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M2 atx powered without pc?

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  • M2 atx powered without pc?

    I need to get a clean 12v power in my car and ever since I upgraded my battery I get close to 14v. I have a spare m2 atx .... Can I use that without the PC to power my device off the 12v rail? I tried plugging it into the car with the ground switch and unswitched wires connected but couldn't locate a 12v wire with my multimeter. Any ideas?
    Last edited by khisanthax; 09-15-2012, 03:46 PM.

  • #2
    It should work just fine. You might have to set jumpers to dumb mode and it might need a load trigger of some sort. You should be able to just use the 4pin for your 12v and ground. My mainboard only needs the 20pin connector so I use the 4pin for my monitor. SNO


    • #3
      khisanthax - just be aware that 14V is normal for a 12V vehicle.
      The alternator should put out ~14.0 to 14.4V under normal conditions. Maybe lower at idle with loads.


      • #4
        thank you guys for replying back despite my bad spelling in the title. what would dumb mode be for the m2 atx? i read the manual and had it on default p1 with the jumber on A. i thought dumb mode might be p0 which is just a regular psu but that doesnt seem to work as i used a multimeter on all the pins and wires on the connectors and only got a reading for two wires that had 5v.

        im guessing that when connected to a mobo there is a feedback signal that tells the psu to fully activate and turn on all the other rails? dobi need to put a jumper on anything else or connect any other pins?

        i guess i never really checked voltage as i do now since i have a voltage meter always in my 12v socket in the car .... but thank you at least now i know.


        • #5
          12V sockets like cig sockets may have voltage drops.

          Strictly speaking, the voltmeter should be across the battery (terminals) since the entire charging system is based on battery requirements (eg, 13.8V in the old days; usually 14.2V and up to 14.4V (max, long-term) these days).

          But a cig socket voltage is convenient, and better than none. Besides, it may be reasonably accurate (ie, if a low voltage drop irrespective of other loads - it depends where the cig power is pulled from, especially if ACC powered.

          Bad spelling? I didn't notice. And your English seems fine.

          Best wishes. OldFart.
          Last edited by OldSpark; 09-16-2012, 07:01 AM. Reason: Improved first line.


          • #6
            Be careful of using a PC power supply like this.. I am not sure about the M2ATX style power supplies but standard PC supplies will self destruct if you use them without a PC load on them. You can get a power supply tester and just leave the tester plugged in and then it would work.

            You might also want to look at the USB DC-DC power supply. This will supply one voltage off a range via switches or you can get closer to the voltage you need if you set it via USB.