM540-0051.jpg
 
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Lyle Williams

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Feb 15, 2017
Location
Australia
So we are talking about maybe a 20m run?

Everything I have experienced about RS485 says this will be easily accomplished. In the real world most RS485 just gets carried on telephone wiring.

(Everything I read on lighting forums says the DMX gods will smite you for even asking.)
 

Crisp image

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Jun 18, 2017
Location
Eastern Victoria Australia
If the cable truly has two independent twisted pairs, then yes, it would work. I do that myself. HOWEVER, I have seen a lot of DMX cable that has four wires twisted together in a "twisted quad", so to speak. That would not work.
Example of "Twisted Quad":
View attachment 18342
I will have a close look and decide what it is.

So we are talking about maybe a 20m run?
Rough guess 35 to 40m if you measure the drop to the connection points
 
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Crisp image

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Jun 18, 2017
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Eastern Victoria Australia
Sure, a piece of ZIP cord and a couple of chuncks of hookup wire will probably carry your two universes--until they don't. A few hundred feet of the proper spec cable will cost FAR less than proper installation of same. Follow the proper spec and do it once and stop worrying about it.
This particular cable is already in the wall so hence my question. If I was doing a new install it would on separate cables for sure.
 

JD

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Jan 1, 2005
Location
North Wales PA
Depends on the cable. Goldmine would be if it were Cat5/Cat6 in conduit, which actually can handle 3 universes even though it is the cheapest.
It all hinges on how the wires are paired.
 
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FMEng

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Belden 8723 is not even close to the correct impedance for DMX, which may cause data errors. There is nothing wrong with using two pair DMX cable, and having a few inches of twisted pair un-shielded in tight shrink tubing. Maintaining uniform pair twist accomplishes most of the noise immunity.
 

JD

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Jan 1, 2005
Location
North Wales PA
Belden 8723 is 52 ohms. You want something that is 110 to 120 ohms. Twisted pairs is the other important characteristic. That's why (ironically) cheap Cat6 is great (110 ohm) although not for portable applications as most is solid conductor.
 
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Robert F Jarvis

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Apr 8, 2017
Location
Sebring, FL, USA
Our U1 and U2 to go onto a 5 wire cable and down the auditorium. U1 on 2 and 3 and U2 on 4, 5. Both tap 1 of course. Downstage we put 1, 2 and 3 (U1) onto a 3 pin female socket and 1, 4 and 5 onto another (U2) 3 pin female socket. If all your doing is separating the wires that's fine. If you want to 'break out' (sniff) U2 on its way to say a dimmer rack then you'll have to run 4 and 5 through an opto isolator
 

Ron Foley

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Feb 13, 2017
Location
Guelph Ontario
Stick with the cat 5 or cat6 six as mentioned above
it is now an acceptable cable and works great
and as was mentioned you cab get (3) universes
there are several companies who make panel mount XLR's with terminal strips
no need to solder.
you can even use the stranded cat5 5 that is used for RJ45 cables to make patch cords and cables