AC signal to TTL help needed

Discussion in 'General Electronics Chat' started by Releeuw45, Apr 28, 2010.

  1. Releeuw45

    Thread Starter New Member

    Jan 10, 2008
    1
    0
    Hi,

    I have a Magnetic (VR) sensor signal from which I want to extract a 0-5 volt square wave representing the zero crossings. One side of the sensor is already connected to ground. Signal is AC and 3V top to top.

    I think best way to do this by adding a DC voltage and window comparator, but I need to know to design the circuitry. Does somebody have example circuits for parts or the complete design to get me started here.
    Let me know if there are other ways to get this done ( IC's, discrete parts)

    Thanks,
    René
     
  2. rjenkins

    AAC Fanatic!

    Nov 6, 2005
    1,015
    69
    A simple comparator should do it, something like an LM311. Keep the ground reference for the input.

    If you don't have a negative supply available, you can use a 7660 or MAX660 etc. to produce one.
     
  3. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    What is the frequency range of the signal from the sensor? What is the waveform?
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    See the attached for a reasonably easy approach using a dual or quad comparator that will operate using a single 5v supply.

    If your application is automotive, use an LM2903 dual comparator.

    If you use a quad comparator, be certain to ground the unused inputs, or you will have problems.

    Adjusting the values of R2 and R3 will change the trigger points. If you use too small of values for them, the triggering may be rather flaky.
     
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