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Thread: Need confirmation on M4 ATX wiring

  1. #1
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    Need confirmation on M4 ATX wiring

    I have been reading the about how to connect the M4 ATX to my Xterra for awhile now and I think I have it but I want to make sure.

    First I have a D945GSEJT motherboard which does not have the 24 pin connect and I believe I can do the 4 pin connect and should still work.

    To connect to the car battery I am using about 10 feet of wire so that will need 8 gauge wire with a 25 amp fuse. I have battery problems and do not want the M4 ATX always turning on so I was thinking about putting a switch on this line as well but I am not sure if this is safe or if I need a relay.

    Then the ignition line I will need a 15 amp fuse just to make sure everything is well protected.

    If there is anything I missed , if I can actually put the switch there and if I do not need to use the 24 pin connector let me know.

    Also, If there is a diagram for wiring the M4 ATX that would be awesome to since I can only find posts about questions about wiring instead of the actual overall wiring of the PSU.

    Thank You

  2. #2
    MySQL Error soundman98's Avatar
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    that really is the wrong psu for that motherboard. it is a atx-compliant psu, which means that some of the wires in that 24pin harness allow the pc to tell the psu when it is turned on and when it is turned off. you can try to hook it up, but you might have issues with starting up and shutting down, or you might need to short the sense pin to get the psu to believe the pc is there..


    you really only need 10 ga wire for the psu, unless you plan on running other devices off the same wire. the fuse rating is correct for the same situation(powering only the psu).
    just be sure to use the same wire, or larger for the vehicle chassis connection.

    using a larger 8ga wire won't hurt anything, the biggest difference is that it allows for room to add other devices, and costs more then 10ga wire.

    for the ignition line, you really only need 18gauge wire, and a fuse is usually not needed, but won't hurt anything to install. if you do use a fuse, use something around 1 amp. that line will not draw any more then about 0.5 amps at the absolute most.


    as for wiring it, check the manual for the psu-- that should give you all the details of it.

  3. #3
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    Thanks for the input Soundman.

    The PSU that mp3car suggest for my motherboard is the carnetix P2140 but it is 40 dollars more expensive then the M4 ATX.
    Quote Originally Posted by soundman98 View Post
    you really only need 10 ga wire for the psu
    That is good to hear that I only need 10 ga because 8 is not as easy to find as I have found out today.

    Quote Originally Posted by soundman98 View Post
    that really is the wrong psu for that motherboard. it is a atx-compliant psu, which means that some of the wires in that 24pin harness allow the pc to tell the psu when it is turned on and when it is turned off. you can try to hook it up, but you might have issues with starting up and shutting down, or you might need to short the sense pin to get the psu to believe the pc is there..
    But back to your first paragraph you said that the M4ATX will not know if the computer is on or not but from my under standing that is what the J8 connection is for that connects to the motherboard's USB header. My understanding from the manual is that once I connect the 4 pin connector (B in the manual diagram) power to the motherboard and J8 (manual diagram) to the USB header then the they both will communicate.

    If I am wrong about that it would be amazing to know because if I have to get Carnetix P2140 I will find the money to do it this is the last thing I need to do everything else is already installed.

    Thank You

  4. #4
    MySQL Error soundman98's Avatar
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    it is not so much the 2 devices talking in the terms of data, as it is a 'activation' pin-- a atx motherboard connects one of the wires in that 24 pin harness to ground whenever it is on. that is simply telling the psu that the mother board is on and running and not to shut power off.

    there are plenty of ways to trick it to doing this, but it might lead to undesirable results later on-- like the psu always staying on, because the wire is always connected, or extra difficulty building a circuit to control the wire to make it appear to turn on and off with the motherboard..

    it wouldn't hurt to try as long as you don't need to hack up the harness, but i do believe that a psu like the carnetix series, or there are other options like the dsx12vd, or the dc-dc usb are going to be a better alternative.. the dc-dc usb is actually cheaper then the m4, and would be more then capable of powering that board..

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