Sensor output high for >30secs, but I need a short pulse

Discussion in 'General Electronics Chat' started by Captain_Mainwaring, May 21, 2014.

  1. Captain_Mainwaring

    Thread Starter New Member

    Sep 5, 2013
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    0
    Hi all,

    I have a design that I need help and advice with. I have a sensor that is triggered when a physical action happens (a bit like a jack in the box) and the output remains high until it is reset by replacing the moving part back into its "loaded" position. However, I would like to use circuitry to get a short pulse (maybe ~50ms or so) when the rising edge of the sensor is detected.

    What sort of circuit would do for this?

    Thanks,

    George
     
  2. Jony130

    AAC Fanatic!

    Feb 17, 2009
    3,962
    1,097
    Simply use a RC differentiator circuit. You can even add a gate as a buffer.

    [​IMG]
     
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  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,813
    1,105
    The simplest circuit is just a capacitor and resistor, provided you don't mind a tapering pulse, and can tolerate a negative-going pulse at the trailing edge of the input pulse.
     
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  4. Captain_Mainwaring

    Thread Starter New Member

    Sep 5, 2013
    5
    0
    Thanks for the guidance guys. Great ideas here. This has led me to find this website below (with cool embedded Java applets) and I plan to develop "4.2.1 Rising edge detector with positive output pulse".

    Again, many thanks Jony130 and Alec_t for giving me the solution !!!

    http://www.doctronics.co.uk/DDE/DDE_04.html#Images_swf/40106_pins

    George
     
    Last edited: May 23, 2014
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