"Is voltage equal to" curcuit

Discussion in 'The Projects Forum' started by bok, Jan 11, 2016.

  1. bok

    Thread Starter New Member

    May 7, 2010

    I have a signal that ranges between 0 and 5 volt, and i need to design a curcuit that outputs a logic 1 if this voltage is equal to 2.4V.
    The tolerance is +-0.5 volt.

    I been trying to crack this for a while, but cant seem to figure it out, anyone got any idea ow to accomplish this?

  2. GopherT

    AAC Fanatic!

    Nov 23, 2012

    Google "comparitor" or "window comparitor" if the lower value is also important. That is, if you also want a logic 1 if voltage is below 1.9V (not in your 2.4V range).

    Also, you may want to discuss/post schematics if what you've tried and failed with so far.
    bok likes this.
  3. bok

    Thread Starter New Member

    May 7, 2010
    Perfekt! The window comparitor is exactly what i am looking for.

    Thanks for your time :)
  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
    Or a single comparitor with hysteresis, sometimes called a Schmitt Trigger.

    For example, output become 1 when input exceeds 2.45V but the input has to decrease below 2.35V for the output to go back to 0. Such a comparitor would have a hysteresis of (2.45-2.35) = 100mV.

    Here is an example. The Reference voltage can be derived with a voltage divider from V(dd). It requires an OpAmp or Comparitor chip that has a full-swing output of 0V to V(dd).

    Last edited: Jan 11, 2016