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A case with perfect grounding

Discussion in 'Cases, Modding & Electronics' started by Octopuss, Sep 9, 2010.

  1. Arctucas

    Arctucas

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    No, it is not. All that will prove is that the motherboard ground is connected to the chassis through the PSU.

    I believe you are confusing "grounding" and "bonding".

    "Grounded" means there exists an equipotential plane between the chassis and earth. In other words, the potential (voltage) difference between the chassis and earth is 0 Volts.

    "Bonded" means two conductive parts are connected in such a way as to present 0 Ohms (or as close to 0 as possible) of resistance between them. However, they may not be "grounded" at all.
  2. Arctucas

    Arctucas

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    You do not need to translate, if you will provide a link, hopefully I can use Babelfish.
  3. INSTG8R

    INSTG8R

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    Tagan used have a nice feature(have had a Tagan in awhile now tho so don't know if they still do it.)
    They actually had a ground loop on the PSU. You just put it under one of the MoBo mounting screws.
  4. erocker

    erocker Super Moderator Staff Member

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    mastrdrver says thanks.
  5. de.das.dude

    de.das.dude Pro Indian Modder

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    the any closed volume closed off by a conductive material cuts off EMI. if you want i can give the mathematical proof too. but it includes calculus.

    if you open your cell phone, you will see these rectangular clip on boxex made on ICs to preent EMI.


    EMI interference causes problems when something is working with waves and frequency ad that sort. EMI can %&^* these up and so you get bad output.

    sound circuitry is something that is hampered by EMI and so erocker is correct.


    if the motherboard ground is connected to the chassis, and the PSU ground is connected to the chassis, that means everyone is grounded. you just need a conductive connection that can flow both ways.
    Last edited by a moderator: Sep 9, 2010
  6. Arctucas

    Arctucas

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    Really? Where did you learn that? What if the PSU grounding conductor is not connected to earth?

    Having been an electrician for more than twenty-five years, I believe you should know what you are talking about before you start giving advice.

    Why do you not just run along now and let the grownups talk?
  7. de.das.dude

    de.das.dude Pro Indian Modder

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    ok, when i said that, i assumed the house wiring was okay. to test if the earthing of the board is ok, you need an AC bulb, connect it to a holder with long wires, take a terminal, jab it into the "live" one of the socket(this should be the right hole, but sometimes people who are not good make the live one on the left too), then the other terminal needs to be jabbed into the earthing. if the bulb glows, your earthing is A-okay!

    and i learnt the EMI stuff in school, and i have it in my first sem mechanical B.E syllabus too.
    other stuff, i learnt from my dad who was an electrician in his youth, but runs a business now.
  8. Arctucas

    Arctucas

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    Alright then, I apologize for being somewhat rude, but I know that improper handling of electrical components and wiring is dangerous and often fatal. I have had electricians under my supervision injured because they "knew what they were doing", so I am concerned when I see someone saying things that are not correct.

    Now, I am giving the requirements of the National Electrical Code (NFPA 70) that is used in the U.S.A:

    The proper way to check if an electrical service is properly "grounded" is inspect the main breaker panel/fuse box. Disclaimer: Electrical service work must only be performed by qualified personnel. In other words, if you do not know what you are doing, hire a professional.

    If the panel is the first point of disconnect, the white or neutral (grounded conductor) wires are connect to a terminal bar and the bare or ground (grounding conductor) wires are connected to a separate terminal bar which is bonded to the panel. The two terminal bars are then connected together (bonded) with the "main bonding jumper", (sized according to the ampacity of the service) and a heavier gauge wire (also sized according to the service ampacity) is connected from the ground bar to the structure's metal cold water line at a point within five feet of where the line enters the structure. It is recommended, and some local codes require, that an auxiliary conductor be connected to second grounding electrode, such as a driven rod. There are other grounding means, but I will not go into that much detail.

    If the panel is not the first point of disconnect (where another disconnecting means is between the meter and the panel), the neutral and ground wires are not bonded together in the panel, rather each still goes to separate terminal bars, but the neutral bar is insulated from the panel, while the ground bar is bonded to the panel. The service grounding conductor(s) is/are then connected to the grounding electrode(s) as before.

    Even then to meet the code requirements, the resistance between earth and the grounding electrode must be 25 Ohms or less. If it is not, a second electrode must be installed no less than six feet away. This may need to be repeated several times. I remember a job where it required four driven rods to get below 25 Ohms.

    The service may be "grounded" without the required electrodes being installed and connected, through the service cable grounded conductor which goes to the utility company's transformer, but it is not the correct method.

    Regarding the EMI, if the chassis is made of metal (aluminum or steel) and completely encloses the internal components, it should act as a Faraday Cage, effectively blocking any stray signals. I noticed that some of the Asus sound cards have EMI shielding on the card.


    EDIT: To check a receptacle outlet for ground, a receptacle tester should be used.
    Last edited: Sep 10, 2010
    de.das.dude says thanks.
  9. PVTCaboose1337

    PVTCaboose1337 Graphical Hacker

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    Pssh. A faraday cage if you don't have a case window. Also, this is assuming that the power supply is in contact with the case. My IBM 5150 is lined with an extra metal liner to act as a faraday cage cause it is a milspec one.
  10. Arctucas

    Arctucas

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    True, you will note that I said "completely encloses", however.

    The PSU mounting screws should be enough to effectively bond the PSU to the chassis.
  11. de.das.dude

    de.das.dude Pro Indian Modder

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    i was thinking....
    and i think the best possible way to make the cage would be to....
    use the plastic coated aluminium foil and wrap it around the card (leaving out the slot pins of course).

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