timer/frequency monitor to drive led

Discussion in 'The Projects Forum' started by Matt@OPS, Jan 21, 2013.

  1. Matt@OPS

    Thread Starter New Member

    Jan 21, 2013
    It's been a long time since I've been in the world of dc component based circuits. My stay in the land of plcs and programmables has left me dumb to the basics of dc circuits. I would appreciate any help offered on this circuit.
    The circuit is supposed to light the led when the switch is closed.
    If the switch is closed for more than 1.2 seconds the led will go out.
    The led to stay lit for .5 seconds after the switch is opened.

    This should allow a pulse of 2 hertz or greater to keep the led lit but prevent it from staying lit if the circuit is stuck high.

    I've tried building it and no luck. I've also tried simulating with different scenarios but I can't get it. I apologize if this seems simple but I admit defeat and bow my head to those who can help.

    Thanks for any help,
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  2. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    The circuit has all sorts of issues! :eek:

    How is this going to work; "The led to stay lit for .5 seconds after the switch is opened."

    Once the switch is opened there is not longer any power to the circuit!

    Also it is unlikely someone is going to flip that switch at faster than 2Hz.

    Please say more about the application, what the input signal is from and what it needs to do (for instance if the LED should only be lit when there is >2Hz signal, all other situations should be LED off).