DMX cables 5pin or 3pin

[Jake G]

I have 8 moving heads, 4 that take 3pin DMX cables, and 4 that can

take either 5pin or 3pin cables. I was wondering if it would be better

to stick with using all 3pin cables or if it would be worth it to use

5pin cables on the 4 that take them and 3pin cables on the others, or if

that is even possible (as I would have to connect them all together on

the same chain).

 

Thanks,

AOS Lighting

[paulears]

despite 3 pin being totally and utterly wrong, as not all your fixtures have 5 pin, then I would go 3 from start to finish, but use identifiable cable, like the turquoise Canford stuff so you can easily identify them as belonging to LX and not the noise department, and go back into the correct case.

[Jake G]

Ok, thanks. So why is 3pin so wrong? What's the significance between the two? Do you think I'll have problems using 3pin cables with an eight unit string of moving heads?

[paulears]

Well there is a published spec for DMX512 and the connector type is also part of it, and it should be 5 pin. Some people take this as meaning that it is just to stop lx and audio kit being accidentally hooked up, while others can use the spare pair of pins for other things - also if the other pins carry some kind of non-DMX information then again, compatiblity is a problem. Some desks use 5 pins outputs for 2 DMX universes on one connector. Martin decided to go with 3 pin, so it was often common to see 3/5 adaptors cable tied to the mains leans, for converting back to the 'proper' 5 pin.

 

Electrically I'd argue the 3 pin is sturdier, but I've never had problems with the '5's. for what it's worth All mine are linked with 3 pins, and the long run back to the desk is 3 at stage end and 5 into the desk.

[IRW]

Well there is a published spec for DMX512 and the connector type is also part of it, and it should be 5 pin. Some people take this as meaning that it is just to stop lx and audio kit being accidentally hooked up, while others can use the spare pair of pins for other things - also if the other pins carry some kind of non-DMX information then again, compatiblity is a problem. Some desks use 5 pins outputs for 2 DMX universes on one connector. Martin decided to go with 3 pin, so it was often common to see 3/5 adaptors cable tied to the mains leans, for converting back to the 'proper' 5 pin.

 

Electrically I'd argue the 3 pin is sturdier, but I've never had problems with the '5's. for what it's worth All mine are linked with 3 pins, and the long run back to the desk is 3 at stage end and 5 into the desk.

 

I'm not entirely sure how clear it is in the 1990 version of the standard, but the 2005 revision makes the case for 5-pin cable stronger, as it goes into more detail on how different start codes can be used in conjunction with new devices that can understand them. At the moment, the most common start code is 0 which in basic terms is your normal DMX universe. What we will probably start to see in the future are functions such as remote device management occuring over the same cable which make use of different start codes which will cause fixtures to perform extra functions

 

e.g. a desk outputs a start code of 124 which a new fixture will understand to mean 'send the desk your lamp-hours'. As the first two hot and cold pins are for constantly sending data packets only from the desk, the fancy new fixtures cannot send the lamp hour data back along the same wires, and that is where the secondary data pair will come in. (and therefore create a full-duplex system)

 

Please note I've written that from memory, based on looking over the latest documentation a few weeks ago, please feel free to correct me if I have got any bits wrong! (Also the figure 124 was just a random number!)

 

Ian

[benweblight]

the fancy new fixtures cannot send the lamp hour data back along the same wires, and that is where the secondary data pair will come in. (and therefore create a full-duplex system)

 

This came up in another thread:

RDM does not use the second data pair. It is carried over the main DMX link. It's done this way because hardly any DMX installations are done with 2-pair cable.

 

That thread covers this topic also and it well worth a read:

The 5 Pin DMX Cable Religion

[gareth]

Standardise on 5-pin cable, and make sure that each of your 3-pin-only fixtures has a pair of 5-pin jumpers cable-tied to the handle or some other convenient point. 3-pin connectors are not compliant with the DMX512 standard, and shouldn't be used - it's as simple as that.

[Tom_Robbo26]

Use 3pin all the way much more convenient even though 5pin is better. The extra pins on the 5pin are really only there for 2 way communication whichi doubt you will need, so if it were me in this case I would use 3pin.

 

HTH

[Ben Langfeld]

Why is 3-pin more convenient? To be honest, it's a really simple matter; it breaks spec, it's wrong, no matter which way you twist it. From memory of the last Mac 250 I looked at, the holes drilled for the 5-pin XLRs are the same as the 3-pin ones. Retro-fit anyone?

[dbuckley]

In The Good Old Days there was some wiggle room to mis-interpret the spec, bu that is no longer the case; all XLRs other than 5 pin are specifically outlawed. The only case for a non-5-pin-XLR is if you dont have space, and then you have to user a connector other than XLR.

 

However, if you are all three pin it puts you in a difficult position. Both Paul and gareth have good answers, which doesn't hep much...

[niclights]

Why is 3-pin more convenient?

 

Because they are much easier to solder and they are cheaper.

 

The standards are clear and this has been discussed many times, but if equipment has 3pin or option 3/5pin then it will work fine on 3pin. If it's an install/self-contained rig where the components are never expected to mate with other fixtures then there is nothing wrong with doing this and, IMO, it is just extra expense and potential additional points of failure to make up jumpers. Weigh up costs v application to decide.

[gareth]

Use 3pin all the way much more convenient

In what way is it more convenient than using 5-pin? And before you even think about saying "because you can use mic cables", do some research, both in the BR archives and on other technical theatre sites. <_<

 

 

Because they are much easier to solder and they are cheaper.

16A connectors have enough pins to carry a balanced audio signal, are a much easier and quicker connector to wire up, and can be had for less money than a 3-pin XLR. But we don't use Ceeforms for mic lines, do we?

[DSA]

16A connectors have enough pins to carry a balanced audio signal, are a much easier and quicker connector to wire up, and can be had for less money than a 3-pin XLR. But we don't use Ceeforms for mic lines, do we?

Perhaps because of the size issue? And I wouldn't put it past some people <_<

 

That aside, if Jake has a load of suitable 3 pin cable which works just fine, I can't see the need to go and spend a fair bit of money on new cable and connectors for no gain whatsoever. He would gain 2 pins not connected to anything (unless he is doing something clever, which sounds unlikely). The cable supplier will be laughing all the way to the bank. It reminds me of that sketch running at the moment, "Yes I did see you coming" etc.

 

OK I agree that of course it is not up to spec, and hardly ideal, but it would perform equally well and hence I feel this is all just another "textbook bashing thread" which serves no worthwhile purpose. I think you get the gist.

 

David

[TomLyall]

As you only have 4 of the offending moving heads, I think it's probably worth considering changing the chassis mount connectors to 5 pin versions. This would mean you could maintain a stock of 5 pin cable only, without the extra cost and connections assosciated with the jumper cables. It'd also be better if you hire extra kit in, or hire your kit out often.

 

Usual warnings about opening kit, invalidating warranty and working with electricity apply.

[Ynot]

Sitting on the fence a little here, and conscious that I may anger a few BR members (or at least peeve them a tad.. <_<) I'll say this:

 

Whilst I recognise that 5-pin is THE specified standard for DMX512 and would in many ways advocate the use of same should I be designing any DMX kit (which I'm extremely unlikely to do!) I do have reservations about the purism sometimes that jumps in on these discussions.

 

Yes - all DMX kit SHOULD be 5-pin, but for a LOT of reasons, many manufacturers (and not just the cowboys, either) have, over the years, used 3-pin. They're cheaper, easier to solder, and (at a push, if you have nothing else) you CAN try to use mic cables to finish a cable run. (That doesn't mean I'd advise that path as a first choice, just that it's FEASIBLE if needed).

 

3-pin plugs are also sturdier. I've lost track of the number of 5-pin plugs I've un-bent pins on, or replaced because they've been handled roughly at connection. Our hazer is STILL awaiting a replacement 5-pin chassis plug because one pin has bost completely. (Fortunately it has a 3-pin option as well, so we can still drive it).

 

That said, I always use quality DMX cable for control leads, but have a growing stock of both 3 and 5-pin cabling, plus reversals, gender benders and 5 to 3 converters.

It would be great if all kit were 5-pin, but in the real world it's not, so I just suck it up and get on with the job.

 

just last week, we ran cables from our two permanent stage feeds (5-pin) to 6 Mac 250 Entours (dual 5 and 3-pin ins/outs), 4 CP Pin Scans (ours) with 5-pins, 4 more Pin Scans (hired) with 3-pins, 1 x CP Silverado (5-pin), jem Haze machine (dual 5/3 but one 5-pin bost as above), Jem smoke machine (3-pin), 10 Showtec LED Pars (3-pin), 1 Zero Betapack (5-pin) and 2 Showtec 4-ch dimmer packs (3-pin). yes, it was a huge task to get everything talking and it took most of the adaptors we have, but in the end it all went well.

 

My point is that whilst it would be nice to change the world, that's idealism.

Realistically, let's just do the best with what we got.

 

To the OP?

Well, if all your gear is 3-pin, then stick to 3-pin, but make sure they're made from proper data DMX cable.

Remember that a) some kit MAY be hot/cold pin reversed, so get some reversal adapters, and if you ever intend to hire in, either make up some 3 to 5's, or spec them when you order.

 

At the end of the day you have to get something that works for YOU. I see no real value in making up loads of 3 to 5's just to convert to 5-pin cables (Sorry, Gareth). that's just added expense for you that's not required unless you intend upgrading and adding more pro kit in the future.

 

TD