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4098 Rising and Falling edge detection

Discussion in 'General Electronics Discussion' started by Jagatha, Jan 2, 2017.

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  1. Jagatha

    Jagatha

    3
    1
    Jan 2, 2017
    Dear Members

    I'm trying this 4098 edge detector for a small project and works fine getting two separate pulses ( with different duration) to sound and alarm. However the cct has a flaw that it puts both outputs same time when I connect the power. The data sheet mention on setting the reset pin to VSS during power on to inhibit the output and could somebody direct me on how to do it please?
    here is the cct I use.. thanks in advance.
    4098.png
     
    Last edited: Jan 2, 2017
  2. Arouse1973

    Arouse1973 Adam

    5,164
    1,081
    Dec 18, 2013
    Have a look for a power on reset IC or circuit. This can be a simple RC network followed by a Schmitt trigger logic gate.
    Thanks
    Adam.
     
    Jagatha likes this.
  3. Alec_t

    Alec_t

    2,883
    770
    Jul 7, 2015
    What is the approximate supply voltage rise time at power-on? An R and a C with a time constant greater than that can be added across the supply (R to +, C to ground) with the reset pin connected to the R/C junction.
     
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  4. Jagatha

    Jagatha

    3
    1
    Jan 2, 2017
    Thank you for your valuable advice. A RC worked perfectly, The input was actually through a 74LS14 so I'm having enough resources there too. Arouse1973, and Alec_t thank you so much for your valuable guidance
     
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