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Momentary connection with rotary switch

Discussion in 'Electronic Basics' started by Jake, Apr 9, 2004.

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  1. Jake

    Jake Guest

    I'm working on a PC project where I'd like a 2 position rotary switch to
    the turn the computer on and off. I need to use the ATX motherboard's
    "soft off" feature (so that my software can shut everything down cleanly)
    instead of just flipping the power on and off with a relay.

    Since it's an ATX motherboard, two pins have to be momentarily shorted to
    turn it on or off. Here's my idea for a circuit right now:

    I'd use a DPDT 2-position rotary switch with one pole on each position
    connected to a +5VDC source. The other end of those poles would be
    connected to separate caps so that, when the switch is in one position, it
    charges one of the capacitors while discharging the other. On the end of
    those caps there is a transistor so that as one cap is discharging, the
    transistor shorts the two pins for a given amount of time (depending on the
    size of the cap).

    I hope that makes sense. I basically need to momentarily short those two
    pins when the rotary switch is in either position. My software then does
    the rest.

    Can anyone think of an easier way (or an improvement of my current idea)?
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