DMX Flow

[champbones]

I am looking to send a DMX signal to a set of lights about 30m away from the nearest lights in the chain and it needs to come back again to the next lights in the chain. Is it possible to send a signal both ways in 1 DMX wire using splitters at each end of the wire or am I just going to have to run a lead each way? Thanks for your help in advance.

[niclights]

I guess it might be possible using pins 4+5 but why would you need to do this?

[paulears]

Don't forget you cannot just 'split' DMX in a passive split, if that's what you mean. as niclights say, you could use cable with two circuits, and do it that way, but to be honest, why not just tape to cables together and do it properly.

[collism]

By far the easiest way would be to get a DMX splitter box if budget permits.

[niclights]

My question was why send away and come back at all? Why not just chain through units in one location, then link to next location etc and terminate?

[MarkPAman]

By far the easiest way would be to get a DMX splitter box if budget permits.

 

If you don't already have a 30m, 5 core, DMX cable, then by the time you get that and add in the cost of parts & time taken to make the adaptors, then the splitter may be a cheaper as well as easier.

[dave1022]

Don't forget, it doesn't matter what order stuff is wired together with DMX. As long as you have the correct dip switch settings and a proper DMX terminator then you can wire the lights in whatever order you want. Therefore, I would suggest wiring in such a way whereby the light that is 30m away is last in the chain, so you don't have to run a cable there and back.

[timmeh2]

Hi

 

Someone I know tried this using standard 5-core cable and had an issue with crosstalk between the two data pairs.

 

All the best

Timmeh

[David Duffy]

As long as the cable has 2 shielded pairs, this should work fine. I have seen installations using RS485 (same as DMX) but at lower speeds, and it worked perfectly with "up and back" runs of approx 100 metres each.

[KevinE]

I guess you're just going to have to try it. Using a cable like CAT5 may work and is at least cheap enough if you end up scrapping the idea.

[David Duffy]

I just did a quick mud map and it could work this way:

 

The "main end" adapter (box or lead set) would have these connectors:

• XLR5M for local input
  
• XLR5F for local output
  
• XLR5F for remote I/O
  

The "remote extension" lead needs all 5 pins wired (2 pair)

 

The "remote end" adapter lead would have these connectors:

• XLR5M input from fully wired (2 pair) DMX lead
  
• XLR5F output to fixture
  

The "remote end" adapter lead would need to plug directly into the fixture, not via another lead. (It can't be in a box, used with a separate lead)

 

If there's any interest, I'll CAD the schematic and post it on my site.

[TomHoward]

What about the male input for the DMX loop out on the fixture?

[David Duffy]

You can't loop anything from the remote fixture. If you need to loop, you'd plug the remote end into a DMX splitter and go from there as normal.

 

EDIT:

Of course there's another solution. That's to use the same type of pair split box/lead at either end. (one with reversed gender) That way you get the loop back. The only down side is it requires the remote fixture to have both input and thru connectors. (almost all do anyway)

[champbones]

Thanks for all your help guys. The reason I would like to do it is because we are a touring act and our setup involves 2 sets of par cans placed away from the stage and the first in the loop has to go back to the next fixture which is on the stage. I cannot go accross from the first set of pars to the last set of pars because it would involve some serious wiring over peoples heads or under foot. I think I am just going to go with using 2 leads, the idea only came about because I accidently ordered 5 pin leads instead of 3 pin! Cheers again for all the suggestions.

[Jivemaster]

With an odd system lead your cable stock is more critical of a single failure, -if the two-way lead gets broken then the show doesnn't work. If you use single leads then one spare DMX lead covers for all failures til the shops open!