In Car PC Power on Power off Circuit

Discussion in 'The Projects Forum' started by 3NRG, Sep 3, 2014.

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  1. 3NRG

    Thread Starter New Member

    Sep 3, 2014
    Hey Guys;
    I am getting ready to put a Windows based PC in my car (a carputer) and I’m bashing my head against a wall trying to come up with a simple way of powering it on/off with the ignition key.

    I’ve set the PC up so that it hibernates when the Power Button is pressed (it only takes 6 seconds to fully hibernate and 4 seconds to re-start Windows, not bad for a DDR2 667 with a 1.66 socket 479).

    Powering on the PC with the ignition key is a simple enough affair by using a 555 timer configured as a “1 Second - One-Shot Monostable Oscillator” with the trigger closed and the output connected to a relay which in turn is connected to the PC power button.

    Powering off the PC is where I’m having problems, I could use a normally closed relay connected to the accessories and use it to trigger another one-shot monostable when the key is turned off but this seems like a really convoluted way of building a circuit.

    Does anybody have any ideas as to how I might build this into a single package? I’d be happy to pay for a schematic with the component values already calculated, I really need to get this project installed.

    Thanks Guys,

    Mark W.
  2. crutschow


    Mar 14, 2008
    Do you trigger the same button for turn off as well as turn on? If so you just need a single one-shot.
  3. 3NRG

    Thread Starter New Member

    Sep 3, 2014
    Yes same button for both on and off, but the one-shot will only fire with power going to it, and once I turn off the key I lose that power,
    Unless I were to use an NC relay connected to constant power and held open with accessory power and when I turn off the key it would then juice the one-shot,
    that's kind of messy.
  4. Georacer


    Nov 25, 2009
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