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Small Diameter DMX cable?


HalloweenBob

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I wanted to know what the smallest diameter DMX cable is. I have an application that requires a DMX in and out to travel through a small hole along with other wires (DC Power wires).

 

I know the debate about using mic XLR cables in place of 3 pin DMX has been beaten to death, but I can easily find lots of thin small diameter mic cable, but have yet to come up with DMX cable that small. I want to use a regular cable with connectors on both ends. I will be needing a lot of these and don't want to buy bulk wire and spend my time soldering connectors to it.

 

So if thin DMX cables exist, I would love to see them. If not, is it a problem to use regular mic XLR cables for short runs of under 5 feet? For that matter, if it is that small a run, can I just use plain old hookup wire with no shielding? I suppose I could spend some time experimenting, but I would rather refer to those with experience in these matters.

 

I'm not trying to do this to save a buck and buy cheaper cables. All of my long runs will be certified DMX cable. I just have a size problem at one particular point that I need to solve.

 

All help from the DMX experts is welcome.

 

If anyone is interested, this is my project: http://HalloweenSkulls.com

You can see it work in the Demo Video. All the wires need to be hidden. in the video the hole that runs up through the neck is just big enough for one cable. Adding a second to daisy-chain another is impossible with the standard size cable.

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I'm confused...you say you need small diameter cable to go through a small hole, yet you say you want to buy it pre-terminated? Surely this then means that you need an XLR sized hole, in which case the size of the cable doesn't really come into it...?!
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Like the skulls :-)

 

Cat5 possibly give you enough cores for DMX I/O + power, terminate with crimp/punchdown makes it quick.

 

and/or distributed DMX IN per head using someat like

 

http://www.ebay.com/itm/LED-Controller-DMX-8-Channel-Output-DMX512-Signal-Amplifier-Splitter-Distributor-/222254953371

 

(mebbe mod move topic to lighting where may get other answers)

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FST/Belden 9501 is about 1/8" and listed in the original RS485 specs, BUT I don't understand how you're going to get it through the small hole without soldering the plugs on after installation.

 

I wanted to know what the smallest diameter DMX cable is. I have an application that requires a DMX in and out to travel through a small hole along with other wires (DC Power wires).

 

I know the debate about using mic XLR cables in place of 3 pin DMX has been beaten to death, but I can easily find lots of thin small diameter mic cable, but have yet to come up with DMX cable that small. I want to use a regular cable with connectors on both ends. I will be needing a lot of these and don't want to buy bulk wire and spend my time soldering connectors to it.

 

So if thin DMX cables exist, I would love to see them. If not, is it a problem to use regular mic XLR cables for short runs of under 5 feet? For that matter, if it is that small a run, can I just use plain old hookup wire with no shielding? I suppose I could spend some time experimenting, but I would rather refer to those with experience in these matters.

 

I'm not trying to do this to save a buck and buy cheaper cables. All of my long runs will be certified DMX cable. I just have a size problem at one particular point that I need to solve.

 

All help from the DMX experts is welcome.

 

If anyone is interested, this is my project: http://HalloweenSkulls.com

You can see it work in the Demo Video. All the wires need to be hidden. in the video the hole that runs up through the neck is just big enough for one cable. Adding a second to daisy-chain another is impossible with the standard size cable.

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The hole is large enough for me to slide through the connector I am putting on one end. I run both cables through that connector first, then all the other wires, then the steel shaft that goes through as well. Once all those are in place, it's very tight, but they can go in and out one at a time.

 

Thank you, I will look into those cables. the hole runs through the vertebrae you can see in the video. That is how the wires are hidden.

 

I just found a supplier for that Belden cable. It looks perfect and is a great size. Looks like a winner. I will be ordering some right away.

 

Bob

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I have a reel (305m iirc) of two twisted pairs within one screen and one 6mm sheath. Better minds will tell whether this would work for 2 DMX lines. It was from RS. Obviously needs connectors. I use it like scroller cable one data pair and one DC 24v pair.
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Could you use a DMX splitter then run DMX as radial circuits rather than daisy chain. This would cost but allow you to only have one DMX pair up the spinal column (no daisy chain output). May save a twisted pair and it's volume.
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AES-EBU digital audio cable would be 110 ohm as opposed to 120 ohm, but much closer than low impedance mic cable and would come in a variety of patch and installation cord sizes

e.g. http://www.canford.co.uk/DFT-DIGITAL-AUDIO-FOIL-SCREENED-STRANDED-CONDUCTOR-TWIN-CABLE

http://www.gepco.com/products/proav_cable/digital_audio/110_sing_26gage_F.htm?v=1

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Just how big is this skull and how long are the cables inside?

Quick and dirty way #1:- Just connect everything in the skull together in a star config and run a single lead down through the neck, put a male and female connector there and daisy chain at that point.

 

Quick and less dirty way #2:- As above but put a splitter at the bottom so that the star config part is isolated from the main DMX line.

 

If the overall dimensions are in the order of a foot or two then you can get away with any old topology. I know it's not according to the spec, and the old terminator business has been done to death, but it will work fine. Where you run into trouble is when the time it takes for the signal to propagate along the cable becomes more than a few percent of the bit time.

 

Dave

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I do know someone who ran DMX to the top of a stand then fanned it out with bell wire to four lanterns as simply a fan out connection, it broke spec but it worked. BUT rule no1 of breaking spec is that it will come to bite you, usually at the worst moment.

 

Lots of DMX splitters all active and isolated, means that the main DMX line remains intact, so minimises any failures.

 

For that short distance you could possibly send control by just a single optical fibre, isolated, independent but maybe expensive.

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I do know someone who ran DMX to the top of a stand then fanned it out with bell wire to four lanterns as simply a fan out connection, it broke spec but it worked. BUT rule no1 of breaking spec is that it will come to bite you, usually at the worst moment.

 

Lots of DMX splitters all active and isolated, means that the main DMX line remains intact, so minimises any failures.

 

For that short distance you could possibly send control by just a single optical fibre, isolated, independent but maybe expensive.

I was wondering if you'd get away with teeing them in as I know it can work.

 

However I also know how easily it can stop working. I spent ages tracing out cables in a nightclub and looking for DMX splitters of which there were a number, in the selection of universes installed at different times.

 

One in particular consisted of of a matrix of 13x13 3 channel led cans, the end of each row was easily visible from a high vantage point and there was only 'DMX in' on the end fitting and 'in & out' on it's neighbour, after that they were obscured by truss. The assumption was the other end of the rows (nearest to the jocks position) were supplied from splitters. Instead we found choc bloc joints in the ceiling tapping off the main line to the start of each row, so effectively the controller fed directly into 13 fittings in parallel then a standard daisy chain of each row. Oh and of course the last fitting on the last row had a terminator fitted.

 

This universe worked perfectly until some other dimmable lighting caused interference which was totally reproducible. The club owners blamed the original installers, they in turn stayed in business just long enough to blame the person who spec'd a cheap brand of lights. I made up some male to male and female to female cables as an experiment to run the DMX backwards and forwards along the rows and never had to return.

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