Zero Crossing Detector

Discussion in 'The Projects Forum' started by alyeomans, Feb 15, 2015.

  1. alyeomans

    Thread Starter Member

    Sep 13, 2010
    29
    2
    As apart of a circuit I am looking to make a comparator based zero crossing detector. I have a question about the correct input condition to the comparator which does not seem to be covered in my www searching.

    The non inverting input has a sine wave signal with amplitude +5V to -5v. Can I use a rail to rail comparator (+5V to 0V) and would this require a diode to block most of the negative side of the signal? There are some rail to rail comparators which will go 0.7v below the negative supply.

    While I can use a -5V supply rail I'd like to understand what can be used.

    Thanks
    A
     
  2. ScottWang

    Moderator

    Aug 23, 2012
    4,853
    767
    This will be the clipping circuit.
    If you want to get a smaller voltage less than 0.6V then you can using schottky diode.
     
  3. ronv

    AAC Fanatic!

    Nov 12, 2008
    3,287
    1,252
    Take a look at this one.
     
  4. DickCappels

    Moderator

    Aug 21, 2008
    2,651
    632
    You can do that with an LM393, but please put a 10k or higher resistor in series with the sinewave input so that nothing gets stressed when the signal swings below ground. Also, the LM393 requires a pullup resistor on its output.
     
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