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    ATX power supply switch

    Hi,

    I want to make a small circuit to switch on/off an ATX power supply. I don't want to connect just the wires PS_ON and GND.

    PS_ON signal must be connected to GND 500ms after pressing a button. Is there any such a circuit without microcontroller?

    Thanks.

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    Re: ATX power supply switch

    PS_ON doesn't have to be grounded, it just needs the voltage on it pulling close to 0V. You can delay the pulse in many ways but before we explain how, we need to know a little more. When you say "after pressing a button" do you mean it should switch on after the delay and stay on, in which case how do you turn it off, or do you mean it should switch on after the delay but switch off again when the button is released?
    Can the circuit use the 5V standby supply, which should be present all the time?

    Brian.
    PLEASE - no friends requests or private emails, I simply don't have time to reply to them all.
    It's better to share your questions and answers on Edaboard so we can all benefit from each others experiences.



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  3. #3
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    Re: ATX power supply switch

    Thanks for answer and sorry for insufficient info :)
    I want to make exactly what power buttons on PC cases do.
    Press and release the button --> ATX power is switched on (PS_ON is connected to GND or close to 0V).
    Press and hold some time (500ms is just an arbitrary value, time delay can be "adjustable" with Rs and Cs.) --> ATX power goes down (PS_ON is released from GND)



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    Re: ATX power supply switch

    On an ATX power supply connecting the PS_ON pin to ground will turn on the power supply, when the PS_ON pin is disconnected from ground the power supply goes off. Logic on the motherboard keeps the PS_ON pin low when the power button is released as the power button is not latched. Holding down the power button for a time will cause the motherboard logic to pull the PS_ON pin high turning off the power supply.



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    Re: ATX power supply switch

    I also dealt quite often with how to operate the On Off button with adjustable timing and other features.
    Yes, this can be done purely analog, delay line as charging or dischrging any capacitor etc. , the disadvantage is the relative complexity, multiple components (R,C, T)
    That's why I have been using the PIC10F200T or PIC10F322 for some time.
    1x PIC10F200 a 0,213$
    1x AO3416 NMOSFER a 0.1$
    1x LED + 1x Button

    And Simple program any as
    while(;)
    {
    If (pin1==0 and pin2==0) {Set pin2=1; Set LED=1;)
    If (pin1==0 and pin2==1)
    {
    for(int x=1;x<10;x++)
    {
    Set LED=0;
    Sleep(100ms);
    Set LED=1;
    If (pin1==0 and pin2==1 and x=9) { Set pin2=0; Set LED=;}
    }
    }
    }

    Small, cheap usable even without PCB
    Yes you must have a programmer any as PICKit3



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  6. #6
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    Re: ATX power supply switch

    Ok thanks.
    It seems to be unpractical using only R,C,T.
    Let me order small PICs :)
    I have PICKit2, I hope it will be compatible with these small PICs.



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