Correct info on using DMX

[RJ]

I am hearing misconception that has been passed along that needs to be corrected. DMX is not expensive as it is being put out. It does not require you to use expensive high end cable and ends different form what you use now. I run DMX on Cat5 cables with the same ends we all use. I was required to buy one $3 XLR end to connect to the enttec dongle. The rest is all cat5 and cat5 ends. Now before someone jumps in and begins telling me how wrong I am I ask that you read the link below where not only does it work, it is being added into the DMX standard to use cat5 (you can skip to the bottom paragraph and read the conclusion if you wish). It also does not require you to spends hundreds and hundreds of dollars in extra equipment. It requires one $60 - $140 purchase, depending on what you want, to handle 512 channels.

I am not telling anyone to use DMX that was a choice I made for myself but I do want to make sure everyone has good information to make choices on and not what we feel or what we think.

I see where one of our professional big brothers is thinking of offering a dmx version of their light controllers. This should add a lot of interesting capabiltitys such as using vixen to controll the commercial dimmers and those that do not DIY to add all kinds of off the shelf devices to their shows. Should provide for some interesting shows since these people can afford most anything on the market to add in to the show. Can you say Lasers?

http://www.esta.org/tsp/working_groups/CP/docs/DMXoverCat5_Summ.pdf

[stempile]

Which enttec dongle do you recommend?

:?: http://www.enttec.com/index.php?main_menu=Products&prod=70303&show=description

[RJ]

Currently KC only has support for the open but I think we are all going to want to go to the pro. I have found a few issues with the open that I am not ready to talk about until KC and I talk. KC has the pro plugin ready for me to test and I just recieved a pro unit to start testing but he has been away. The pro is actually easier for KC to write code for so I don't expect it to be a problem. The difference is the Pro has a microcontroller on it doing the work so the DMX stream is maintained with perfect timing. The open uses the computer to generate the stream and can have timing glitches. The pro should also work out under vixen to be faster to refresh allowing lower event timing. I will be able to tell you more after the testing and comparing. The bad of the pro is it cost $140 not $60. but it also isolates your computer from everything so that surges or mistakes don't blow up your computer.

[P. Short]

But it's not truly DMX512 if you aren't using the right connectors or cables. It might be cheaper, but it is not DMX512.

--

Phil

[DynamoBen]

You are reading that document out of context. That document is part of a bigger series that was talking about DMX cabling for permanent installations. Yes you can use UTP for DMX but if you read the whole series it does say that you must run it in grounded metallic conduit. In places that don't conduit STP must be used and both ends properly grounded. In regards to connectors and cabling Phil is correct these items are also specifically called out in the DMX standard.

That being said I had some friends try running DMX over barbed wire, and it worked. Granted it only went a few feet but it still worked. DMX is pretty robust and running a few hundred feet over UTP may not be an issue.

I’m with you on the expense of the cables and connectors, they aren’t cheap and they are very specialized. That is why you see so many companies ignoring the standard and using 3 pin xlr’s instead of 5 pin. The thing to keep in mind is the standard was designed to avoid a couple of things that don’t necessarily apply in what we are doing. They didn’t want someone to accidentally plug a mic into a DMX line. Unless you have mics lying about this shouldn’t be an issue. They also wanted to guarantee data integrity across a 5000’ cable with 32 devices on the line. This part of the DMX standard actually comes from the RS485 standard.

In the end do what works best for you. If you run into problems just know that cabling could very well be your root cause. The only concern I have with UTP in your application is running it near, around, or over AC. You may run into some data flakiness, but other than that knock yourself out.

[ErnieHorning]

But it's not truly DMX512 if you aren't using the right connectors or cables. It might be cheaper, but it is not DMX512.
So does that mean it’s really not RS232 because you ran it through a cable that was 100 feet long? Ethernet isn’t really Ethernet because you used screw terminals?

Granted it doesn’t follow the spec, may not work and you’re on you own if you do things that don’t follow the standard. There are certainly plenty of things that us DIY’ers does that violate standards.

I may be looking at DMX for next year because I like what can be accomplished with it. I’ve also heard DynamoBen talk about it for the last year, so it keeps getting refreshed in my mind. I like making all of my electronics and I can make most things cheaper than commercial products sell for. It’s not likely that being compatible with commercial counterparts won’t be one of my higher priorities, especially if the cost difference is high just to do so.

[stempile]

It would be interesting to see the Ren-C handle, RS-232, RS-485 and DMX. I searched for info on both together, as I though someone mentioned a renard with DMX protocol, but since a search with DMX brings up posts with people's signatures with DMX, the results were many...

ms

[ErnieHorning]

RJ mentioned it here in his first post:
http://www.christmasinshirley.com/forum/viewtopic.php?t=397&highlight=dmx+renard

[RJ]

This may not surprise you but I disagree. DMX512 is both a communication protocol and a set of standards by which manufactors are to garentee to meet the set limits of the standards. When I say I am using DMX512 I am not refering to the cabling spec part of the standard I am refering to the protocol. Ben as far as the misreading it out of context I have read the text of all parts. I do not recommend the users tie wrap the cat5 to the power cables but common sense should tell me to not do that with dmx cables either. I know it upsets you when I disagree with you both on these techical issues. and I know how intelligent you both are. There is a big difference in what is required as standard practice for people like you and I who work in these areas and what is needed for a bunch of people putting on a christmas show for there friends. I really doubt ESTA will lose any sleep over a bunch of DIY christmas light nuts using cat5 for there light displays.
I do know a little on the subject. I have been a certified network engineer for going on 25 years and have done my share of data cableing as it was my business doing just that for 7 years and I understand both of your points in that the standard is the standard but it just isn't a big deal for these people. If you google "DMX over cat5" and ignore the hits on DMX over ethernet you could read yourself to death with everything from projects using it this way to even some commercial equipment using it (which I agree I think is bad practice when you produce something commercial to step out of bounds on standards.). I posted just one of the comments of people who have been using it in non permanent install with absolutely no problems below as a link. I would say to those questioning my position on it to put it into prospective. This is not a multimillion dollar concert we are dealing with here. If it were almost all of the equipment we are currently using would not even be allowed to be used so why get upset over the cable. When I first arrived here everyone was building 595's and running them off the lpt port. Were they using IEEE 1284 Rated cable which is a standard? No they were using Cat5 and no one was having a fit over it. It worked and IEEE arrested no one. I even laughed when I was told we could not exceed 25 feet because the standard said so. I ran my ledTriks on 125 ft off the lpt port with cat5 I think that was agianst the standards. We fell out of the standard when we used different cable so why would it even apply.

I hope you two can understand I am saying it will work fine not that you are wrong. Even the testing we spoke about already by ESTA showed that even with out conduit the cat5 worked well. Yes the new standard will call for it to be in conduit but they tested it without it during the testing also and found it to be fine at 1000 ft.

The biggest issue with none permant installs and cat5 is it does not like to be coiled up flexed, etc over and over so it normal should be used in permanant installs only. Might be a good idea to recommend stranded cat5 if you will use it over and over. I will be happy to post a video of my dimmer running on 1000 ft of cat5 with it wrapped in the power cords for everyone. The point is folks that on the technical end they both are correct and we are suppose to use the correct cable and ends until otherwise the standard says. But on the pratical end you do not need to run the expensive cables and ends for your light show on DMX protocol. You will not be meeting the DMX standards but I won't tell if you won't. Your lights will still blink.

I have a lot of respect for both of you so take this for just what it is, a disagreement with you on the practical aspects for the typical user here and not an assult on you.

This was the 4th hit after a google search read down the whole page.

http://groups.google.com/group/hstech/msg/497092b121ffa723

If someone wants to use the correct cable please do. I am not here to talk anyone out of doing what makes them confortable. If no one wants to run DMX thats ok to. I just want everyone that does want to run DMX to know that it is an option for you if you wish.

[DynamoBen]

I agree that DMX over cat 5 should work fine in most situations. The standard is designed to guarantee results and outline how manufactures should implement DMX on their equipment. Personally I've run DMX down mic cable which has the wrong capacitance. I only ran it for about 100' and things worked OK, it didn't look so hot on a scope but it worked.

As far as the statement about Ethernet with screw down connectors. The better comparison is category 5, not Ethernet. Without RJ45s, and distance limitations you can't certify a network to the Cat 5 standard. Same with DMX without the connectors and cabling you can’t “certify” the setup to the DMX standard.

In the end do what works, it is important that people know what the standard says and make their own choice. While Mic cables may have worked in the past for me I have answered countless technical support phone calls from others reporting DMX "jitter" when they do the same. The standard guarantees your results, but there is more than one way to send data. :)

If we move to ACN or ArtNet this will all be a none issue. ;)