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OT: Leaf blower to dust out a computer?

Discussion in 'Electronic Design' started by John Doe, Mar 8, 2007.

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  1. John Doe

    John Doe Guest

    Please pick and choose from these questions.

    Has current integrated circuit design practically eliminated static
    electricity hazard when working inside a PC?

    I'm a little confused about using compressed air to clean out a
    computer.

    The stuff in the cans, is the straw made of some antistatic material
    or is it just plastic?

    Blowing air through plastic can produce static electricity?

    I'm very aware when static electricity is present, and I understand
    that the worst time is in dry air, but I'm not sure about the how
    and why.

    Partly curious. Thank you.
     
  2. I just vacuum it with the brush.
    The brush is soft enough not to scrape components of the peeseebees.
     
  3. I take them outside and use the 90PSI industrial strength air compressor on
    them. That gets the dust out, those little cans and vacuum cleaners are a
    waste of time and money. This is a job for horsepower. ;-) Just don't let
    the fans spin and everything will be okay.
     
  4. John Doe

    John Doe Guest

    By the way. It might sound like a troll but it's not. I did a quick
    search of the archives and didn't find the answer to this common
    question. A retired engineer told me that the air flowing through
    the plastic leaf blower tube can produce static electricity, that's
    one reason I ask.
     
  5. D from BC

    D from BC Guest

    Maybe set up an experiment that measures the amount of static
    electricity produced in a computer chassis from the air from a leaf
    blower?

    My physics is a bit crappy...
    I'm not clear on how rushing air (which is mostly nitrogen) on a PCB
    mounted on an earth grounded chassis can create damaging charge
    differences. Electron stealing happening?

    I don't recall getting zapped when I blast sawdust off my clothes with
    an air gun..

    But I do know that static electricity from a helicopter can be
    lethal....
    http://en.wikipedia.org/wiki/Helicopter_support_team
    D from BC
     
  6. whit3rd

    whit3rd Guest

    A PC with a lot of installed components doesn't have
    sensitive points; the wires that go to sensitive MOS inputs
    are all connected to OUTPUT circuits that act as voltage
    limiters (clamps). After you unplug something from your PC,
    the fingers of that board (or pins of that CPU) are potentially
    at risk.

    Yes, modern designs are much less at risk than those of the
    1980s, and while everyone claims antistatic precautions are
    'very important', there aren't lots of failures from that source
    to back them up. 2000V stress tests are part of lots of
    modern designs, but the handling 'precautions' still are
    based on the experiences of a quarter century ago.

    I've seen plastic washers and carbon resistors in antistatic
    bags with warning stickers. Those components have NO
    static sensitivity, short of taking lightning strike damage...

    The canned-air units might develop some static charge on
    the tube, BUT that tube is tiny (the 2000V test is for a full
    sized human at voltage) and the charge is likely never to
    leave the insulator surface. Your PC will never know it's
    there.
     
  7. Its more likely that a static charge will be built up inside the leaf
    blower (or whatever) based on its component materials and contaminants
    (dust, moisture) in the air.

    Once that comes in contact with components in proximity to a grounded
    chassis, this charge can be transferred to adjacent (ungrounded)
    components. At some point, this will build up to a voltage w.r.t. ground
    that exceeds component ratings.

    Canned air, being relatively clean and dry is less able to generate and
    transport such a charge.
     
  8. JH

    JH Guest

    10 yrs ago I worked in the mfg plant area of a SMPS OEM as a product
    and test engineer. There were some compressed air lines with hoses
    about here and there for some reason (I think that section of plant
    had been used for other things in the past). We weren't using the
    hoses but the same hard line they came from was used for the air
    powered screwdrivers. I remember the nozzle on the ends of them had a
    fitting with radiation warning stickers on it. I asked someone about
    it once and apparently there was some sort of low level source in
    there emitting radiation intended to bleed off any static charges that
    would build up. I've never researched this since so I could off on
    the explanation I was given.

    JH
     
  9. Guest



    The OP has been told the truth...but as the commercial says: It Isn't
    the Heat, It's the Humidity. The magnitude of the electrical charge
    that can build up due to moving air (which, like the moving belt in a
    Van de Graf generator, is not a conductor) depends mostly on the
    ambient relative humidity. WRT leaf blowers: Here in Albuquerque,
    I've twice started fires with my B&D Electric Leaf Blower with a
    thick, loud-enough-to-be-heard-over-the-blower, visible in bright
    sunlight, blue spark from the end of the nozzle to the pile of lawn
    debris. Also here, I get very visible sparks from the red-plastic
    tube of a can of "Dust Off" to ground when the humidity is as low as
    it often is (0 to 10 percent). Same with vacuum cleaners. So: I
    don't use anything involving moving air (or carbon dioxide: Dust-Off)
    on electronics until monsoon season. You might consider checking the
    relative humidty (or measuring it...which is much better) before
    "cleaning".

    OR: Get a Polonium 210 source to attach to the end of your vacuum
    cleaner nozzle (a violation of Federal Law if you do this
    yourself...by disassembling an ionization-type smoke detector, for
    example). Might also cause you to be cavity-searched the next timeyou
    fly commercial.
     
  10. D from BC

    D from BC Guest

    I wonder if an earth grounded mesh put in front of the leaf blower
    nozzle would reduce the amount of charged air.
    Maybe then it could to be safe to blow an earth grounded computer
    chassis?
    (I'll admit I think its a nutty idea to use a leaf blower..but it's
    entertaining. )
    Did the OP mention if the leaf blower was gas powered? :)
    D from BC
     
  11. D from BC

    D from BC Guest

    You might be interested in my post entitled
    "It's a Computer and an Air Cleaner"
    http://groups.google.ca/group/sci.e...+an+air+cleaner&rnum=1&hl=en#1f5277e3d898aeed
    D from BC
     
  12. w_tom

    w_tom Guest

    Yes moving air can create charges that product static electricity.
    But as whit3rd noted:
    A system resilient to thousands of volts per IEC1000-4-2 would use
    devices such as:
    http://datasheets.maxim-ic.com/en/ds/MAX1487E-MAX491E.pdf
    Swtiches are also rated for 20,000 volts. However all these claims
    come with an assumption. Once those parts are no longer part of a
    'system', then its protection does not exist or is easily
    compromised. All these protetion solutions - even a plastic switch -
    assume that static electricity has an alternative (shunt) path that
    does not pass through electronics.

    Same 'system' that makes static electric discharges irrelevant must
    also make static electric discharges not cause a computer crash. How
    to find a 'system' design error? Leather slippers and a nylon rug on
    a cold winter day make an excellent testing tool when 'system' is on a
    glass table top. Yes, glass because so many other table tops are
    acutally too conductive at those testing voltages.

    Static discharge to every part of a system's externals must not
    cause any software interruption. This is the same protection system
    that also makes electronics so resistant to larger and hardware
    destructive transients.

    A plastic switch that is not mounted conductive to its chassis
    therefore no longer provides 20,000 volt protection. Just one example
    of why all 'systems' should be fully static electric resilent AND why
    disconnecting anythnig from a 'system' can make that part suspectible
    to static electric damage or overstress.
     
  13. Barry Lennox

    Barry Lennox Guest

    I have never damaged one, while it's assembled

    Yes, but it's the particles in the air that develop a charge, not the
    air itself. The main determinant of how much voltage is the humidity.
    A dry day with lots of particles (dust, pollen, even dry snow) in the
    air can be a real shocker!

    Niels Jonassen wrote an excellent series of articles on static and ESD
    a while ago. You can find them here

    http://www.ce-mag.com/archive/2000/novdec/mrstatic.html

    Personally I just wash down a PC with the old HP "secret cleaner"
    formula (80% water, 20% IPA with a few drops of washing-up liquid),
    then blast it with shop air at 80-90 psi. Don't hit the fans with that
    air though, they can spin up pretty fast! Then let it dry out in the
    sun for a while, or 30 mins in an oven if it's crap weather.
     
  14. Most definitely NOT. In fact, given the increasingly smaller
    process sizes, I would say that many chips are actually MORE sensitive
    to ESD than from a few years back.
    Understandable. There's a lot of myths and misinformation about it.
    Just generic plastic. However, there's not enough there to jump an
    air gap.
    Actually, my understanding is that there's less danger from ESD, to
    the computer's innards, than there is from tiny bits of debris or drops
    of oil, or other contaminants, that may be present in the air stream
    from the compressor. There is also the risk, with excessive air pressure
    (some have been known to use 50-100 PSI) of literally blowing smaller
    components right off the board involved.

    My first recommendation, for any type of cleaning such as you
    describe, is that you use a good-quality ESD-safe service vacuum. 3M
    makes a very nice one that, although pricey (in the mid-200's), is
    durable as blazes and is actually rated to suck up toner with the right
    filter.

    I know, from direct experience, that vacuuming a board or component
    in this manner removes far more dust and gunk than blasting it with air.

    If you must use compressed air to clean, make sure that your line
    has top-rate filtration for both dust and fluids, and don't use more
    than about 30 PSI.

    Happy cleaning.
     
  15. Yes it can, Fluids do it, air is a fluid. Plastic is an insulator.

    Cheers
     
  16. John Doe

    John Doe Guest

    I really appreciate all discussion, very informative as always. A
    leaf blower won't thoroughly clean, but it doesn't present a clear
    hazard unless the air is dirty. I thought (wrong) it was an obvious
    electrostatic hazard. Thanks.
     
  17. Tim Williams

    Tim Williams Guest

    Po-210 isn't that hard, you can still get antistatic brushes AFAIK.

    Doesn't last very long though. Hardly seems worth it.

    Am-241 in smoke detectors is somewhat longer lived, but there's hardly any
    of it.

    Tim
     
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  19. mg

    mg Guest

    I've never worried a lot about the dirt in a computer. I do worry a
    lot about ESD. Whenever I have my computer case open, though, I do use
    one of those pressured air-cans to clean it up a little bit and I
    always wear an ESD wrist-strap. I concentrate mostly on the fans and
    heat sinks.

    When I give away an old computer to family or friends, I try to
    replace all the fans, including the CPU fan.

    I did have a CD/DVD burner go out a while back and I know that I
    haven't used it all that much. I do wonder if it might have something
    to do with the dander my dog produces when she's shedding.

    I monitor internal temperatures once in awhile with software.
     
  20. Actually, this is about the stupidest question I've ever heard of. If
    you would seriously consider blowing the dust out of your computer with
    a leaf blower, then you probably shouldn't be allowed to operate either.

    Good Luck!
    Rich
     
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