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DMX signal over 4 conducter 18 guage speaker wire

Discussion in 'DMX, E1.31 & Networking' started by jerrymac, Dec 21, 2012.

  1. jerrymac

    jerrymac Apprentice Elf

    Mar 29, 2011
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    Quitman GA
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    I am having some dmx issues and wonder if it is my cabling. I am using 4 conductor speaker wire (from mono price) with waterproof connectors. I am sending dmx signal through cat 5 to the first dmx controller and injecting 12volt power into the speaker wire and connecting the cat5 to two of the 4 speaker wires, then sending all down the line and re-injecting power at various points. I am using what you might best describe as a trunk like with taps off the trunk at various points (insulation stripped back and line soldered to the wire and re-insulated).
    I am havng a number of on and off issues and wonder if running dmx data over non twisted wire next to 12volt power wire in the same caseing is causing RFI or some other interferance.
    Since many of you are very knowledgeable in these things,
    Would issues be likely running power and data down 4 condutor non twisted wire. I know David (Holliday Coro) uses cat5 with no major issues but this wire is not twisted although it is insulated. The wire is 18 gauge.
    Or should this wiring type be reasonable?
  2. David_AVD

    David_AVD Bite my shiny metal ass! Community Project Designer Generous Elf

    Jun 12, 2010
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    Victoria Point (Brisbane)
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    DMX is RS485 (differential) signalling and as such is recommended to use a twisted pair.

    You can send RS485 down a non-twisted pair, but the common-mode rejection will be compromised.

    Whether you have issues would depend on how much interference the power wires induce into the data wires.
  3. fasteddy

    fasteddy I have C.L.A.P Global Moderator Generous Elf

    Apr 26, 2010
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    Albion Park NSW
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    The standard for DMX is to use a cable with impedance of 120 Ohms, Cat 5/6 is close enough to this that it has been included in the DMX standard. For any DMX data it is best to use cable designed to send data

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