DMX splitter

Well said Phil. I am not sure how we could disagree as I only have 12 posts (LOL) but you are right it did come across as a marketing scheme and it was not meant to be. I only can honestly and truthfully relate to our equipment, as I am involved with the designers during the design process, so I certainly can see how that can look...for that I apologize.


I have the actual USITT manual (I believe we have the 1990 revision at the office) so I have to get the exact working regarding the active/repeated data line within the protocol.


Greg
 
I've read over the TI document and the excellent Maxim artcile (http://www.maxim-ic.com/app-notes/index.mvp/id/763) and they don't have any problem with the method I use with the three way RJ45 splitters as long as the stubs are short, which they are.
Here is a video that shows a scope trace of my 2011 display which had dozens and dozens of 3 channel controllers over hundreds of feet of cable. Not a perfect signal but still worked just fine - I think this shows how durable RS-485 is.
http://youtu.be/vv9c8Z6aFbI?hd=1&t=5m28s
This is real data, with a real display, not theory.
 
Well,
I sure didn't mean to open that can of worms, but I do have to admit it is very interesting. I can definetly say I learned alot.
ZMAN, how can I go about aquiring the Lynx splitter?

Thanks everyone, again you all are very helpful.
Mark
 
Going back to the OP's intented question:

A DMX source in the middle of a LONG line of DMX cabling in either direction. This application requires a splitter. Or an additional few hundred feet of cabling.

If you're up to soldering something yourself, you could make something for the $10 mark (I'm at work so I'll post some schematics and information later). If you'd like to buy something, audiovisualdevices sells some DMX splitters, as well as seasonal entertainment, and a few other places.

Using a "passive" splitter such as the one used for a stub wiring will definitely cause more issues than you will want to figure out. The stub method works for something on the order of 1-2' not 75'.
 
ChillOutDocDoc said:
A DMX source in the middle of a LONG line of DMX cabling in either direction. This application requires a splitter. Or an additional few hundred feet of cabling.
Click to expand...

Require is an objective word - I'll agree that the signal is cleaner when i don't inject at the middle but I've done it over hundreds of feet of cable and it does work. So, "required" is subject to your needs. Running a factory with PLC's and processes that can kill people? You bet - 100% to spec -grounds, termination, high quality cable, spec specific installation. This is Christmas lights, not control of robot welders.

My suggestion is to do what I've done - try your anticiplated design and check it with a scope.
 
I'm not going to continue to debate and debacle the fact that what "does" work and what is supposed to happen are two different things. Just because I could drive 120mph in my car doesn't mean I will.

Most hobbiests don't have a few hundred to drop on a scope and would rather just have a reccomendation on what to use.

Your three options:
"Cheap" Splitter Dmoore reccomended - available from dmoore
Non-Isolated Splitter - DIY or from Pondude, David_AVD and others
Isolated Splitter - DIY or from David_AVD, and others

If the first doesn't work, pick the second. The third has the benefit of isolation so that heaven forbid high voltage power gets on your data line, it stops at the splitter.

I agree with dmoore's ideas of "test it and see if it works" but I'd prefer to have everything as close as possible to the "way it should be" two different approaches, two different layouts.
 
From reading the below thread i believe that using these 'passive' splitters is not technically correct to standards but works for DM and his customers in the real world. By taking this approach you must understand that it does come with some risk of not working, but at the same time I know DM will give excellent support if thats the case.
Most of the things we do in this hobby deviate somewhat from the standard mainly to save money and make the hobby affordable, some things deviate more than others and when ever we deviate from the standard then we run the risk of having potential issues with our setups.
Personally im not a big fan of this method, but i can understand why its being used and why people would use it. Its another option for the lighting community amongst the many other options available. Each display is individual so what may work for me may not work for others.

So all i can say is with whatever system you choose then its a matter of test, test and test again to make sure you iron out any potential issues before show time
 
ponddude said:
Well said Phil. I am not sure how we could disagree as I only have 12 posts (LOL) but you are right it did come across as a marketing scheme and it was not meant to be. I only can honestly and truthfully relate to our equipment, as I am involved with the designers during the design process, so I certainly can see how that can look...for that I apologize.
I have the actual USITT manual (I believe we have the 1990 revision at the office) so I have to get the exact working regarding the active/repeated data line within the protocol.
Greg
Click to expand...

Greg
... said with a grin .. we have disagreed before :) but you and (vendors in general) are welcome to participate on the forum.

Cheers
Phil
 
mmkooiman67 said:
Well,
I sure didn't mean to open that can of worms, but I do have to admit it is very interesting. I can definetly say I learned alot.
ZMAN, how can I go about aquiring the Lynx splitter?

Thanks everyone, again you all are very helpful.
Mark
Click to expand...

Mark,
Technical people love to disagree :) . A least this discussion on Technical Standards etc has remained polite and constructive unlike some other threads on other forums.
I was going to split it off but it has all stayed close to topic and is relevant to the discussions.

-------------
In re-reading this thread i noticed something i missed in your requirements.
The need to feed the DMX sgnal from the middle of the string

Recommendation:
If you are feeding a DMX signal in two different directions in the following layout

EndDevice <- Device <- Device <- DMX Dongle -> Device -> Device -> EndDevice

Then you should put a DMX Active Splitter were the DMX Dongle is.
Edited out as David in the post below is correct, my apologies for misleading.

Edited out other info from here

Cheers
Phil
 
Actually, using an RJ45 "splitter" right at the DMX dongle (via a very short cable) should be perfectly acceptable and within the RS485 guidelines. It's when the cable between that first split and the dongle is long that your are out of spec and problems can occur.
 
If you are going to do this:
EndDevice <- Device <- Device <- DMX Dongle -> Device -> Device -> EndDevice

Then you should make sure you DMX dongle doesn't have a 120R load. The terminating resistor should only be on the EndDevices.
 
I'll let you know how they go when i get all the boards an parts an test them

kool-lites said:
smartalec said:
I have this dmx splitter im making for myself, just 8way opto an dc-dc isolated
http://smartaleclights.webs.com/apps/photos/photo?photoid=154382652 for the Circuit diagram
http://smartaleclights.webs.com/apps/photos/photo?photoid=154382651 the circuit board i have coming to me
This circuit should work an can work out quite cheap as well (avg $30 each)
thought i might show this off
Click to expand...
$30 including 9 dc-dc converters is darn good. I'll buy a couple.
Click to expand...
 
ChillOutDocDoc said:
Most hobbiests don't have a few hundred to drop on a scope and would rather just have a reccomendation on what to use.
Click to expand...

What has happened to the industry is that we've gone from a nice, simple, working, one-size-fits-all solution with LOR hardware and the LOR protocol to a mis-match of DIY solutions. Of course I'd never recommend than an LOR only user has a need for a scope or even understand what RS-485 is - because it just didn't matter - LOR stuff just works(sans a few stickies for people with high channel counts).

Speaking on a residential level, there really isnt' a "hobby" company making the diversity of products we are using - that all work together with a "standard". So, you have a little of this, a little of that, this cabling type, that cabling type, this output interface, that output interface, this pixel type and that pixel type and add it all up, it's very unlikely that anyone has the "same" setup like would have been very common under LOR.

So, since you can't exactly go back to most vendors, such as those, say...in China... and say to them - but it should work with this or that - the only person you can count on is yourself and if you are lucky the support of others with more knowledge. Of course that support is limited based on the complexity of your display.

So, what does this have to do with scopes? We'll I'd argue that if you want to play ball with the DIY hardware - you need to get the tools neccessary to do it. Does a weekend race car guy not have a $200 torque wrench, air compressor, power tools - of course not - if he wanted to just drive his car around on the weekends and not race he wouldn't need it - that's what his neighborhood mechanic is for. The stuff many people here are doing requires the tools AND the knowledge neccessary to do it. If someone goes head first into pixels, E131, complex networks with different controllers - the only one you can 100% depend on is ... yourself. No picking up the phone and calling LOR on Dec 2nd on why your network isn't working...and you better have the tools and knowledge to fix the problem yourself because people are going to be busy with their own displays.

Get that scope, get that logic analyzer, get educated as best possible - December is coming and it's going to get nasty out there this year.

:D
 
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