The DMX termination plug

[McCready00]

Is it still used in the industry? I just never seen someone using it so far. Is it because the news machines don't need it? If you are still using it... then when?

Thanks

[Wolf]

I still like to use them. Some people feel that the risk of corrupt information coming back up the line is very slim and dont feel it is necessary to use them. While the chance is slim the one time you dont use them is the time that something will happen and you may spend 20 mins trouble shooting instead of programing. Although some manufactures do have built in terminators so that is not necessary to use them (most boards have them).

[DaveySimps]

I still use them in all of my rigs. I also see them reguarly in touring productions with new gear.

~Dave

[church]

I always use them, the problems are most likely to occur at the end of a long termination and/or when you are approaching the 32 unit load. This is when the DMX signal is approaching its minimum signal parameters.

This is also why using an optically isolated DMX splitter improves the "reliability" of the command link - because it includes line drivers on the output you have the ability to drive another 32 units on each output.

[Kelite]

Is it still used in the industry? I just never seen someone using it so far. Is it because the news machines don't need it? If you are still using it... then when?

Thanks

When responding to Right Arm or Smart Color tech calls, a large percentage of DMX related misbehavior is traced to DMX termination (or lack of, in this case). Moving lights and color scroller PSU's rely upon a clean DMX signal though the entire run, and the longer the DMX run the more chance of reflection, as Church has pointed out.

DMX termination is very similar to car insurance. Sometimes you'll need the insurance when away from the system, and someone adds/subtracts/substitutes fixtures within your run. It seems rare that these changes are mentioned to the designer/TD/ME until a problem occurs...


This is a very valid observation, McCready00. I would stick with a DMX terminator at the end of each run.

[icewolf08]

You should always terminate your DMX lines as it is the proper way to run a DMX distribution system. I have seen plenty of unterminated DMX systems work fine, but at the same time you may not know if some internal motor is a fixtures is sitting there twitching because of reflected data. A terminator costs $5 and 5 minutes to build, so keep them in stock and use them, better safe than sorry.

[rmarston]

I agree - DMX was developed to be a very robust data buss based on EIA 485. But that buss was designed to be terminated with a 120 ohm resistor. It's a simple to add a terminator to each DMX buss to prevent the possibility of reflected data screwing up any fixtures.

Rick

[avkid]

A terminator costs $5

You're paying too much for parts!

[zuixro]

You're paying too much for parts!

Yeah, Mouser has the connectors for $2.68. The resistor is just a few cents.

[derekleffew]

See the Glossary entry: http://www.controlbooth.com/forums/g...ight=terminate.

... Although some manufactures do have built in terminators so that is not necessary to use them (most boards have them).

This is an absolutely UNTRUE statement. By definition, the control console or DMX source cannot terminate the line. Some dimmer racks and devices have a termination switch. I (and others) have yet to be shown a moving light or LED fixture that has "auto-termination" or "self-termination." I cannot recall ever seeing a fixture with a termination switch.

McCready00, you might find this poll useful: http://www.controlbooth.com/forums/l...ight=terminate. "DO as we say, not as we do."

When responding to Right Arm or Smart Color tech calls, a large percentage of DMX related misbehavior is traced to DMX termination (or lack of, in this case).

Kelite, your manuals need some revision. In previously researching this topic, I found that the RightArm manual does have a one-line remark (with an error!), but could not find any mention of 5-pin termination in the SmartColor manual. See this post: http://www.controlbooth.com/forums/w...tml#post103731.

[Malabaristo]

I (and others) have yet to be shown a moving light or LED fixture that has "auto-termination" or "self-termination." I cannot recall ever seeing a fixture with a termination switch.

Actually, current models of the Source Four Revolution are self-terminating. There's a switch built into the female XLR that connects a termination resistor when nothing is plugged in. Here's a link to the manual. Page 4 is where that feature is described. Apparently they've been that way since at least the beginning of 2007.

[derekleffew]

Thank you for the correction, Malabaristo. Are you aware of any other fixtures having this feature?

[gafftaper]

EDI Scrimmer Sticks (portable dimmers) have a terminate switch on them. That's the only thing I've seen with one.

[Malabaristo]

Thank you for the correction, Malabaristo. Are you aware of any other fixtures having this feature?

Nope, that's the only one I've seen. Of course, ETC products are what I'm most familiar with, so that shouldn't be terribly surprising. As simple as it is, though, I'm sort of surprised it hasn't been a more popular feature. Especially since lack of termination is so frequently the cause of DMX problems.

[gafftaper]

Nope, that's the only one I've seen. Of course, ETC products are what I'm most familiar with, so that shouldn't be terribly surprising. As simple as it is, though, I'm sort of surprised it hasn't been a more popular feature. Especially since lack of termination is so frequently the cause of DMX problems.

Seems like a really cheap and easy feature for manufacturers to install.

[dannyn]

For how cheap they are, I do no see why you would not use one. If anything it gives you a piece of mind.

[STEVETERRY]

Actually, current models of the Source Four Revolution are self-terminating. There's a switch built into the female XLR that connects a termination resistor when nothing is plugged in. Here's a link to the manual. Page 4 is where that feature is described. Apparently they've been that way since at least the beginning of 2007.

This is correct. I forgot that we implemented this in 2007. Moral of this story: never ask the VP of R&D about product details.

:-)

[porkchop]

The tour I'm on doesn't even have a single terminator in stock. This drives me nuts if you ask me you should terminate every dmx run. Like we've illustrated they are cheap and often the misbehavior can be seem by people not looking for it. I have seen High End techno's that need to be terminated always, but I can't say that I've noticed any thing not working right with our current unterminated rig.

[JD]

Anybody that has looked at the signal with & without on a scope will opt to terminate!

[Blackfaer]

I can detect a noticeable difference when I take my terms off my units; my technobeams will occasionally bounce around as if receiving occasional incorrect settings. It's foolish not to use terminators if you are running anything more than a few feet from a splitter or console.

I'm not familiar with any movers (I haven't used the Revolution) that have self-termination, but many dimmer systems have either a switch or they auto-terminate. I seem to recall that some of Wybron's color scroller power supplies self-terminate, but that might just be referring to the scroller data lines, not the actual DMX. I'm not sure.

[derekleffew]

Nope, that's the only one I've seen. Of course, ETC products are what I'm most familiar with, so that shouldn't be terribly surprising. As simple as it is, though, I'm sort of surprised it hasn't been a more popular feature. Especially since lack of termination is so frequently the cause of DMX problems.

For anyone interested in building one's own DMX devices, here is the Neutrik spec sheet on the connector in question, as used on the ETC Revolution: Neutrik - Industrial - A Series - NC5FAV-SW.



The SmartPack uses this connector also, as evidenced in this statement:
DMX may be daisy-chained from one panel to another utilizing the XLR connectors on the front of
the unit. When daisy-chaining DMX, utilizing only the XLR connectors, the DMX-Thru connector is
self terminated when no connection is made.
from this document: http://www.etcconnect.com/docs/docs_...SetupGuide.pdf.

[TimMiller]

personally i would prefer pushing a termination button or plugging in a terminator over relying on a fixture to self terminate. I would fear that something would eventually get corroded and the fixture would decide to terminate or not terminate when it should and with my luck i would have a fixture in the middle of the run decide to terminate itself on top of the fixture at the end being terminated and cause the entire data run to freak out due to there being two terminators on the line. If it can go wrong it eventually will. I still cant get over the time i had a data cable coming off of the first fixture decide to quit during the second song in a show. It had been working fine for the previous 2 days of programming.