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Thread: ATX DC-DC power supplies

  1. #1
    Join Date
    Dec 2000
    Bellevue, NE USA

    Post ATX DC-DC power supplies

    For all of you that currently own/use an ATX power supply, how do you get your motherboard to turn on when you start the car? Did you devise some sort of circuit to short the two pins on the motherboard in order to simulate the push of the button on an ATX case??

    I'm considering going to ATX, but I need to know how to start the computer.

  2. #2
    Join Date
    Apr 2001
    Here, There, Everywhere


    a few ways, the first two are both dependent on the motherboard.

    The first method which I use is to adjust what happens to the computer when power is applied after power failure. I have mine set of course to "startup" but there is options like "Goto Standby", "Do Nothing", etc. Since everytime I apply power to the ATX PSU the computer considers it a resume of power after a power failure and the PC boots, perfect.

    The second method which I could not use since the m/b didnt suppport it is to change the funcionality of the soft-power switch (those two pins on the m/b u are talking about). Some mb's allow you to change to a setting to allow the shorting of the pins, leaving it always on. Other motherboards of course with the shorting of the pins will power-up, then shut down 4 seconds later, since holding in the power button for that period tells the computer to shut down straight away (after a PC crashed, etc)

    Most modern boards support method 1, which works fine. Failing that, yeah a simple 555 timer circuit/relay should do the trick on the soft power switch, tho that means a bit more work....

    sheesh, what a rant and rave from me! hope that helps...
    Project - GAME OVER :(

  3. #3
    Variable Bitrate
    Join Date
    Mar 2001


    As magnetik said, most ATX motherboards have an option for what to do after power is restored. In this case, tell it to turn on.

    The other is to wire a momentary switch to the ATX power button pins. Then press that.
    Player: Celeron II 633MHz, 256MB RAM, 20GB IBM 9mm 2.5" Laptop HD (180G/2ms), onboard ethernet/sound/video/tvout, 10"11"x3" case, MPBS1 70W DC-DC PS w/auto-shutdown controller, in-dash lighted switches, 7" NTSC TFT widescreen in-dash LCD, touchscreen, rear-window brake light installed Garmin GPS35 GPS, credit card sized IR remote w/IRMan, mini-wireless keyboard/mouse (sits under seat), PowerMate black knob, MP3s and GPS Navigation (Winamp, CoPilot, SA8.0).
    Car: 1993 Nissan Maxima, Black Emerald


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