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DMX/Ethernet


kurzweil_dude

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A thought randomly came into my head the other day and I was wonderin if youlot had any views on it, but...

 

Do you think that DMX will ever be replaced with another format such as Cat6 (or higher) Ethernet? Or is the industry too headstrong regarding DMX nowadays that it just wouldnt happen? Or has is happened already in places and Im too dense to have noticed?

 

** laughs out loud **

 

All thoughts are good! Discuss away!

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Would these ever be able to be used for DMX over ethernet - a kind of one cable solution

Well you could if you didn't really mind if your show didn't quite look the same as how you programmed it. And as long as you weren't ina building where the different ring mains weren't on different phases.

 

Transferring files between PCs over a noisy ethernet line isn't really a problem. The OS will just keep trying until it gets through. For lighting though you want your cues to happen on time. You also don't want different parts of your DMX frame to arrive at different times.

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The topology of ethernet is also 'wrong' for a lighting system - don't go throwing away your DMX cables too soon. All of the existing ethernet standards are used to transport DMX over the ethernet topology, then break it out back to DMX at the other end, which gives you the benefits of cheap and readily available installation cables for the infrastructure but durability and the correct topology for the link to the fixtures.
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This could be solved by a three way switch in each fixture. Two external ports to allow daisy chaining and an internal port which feeds the fixture (this could be on the same PCB, not neccesarely a seperate component inside the fixture).
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This could be solved by a three way switch in each fixture.

 

Only partially. It's then an "active" passthru, so would still mean that any "downstream" devices would fail if the power were to fail on an upstream device.

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and..

Cat6 (or higher) Ethernet?

 

Pedant: There is no such thing. Cat6 is a cabling standard. Ethernet is a protocol. But I digress...

 

 

I wouldn't be too concerned about the latency - The "worst case" scenario at 100Mb/s is a latency of about 100microseconds per device. But that implies a "store&forward" model and maximum packet size. In practice, it's much less.

 

Nevertheless, Ethernet is fundamentally a star technology these days, not chain.

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ut the whole issue of phases/rings etc. does confuse the concept.

Why? Nearly 20 years ago the company I was working for had a building managment system installed.All the control signals were sent via the existing mains wiring,not just between 3 phases but 3 diffrent 500kva transformers.

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As it stands,

The ethernet standard is not 'defined' to run over power lines, The original term (I believe) for comms over power lines is 'Bi-Line' comms, where frequency modulated carrier (FM) at a much higher frequency than mains (50/60 Hz) frequency is used.

 

The problem with this stuff, is that it's limited to the 'local' mains line, unless you have 'bridges' that can cross over transformers or phases.

Another thing is that a genset controller system might be sent to 'infinity' by this carrier frequency - From the engine/genset controllers I've played with , there is no high frequency filtering on the alternator outputs(controller inputs), so this will/might be a problem.

 

National Semiconductor had a nice 'Bi-Line' carrier chip many years ago (cannot remember the number). I think it was on the 'extinction' list, but funny enough, interest in this type of communication is growing, some ~15 years after the chips were first made. There might be other similar comms controllers around, it's been a long time since I've looked at this.

;)

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