What is debounce?

Discussion in 'General Electronics Chat' started by dthx, May 4, 2013.

  1. dthx

    Thread Starter Member

    May 2, 2013
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    I know I'm setting myself up for a wide variety of replies to this question?
    But...could someone define "debounce"....
    thanks
    D.
     
  2. Brownout

    Well-Known Member

    Jan 10, 2012
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    It's when all the air goes out of the basketball. Just kidding...

    When a mechanical switch is used as a data input, the contacts "bounce" upon contacting and un-contacting. This can cause havoc in digital systems. So either a network is used to insure only one of the bounces is sensed by the logic, or a software process is used to capture the correct logical level and ignore the bounces.
     
  3. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    When a mechanical switch closes or opens, the contacts vibrate and open/close dozens of times in reality. Debounce means some way to electronically filter out the bounce to make a circuit function correctly.

    More details to follow by other members, usually capacitor filters or software delays.
     
    Last edited: May 4, 2013
  4. tubeguy

    Well-Known Member

    Nov 3, 2012
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  5. #12

    Expert

    Nov 30, 2010
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    Excellent explanation, tubeguy.
     
  6. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Tubeguy's link has an additional link to ONSemiconductor DATASHEET (MC14490) that describes debounce as: "the elimination of extraneous level changes that result when interfacing with mechanical contacts."

    unfortunately, that is how they describe the chip's funnction - without ever saying the word, "debounce". I would never have thought of looking for a "bounce eliminator circuit". No wonder I have never heard of the chip nor seen it used in a circuit. Nobody knows it exists.
     
  7. #12

    Expert

    Nov 30, 2010
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    Gotta love that College-Speak.:D
     
  8. tubeguy

    Well-Known Member

    Nov 3, 2012
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    How the heck did we get along before Google ? :cool:
     
  9. ScottWang

    Moderator

    Aug 23, 2012
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    Here are some results when I searching on google for debouncing.
    Almost of time that I am using "debounce circuit" to search.

    debounce - 398000 results.
    debouncing - 145000 results.
    debounce circuit - 165000 results.
    debouncing circuit - 70200 results.
    switch debounce - 193000 results.
    switch debouncing - 78200 results.
    bounce eliminator circuit - 673000 results.
     
  10. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Interestingly, if you use "" to search exactly, "bounce eliminator circuit" you only get 51 results and a message...

    "In order to show you the most relevant results, we have omitted some entries very similar to the 51 already displayed."
     
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