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  1. #1
    Join Date
    Dec 2014
    Posts
    18

    Noise issue with limit switches

    Hello,
    I am driving my CNC with an Arduino and GRBL software.
    It works great but I have a noise issue with the limit switches. Each times the fridge turns off or on, it generates a spark which raises an "hard limit" alert.
    Ok, the best option would probably be to install the CNC at another place but I can't...
    The cables going from the controler box and the switched are shielded to the power supply's ground.

    I have read here that capacitors may help, but I am wondering where is the best place for them, A or B ?



    Thanks for your help.

  2. #2
    Join Date
    May 2012
    Posts
    7

    Re: Noise issue with limit switches

    Both... little cap at 'A', something like 100pF. Bigger cap ( 100nF) at 'B'.
    And... I've had 'strange intermittent triggerings' disappear after covering the optocoupler with grounded foil tape - as though the photosensitive transistor is also 'EMR' sensitive.

  3. #3
    Join Date
    Dec 2014
    Posts
    18

    Re: Noise issue with limit switches

    I'll do that!
    Thank you for the advice BitHead

  4. #4
    Join Date
    Dec 2014
    Posts
    18

    Re: Noise issue with limit switches

    Hi,
    Just a quick feedback.

    100 pF added in position A : no change
    100 nF added in position B : problem solved !!

    I can now use my CNC and have some fresh food/drinks available thanks to 6 little caps
    Thanks again

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