Cat 5 as DMX ?

[Will_Tech]

Hi all.

 

I am currently working on a lighting install were we will be fitting 12 Geni Mojo Scans.

We have yet to install the DMX line from the stage to lighting booth. I am not a lampy I deal with sound but I have been roped into doing this. I have been told that instead of laying a 2 pair DMX cable we can use Cat 5 instead. This intrested me as we have a large amount of Cat 5 and using this would save buying cable.

 

It will be a permanent installation and the cable will be layed under the floor out of reach of anyone.

So is it possible to use Cat 5 occasion ?

 

Thanks, Will

[Tomo]

Yes.

 

Cat5 has been tested by ESTA and is acceptable as a DMX cable.

 

There is even a standard colour code for the pinout:

 

http://www.etctoolkit.com/wb/media/images/pinouts/usittcat5.png

[JDP]

It CAN be done with CAT5.

 

BUT if you have told your clients you are going to install DMX Cable, and no doubt charged them for it, the DMX Cable is what you should install...

[Will_Tech]

Yes.

 

Cat5 has been tested by ESTA and is acceptable as a DMX cable.

 

There is even a standard colour code for the pinout:

 

http://www.etctoolkit.com/wb/media/images/pinouts/usittcat5.png

 

Cheers.

Does it matter if it is shielded or not?

[tokm]

AFAIK most forms of Cat5 aren't shielded. Its the twisted pairs/core's design that maintains data integrity.

 

I'm sure someone'll be along soon enough to give a more technical/in depth answer, but the long and short of it is no.. in this case/when using this cable, it doesn't have to be shielded :** laughs out loud **:.

 

T

[musht]

UTP is Unshielded Twisted Pair, slightly rarer STP is Shielded, usually foil, Twisted Pair.

 

Use punch down or crimp on plugs with solid core, it work hardens and snaps with screw terminals.

 

If they whine about wanting `proper` DMX cable, in an install CAT5 IS one of the proper DMX cables, pull them an extra run of cable while your down there, CAT5 can carry an awful lot of useful things, just terminate unremovable ones unremoveably.....

[Tomo]

Use punch down or crimp on plugs with solid core, it work hardens and snaps with screw terminals.

Half right.

On solid-core, use punch-down terminals.

Do NOT fit male RJ45 connectors, and do NOT solder.

 

Male RJ45 don't terminate onto solid-core properly - it might work to start with if you get lucky, but it'll often die after a while.

 

On this kind of cable it really matters what you use to terminate!

[Germaine]

Am I the only person who'd be tempted to common the Earths and get an extra universe down the cable. Can anyone think of a reason not to?

[mutley]

Am I the only person who'd be tempted to common the Earths and get an extra universe down the cable. Can anyone think of a reason not to?

 

The fact that DMX, which is technically RS455 data, is a BALANCED signal, and commoning the "grounds" would cause a whole load of problems by combining the two signals!

 

For the price of Cat5 (less than £50 for 305m!/1000ft at CPC), just do multiple runs!

[david.elsbury]

Use punch down or crimp on plugs with solid core, it work hardens and snaps with screw terminals.

Half right.

On solid-core, use punch-down terminals.

Do NOT fit male RJ45 connectors, and do NOT solder.

 

Male RJ45 don't terminate onto solid-core properly - it might work to start with if you get lucky, but it'll often die after a while.

 

On this kind of cable it really matters what you use to terminate!

It is actually possible to purchase crimp on plugs for solid core cable. The cable is of course less flexible and might die after a while... but it can be done :** laughs out loud **:

[daemon]

The fact that DMX, which is technically RS455 data, is a BALANCED signal, and commoning the "grounds" would cause a whole load of problems by combining the two signals!

 

For the price of Cat5 (less than £50 for 305m!/1000ft at CPC), just do multiple runs!

 

Do you really understand what a "BALANCED" signal is ?

[Wol]

I thought DMX was based upon RS485, not RS455 :-S.

 

DMX is a differential signal, with hot and cold signals, and a ground. Usually in the circuitry, I'd have expected the grounds between different universes to all be, well, ground! If you have three universes coming out of a desk / DMX converter or whatnot, then I'd guess the grounds are already connected together internally, so joining them together externally won't make that much difference or cause many problems.

 

 

And merry christmas to all :-)

[dosxuk]

We have a multicore built for 3 universes (two seperate stage boxes with 3+5 pin connectors per universe and an ethercon socket for the link) doing exactly this, no problems in usage either running over 100m.

[smalljoshua]

But as mentioned earlier in the thread, do not connect the Pin 1 Ground just the Hot/Cold Pin3/2 so there would be no Grounds to common. If you were to common the Cold or Hot Pins however then you would be confusing the entire RS485 Topology.

 

Josh

[mutley]

OK, I was a bit drunk after the xmas eve festivities when I posted that, but it made sense to me at the time!... :rudolph: :** laughs out loud **:

 

My bad: RS455, RS485, RS Components, RS Cosworth, whatever! "Duhzzn't mattah aftah a few drrrinksh!"

 

I also interpreted the OP's term of "ground" as being the 'cold' or 'data -' wire since the majority of Cat5 doesn't have a screen (yes, I know you can get STP (or 'FTP' as CPC call it)), so there would be no 'grounds' to combine!.... So I was thinking that the OP wanted to combine the 'colds' (no Beechams necessary!) to free up more wires for more DMX universes... After all, there is no mention of GROUND on the Cat5 wiring layout diagram provided by Tomo...