DMX help

[labby]

Hi all, just a quick question about DMX. ive noticed that there is a US and a EURO standard, can anyone tell me what the difference is between them? ive had a couple of fixtures which needed to be addressed 1 DMX channel up from where I wanted to put it in order to get it working. is this because of the different standards? many thanks

[IRW]

ive noticed that there is a US and a EURO standard

 

Is there?

[boatman]

There is only one DMX standard originally specified by USITT and now managed by ESTA. The ANSI (European) version is identical.

 

This is from the ESTA website:

 

ANSI E1.11 - 2008 (R2013) is a reaffirmation of the 2008 edition. ANSI E1.11 describes a method of digital data transmission for control of lighting equipment and accessories, including dimmers, color-changers, and related equipment. It intended to provide for interoperability at communication and mechanical levels with controllers and controlled equipment made by different manufacturers. It is an update and expansion of the protocol developed by the United States Institute for Theatre Technology, Inc. and published as "DMX512/1990, Digital Data Transmission Standards for Dimmers and Controllers."

 

If any device doesn't behave the way its manual says it should then are two possibilities. Firstly the device may not comply with the standard or secondly there's a fault in your installation. The most common installation fault is not having terminators on the lines.

[nuttytechy]

I thought I was only one with this issue.

 

If I connected my father inlaw's Dj equipment fixtures to a laptop running M-PC and a enttec DMX to usb then I would have to +1 on those DMX channels and that was only with certain equipment but when I connected the same equipment to a Zero88 frog lighting desk then the DMX addressing would be correct. I always thought it would be my enttec and M-PC having issues with some of the fixtures.

[boatman]

I thought I was only one with this issue.

 

If I connected my father inlaw's Dj equipment fixtures to a laptop running M-PC and a enttec DMX to usb then I would have to +1 on those DMX channels and that was only with certain equipment but when I connected the same equipment to a Zero88 frog lighting desk then the DMX addressing would be correct. I always thought it would be my enttec and M-PC having issues with some of the fixtures.

 

It sounds as though the data structure of the DMX stream generated by M-PC is incorrect. Have you tested the Enttec interface with the Enttec software?

[Ynot]

If any device doesn't behave the way its manual says it should then are two possibilities.<snipped>

The most common installation fault is not having terminators on the lines.

Off topic for this thread but I'd have to disagree there...

In my experience the most common causes of devices misbehaving are:

 

Faulty cables - eg broken wire inside a plug/socket or contacts touching either directly or with a HR connection, again usually inside an XLR

Mis-wired cables - eg hot/cold reversal

Devices wired not to standard - ignoring the fact that 3-pin XLR is not officially standard anyway, many bits of kit were historically wired up hot/cold pins reversed on 3-pin in/out (though this is much improved these days)

 

Lack of a terminator is not THAT common a cause of issues, certainly not on smaller DMX runs. Using one is good practice, yes, but hardly a massive problem for many rigs.

:)

 

 

[Tomo]

Fit a damn terminator.

 

End of discussion, seriously.

 

There are exactly zero reasons to "not bother", and hundreds of reasons to just fit one.

From your list - the terminator will pinpoint a broken wire.

[timsabre]

Whatever the pros and cons of fitting a terminator, it would have no effect on the problem being described here, which is a strange one I've never come across.

 

The only explanation I can think of is the cheap DJ equipment is not keeping up with the DMX stream and is missing a channel, so you have to add one to the address to get it to work as you were expecting.

I have seen this with slow/cheap fixtures, however it's normally an intermittent problem where it flickers between the correct address and +1 address, I've never seen one consistently work at the +1 address.

[MarkPAman]

I seem to remember using some old DJ kit that said in the manual (and if you were lucky, also on the back of he unit) to set it to 1 below the the address the board was set to. Always the old dip switch type, and I guess this was because having all switches off - address zero - would be meaningless otherwise.

 

If this behaviour changes with the desk running it though, then that's not it.http://www.blue-room.org.uk/public/style_emoticons/default/blink.gif

[itiba]

I recall on some older fixtures with dip switches that 000000000 was treated as address one (just like Artnet Universe numbering) and so the address would have to be out by one. Which fixtures do you have this issue with?

[nuttytechy]

I thought I was only one with this issue.

 

If I connected my father inlaw's Dj equipment fixtures to a laptop running M-PC and a enttec DMX to usb then I would have to +1 on those DMX channels and that was only with certain equipment but when I connected the same equipment to a Zero88 frog lighting desk then the DMX addressing would be correct. I always thought it would be my enttec and M-PC having issues with some of the fixtures.

 

It sounds as though the data structure of the DMX stream generated by M-PC is incorrect. Have you tested the Enttec interface with the Enttec software?

 

Hey buddy. I have checked the DMX stream and tested the Enttec interface. What had got me puzzled was that some of the fixtures like the Martin Destroyers and Punishers were fine but when I used NJD datamoons or LyteQuest Motorheads then I would have to set the DMX address 1 up. As it is one of those niggles when I'm used to, Whenever I am setting up then Its implanted permanently into my head ** laughs out loud **

[timsabre]

I recall on some older fixtures with dip switches that 000000000 was treated as address one (just like Artnet Universe numbering) and so the address would have to be out by one. Which fixtures do you have this issue with?

 

But he says the behaviour changed back to normal with a Zero88 desk, so as Mark says, this would not be an explanation. (I remember fixtures like this too)

[Ynot]

Fit a damn terminator.

 

End of discussion, seriously.

 

There are exactly zero reasons to "not bother", and hundreds of reasons to just fit one.

From your list - the terminator will pinpoint a broken wire.

Sorry, Tomo - but don't think anywhere in my post did I suggest NOT fitting a terminator - just that in many situations the lack of one wouldn't cause major issues UNLESS there was an inherent fault on the line.

 

And the actual statement I made was "the most common causes of devices misbehaving are:" and I will stand by that. The lack of a terminator in MOST CASES won't necessarily cause problems on a line that doesn't already have an actual fault somewhere on that leg of a DMX run.

I'm talking about the most common actual faults that cause DMX misbehaviour.

 

 

 

[Don Allen]

What information would be really useful here would be the DMX timing information, which unfortunately needs a DMX tester, something most users don't have. I have 20 "vintage" as in four years old ? RGB 36 x 1w outdoor IP65 led fixtures. All of them work on a Showtec SM-8/2 scanner controller, which is usefull for controlling architectural lighting, but three of the fixtures will not work correctly on the controller, they strobe and have random behavior. The fault is that the DMX output of the SM-8/2 is slower than most other desks and controllers. I am using a Showtec DMX tester DR DMX II to get the DMX timings. I get a Bk:106uS from the SM-8/2 controller. The Showtec LED Commander 50717 has a Bk: 002mS. My LSC Atom desk has a Bk:528uS. From these tester readings, the SM-8/2 appears to have too short a break.

 

Probably a different batch of microcontrolers or firmware in the three odd units. I wonder if this is the cause behind the offset DMX addressing. Remember the previous post on a smoke machine addressing problem ?

[timsabre]

106us is well within spec for breaktime, it has to be longer than 88uS. A lot of fixtures will accept anything longer than 36uS because they read 9 bits and assume if the 9th bit is zero, it is a break.

 

I would guess the problem is that the mark-after-break time or the idle time between the channel bytes is too short / fast so the unit is intermittently missing the next byte sent.