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ACPI Wiring question.

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  • ACPI Wiring question.

    OK my P1900 is going in my car this weekend. I am placing a switch on my center console that controls the IGN signal to the carnetix. This is for disabling the PC similar to a valet switch. I also have a momentary switch installed. The momentary switch I would like to tap it into the laptop along with the P1900 ACPI wires. If the computer freezes I can hold the switch and reboot.

    So the main question is once the P1900 is wired into the power switch. What happens if I use the original switch when the P1900 is running the laptop. Like say if I press the power switch does the P1900 know to start the shutdown procedure even though there is no change on the IGN signal?

    Also I have read over the manual and seem to know what I am doing, seems straight forward, but if there is anything common that I may miss, feel free to remind me

  • #2
    All the P1900 will do is send an electrical pulse to the ACPI motherboard headers. That pulse simulates a press of the power button.
    If the PC is on when it receives that pulse, the PC will shut off, and vice-versa.
    Have you looked in the FAQ yet?
    How about the Wiki?

    Under normal circumstances, a signature would go here.


    • #3
      So basically if the PC was shut off using the power switch after the car is running and IGN is still ON the computer would commence a boot sequence when turning off the car because it would assume the computer is still running? so basically all I could use the switch for is for hard restarts? correct?


      • #4
        when the pc turns on, it shorts some wires in the 20 pin harness. this allows the psu to know what the pc is doing.

        if you start the car, the pc turns on, and while at a stoplight, decide to turn off the pc using your dash switch, the pc would turn off, and when you get to your destination, and turn the car off, the psu would see that the pc is off, and would not send another power switch pulse in a effort to turn it off.
        My OLD 2001 Mitsubishi Eclipse GT:
        "The Project That Never Ended, until it did"

        next project? subaru brz
        carpc undecided


        • #5
          Soundman is right however I have had instances when the 1900 gets out of sink with the PC and the PC ends up continuing to run after I have left the vehicle but no harm done; it's only running on the laptop battery so the no draw on the vehicle. You do end up powering down the laptop with the switch though before starting the vehicle so everything will be in sink; otherwise the 1900 powers up and turns off the laptop. It doesn't happen very often and I can't remember what events led up to the situation but just be aware. It catches you off guard the first time because the 1900 is running, the touchscreen is running but no image (because the laptop has just been shut down).
          My 2007 Ford F350 Work Log located HERE


          • #6
            Thanks for the replies. Just got it today and I will report any problems.