The 5 pin DMX Cable Religion

[Pete]

Ok sorry Leggy.

My post was just meant to kinda say "horses for courses"

[Ekij]

Oh, Lord, grant me the wisdom to change what I can, but accept that which I cannot

The correct quote is:

Lord grant me the serenity to accept the things I cannot change,

the courage to change the things I can, and

the wisdom to know the difference.

 

And now that there are alternatives to Martin in my local hire marketplace, I can vote with my wallet!

Exactly! Thats what we should all do to encourage the manufacturers to go 5 pin. It doesn't hurt to tell the hire shop this is why you're not touching their 3 pin gear.

[Ynot]

Oh, Lord, grant me the wisdom to change what I can, but accept that which I cannot

The correct quote is:

Lord grant me the serenity to accept the things I cannot change,

the courage to change the things I can, and

the wisdom to know the difference.

THAT'S the one - thanks. :)

 

And now that there are alternatives to Martin in my local hire marketplace, I can vote with my wallet!

Exactly! Thats what we should all do to encourage the manufacturers to go 5 pin. It doesn't hurt to tell the hire shop this is why you're not touching their 3 pin gear.

Well, forgive my cynicism, but whilst I would agree that this would be the only way to succeed in getting the likes of Martin to change their plans overall, I seriously doubt that there will be many LD'swho'll modify their rig specs based on whether the kit has 3 or 5 pins on the XLR's. It would be higher on my list of priorities to be honest that the lantern does what I want it to do and that I could rely on it to do such.

 

TD

[thinkoutside]

I think DMX religion is probably not such a good name.

This point has been discussed before and the decision that was generally reached was that by using sub standard cable etc you were endangering your control line. Fine if you a NJD boy and your scans behaving strangely isn't a problem.

 

You say that the correct stuff is to expensive per foot. I cant see how this is true. I wouldn't like to be on your crew the day the cable lets you down,because it will be on a key job for your biggest client.

 

I'd also like to say that provoking people with lines such as "OK, I know it’s coming but just for kicks, why don’t you start the rebuttal with “Back in my day…” and end it with “Because I said so.” Probably isn't in the best spirit of the board.

 

This point was not discussed before… You don’t seem to understand the point I’m trying to make. Here it is again in… I hope this helps clear this up…

 

My two main points seam to have been misunderstood. My first point focused around a hypothetical cable solution. I wanted to see if anyone had found an alternative to the DMX standard that was just as reliable but had some better attributes such as lower price. My thinking was that there is room for a new standard that would be more cost effective and fix some of these other issues. I was not advocating using 3 pin cables over 5 pin ones. I was merely stating that some people are going to want to know what all their options are based on a few key factors. I knew there would have to be more things the equation would need but I wanted to through it out there to get some ideas. I did allude to a connivance factor when I said that one may want to take into account how to differentiate their cables but I did not mention how.

 

My second point revolved around how to wire up 3 pin fixtures with the same reliability as the DMX standard when 3 pin is the only option. (Ynot seemed to get this but some of you seemed to think I was suggesting something else) It should also be made clear that I at no time was considering using standard mic cable as solution (Though I find it to be an advantage that 3 pin cable can use it as a last resort if needed).

 

I wish I had the luxury to vote with your wallet but I’m sure I’m not the only who does not always have the option.

 

Lastly, I would like to make it clear that I was not in any way try to be malicious when I posted how one should start or end their posts. Tone can be mistaken when it’s just print. I was just trying to add a little fun to the commentary. Sorry if any of you took it the wrong way. BTW: Just so you all know I’m not only happy to see the responses but I very thankful to get everyone’s opinion. :D

[Andrew C]

It might help if we were to be a bit clearer with naming things. You seem to want to use 3 core cable, and 5 or 3 pin connectors.

 

In my not so humble, I deprecate any use of 3 pin connectors for DMX, it has just been a royal PITA to me too often. However, as no-one really uses the 2nd pair, leave that out and use 1 pair screened 120Ω for flexible. I would choose the specific cable for flexibility and durability; probably rubber sheathed. I would use either 2 pair or UTP for installed cables. The factors affecting choice here would be large csa for a low resistance and LSF if mandated by local requirements. Depending on the install, price would be a secondary consideration, as the amount saved by being cheap here, will be more than covered by not loosing one show. As has been mentioned, Avo use the 2nd pair for additional unviverses, so if you do go the one pair route make sure that you warn visiting Avo users!

 

Not sure if anyone has linked to it yet but summary of the USITT report on the use of UTP is here as a small PDF. Is this what you are looking for?

 

My task for today is installing some audio and UTP (which will be used for TCP, video over CAT5, remote "Go" functions on the LX desk, and occasional DMX).

[dbuckley]

My first point focused around a hypothetical cable solution. I wanted to see if anyone had found an alternative to the DMX standard that was just as reliable but had some better attributes such as lower price.

 

History is on your side here.

 

When I started out you needed one control conductor per channel, so control cables were multicores, so if you had a sixty channel desk, then you needed multicore cables with sixty conductors plus ground to get from desk to stage. Then multiplexed control arrived, putting all those control channels down one cable.

 

We now live in a time when shows have multiple uinverses. So we now have multiple DMX512 cables.

 

Once again, there is innovation, you can now use a single ethernet cable to replace many DMX512 cables. Theres trivially few fixtures with Ethernet connectors on them today, but that will eventually change. Today you need magic boxes to convert between Ethernet and DMX512. You can either use literally DMX512 over Ethernet, like ArtNet, or distributed control, for example, the Hog3 and the DP boxes. You still need the black box to get to DMX512 for the fixtures, but only at the point where the fixtures are.

 

However, I would bet that most DPs end up right next to the Hog3 and DMX512 cables are run log distances to stage...

 

But, at this time, and unless I was asleep and missed it, there still isnt a single Ethernet control protocol like DMX512 that everyone can adhere to. I really doubt that it'll be ArtNet, which although tolerable now, started out very badly, in terms of its ability to be usable on a typical Ethernet network. But at least the physical details of how to connect to a network, and indeed what is a network was all done and dusted years ago, its just a protocol issue now, and thats just programming.

 

My second point revolved around how to wire up 3 pin fixtures with the same reliability as the DMX standard when 3 pin is the only option

 

Can't happen. In the real world it works well enough (there are, after all, a lot of XLR3 equipped fixtures out there that waggle around every day) but because of the lack of a defined standard for DMX512 over XLR3 it'll never be as easy as in the standardised world. We are where we are. The only good news is that finally the XLR3 manufacturers are now fitting both connectors, so by the time it doesnt matter any more (ie Ethernet is on fixtures) XLR3 will have died out.

[Ynot]

As has been mentioned, Avo use the 2nd pair for additional unviverses, so if you do go the one pair route make sure that you warn visiting Avo users!

Ummm....

I'd not heard this one before (must've also missed it in this thread, if it was mentioned here) but if you're suggesting that AVO consoles send out a second universe of DMX on pins 4 and 5, then does that not fall outside of the standard as per USITT? And is that not FAR worse a situation than anything 3-pin might throw at us?

 

Just a thought.

[Andrew C]

I'm not quite sure what this means:-

 

http://www.avolitesshop.co.uk/avo/products/images/pearl2004xl600.jpg

 

but it doesn't LOOK complient to me!

[david.elsbury]

Somewhat OT, but at my church venue, I made up XLR5- RJ45 adaptors to run DMX over the installed CAT-5. Works fine, UTP cable. One pair to pins 2/3, second pair to pins 4/5, another wire to pin 1. If I ever get an Avo (I wish!) the adaptors will work, or if I want to control a hazer down to the stage or whatever (local hire co has hazers with XLR5's for the remote) then I can.

[PhilR]

As has been mentioned, Avo use the 2nd pair for additional unviverses, so if you do go the one pair route make sure that you warn visiting Avo users!

Ummm....

I'd not heard this one before (must've also missed it in this thread, if it was mentioned here) but if you're suggesting that AVO consoles send out a second universe of DMX on pins 4 and 5, then does that not fall outside of the standard as per USITT? And is that not FAR worse a situation than anything 3-pin might throw at us?

 

Just a thought.

 

It's complient in that the extra pins are used for data, which the specification specifically alows for (see the quote from USITT on page 2), and any fixture that's fully complient with DMX-512 should be allowing for the possiblity of signalling data on the line (an entirely different matter to power going through those pins), whether they choose to ignore it, send it on to the next device or otherwise.

 

It actually has its roots in the older 1024 channel consoles which were boosted to 2048 channels in this way. A Y splitter plugged into the outputs allows for pins 1, 2 and 3 to go down one line and pins 1, 4 and 5 to go down another. It's essentially irrelevant to any desk with four outputs anyway - you can use the separate ones, and since the Y splitter is generally be placed at the console end of your line single core shouldn't be an issue either - you've split the DMX before the number of cores becomes an issue.

[Andrew C]

Somewhat OT, but at my church venue, I made up XLR5- RJ45 adaptors to run DMX over the installed CAT-5. Works fine, UTP cable. One pair to pins 2/3, second pair to pins 4/5, another wire to pin 1

Have a look here at USITT for how it should be wired. :D

 

And thinking a bit more about the Pearl, yes I see now what they are doing, and it really is quite clever...

[Ynot]

It's complient in that the extra pins are used for data, which the specification specifically alows for (see the quote from USITT on page 2), and any fixture that's fully complient with DMX-512 should be allowing for the possiblity of signalling data on the line (an entirely different matter to power going through those pins), whether they choose to ignore it, send it on to the next device or otherwise.

Hang on....

There seems to be a bit of a double standard here....

Either the DMX standard as quoted by the USITT is 2/3 on a 5-pin ONLY or it's not.

Whilst pins4/5 are quoted as being for other data use, I seem to recall that was return data, or something, but haven't seen it stated that this could be another DMX universe....

And even if it was feasible, then it flies even further against any possible standards by virtue of the fact that you now would need to have not only 3 to 5 pin converters and pin reversals in both flavours but you'd ALSO have to have two different flavours of 5-pin lead (assuming the logical conclusion that the dual-universe is taken on 4-core screened cable out to the stage).

 

Now THAT would be ruddyconfusing!!

 

:D

[david.elsbury]

Have a look here at USITT for how it should be wired. :D

Aha! I swear, that's the link I was looking for when I made them up. I couldn't find it though. Oh well, maybe I'll change them one day.

[Andrew C]

Either the DMX standard as quoted by the USITT is 2/3 on a 5-pin ONLY or it's not.

Whilst pins 4/5 are quoted as being for other data use, I seem to recall that was return data, or something, but haven't seen it stated that this could be another DMX universe....

All the cables should be two pairs, screened in pairs. If you stick to this you only need one type of cable. If you break the standard, then yes another flavour of splitter is needed to utilise the 2nd pair. As to the other pair, ISTR that what the data it was reserved for was not specified (NOT power though!). Somewhere further up the thread it was stated that the revised standard uses pair 1 for monitoring as so many installs have failed to use pair 2.

 

USITT FAQ again!

[Ynot]

All the cables should be two pairs, screened in pairs. If you stick to this you only need one type of cable. If you break the standard, then yes another flavour of splitter is needed to utilise the 2nd pair. As to the other pair, ISTR that what the data it was reserved for was not specified (NOT power though!). Somewhere further up the thread it was stated that the revised standard uses pair 1 for monitoring as so many installs have failed to use pair 2.

 

USITT FAQ again!

I say again... HANG ON!!

 

To quote the above linked FAQ...

Explain the second pair, and why I should install and use 2–pair cable.

DMX512/1990 says the optional data link is for data – that's all. It doesn't say anything about the direction of the data or what kind of data, other than it conforms to the electrical specification of EIA 485. DMX512–A discusses implementation more thoroughly than its predecessors.

 

Several companies use the second pair for various legitimate functions which may be proprietary, but are not always. Some companies do not wire pins 4 & 5 at all, some wire them through. You will have to check with the manufacturer directly or through their documentation. This ambiguity is addressed in the new ANSI version of the standard developed though the ESTA Technical Standards Program. Compliant legacy equipment should have no problem working with products compliant with the new version and vice–versa

 

There are those on this thread who are adamantly quoting the USITT standard as gospel, thou shalt not deviate from it one jot, else said cable etc cannot be called DMX....

 

But here we have a blatant statement that belies the credibility of the whole thing.

ie "Here's a standard set of wiring and interface info" but "Oh, by the way, because this bit wasn't taken up on the original spec, so you can use it for what you like (within EIA 485) - and that may be another DMX feed".

Sorry, but to me that smacks of the double standard!!