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Electronics with Pos, Neg and Drain wires

Discussion in 'Musings With Maine Sail' started by Ward H, Jan 20, 2019. Add this thread to a FAQ

  1. Ward H

    Ward H

    Joined Nov 7, 2011
    2,082 posts, 359 likes
    Catalina 30 Mk III
    US Barnegat, NJ
    I'm ready to run power connections to a chart plotter, SeaTalkng network and ACU for an auto pilot.
    All three need a positive, negative and "rf drain" connection. Manuals state if the boat does not have a separate RF drain connection to connect the RF drain to the battery negative connection.

    Two of the devices have power cables I need to extend. One device needs a power cable.

    Do I need something like 14-3 to make these connections? The only 14-3 I've found is listed as AC cable. Maybe because the wire colors are black, white and green.

    Thanks
    Ward
     


    Last edited: Jan 20, 2019
  2. Ron20324

    Ron20324

    Joined Jan 22, 2008
    6,707 posts, 798 likes
    Beneteau 323
    US Annapolis MD
    Uummm... I believe you can connect the drain to the neg at the device and just run a 2-wire. I'm not sure where you would connect a drain to otherwise. I'm sure "Sparky" has a better answer?
     


  3. Ward H

    Ward H

    Joined Nov 7, 2011
    2,082 posts, 359 likes
    Catalina 30 Mk III
    US Barnegat, NJ
    That sure would simplify things.
     


    jssailem likes this.
  4. LeslieTroyer

    LeslieTroyer

    Joined May 20, 2016
    2,234 posts, 943 likes
    Catalina 36 MK1
    US Everett, WA
    That is what I’ve done.
     


    jssailem likes this.
  5. uncledom

    uncledom

    Joined Jun 11, 2011
    1,109 posts, 231 likes
    Hunter 41
    US Lewes
    Ward if you have a cable with a true drain wire in, such that it is wrapped on the inside like a shield, make sure you only ground one end or you could induce noise on the cable.
     


  6. Bill Roosa

    Bill Roosa

    Joined Jun 6, 2006
    6,983 posts, 145 likes
    Hunter 40.5
    US Harrington Harbor North, MD
    SeaTalk (NEMA 2000) supplies power to all the units from the network cabling so not sure what devices you would be powering AND connecting to the network.
    This is an electrical noise shilding issue not really an RF noise being produced by the cables one. Just grounding it with a small diameter wire (14 gage would be massive overkill IMHO) will be sufficient to protect the cables inside the network cabling from RF interference.
     


  7. LeslieTroyer

    LeslieTroyer

    Joined May 20, 2016
    2,234 posts, 943 likes
    Catalina 36 MK1
    US Everett, WA
    Lots of devices are connected to the the network AND external power, VHF, AIS Xmit, Auto Pilots, Chart Plotters all can pull more than the network can supply so they have external power.
     


  8. Ward H

    Ward H

    Joined Nov 7, 2011
    2,082 posts, 359 likes
    Catalina 30 Mk III
    US Barnegat, NJ
    @LeslieTroyer, I'll need two power lines up to the pod, one for the chart plotter and one for a USB charge port. Do you think I can run a 14-3 wire and use ground for the return for both positives? I figure 14 wire should handle both loads easily.
     


  9. LeslieTroyer

    LeslieTroyer

    Joined May 20, 2016
    2,234 posts, 943 likes
    Catalina 36 MK1
    US Everett, WA
    The only concern I would have is if you plug a noise plug into the 12v socket.
     


  10. sesmith

    sesmith

    Joined Jul 1, 2010
    617 posts, 107 likes
    Seaward 25, Catalina 350
    US Ithaca, NY


  11. Mark Maulden

    Mark Maulden

    Joined Jan 25, 2011
    1,801 posts, 181 likes
    S2 11.0A
    US Anacortes, WA
    Ward, connect all your devices per manual. If you are worried about RF interference, you need to identify what a source of RF might be and protect from it accordingly. You probably have no sources unless you have high power xmttrs on board. Forget about discussions on skin effect vs wire size etc. You are not dealing with frequencies so high that skin effect becomes an issue. One could make a case that digital rise/fall times can fourier to high frequencies, however, wire inductance will slow those times and round off waveform corners which are the usual noise sources. As for yor USB port, run separate power AND ground up the pedestal. The power and ground “source” to be as close to battery as possible. Batteries are excellent noise filtering capacitors and who knows what noise source can be plugged into USB. You might also entertain running USB up the opposite pedestal tube for separation from electronics. As for the “drain” wire, if you are concerned, connect it to power negative.
     


    Ward H likes this.
  12. Ward H

    Ward H

    Joined Nov 7, 2011
    2,082 posts, 359 likes
    Catalina 30 Mk III
    US Barnegat, NJ



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