Connect with us

Logic gates + noise

Discussion in 'Electronic Design' started by Jon Slaughter, Aug 25, 2008.

Scroll to continue with content
  1. I was playing around with some logic gates and they seem to be extremely
    sensitive.

    If I take an AND gate and breadboard it, and put both it's inputs to high(by
    a jumper wire of about 1.5in), and touch the jumper wire which is sheilded,
    the output fluxuates ;/ I could understand leaving the input floating but
    when it's directly jumped to high? Is this normal or something else going
    on?
     
  2. Potentially... I didn't think that maybe there would be minute vibrations
    that would be enough to cause contact issues... thats the best explination
    at least
     
  3. Something else is going on.
    Likeliest culprit is a bad connection on the input. Measure the
    voltage directly on the chips input pin and see if it really is logic
    high.
    Check your ground and power connections on the actual chip pins too,
    they could be making bad contact.
    Try the other AND gates in the package.
    Some trickier culprits will depend upon what logic family you are
    using.

    Dave.
     
  4. Also make sure that the original poster is grounded, to eliminate static.

    --
    Dirk

    http://www.transcendence.me.uk/ - Transcendence UK
    http://www.theconsensus.org/ - A UK political party
    http://www.onetribe.me.uk/wordpress/?cat=5 - Our podcasts on weird stuff
     
  5. Try powering the chip through Vcc... ;)

    Sometimes cmos chips will power up through the inputs, and seem like
    they work, but it'll lead to strange results. Make sure you have Vcc
    firmly tied to your 5V rail.

    Regards,
    Bob Monsen
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-