Shag Floor danger?

Discussion in 'A+ Certification' started by Dave Hardenbrook, Feb 27, 2008.

  1. How dangerous is it from a grounding standpoint to do work inside a
    computer while standing on a shag floor? I currently work out of my
    home, and the only room in the house with sufficent lighting to do work
    inside a PC has a shag floor. I have taken every other precaution to
    avoid ESD -- I put the PC on a desk on an anti-static mat, I touch the
    chassis before starting, I wear a wrist strap, I even strip to the waist
    to avoid possible ESD from my clothes. Yet, I have had two systems now
    unexpectedly go totally dead on me, and I'm wondering if it could
    possibly be because I'm standing on a shag rug where I work?

    Dave
     
    Dave Hardenbrook, Feb 27, 2008
    #1
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  2. Dave Hardenbrook

    John O Guest

    Shag, as in shag carpet? That's shagalicious, baby!

    Seriously, you need humidity. Check ebay for a sling psychrometer, measure
    the humidity, and get a humidifier. With the right amount of humidity your
    static problems will go away.

    -John O
     
    John O, Feb 28, 2008
    #2
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  3. Dave Hardenbrook

    Bill Eitner Guest

    Another trick is a mix of fabric softener (like Downy) and water
    in a spray bottle. In the dry months when humidity is low,
    mist the carpet around the work area. Also, motion causes
    static to build up. Once you've grounded yourself don't move
    around any more than you have to, and especially don't sit on
    a chair and rub your feet on the carpet. Don't walk around
    with sensitive components (mobos, memory sticks, drives, etc.)
    unless they're in Faraday cage (metalized/shielded) bags or
    boxes. Test the integrity of the ground you're connecting
    to. Make sure it's not open. Wear cotton clothes. Keep
    plastics out of the work area. Cellophane tape and styrofoam
    cups are especially static prone. An ionizer and static meter
    can be helpful as well. It doesn't help to touch the chassis
    if the mains (AC supply) cord has been unplugged. The key to
    an anti-static mat is the star ground point. A ground (Earth)
    reference is brought to the star ground point and everything
    else is connected to that point. The wrist strap connects
    there. A clip lead to the computer case connects there (so the
    case is at ground without the mains cord). And any conductivity
    the mat material provides flows to that point. That's the big
    idea; everything at an equal potential (voltage) thus preventing
    unexpected current flow through sensitive paths that can not
    handle it.

    And what does "totally dead" mean? What actually failed?
    Static discharge damage isn't voodoo. It's possible to find out
    whether static discharge was present or not. Static
    discharge damage is often cumulative. Much of it happens
    during manufacturing before the products are even in the field.
    A good analogy is to arteriosclerosis (narrowing of arteries).
    Static discharge damage can narrow conductive pathways without
    completely opening them. If a pathway can still do its job
    (pass enough current without opening up like a fuse), it appears
    as though no static discharge damage ever took place. It's
    only when the hard failures and intermittent problems occur
    that any thought is given to static discharge damage. Then
    it's assumed that a perfectly good device was zapped into its
    present state by one recent occurrence. That's not necessarily
    true. It can be that a previously narrowed pathway fails
    because it was barely capable of conducting the necessary
    current over a period of time. Mild surges, which aren't
    necessarily abnormal over the course of typical operation,
    can cause damaged pathways to open up without any recent
    static exposure. What I'm trying to say is that over time
    the odds of failure due to manufacturing and other handling
    pile up. Your two failures may only have been coincidental
    with your handling of the systems. And even with in depth
    analysis you'll never know for sure whether it was your
    handling, previous handling, or a combination that caused
    the failures. And that assumes it is determined that static
    discharge damage was the cause--which isn't always the case.
    Devices fail for other reasons. And if you're really
    concerned about the carpet (which I don't think you should
    be), you can get or make a conductive floor mat and foot
    straps for the work area. If you habitually rub your feet
    on the floor or move around a lot when you work, that might
    be worthwhile.

    Always remember the golden rule: everything at an equal
    potential. Earth ground isn't the only reference potential--
    but it's common and handy in that static charges will
    dissipate into it. Movement (motion) and objects brought
    into the work area promote static, while humidity, ionization,
    and the fabric softener/water blend work against it, and
    a low resistance ground path dissipates/absorbs it.

    I hope this helps.
    --
     
    Bill Eitner, Feb 28, 2008
    #3
  4. Dave Hardenbrook

    Bill Eitner Guest

    I forgot to add a link:
    http://en.wikipedia.org/wiki/Electrostatic_discharge
    Good article and external links.
     
    Bill Eitner, Feb 28, 2008
    #4
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