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Thread: How can I turn on PC motherboard with Teensy 3.2? (measurements inside)

  1. #1

    How can I turn on PC motherboard with Teensy 3.2? (measurements inside)

    I'm trying to connect a Teensy 3.2 to a PC motherboard to turn the PC on/off. The motherboard header is 2-pin (PWRBTN# and GND), like all PC motherboards.

    I'd also like to use a 2-pin Y-splitter to enable both my Teensy and the physical PC power button to turn the PC on/off.

    The voltage between the PWRBTN# and GND is 3.458v. If I short PWRBTN# and GND (turns the PC on), the current is 0.83 mA.

    1) Can I use a simple Y-splitter to connect my Teensy and physical PC power button together?
    2) How can I wire the motherboard to my Teensy and then use it to turn on/off the PC?

  2. #2
    Senior Member
    Join Date
    Apr 2013
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    The Y splitter should be fine since the buttons are open circuit when not pressed so it will give the needed OR logic.

    The actual teensy activitation is a bit trickier. The safe option is to use a transistor, and use the teensy to turn that on and off.

    If the current is just 0.83mA and peak voltage 3.458V you can probably get away with directly connecting the teensy Pin via a 300 ohm resistor and toggling it between Input (no pullup) and output LOW. So:

    digitalWrite(pinX,0);
    PinMode(pinX,OUTPUT);
    delay(100)
    pinMode(pinX,INPUT);

    All of this depends on exactly how high the voltage goes, and what hardware is doing the pullup. There is a risk that you will damage the Teensy if you have missed anything with how the button works and anything that tries to drive the pin high externally risks the mother board. Should be fine since you are by no means the first to try this sort of thing, but would not do this with a machine you cannot in a pinch afford to replace (say one you do not actually own!).

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