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  1. #1
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    GND For Connector Shielding

    I have 4 connectors

    1. Power
    2. USB
    3. Ethernet
    4. USB

    All placed in a proper straight line so that when placed in a enclosure, the same are properly flushed.

    The body of the connector (Shielding) is done for each of them via a 0.1uF and 1M Resistor to GND.

    The outer casing (or the part where these connector sit is of a metal)

    Because the cutouts are perfectly in line with the connector size. The metal touches the connectors outer body.


    I notice that the board is working fine when i am using it without putting it on the casing but the moment i use the casing, USB doesnot work (I will have to remove it completely and reprogram using a external program) and it works again.

    Why could this behavior be happening??

    Image of sch and metal slot shown
    Last edited by tiwari.sachin; 23rd January 2020 at 14:26.

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  2. #2
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    Re: GND For Connector Shielding

    You’ve got three different grounds shown there, that’s a little confusing. Where do they all go? Where do the shield connections of each connector actually go besides ground?



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    Re: GND For Connector Shielding

    All the shield has to be ground... via a resistor and cap in parallel as shown for ethernet and serial.

    I have unfortunately connected usb directly to ground... probably missed it

    Power ground point in the return path
    He again I needed to have a parallel resistor and cap for shield which I missed.

    So it it ok to have it for all connector shields and same for top metal plate



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    Re: GND For Connector Shielding

    Why are they not ALL connected directly to ground anyway?

    Brian.
    PLEASE - no friends requests or private emails, I simply don't have time to reply to them all.
    It's better to share your questions and answers on Edaboard so we can all benefit from each others experiences.



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    Re: GND For Connector Shielding

    Should they be??
    What's the best practice?

    Will there not be issues with esd if connected directly



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    Re: GND For Connector Shielding

    Hi,

    ESD? No. This is electrostatic discharge.

    EMC. Electromagnetic compatibility.
    A metal case should be considered as a faraday cage. Where the whole case should have the same voltage at any place.
    I'd use a common shielding_GND (on the PCB)!for all connectors. With one RC to the system_GND.

    But I see no problem with your circuit for now, since the C should act as short circuit for HF.

    There rather is another problem.
    * other connections to the GND or case, like a GND loop via earth_GND.
    * or HF noise introduced by an external device (like an SMPS)
    * maybe a soldering fault or PCB fault that generates a short circuit between USB_shield and USB_+5V .... or something similar.
    * maybe you don't have a solid GND plane on your PCB ... causing a loop via GND traces on your PCB.

    Klaus

    Btw: Yes, the different GND symbols are confusing.
    * if they refer to the same signal, then use the same symbol.
    * if they don't refer to the same signal, then give information where the belong to / how they are used.
    Please donīt contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



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