Building DMX Cables

[JoeML]

So I just bought 27 NC3(M/F)XX ends with all the color boots for fast set up of my light shows. I'm currently using 12 Martin Mac 500's.

I looked everywhere online, and nobody had a answer for this question, which I will ask here first.

Can I use DMX5 cable in a DMX3 connector?

The reason for this question is simple in my mind. If I want to upgrade my connectors to DMX5, I already have the wire. Or if I have a bad wire in the cable using DMX3, I can use 1 of the 2 wires that aren't being used. Its a bulkier cable, hopefully more durable.

But at the same time, I've read DMX5 is rarely used. So why do we even have it, except for some high end system stuff. I'm thinking about getting some ETC Desire fixtures in the future, that use the DMX5.

And I still don't have the cables yet, but there is some good stuff around. I HATE the idea of having anything the ADJ in my inventory, but there cable seems to be good, from what I've read. I'd really like to know the brand name of cable that HOSA uses! But I haven't found that either. I think its dura-flex or something.

Looking for very good DMX cable in a 500' length spool. But not over $350

Simple answers would be helpful even with ballpark figures

 

[mstaylor]

Yes, you can use 5 wire in a 3 wire XLR.

 

[DuckJordan]

First things first check out the search function on the forum as the topic of 3 pin vs 5 pin XLR connectors for DMX use has been covered far too many times. as long as it has 120 ohm data rated cable you can use it.

 

[JD]

Current DMX 512 protocol is to use two pair cable. The first pair is connected to pins 2 and 3, the second pair is connected to pins 4 and 5. The shield is connected to pin 1.

That being said, I can't think of any equipment that is actually using the pair connected to pins 4 and 5! It just never came to be.

The wiring for the 3 pin and 5 pin XLRs is the same for the first 3 pins. No point in using cable that has a second pair, unless you want to do something non-standard (like some of us do) and use the second pair for a second universe or a com line.

When buying the wire, it is fine to use 3 conductor wire (single pair and a shield), just make sure the wire is rated for DMX usage and isn't mic cable. Although people use mic cable all the time, it is a different impedance and may cause problems. Or, as some say, "it will work great until someday it doesn't."

EDIT: as noted above, there are many, many threads on this forum on the topic of cable and connectors, and the need to terminate at the end of the run.

 

[mstaylor]

He is looking more for cable recommendations than how to convert. This is something I don't generally buy in bulk form so I had no information for him.

 

[DuckJordan]

Current DMX 512 protocol is to use two pair cable. The first pair is connected to pins 2 and 3, the second pair is connected to pins 4 and 5. The shield is connected to pin 1.

That being said, I can't think of any equipment that is actually using the pair connected to pins 4 and 5! It just never came to be.

The wiring for the 3 pin and 5 pin XLRs is the same for the first 3 pins. No point in using cable that has a second pair, unless you want to do something non-standard (like some of us do) and use the second pair for a second universe or a com line.

When buying the wire, it is fine to use 3 conductor wire (single pair and a shield), just make sure the wire is rated for DMX usage and isn't mic cable. Although people use mic cable all the time, it is a different impedance and may cause problems. Or, as some say, "it will work great until someday it doesn't."

Actually, it is used, Quite frequently but more for video networks than our standard theater setups. The second set is for fixtures to talk back to the console. DMX out to fixture then the fixture sends info back to the console it helps when dealing with trouble shooting large moving light rigs that are in the air just how ACN is currently working towards. Its for letting the lights tell you, Hey, I have a bad lamp, or something is wrong with my motor for the gobo rotation, or other things that sensors in the movers would be able to pick up.

 

[JD]

Actually, it is used, Quite frequently but more for video networks than our standard theater setups. The second set is for fixtures to talk back to the console. DMX out to fixture then the fixture sends info back to the console it helps when dealing with trouble shooting large moving light rigs that are in the air just how ACN is currently working towards. Its for letting the lights tell you, Hey, I have a bad lamp, or something is wrong with my motor for the gobo rotation, or other things that sensors in the movers would be able to pick up.

That's what it is designed for, but in the lighting world, what fixtures are currently using that feature? (Factory units)

 

[JoeML]

Ok, So I can use the cable in a DMX3 connector!

But on the wire, If i were to buy lets say 110 ohm wire, would i need to make a 110 ohm terminator to match the wires impedance? Or will my 120 ohm still do?

And should I worry about Capacitance Ratings, Single or Double Shields,Twisted pairs or 4 wires twisted together inside of shield, meets USITT standards, Temperature limits and a drain wire vs shield?

 

[JoeML]

@JD
I think that's what the ETC Desire fixture is doing, but not sure. I think you can change the settings on the fixture from your console! If I read it correctly

 

[mstaylor]

You need to buy cable that meets the DMX spec. You can do it with noncompliant cable and it will work until it doesn't. I am assuming you are making three pin cables because your DMX toys all have three pin. That's fine just make sure you follow the pinout and use proper cables. Also make some terminators.

 

[derekleffew]

...Can I use DMX5 cable in a DMX3 connector? ...

First, there's no such thing as "DMX5 cable" or "DMX3 connector." But hopefully you knew that, so we'll move on.
This summer will be the 25th anniversary of the ratification of USITT DMX512-1986. In my opinion/estimation/speculation, If the geniuses behind the CPWG haven't come to agreement on the use of the 2nd pair by now, they never will. They've mostly moved on to RDM and ACN, and are unlikely to revisit or revise significantly DMX512. Save the money and buy single-pair+shield cable. If you do use 2pr+shld cable with XLR3 connectors, care must be taken to heat-shrink or otherwise isolate the unused wires inside the XLR shell. Don't just cut them flush so they can eventually short to something.

...Looking for very good DMX cable in a 500' length spool. But not over $350...

So ≤ 70¢ a foot? Any data-grade, RS-485 recommended, 110-120Ω 22-24g single pair+braided shield will work fine for DMX. Search for Belden 9841 or equivalents by WestPenn, Alpha, or Gepco. If you feel you must have 2pr.+shield, do a price search for Gepco DLC224.

Actually, it is used, Quite frequently but more for video networks than our standard theater setups. The second set is for fixtures to talk back to the console. DMX out to fixture then the fixture sends info back to the console it helps when dealing with trouble shooting large moving light rigs that are in the air just how ACN is currently working towards. Its for letting the lights tell you, Hey, I have a bad lamp, or something is wrong with my motor for the gobo rotation, or other things that sensors in the movers would be able to pick up.

Sorry, incorrect. I challenge you to cite any fixture, console, or device that utilizes the second pair for fixture talkback, or anything else for that matter. See also this post . (The thread contains some valid and invalid uses, which are ineligible for this challenge.)

...I think that's what the ETC Desire fixture is doing, but not sure. I think you can change the settings on the fixture from your console! If I read it correctly

You read correctly. With the Desire and appropriate ETC RDM-equipped console. But it doesn't use pins 4&5 to do that. RDM operates over pins 1,2,3, simultaneously with the DMX signal.

 

[JoeML]

I plan to redo my terminator with the new connector, to keep it clean looking. I know about the need of terms, and all that DJ cheap BS, which I do stay away from. ~Once you go pro, that's the way to go!~

I'm just wanting to have a new clean, professional looking area for my wire runs, connections and fixtures.

 

[rochem]

That's what it is designed for, but in the lighting world, what fixtures are currently using that feature? (Factory units)

More than you'd expect, actually. More and more products are being rolled out that are "RDM-ready", the problem is that people just aren't using it! The one that immediately comes to mind is Wybron. They've had a proprietary talkback system in place for their scrollers for quite some time - this is why you could check the status of your scrollers from the PSU. With the new Coloram IT family, this talkback functionality is integrated with RDM protocol, allowing you to receive feedback and even address the scrollers via RDM. A friend of mine is the house electrician at a theatre in Texas that just got a major upgrade, and they use their Eos to talk to their Coloram ITs*. I can't remember many more off the top of my head, but I have a rental package that includes Mac IIIs in the air right now, and those are also RDM-enabled (though I have yet to actually try to use it... perhaps that's a project for this week...).


*I know they have RDM enabled between the Eos and the ITs, but I'm not sure what functions they actually use it for.

 

[JoeML]

First, there's no such thing as "DMX5 cable" or "DMX3 connector." But hopefully you knew that, so we'll move on.

Yes, didn't know if this was more of a high school forum

So ≤ 70¢ a foot? Any data-grade, RS-485 recommended, 110-120Ω 22-24g single pair+braided shield will work fine for DMX. Search for Belden 9841 or equivalents by WestPenn, Alpha, or Gepco. If you feel you must have 2pr.+shield, do a price search for Gepco DLC224.

will this still be the black & round or grey and looks like a cat5 cable?

You read correctly. With the Desire and appropriate ETC RDM-equipped console. But it doesn't use pins 4&5 to do that. RDM operates over pins 1,2,3.

Didn't see any other connector, so I just thought. But thanks for informing me!

 

[derekleffew]

Will this [Belden 9841] still be the black & round or grey and looks like a cat5 cable?

Got me there. 9841 is round, but only comes in gray. For your purposes, since you can't afford/don't need the Rolls-Royce, indestructible ProPlex, I've heard Accu-Cable is actually not bad. Seems to be priced right, at ~35¢/ft.

BTW, MAC 500's came new from Martin with a 5m data cable included. It was quite thin, and used an odd style of XLR3 connector, but I never had a problem with any of those cables, for several years and fairly hard usage.

There's also this thread: http://www.controlbooth.com/forums/lighting-electrics/15407-facts-about-dmx.html , which you might find amusing. Not helpful, I realize, but amusing nonetheless.

To answer another of your questions, there's no appreciable difference between 110Ω and 120Ω cable. A 120Ω terminator, DMX will work fine with either.

 

[JD]

More than you'd expect, actually. More and more products are being rolled out that are "RDM-ready", the problem is that people just aren't using it! The one that immediately comes to mind is Wybron. They've had a proprietary talkback system in place for their scrollers for quite some time - this is why you could check the status of your scrollers from the PSU. With the new Coloram IT family, this talkback functionality is integrated with RDM protocol, allowing you to receive feedback and even address the scrollers via RDM. A friend of mine is the house electrician at a theatre in Texas that just got a major upgrade, and they use their Eos to talk to their Coloram ITs*. I can't remember many more off the top of my head, but I have a rental package that includes Mac IIIs in the air right now, and those are also RDM-enabled (though I have yet to actually try to use it... perhaps that's a project for this week...).

But once again, RDM runs overlaid on the first pair (2 and 3) so 4 and 5 remain unused.

 

[DuckJordan]

I bow to derek's vast knowledge and retract my previous statement. I wasn't remembering them correctly.

 

[len]

But at the same time, I've read DMX5 is rarely used. So why do we even have it, except for some high end system stuff. I'm thinking about getting some ETC Desire fixtures in the future, that use the DMX5.

On a side note, this isn't really true. Most of the top end units are all 5-pin. A lot of fixtures have both 3-pin and 5-pin connectors because the end customers are requesting both and it's just cheaper to make one unit with both than to stock 2 different products with such a minor difference. As long as all the parts of the cable are dmx-compliant (except for the 3-pin part) and can accurately carry signal, it doesn't really matter. Personally, I think it makes sense to ONLY use 5-pin for dmx, 4-pin for scrollers, and let audio have 3-pin. There would be far less confusion over which cable belongs where. But the marketplace has dictated otherwise.

 

[starksk]

... With the Desire and appropriate ETC RDM-equipped console. But it doesn't use pins 4&5 to do that. RDM operates over pins 1,2,3, simultaneously with the DMX signal.

Derek is correct here. Desire has a 5-Pin XLR connector to be compliant with the DMX standard, but pins 4 & 5 are unused by the fixture and just pass from the input connector to the output connector to allow those (rare) devices that may be using those pins to continue getting the signal.

 

[derekleffew]

...to allow those (rare) devices that may be using those pins to continue getting the signal.

...to allow those [-](rare)[/-] (non-existent) devices...

Two of the biggest headaches/controversies/frustrations in lighting during the past thirty years:

1. 3pin vs. 5pin
2. Reverse Ground and Neutral or not

and Mr. STEVETERRY had a hand in both of them. Hmmm.