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555 timer

Discussion in 'General Electronics Discussion' started by novolts, Aug 11, 2009.

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  1. novolts


    May 24, 2008
    I need some lelp please
    I have used a electronics simulator programe to test a 555 moostable circuit the timer is working ok under the simulator I trigger the timer via a low pulse at pin 2 and the timer works.My problem is that my trigger voltage is 24volts dc si I introduced a 4060 inverter and I change the high to a low via the inverter.
    Under normal circumstances would I need to put a resistor in series with the input & input of the 4060 and do I need to connect the spare inputs of the 4060 to the positive rails.
    thanks to all
  2. Resqueline


    Jul 31, 2009
    As long as the trigger signal has a higher voltage than the IC's supply you'll need to use a resistor, and maybe even a clamping diode from input to Vcc.
    It is recommended to connect unused inputs to something to avoid noise pickup (can increase current consumption etc.).
  3. novolts


    May 24, 2008
    Resqueline, thanks for your reply
    kind regards
  4. amdNRA


    Sep 3, 2009
    A 4060? :eek: That's a ripple counter! The inverter is the 4049. No need to do that or inverters...Just use an optocoupler between the 24v and the trigger input. You can even invert the signal logic status depending how you wire the transistor of the opto. Hope this helps, Gil. :)
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