indication of voltage spike signal and latch

Discussion in 'The Projects Forum' started by ummux, Nov 20, 2009.

  1. ummux

    Thread Starter New Member

    Oct 2, 2009
    3
    0
    I wonder what electronic IC or PIC can be used to detect a spike voltage signal (the voltage change rate is very large compared to noise and peak occurs in 1-2millisecond) and output a switch signal (latch to keep active high)?

    Any IC can do the job, circuit as simple as possible and without using capacitor.
     
  2. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    1mS provides plenty of time to trigger many latching circuits. Even a small sensitive gate SCR should work. Since, as you say, the spike voltage is much greater than the ambient signal you should be able to use a simple voltage divider, but depending on how large Rin is you may have to use a small compensation cap across the Vinput resistor Rin. If need be, but I doubt it, a 555 can be used as a pulse stretcher and made to latch.
     
  3. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    Here's a 555 being used as a latch. Note the absence of timing components. Please ignore the push button pulse source in the schematic. I used it for the Interactive mode in my Spice.

    Edit: Modified graph to show a +12V Vcc base line.
     
    Last edited: Nov 21, 2009
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Why no capacitor?

    A simple RC differentiator circuit works very well to find spikes and dips.
     
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