Need advice on tracing /testing DMX lines

derekleffew said:

Never say never. I've done it. Having all the ports start at 001 just means you're using the desk as (or in lieu of) an opto-splitter. Not a problem until or unless @Ravenbar needs to control more than 512 addresses.

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That's essentially what I'm doing. Without knowing the exact topography if the install, Using multiple ports on a single universe is all I can get to work.

I'm also using 100'ish of cable to get the signal from the nearest DMX output port to the spot where the dimmer pack is located. For some reason, when they did the install, they put all the DMX outputs in the air. I've had to run a cable from mid stage on the floor, across and up into the ceiling then finding it's way through the grid, over the main curtain, and dropping back down to the 1st Electric. I've currently got (3) 25' cables run and that has got me from the dimmer pack, over, up and around to exactly over the main curtain. Probably got another 10' or so to go until I get to the outlet.

Ravenbar said:

That's essentially what I'm doing. Without knowing the exact topography if the install, Using multiple ports on a single universe is all I can get to work.

I'm also using 100'ish of cable to get the signal from the nearest DMX output port to the spot where the dimmer pack is located. For some reason, when they did the install, they put all the DMX outputs in the air. I've had to run a cable from mid stage on the floor, across and up into the ceiling then finding it's way through the grid, over the main curtain, and dropping back down to the 1st Electric. I've currently got (3) 25' cables run and that has got me from the dimmer pack, over, up and around to exactly over the main curtain. Probably got another 10' or so to go until I get to the outlet.

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@Ravenbar You are using DMX cable, correct? Correct impedance and construction, NOT a twisted pair microphone or line level audio cable?? Three or five contact connectors are of less import than the construction and impedance of the cable. Terminating every individually driven run is also important to minimize reflections.
Toodleoo!
Ron Hebbard

RonHebbard said:

@Ravenbar You are using DMX cable, correct? Correct impedance and construction, NOT a twisted pair microphone or line level audio cable?? Three or five contact connectors are of less import than the construction and impedance of the cable. Terminating every individually driven run is also important to minimize reflections.
Toodleoo!
Ron Hebbard

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https://www.amazon.com/gp/product/B0189X13NM/?tag=controlbooth-20

This is the cable I'm using. Sold as 3-pin DMX cable and says so printed on the jacket. Last year I resorted to using what the school had for 5-pin cable and then using most of their mic cables as well.

I opted for 3-pin as the fixtures I'm controlling and the USB-DMX converter I'm using are 3-pin.

I do need to poke around in my parts bins and make a terminator. Does the resistor value matter much for a terminator?

Ravenbar said:

https://www.amazon.com/gp/product/B0189X13NM/?tag=controlbooth-20

This is the cable I'm using. Sold as 3-pin DMX cable and says so printed on the jacket. Last year I resorted to using what the school had for 5-pin cable and then using most of their mic cables as well.

I opted for 3-pin as the fixtures I'm controlling and the USB-DMX converter I'm using are 3-pin.

I do need to poke around in my parts bins and make a terminator. Does the resistor value matter much for a terminator?

Click to expand...

@Ravenbar From memory, people use a 120 ohm resistor soldered between contacts 2 and 3. The resistor can be an eighth, quarter or half Watt basically whichever Wattage rating you can most conveniently muster. Use real solder. I found one secondary school student who was using some form of "liquid solder" plastic goop he was squeezing out of a tube; ugly, icky sticky gooey stuff; @FMEng @Ancient Engineer @jfleenor and @derekleffew would've despised the stuff. Even up here north of Donald's walls a box of 100 Phillips 1/8th Watt metal film resistors only cost me $3.00 Canadian ten or fifteen years ago. The resistors should cost only a few pennies per resistor, the connectors will cost far more than the resistors. It's useful to label your terminators so the uninformed don't assume they're unwired spare connectors and remove them to make new cables.
Toodleoo!
Ron Hebbard

RonHebbard said:

@Ravenbar From memory, people use a 120 ohm resistor soldered between contacts 2 and 3. The resistor can be an eighth, quarter or half Watt basically whichever Wattage rating you can most conveniently muster. Use real solder. I found one secondary school student who was using some form of "liquid solder" plastic goop he was squeezing out of a tube; ugly, icky sticky gooey stuff; @FMEng @Ancient Engineer @jfleenor and @derekleffew would've despised the stuff. Even up here north of Donald's walls a box of 100 Phillips 1/8th Watt metal film resistors only cost me $3.00 Canadian ten or fifteen years ago. The resistors should cost only a few pennies per resistor, the connectors will cost far more than the resistors. It's useful to label your terminators so the uninformed don't assume they're unwired spare connectors and remove them to make new cables.
Toodleoo!
Ron Hebbard

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I've got a pile of resistors and a bunch of connectors(3-pin) as well. It's amazing what you can find in the crawlspaces of an auditorium built in the 60's. A pile of cut off ends from old snakes provides plenty of parts for something like this.

Not worried about anyone else tearing them apart/making new cable with them as I'm the only one that repairs things there. Most of the time, they don't even replace blown lamps. I've got a label maker on site and will label them as well.

derekleffew said:

Never say never. I've done it. Having all the ports start at 001 just means you're using the desk as (or in lieu of) an opto-splitter. Not a problem until or unless @Ravenbar needs to control more than 512 addresses.

Click to expand...

Thanks for supporting my solution. If that happens(I go over 512 addresses, with the current equipment). I'll surely be the one to know. Current system is using 120 addresses. I'll be using 6 additional channels for the LED strip controllers and maybe 6 more channels to control (2) Chauvet USB abyss fixtures(I told the director I was thinking the show needed movement to the lighting, and maybe we should use the water effect projectors we bought last year.) A total of 132 channels.Even if I were to find a way to use the (2) 7ch RGB pars and 4 ch dimmer pack I personally own, that's still only 152 channels.

The part I'm not understanding, is I before I "double patched" the board, I tried addressing the fixture to 1, and bringing up channel 1, when 513 patched to ch 1 and got nothing. Hence my confusion, and thinking there was a problemn with the system somewhere. I've also go zero experience working with multiple universes and limited experience with DMX controlled things.

That was with a dmx line directly from the board's dmx-2 output? In theory that should work...
I've had weird gremlin issues with fixtures that didn't like to be addressed 001, so I would try to patch on a different "dimmer" and "channel", cuz well, who knows, maybe universe 3 will like your light better.

Lynnchesque said:

That was with a dmx line directly from the board's dmx-2 output? In theory that should work...
I've had weird gremlin issues with fixtures that didn't like to be addressed 001, so I would try to patch on a different "dimmer" and "channel", cuz well, who knows, maybe universe 3 will like your light better.

Click to expand...

I believe so. The board has cables connected to outputs 1 and 2. Patch had all universes patched to the same channels. I know I tested with the fixture connected directly to output 3 of the board and got nothing. Changing to all universes start at 1 and the light worked connected to port 3, and on the DMX out ports in the air.

Hmm, so that means that all the ports at least do send signal. Maybe something goofy in the patch? If you're sending from dmx-3, universe 3, it would start at 1025.
It seems like you're saying the board was patched like Ch 1. [ 1, 513, 1025 ] , but when I think of 1:1 patching, that means Ch1. [1] , Ch. 513 [513] , Ch. 1025 [1025]

I just went back and noticed your 400 ch limit... Dang. I would try clearing the patch, and put just 1025 in ch. 1

Just an update. I finally figured out exactly what was going on. It was the patch that was wierd, but I didn't notice it. For some reason, instead of having the channels patches so all the universes address 1 was ch 1. Ch 1 was patched as 1, 401, and 801, as so on.

Since it's only a 400 channel board, I'm going to leave it "double patched" since that is easy to understand and being less than a single universe of addresses. No reason they would ever run into issues with it like that.

Other boards like Express family do that automatically. Patching limited channels to massive (for the time) DMX addresses the 1-1 function crammed them all in.