DMX in rant

Questions on Palette and Light Palette operation and features
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amoyer
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DMX in rant

Post by amoyer » Sat Jan 23, 2010 2:58 pm

Ugghhh! Why is it that DMX in can't just be an easy thing like it used to with our 550i? With the 550i it was simple with every console that I remember have to use with it. You dropped the touring console in place, took DMX out of the touring console and plugged it into the 4th port of the 550i and you're off to the races. Easy peasy!

We have a show in today that is touring with an ETC Express. Dimmers are off of one universe of the ETC and scrollers off of another. I plug the dimmer universe into a port on a N21 node and it doesn't see valid DMX. I then take a SN110 node and configure one of it's ports to accept DMX in and the node sees valid DMX. I patch the Shownet inputs to fixtures on the Light Palette Live. Bring up a cue on the ETC Express and all looks good. We then pound through a bunch of the cues and they all seem to be going well. I then sit in a cue and after 6 seconds the cue drops and returns 6 seconds later and this continues.

DMX is DMX right? We have standards on communication protocols for a reason right? Why is it that every console out there just doesn't spit out the same flavor, colour, etc of DMX? I realize that there were some changes to the standard, but along the way it seems like everyone has put out devices that have not met standards. We talked about many issues here with consoles that don't output enough DMX dimmers to meet the DMX spec (Strand 100 & 301 were brought up recently).

Sure, it would be great if I could take the show from the ETC Express and load it up into our LP Live but we are not operating the show and their operator wants their console. So we do our best to make this work, but now our only solution is to pull the LP Live and our nodes out of the chain of things and go straight from the touring console to our dimmers. We might have to rethink the plan on just running shownet to the new dimmers this summer since we wouldn't be able to do this workaround.

Ugghhh... time to get back at it...
Andrew Moyer - Oakville Centre for the Performing Arts
Light Palette Live (v10.8.6)
Rack Palette (v10.8.6)
Classic Palette ii(v10.8.5)

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jgoss
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Re: DMX in rant

Post by jgoss » Sun Jan 24, 2010 1:15 am

What DMX speed was the Express spitting out? I have found that my Shownet nodes respond quite well with any ETC console spitting out at "Fast" or "Medium." "Maximum" speed will not work, and I can't say I've ever tried "Slow."
Off the top of my head I do not recall what the refresh rate is for each of those speeds, but I have it written down somewhere. The Shownet nodes are very particular about the refresh rate of the DMX, perhaps that's the issue. Or, was it related specifically to the consoles ability to input the DMX properly?
Jon Goss
Head Electrician, Ballet Opera House
Arsht Center for Performing Arts
Miami, FL

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amoyer
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Re: DMX in rant

Post by amoyer » Sun Jan 24, 2010 2:45 am

jgoss wrote:What DMX speed was the Express spitting out? I have found that my Shownet nodes respond quite well with any ETC console spitting out at "Fast" or "Medium." "Maximum" speed will not work, and I can't say I've ever tried "Slow."
Off the top of my head I do not recall what the refresh rate is for each of those speeds, but I have it written down somewhere.
I tried all 4 options with no luck.
Andrew Moyer - Oakville Centre for the Performing Arts
Light Palette Live (v10.8.6)
Rack Palette (v10.8.6)
Classic Palette ii(v10.8.5)

GaryDouglas
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Re: DMX in rant

Post by GaryDouglas » Mon Jan 25, 2010 12:30 pm

FIrstly, DMX is NOT DMX. Not all DMX is created equal.

There's enough variance in the standard that many bits of gear that claim compliance do not actually comply with all versions of the standard, or all of the possible timing variations. The DMX/1990 standard is very different than the current spec, and the 2 are not 100% interoperable at all of the edge cases.

DMX does not guarantee interoperability across all manufacturers gear --it just provides hope, but the burden of dealing with it always lies on the receiving end, and many receivers simply can't deal with all the possible flavors of DMX.

The reason gear is all different is that DMX is a bit odd, and many manufactureres employ a "good enough" approach to DMX transmission & reception. Modern processors can do most of the spec, but some have difficulty toward the edges ( Extreme fast or extreme slow). Much of the variance can be resolved in software, but software is expensive, especially when a node price point is very low.

This is a sad reality, and I know a number of companies that exist solely because of the incompatibility of DMX gear. Tons of widgets exist to fix these issues.
Gary Douglas - Lead Software Developer - Pathway Connectivity - A Division of Acuity Brands Lighting Canada.

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JohnGrimshaw
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Re: DMX in rant

Post by JohnGrimshaw » Mon Jan 25, 2010 5:56 pm

It is a huge shame that this...
GaryDouglas wrote:Tons of widgets exist to fix these issues
... does not include the N21.

If you just take Ethernet to DMX devices as a class of products, there are a variety of very capable options out there that avoid this particular "inability" of the N21. I have long held the opinion that Strand's Ethernet node should be cable of more then just Shownet. From what I have heard, there is an ongoing discussion to allow ACN as an option throughout the Strand range. If this happens to present as a firmware upgrade for the current range of nodes, perhaps pressure should be brought to bear to give the N21 node a better ability to deal with the "fringes" of DMX compatability.

This is not the forum for that pressure, though. EVERYONE should talk to their local strand rep.
...and for more entertainment industry trivia and useless facts, just ask:
John Grimshaw
Managing Director
Stage Fast Pty Ltd

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