74191 counter activated with push button pulse

Discussion in 'The Projects Forum' started by YanYi, Oct 13, 2014.

  1. YanYi

    Thread Starter New Member

    Oct 13, 2014
    2
    0
    Hello!

    I'm building a count down counter with 74191 chip and intend to activate it using a push button. Already built a push button with switch debounced and it outputs a 1 second pulse. But I'm stuck at what appears to be a simple problem - how do I activate the counter only when the button is pressed?

    Can't connect the debounced pulse to the Count Enable input because it's just a pulse, thus it will only enable the counter for one second. I thought of connecting a JK-Flip Flop to the push button, toggling the state. Is there a simpler way than this?

    PS: I'd like to know a simple way using push button; for DIP switch it's straightforward - just connect the output to the Count Enable, since it will always remain asserted once switch is on.
     
  2. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
    2,805
    834
    Can you use another pushbutton switch? A latching switch will remain on with a single press. Something like the switch in this link.
    http://www.adafruit.com/product/1478
    If not, then I think using a flip flop is your best bet.
     
  3. YanYi

    Thread Starter New Member

    Oct 13, 2014
    2
    0
    I see. Thanks DJ!
     
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