DMX across phases?

[ddproduction]

Hi all,

just a quick one:

Does anyone know if DMX signals are likely to be affected across phases i.e. if the board and dimmers are on separate phases, will this cause any adverse effects?

 

 

 

Thanks! :** laughs out loud **:

[TonyMitchell]

The DMX control protocol is electrically isolated, so no it will cause you no problems.

 

Indeed it is common for larger dimmers to operate across multiple phases.

[Unfathomable]

I have always been advised to add a splitter with opto-isolation or similar to act as a buffer should anything try to fry your desk (better lose the >£100 splitter than the desk, right?). Nothing wrong with doing it though.

[csg]

DMX will operate correctly over different phases, with most touring dimmer racks being 3 phase, this would soon show up to be an issue if it were not the case.

 

The important thing to maintain is the earthing of the system - DMX networks can get upset when connected between different electrical systems, earthed to different grounds. In this scenario, there is the potential for equipment damage in severe cases, and in all cases isolation should be used between the systems.

[ddproduction]

Thanks for all this - we are working in a village hall so earthing shouldn't be a problem :** laughs out loud **:

[d_korman]

Thanks for all this - we are working in a village hall so earthing shouldn't be a problem :** laughs out loud **:

 

I've always found with Village Halls that earthing is the biggest problem - in fact I've got a show at one of these in two weeks time where we always have DMX issues, in spite of usein DMX distribution and terminators!

[Sound In Gloucestershire]

yeah village halls are always the worst in my personal experience, random pops and cracks and lights acting funny!

[timsabre]

Just going back to post #2

 

The DMX control protocol is electrically isolated, so no it will cause you no problems.

 

This is incorrect (unless you have specifically fitted isolated DMX splitters). DMX is not electrically isolated.

 

Csg is right that it's the earthing that will determine whether you have problems or not.

[Brian]

DMX receivers, if designed as per the recommendation of the spec, are isolated. Sadly, most manufacturers ignore this and simply implement the 'allowed' topology of non-isolated receivers, or worse, grounded receivers.

[timsabre]

DMX receivers, if designed as per the recommendation of the spec, are isolated. Sadly, most manufacturers ignore this and simply implement the 'allowed' topology of non-isolated receivers, or worse, grounded receivers.

 

They don't ignore it, it's an engineering decision based on cost. I design this stuff for a living and a lot of the time the large additional cost of isolating the DMX cannot be justified in the cost of the product. Hence the vast majority of DMX equipment is not isolated, only the really expensive stuff is.

[Grum]

DMX receivers, if designed as per the recommendation of the spec, are isolated. Sadly, most manufacturers ignore this and simply implement the 'allowed' topology of non-isolated receivers, or worse, grounded receivers.

 

They don't ignore it, it's an engineering decision based on cost. I design this stuff for a living and a lot of the time the large additional cost of isolating the DMX cannot be justified in the cost of the product. Hence the vast majority of DMX equipment is not isolated, only the really expensive stuff is.

 

Or another way of putting it would be that your company chooses to ignore the specification in order to produce a product at a lower cost.

 

Two sides of the same coin.

[ddproduction]

OK I see, the question I was tending to is will using DMX cross-phase cause any damage / adverse effects to the lights/dimmers/supply? :)

[Ynot]

OK I see, the question I was tending to is will using DMX cross-phase cause any damage / adverse effects to the lights/dimmers/supply? :)

And the answer, as already quoted, is a firm 'no' - it will NOT be a problem.

Isolation of the DMX stream from the desk itself is good practice, BUT is not essential.

[timsabre]

DMX receivers, if designed as per the recommendation of the spec, are isolated. Sadly, most manufacturers ignore this and simply implement the 'allowed' topology of non-isolated receivers, or worse, grounded receivers.

 

They don't ignore it, it's an engineering decision based on cost. I design this stuff for a living and a lot of the time the large additional cost of isolating the DMX cannot be justified in the cost of the product. Hence the vast majority of DMX equipment is not isolated, only the really expensive stuff is.

 

Or another way of putting it would be that your company chooses to ignore the specification in order to produce a product at a lower cost.

Two sides of the same coin.

 

No, this is not another way of putting it. Using the word "ignore" is an offence to all those engineers who labour hard in darkened rooms to bring you new DMX toys at a price you can afford. The specification either allows it or it doesn't and in this case, it does.

 

Sorry to go off the topic.