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Do you terminate your DMX lines?

Discussion in 'Lighting and Electrics' started by derekleffew, Oct 8, 2007.

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Do you terminate your DMX lines?

  1. Yes, ALWAYS!

    33.9%
  2. Well, sometimes. Especially if there's a problem.

    42.4%
  3. No, NEVER!

    18.6%
  4. I don't use DMX

    5.1%
  1. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    It's getting boring around here--time to bring up a controversial topic, again.
     
  2. SerraAva

    SerraAva Active Member

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    Dimmers, haven't unless built into the racks. Movers, just about always as there is always a few hundred feet or so of cable between them and the board. LEDs, sometimes, really long runs can make them act a little weird. Other DMX things like foggers and what have you, haven't done or had to yet. Always try to run things through an iso too.
     
  3. Logos

    Logos Well-Known Member

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    When I put in my own rig of DMX gear I always terminate at the last device. It isn't expensive it isn't hard and it avoids problems. If I am splitting a line out from the desk or tagging onto an exisitng system with a splitter or node I try to make sure every line has been terminated but you can't always be sure. I rarely have problems so maybe it's a waste of time. But then I rarely have problems and that could be why.
    My runs tend to be short by most standards. I have 1 100 meter cable and a couple of 30 meter DMX cables but most of my DMX cables are only 10 - 12 meters long.
     
  4. len

    len Well-Known Member

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    I seldom have issues, but I think that's because I use a splitter and high quality cable.
     
  5. beam_1973

    beam_1973 Member

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    I have a bunch of fixtures with termimation dip switches on them, so they are easy ... the ones without, hmm, let's NOT discuss those shall we.
     
  6. soundlight

    soundlight Well-Known Member

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    We always terminate. On your way to run the DMX line, you just grab a terminator out of the IQ (Intelligents) roadbox, and plug it in to the last dmx "thing".
     
  7. ship

    ship Senior Team Emeritus Premium Member

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    About four years ago I asked our electronics repair department for some 120ohm resistors to use in making up some terminators. I was given a 100pkg of them. In the past few years while I have made less terminators than say 3:5 or 5:3, much less 5:5 or 3:3 type adaptors in their various versions, I’m now about left with like 20 terminators out of the 100 left. This after whipping out a quick dozen just a few weeks ago in both 3pin and 5pin versions.

    Been a few years since I was able to tell what gear might need either terminator or much less “Martin reverse adaptor” but it could be said that 80x terminators in the past few years might say something still about the need for them with some gear, and or the it won’t hurt factor. This granted in new gear it’s at least 100 or more new moving lights bought per year in adding to the inventory over the years.

    Were I doing shows, granted I would know if my gear needed a terminator or not, when I didn’t I would have them requested, this much less have a dozen in my road box for the issues of weird stuff going on type things. First I would plug one in if not otherwise knowing the cause by process of elimination or what’s the cause.

    Hmm, like 80x terminators made in the past few years... some no doubt have been lost or lifted but not so many persay theorized to be swept up off a floor, I mark and disquinguish my terminators by way of corporate heat shrink label over the plug so even if it’s seen to be just a plug laying on the floor - perhaps a worthless to a IA guy the might have been cut off a cable, it has our name on it and it’s different than just a plug. Such a thing if seen on a deck has more hope of winding up in one of our road boxes than just an un-marked plug that might get trashed. Such terminators get marked in a way that they are more than just thrown out - theoretically at least. Thus the 80x I made in the last few years says that even if most moving lights already sense if it’s the last in line as a concept I would expect, there is still gear out there that don’t.
     
  8. Van

    Van CBMod CB Mods Premium Member

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    I don't have a choice, with Gordon hanging around the theatre. If it's not terminated it's CrrrrrAP!
     
  9. Grog12

    Grog12 CBMod CB Mods Premium Member

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    Nope. Haven't terminated a mover run since '01. Also haven't had issues.

    I also want to know who voted that they dont' use DMX
     
  10. Radman

    Radman Well-Known Member

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    Someone with either a very low or very high budget.
     
  11. SerraAva

    SerraAva Active Member

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    Hughesie89, you can see who voted how by clicking on the yellow, underlined numbers on the right of the poll.
     
  12. gafftaper

    gafftaper Senior Team Senior Team Fight Leukemia

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    Oh that Hughesie, he doesn't use DMX he uses metric DMX.

    He Charc, I believe if you only have one intell in the system it's impossible to have reflection problems. So termination is not needed. (Please correct me if I'm wrong here guys)
     
  13. Edrick

    Edrick Well-Known Member Premium Member

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    I voted no because our highschool didn't have any Intelligent Lighting so I've yet to deal with it. We had a straight DMX run from the Booth to the Dimmer Rack and that was it.
     
  14. Van

    Van CBMod CB Mods Premium Member

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    <insert gong noise here>
    Gaff, you can get a "refelction" off of a bad solder joint. Whether or not you have Movers in your rig is completely beside the point. Movers will tend to make DMX reflection issues much more apparent, kind of like using a high sample rate on an oscilliscope to see abnomalities in a wave form, as opposed to using a multimeter, because they are more "sensitive" to the disruption of the data stream.
    I used to do Communications, for a S&R group. I always had a SWR meter attached inline to monitor the standing wave ratio in the output cable of 10 - 16 meter cables. The chances that one would develope just out of the blue was slim, but if perchance a solder connection failed, or condensation got into a connector etc, etc, it's better to be safe rather than sorry.
    Now if you are using a good Opto-isolator, or if you board has one built in, you could probably get away without ever terminating, However, Older board, more movers, etc, etc, it's not a chance worth taking.
     
  15. SerraAva

    SerraAva Active Member

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    From Mr Doug Fleenor himself: http://www.dfd.com/whyterm.html

    Reflections can happen with just one intel, or anything in a DMX line. Sometimes Opti-Iso splitter or whatever you call it can help, sometimes it can't. The main thing a splitter does is it stops problems with one line effecting other lines. It also helps amplify DMX signal for longer runs. Also changing your DMX speed can help at times too.

    A theatre I use to do work in had an old set of Colortran ENR series dimmer racks. They would ghost all the time thanks to bad/not enough power and a poor data path/line. Setting the board, an Express 125, to output DMX signal at its lowest speed helped the problem a little. The thing that helped the best however was an Iso-Splitter. It helped boost the signal and and allowed the DMX speed to be ran at the fastest setting, not effect other things in the signal path now. If I could, I would have tried terminating it as well to see if it would help, as it had in past experiences.
     
  16. n1ist

    n1ist Well-Known Member

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    I always terminate DMX, both at the last fixture and unused outputs of my splitter. Anything I build that speaks DMX, I include a termination resistor and switch so at least I don't have to hunt for a terminator for those boxes. Why take a chance, when terminators are cheap to build.
     
  17. fosstech

    fosstech Active Member

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    5-pin XLR plugs are cheap, 120 ohm resistors are cheaper. Why not just build a few for $10 and call it cheap insurance?

    Even though we have a DMX Pathfinder patch system/opto splitter, we still make it a general practice to terminate at the end of every DMX run whether it be enabling termination on the last device or plugging in a terminator plug.

    And Ship, I can sympathize with you on the Martin adapters...just got done today running DMX to five MAC600's with all 5-pin cable...we've got a couple bins in the cage devoted to the 3/5 pin adapters.
     
  18. JD

    JD Well-Known Member

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    Neutrik Connector- $1, Resistor $0.10, time: 2 minutes to assemble. Cheap insurance. I've pulled the terminators off a couple of times and not had a problem, but still, it's so darn cheap, why even take the chance on a show? All you need to do is connect the right length of wire up (standing wave) and all heck will break loose. So many reasons to terminate, and the only reason I can think not to is the inconvenience of remembering to take 10 seconds to plug it in the last unit. (or flip the term switch if so equipped.)
     
  19. icewolf08

    icewolf08 CBMod CB Mods

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    Where are you getting Neutrik connectors for $1, because I would love to get them for 1/5 the price that I normally pay.
     
  20. JD

    JD Well-Known Member

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    Just search Ebay for "xlr connectors." Here's one batch of 20 new for $18:
    http://cgi.ebay.com/20-XLR-3-Pin-Mi...ryZ32838QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
    (if the link works)
    Now, we are talking the 3 pin XLR's here, so I can't be much help on the 5 pins, but I think Newark Parts is selling them for about $2.50, but I haven't bought any in two years so who knows!
     

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