Design Issues and Solutions DMX- tell me why this is wrong.

[sk8rsdad]

Some light reading to get started on the topic of why splitting DMX is wrong. The whole topic of electromagnetic wave theory is a very complex subject.

Reflections of signals on conducting lines

en.wikipedia.org

 

[Chris Pflieger]

The odd thing is it seems like this is an install? I can't imagine someone building it this way.

No need for me to imagine it - I lived.

 

[JonCarter]

"Copper is copper!"

(As long as it's the right impedance.)

 

[Ben Stiegler]

The odd thing is it seems like this is an install? I can't imagine someone building it this way.

Oh, I sure can ... have seen too numerous to count instances like this in "professionally" designed facilities ... not just Dmx but audio, networking, and massive electrical code violations and safety issues. I'm a compulsive inspector of any place I go that has either interesting or odd looking tech, or stuff behaving badly. It's shocking! how much stuff out there has been implemented by El-Wrongo Designs.

 

[RonHebbard]

Oh, I sure can ... have seen too numerous to count instances like this in "professionally" designed facilities ... not just Dmx but audio, networking, and massive electrical code violations and safety issues. I'm a compulsive inspector of any place I go that has either interesting or odd looking tech, or stuff behaving badly. It's shocking! how much stuff out there has been implemented by El-Wrongo Designs.

Friday afternoon / Let's get 'er done and go drink beer installs (by designers &/or installater's); say it isn't so.
Think POSITIVE.
Test NEGATIVE.
Toodleoo!
Ron Hebbard

 

[Crisp image]

I would suggest it was done by someone who had just enough knowledge to be dangerous but not enough to do the job properly.

 

[gafftaper]

Your situation reminds me of something @STEVETERRY said around here a long time ago. It went something like this:
DMX is amazingly forgiving and flexible. You can use mic cables instead of proper DMX cables and it will work... for a while... until it doesn't. You could even run DMX over a barbed wire fence, but it wouldn't be a good idea.

Looks like you have an amazing theater you are growing there!

 

[FMEng]

Murphy's law has a corollary about DMX: Improperly cabled and terminated DMX will work during rehearsals but it will fail on opening night.

 

[almorton]

Usually at the interval, having lulled you into a false sense of security.

 

[derekleffew]

You could even run DMX over a barbed wire fence, but it wouldn't be a good idea.

Pretty sure it was Doug Fleenor who first said that. I recall it being requoted by @icewolf08 .

 

[Amiers]

Pretty sure it was Doug Fleenor who first said that. I recall it being requoted by @icewolf08 .

The original DFDs ran on a small strand of barbwire

 

[gafftaper]

Pretty sure it was Doug Fleenor who first said that. I recall it being requoted by @icewolf08 .

Ah... yeah. I'm 51 and don't remember things anymore. It could easily be Doug or Steve. It may also be that "it'll work, until it doesn't" is from one of them and the barbed wire bit is from the other.

 

[JonCarter]

In general: Unless the blueprints, specifications and instructions are SO DETAILED that it WILL WORK when the install is finished (in which case, the installers will never read the blueprints, specifications and instructions or won't understand them if they do), allow the installers to pull wire and let somebody WHO KNOWS HOW THINGS ARE SUPPOSED TO WORK make the final connections and test!

Nothing against the IBEW, but they don't, and can't be expected to, know all the operational details of what they are installing.

 

[StradivariusBone]

Ah... yeah. I'm 51 and don't remember things anymore. It could easily be Doug or Steve. It may also be that "it'll work, until it doesn't" is from one of them and the barbed wire bit is from the other.

Important bit around 3:15 if the embedding doesn't work.

 

[TimMc]

I note the flux capacitor gets its introduction at 4:20.

Doug's videos are fun, succinct, and have enough "key words" that an observant person can search the Intertoobs for hours of reading pleasure.