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Ground Loop?

Discussion in 'General Electronics Discussion' started by MattyMatt, Apr 27, 2011.

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  1. MattyMatt


    Mar 24, 2011
    Okay, this is more of a laugh than something serious... I just wanted to make sure my thoughts were correct before I started laughing too hard and making an idiot of myself.... I was reading this post/review of a product (below, italicized) I am considering buying... this is an external hard drive enclosure, and thought to myself... Yes, that does remove the "shock" but it also creates a ground loop.... which could cause other issues down the line, particularly with audio coming out of the computer.

    Other Thoughts: Where static electricity discharges occur, enclosure must be connected to computer case by a separate grounding wire. If not, static charge from spark when case is touched will travel to computer through eSATA or USB wire, destroying the chips in the computer's interface
    (It happened to me once with another device. Needed to replace motherboard.)

    And if this is the case.... why have I NEVER had this problem with any of my other enclosures that are metal, to this day (we're talking quite a few years now)?

    This external enclosure is using a DC 12V power supply (120VAC to 12VDC adapter).
    Keep in mind that one of the lines of USB, along with the shield of the USB cable is grounded to the other side of the connection on the computer side.

    Thanks for any and all responses!
    Last edited: Apr 27, 2011
  2. Resqueline


    Jul 31, 2009
    Anything is possible, and the quoted text references the ideal solution to ESD. USB cables at least has the capability of providing the mentioned grounding wire/screen.
    A ground loop is not a loop unless the wires takes separate routes, so in the case of where the screen in a screened wire provides the grounding I'd not call it a ground loop.
    The harddisk would have to be mounted insulated from the case if this kind of ESD protection to have much of an effect though.
    Electrostatic buildup can be very different in different locations, depending on humidity (temperature differences, distance from open water), flooring, footwear, etc.
    How painful zaps have you ever induced on your equipment? I attended a school once somewhere where discarges to the table frames would freeze the computers on them.
    We're talking about 40kV or so here, the discarge of which tends to make you very weary about touching anything because of the pain involved.
  3. MattyMatt


    Mar 24, 2011
    Gotcha, I appreciate the clarification Res, it just seemed a little odd, perhaps the poster of the review worked in a very static sensitive environment... that would explain a lot.

    As far as pain induced by ESD... I'd have to say I did have one occasion where i worked in an older radioshack store, that had some SERIOUS electrical system problems, that whenever I would go down to the basement storage area to move some product around there was an old repair shop still kinda setup down there, and whenever I put something on the shelf that used to be one of the workbenches (which was metal... and later I found out, was not grounded!), if I touched ANY part of that bench/shelving area, I got a massive jolt.

    Though most of my home workshop area's are carpeted I generally work barefoot and with a ESD strap to prevent anything from happening.
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