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Looking for latch circuit advice

Discussion in 'Electronic Design' started by Jon Yaeger, Dec 31, 2004.

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  1. Jon Yaeger

    Jon Yaeger Guest

    I've got an ATX power supply that I'd like to turn on and off using a
    momentary contact switch. I won't be using it with a computer that has a
    flip-flop type latch circuit - I'll have to breadboard a simple circuit that
    will do the trick.

    There is a 5V DC signal available as a trickle supply. The power supply also
    has a signal lead with 5V which turns on the unit when grounded. It doesn't
    latch on.

    To summarize, I want a circuit to latch the power supply on (using its own
    5V signal & circuit) when the momentary SPST switch is depressed; and off
    when it is pressed again.

    Does anyone know of a suitable on-line circuit?


  2. Tim Wescott

    Tim Wescott Guest

    You should be able to do this with a toggle flip-flop and a debounce
    circuit. At most this would take a 555 timer and a 7476 -- or save
    space and do it with a PIC.
  3. CFoley1064

    CFoley1064 Guest

    Subject: Looking for latch circuit advice
    Hi, Jon. Make it easy on yourself, and use a small push-on/push-off switch,
    like Radio Shack p/n 275-617 for $2.29 USD. KISS principle (Keep It Safe &

    However, if you insist, get yourself a CMOS inverter IC and do something like
    this (view in fixed font or M$ Notepad):
    | 10K |
    | |\ |\ |
    o--| >O--o---| >O-'
    | |/ | |/
    | .-.
    | | |220K
    | | |
    | T '-'
    | --- | ||
    '--o o---o-----||--.
    || |
    .1uF |
    created by Andy´s ASCII-Circuit v1.24.140803 Beta

    This should do the job.

    Questions of this type usually get a better reception on

    Good luck
  4. Jon Yaeger

    Jon Yaeger Guest

    I appreciate your advice - thank you!

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