# Do you terminate your DMX lines?



## derekleffew (Oct 8, 2007)

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


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## SerraAva (Oct 8, 2007)

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.


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## Logos (Oct 8, 2007)

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.


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## len (Oct 8, 2007)

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


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## beam_1973 (Oct 8, 2007)

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.


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## soundlight (Oct 8, 2007)

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".


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## ship (Oct 9, 2007)

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.


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## Van (Oct 9, 2007)

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


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## Grog12 (Oct 10, 2007)

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


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## Radman (Oct 10, 2007)

Grog12 said:


> 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


Someone with either a very low or very high budget.


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## SerraAva (Oct 10, 2007)

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


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## gafftaper (Oct 10, 2007)

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)


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## Edrick (Oct 10, 2007)

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.


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## Van (Oct 10, 2007)

gafftaper said:


> ....................................................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)


 

<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.


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## SerraAva (Oct 10, 2007)

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.


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## n1ist (Oct 12, 2007)

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.


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## fosstech (Oct 13, 2007)

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.


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## JD (Oct 13, 2007)

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.)


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## icewolf08 (Oct 13, 2007)

JD said:


> 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.)



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


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## JD (Oct 13, 2007)

icewolf08 said:


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



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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## avkid (Oct 13, 2007)

icewolf08 said:


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


Ditto.......


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## avkid (Oct 13, 2007)

JD said:


> 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


Have you actually bought these?


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## JD (Oct 13, 2007)

Can't be sure without digging for invoices as to who I last got them from. Haven't bought any this year, but this guy has a rating of over 16,000 and 100% positive feedback.


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## fosstech (Oct 13, 2007)

I can't remember where I saw it, but a while back somebody made up some terminators with an LED sticking out the strain relief of the plug. Whenever DMX was being transmitted down the line (and reaching the terminator), the LED would be flickering.


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## soundlight (Oct 13, 2007)

Fleenor makes 'em, and I know that I've seen them somewhere else (another style), but can't find that source right now. Anyway, here's the Fleenor link.

http://www.dfd.com/term.html


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## PhantomD (Oct 14, 2007)

It ain't terminated, no issues.


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## n1ist (Oct 15, 2007)

I have used those cheap XLRs. I'm not a fan of them for cable mounts (the cord grips are a bit cheap...) but for terminators, I just solder on the resistor and pour in either some epoxy or hot-melt glue to hold things together.


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## len (Oct 16, 2007)

JD said:


> Can't be sure without digging for invoices as to who I last got them from. Haven't bought any this year, but this guy has a rating of over 16,000 and 100% positive feedback.




Be wary of extremely high numbers. I saw one seller with high numbers, until you read them. He would have 10-20 quotes posted at the exact same time, with the exact same comment, from different buyers. The odds of that happening are astronomical.


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## RonaldBeal (Oct 16, 2007)

n1ist said:


> 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.



Terminating unused splitter outputs is completely unnecessary. because each output (or pair of outputs) is on a different driver, reflections on one line wouldn't affect any others. That is one of the purposes of an opto-splitter. Additionally, the distances from the driver to unused output ports are so close, that there is not enough length for reflections to form.

RB


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## pacman (Oct 16, 2007)

Yes, I terminate everything that doesn't have built-in termination, except the opto-splitter.


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## Stoldal (Oct 16, 2007)

I Normal don't terminate, but i don't have that complex of a system. Normal it is just a Response 96 , two cyberlights CX. One show i did had 20 LEDs + my normal set up, and still no problem with out a terminator


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## SerraAva (Oct 16, 2007)

Its hit or miss. Sometimes you will have problems, sometimes you won't. It really has to do with the length of the run in question. The longer the run, the more likely you are to have issues. In a installed setting, if you don't have problems when its first installed, you most likely never will unless you add more to the system. 

It generally takes about 500+ feet of data before you run into problems. Thats 500 feet either from the board, or from an opto. Most never run into this. Generally when running that much data, you would want some optos to amplify the signal, which starts the 500 feet all over again. 

I have one set of lights that I use in clubs that have problems with only about 100 ft of cable and need to be terminated always. There are many factors involved. As it has been stated, its so cheap to terminate, its much better to do it instead of allowing problems to occur.


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