Decoupling the ADC input

Discussion in 'General Electronics Chat' started by R!f@@, Apr 6, 2014.

  1. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
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    I salvaged a PS3 joystick. It's crappy. The Joy part get's stuck sometimes but I think it would do for testing the program.

    About decoupling. I am putting a 10μf across the 5V at the Joystick PCB decoupled with a 100nf.

    The center pin of the VR is also decoupled to ground with a 100nF.

    Question is, will these caps be enough ?

    The VR is used as ADC input.
     
  2. t06afre

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    May 11, 2009
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    Puting a "decoupling" cap across the ADC input. Will filtering out some jitter. But also give a slower response time to changes on the input. For a joystick you may even select a higher value. Do some testing and find a value that you are happy with
     
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  3. R!f@@

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    You mean the 100nF ?
     
  4. t06afre

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    Yes try variations larger than 100nF, if you feel for it.
     
  5. R!f@@

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    100nF works fine.
     
  6. THE_RB

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    The cap is best placed close to the PIC ADC input pin.

    The resistance of the pot then gives you RC low-pass filtering so you won't get any high freq noise at the ADC input.

    And it's always a good idea to multi sample the ADC over time, then average the readings together (like we discussed in your other thread). That increases resolution and removes low freq noise (like mains hum).
    :)
     
  7. MrChips

    Moderator

    Oct 2, 2009
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    Just so that you know, when doing signal averaging, if your samples are equally spaced in time and the total number of samples span one full AC mains cycle or any multiple of full cycles, you can significantly reduce AC mains noise.
     
  8. THE_RB

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    That's exactly what I told him in the other thread. :D
     
  9. R!f@@

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    You guys talk tht it so easy. :(
    Not for me yet.
     
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