ESD, Parallel Ground Paths and Wrist Straps

Discussion in 'General Electronics Chat' started by Redstone2, Jan 31, 2011.

  1. Redstone2

    Thread Starter Member

    Oct 21, 2010
    20
    0
    Hello All,
    This weekend I added a workbench to my shop (Christmas present from wife – a super girl) freeing up a bench that has a sheet metal covered top. Just read http://www.allaboutcircuits.com/vol_3/chpt_9/1.html. My workshop is a 10’ x 10’, detached from dwelling and feed with a single 120v / 20 ampere branch circuit.
    I have a phobia attaching a grounding wrist strap that is connected to my electrical service grounding conductor. Some of my concerns:
    · Parallel grounding paths. Should I be concerned with LAN connected computers? My networked computer in the shop might have a different potential than the ground lug at shop receptacle. What about co-ax TV connections? My concern is touching a surface with a different impedance during a fault of some type.
    · What about nearby lightning? I have lost several appliances and one utility transformer to indirect lightning. Is strapping my body to the grounding conductor a bad idea with thunder storms in the area? A portion of the 120v/20ampere branch circuit is under ground.
    · Would an additional driven ground rod at the shop be a good idea? I have a disconnect switch (like the ones used for HVAC condensers) mounted on the bldg exterior where the branch circuit enters the shop. The disconnect has a ground bus bar that I could add a #6AWG from a driven rod.
    · Just a “regular” ¼ watt 10 mega-ohm resister for the bench and strap?
    Thanks for any input.

    Regards,
    Tom
     
  2. Wendy

    Moderator

    Mar 24, 2008
    20,764
    2,534
    Your concerns are well founded. I wrote the article in question, a separate ground as you suggest would be superior. If you go this route use is as the primary ground and you can not go wrong, ignore the ground offered by your AC outlet. You will have a better than average setup.

    At 10MΩ wattage does not matter, so go for it. It is mechanically weaker, you could beef it up with a dowel next to it or whatever for mechanical strength, but the wattage simply is not an issue.

    Thanks for the feedback. I went back and reread my article with fresh eyes.

    Afterthought: Many irons offer 3 prong electrical plug ins. There is nothing wrong with this. A lot of them also offer a grounding point, again nothing wrong with this. Using any electrical appliance during a thunderstorm is definitely not a good idea, especially if you have yourself connected somehow. Even with a separate grounding point (which I like) it is probably a good idea to put the soldering iron down, unplug the test equipment, and wait it out.
     
    Last edited: Jan 31, 2011
    Redstone2 likes this.
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