The DMX termination plug

Malabaristo said:
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.
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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.

proxy.php


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.
Click to expand...
from this document: http://www.etcconnect.com/docs/docs_downloads/manuals/SmartPack_Portable_SetupGuide.pdf.
 
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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.
 
In addition to working in theatre, I also sideline as a mobile DJ during my non-theatre weekends. A while back I invested some money into four intelligent lights for my DJ setup. I bought four of them, and when I placed the order the salesperson on the other end "highly recommended" I also purchase a DMX terminator that would plug into the "out" DMX port on the final light in the daisy chain. He said that not using a terminator would cause addressing issues and could cause my lights to behave oddly. So I added the $29.99 to my order to buy the thing.

Last week I did a gig and when I got there I discovered that I had forgotten the terminator at home. Not having enough time to run home and get it, I set up my lights without the terminator attached and to my surprise the lights behaved just as they always have, and exactly as I had programmed them on my controller.

My question is... Is a DMX terminator on moving lights even necessary, or did I get tricked into spending more money?
 
Sometimes they work and others they don't. You could go years without one with the same rig and never have a problem then one day need it when those weird problems show up. You did pay to much for it though, you can buy them for $10 on ebay, or make one very easily yourself with a bare dmx plug and a resistor.
 
Darn, I really *did* overpay. Crap. Well, I guess I'll never buy anything else from that store again!
 
No, I don't think that's necessary. The Sensor racks most likely have built in termination. I say that because never have I seen a terminator sticking out of a Sensor (or any) dimmer rack. Now dimmer packs are a different story in most cases.
 
Some DMX devices are self terminating, you'll just have to check the manuals for each one and see if that's the case. It's usually higher end fixtures that will have it.
 
techieman33 said:
Some DMX devices are self terminating, you'll just have to check the manuals for each one and see if that's the case. It's usually higher end fixtures that will have it.
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Care to name these alleged "self-terminating" fixtures?
 
ETC SmartPack [rackmount version] and later models of Revolution [labeled when fitted].

David
 
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Using a DMX terminator is somewhat similar to wearing a seat belt (other than there are no laws about DMX termination, just recommendations). If, in the event of signal reflection due to wireless devices, faulty/worn cable, failing PCB components within a lighting fixture, etc., the signal will pass in only one direction and not 'bounce back' down the line.
Imagine throwing tennis balls at a wall, and every so often a thrown tennis ball returns and strikes one which has just left your hand. This is similar to DMX reflection in an odd type of analogy. Now stick carpet tape all over the wall and resume throwing the tennis balls. These balls now stick to the wall, limiting the liklihood of them reflecting back and striking oncoming tennis balls.

I know, simplified explanation of a non-simple phenomenon but still somewhat effective in understanding reflected data.


Go in peace, terminating as recommended-

;)
 
sk8rsdad said:
I suspect the Source Four LED uses the same parts but haven't checked the manual.
Click to expand...

Indeed, the Source Four LED is self-terminating. Thanks for adding those....you'd think I'd know that. Ugh.

We've been through this discussion before, as I am reminded. A couple of points....

- Self-terminating connectors are available from Neutrik
- These connectors were co-developed with ETC
- They are not cheap, which is likely why not many manufacturers use them
- They disconnect termination when a male is plugged into the pass through female
- If you get in the habit of always using terminators, it doesn't matter whether products are self-terminated or not
- Having a termination switch available on the product is not the definition of self-terminated, but is appreciated when termination at end-of-line is needed
- Terminators never create problems, unless there is a wiring issue or receiver chip failing
- Many systems run fine without termintors everyday, BUT!!!
- Control problems can, and do, occur without warning even after minutes, days or years of working without issue.

Terminators are your friend [not the movie kind].

David
 
David North stated the facts about terminators very well. In addition, I can add a couple of other points:

- Any system that works without a terminator, but "breaks" with one installed is a system that should not be able to operate at all. The terminator is just showing up the problem. It's only works without the terminator because you are lucky. [Edit by mod: see the thread http://www.controlbooth.com/threads...terminator-was-the-problem.28635/#post-254583 .]

- $20 for a terminator isn't necessarily a ripoff. If it's just a tin plated 5 pin XLR with a 120 ohm 1/4W resistor inside, then yes, that's a bit expensive. However, if the connector has gold pins, a proper 1/2W (or larger) resistor and good marking, $20 isn't out of the question. If you add other features like surge protection, the price can go higher still.

- The practice of termination is called out in the EIA/TIA-485 electrical standard. This is the electrical standard on which DMX512 is based. (just an interesting factoid).
 
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As for paying $29.95 for a terminator, I wouldn't waste $20 worth of time worrying about it! Just keep it in the back of your mind and double check prices this vendor charges on future purchases.

Some terminators do cost more and may actually have other parts in them (such as 5 volt MOV's between each signal pin and pin 1) but the only part required by the standard is the resistor between pins 2 and 3.
 
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