Grounding Strap and Wall Outlet Ground

Discussion in 'General Electronics Chat' started by foolios, Nov 9, 2009.

  1. foolios

    Thread Starter Active Member

    Feb 4, 2009
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    I don't think I have many things in my room to ground to so I took a power cord and left only the ground plug on it.
    Then I attached my wrist strap to the ground wire on the other end.
    The funny thing is I found a green ground wire and a bare ground wire in the cord. I didn't know it had a bare ground wire in there as well. So I twisted that bare one around the green coated one.

    ::"image removed due to hosts image bandwidth constraints"

    I then checked for continuity from the ground prong of the power cord to the metal plate on my wrist strap and found that it's working as designed.

    Now my question is, do you think that this is will work for keeping electronic components safe from static?

    Are there any other safety issues with my using ground through the outlet like this?

    Thanks so much in advance.
     
    Last edited: Jan 23, 2010
  2. BMorse

    Senior Member

    Sep 26, 2009
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    Just don't touch anything "Live" such as the Neutral or Hot of the AC line :eek:...... It would be better to connect your grounding strap to an Earth ground instead of your mains ground :).....


    My .02
     
  3. kurt.brinker

    New Member

    Nov 9, 2009
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    you need to be connected to the equipment you are working on. I suppose this would keep you grounded albeit somewhat unconventional.
     
  4. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    I'd suggest not using the mains ground as well, rather a cold water pipe or other item you are certain is in contact with earth.
     
  5. creakndale

    Active Member

    Mar 13, 2009
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    The cord you have made is a perfectly good/portable solution. If you have one of those electrical receptacle testers, use it on each outlet you plan to plug into just to make sure it's wired correctly.

    You might think about getting an ESD mat and connecting it to your grounding cord and then plugging your wrist strap into the ESD mat.

    http://www.esdproduct.com/ESD_Safe_Workstation_Layout.php

    creakndale
     
  6. BMorse

    Senior Member

    Sep 26, 2009
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    If you are going to keep using the outlet grounded wrist strap, I would suggest only working with the hand that has the strap on it, and keep the other hand behind your back, less chance of you completing a mains circuit through your body, and it will just zap the heck out of your hand :) and not stop your heart....
     
  7. foolios

    Thread Starter Active Member

    Feb 4, 2009
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    Excellent idea.
     
  8. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    From the look of the cord/plug, it looks as if you are in North America?

    Instead of using the plug and cord, get a length of single conductor wire and put a ring terminal on one end. Remove the screw that holds the cover plate on the outlet. Put the screw through the ring terminal and reinstall the cover plate.

    This connects the ground of the outlet and at the same time keeps it away from the "live" connectors of the outlet.

    In North America ground of the outlet/service box is tied to either a water pipe or earth ground rod by code. I don't know about other countries.
     
  9. t06afre

    AAC Fanatic!

    May 11, 2009
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    I often put the Grounding Strap around my ankle. It gives me better work conditions.
     
  10. Wendy

    Moderator

    Mar 24, 2008
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    I hadn't thought of it, but I would use a screw. That plug looks dangerous, the other pins aren't there to keep it pinned in place, and the one pin could float in a broken or cheap outlet.
     
  11. SgtWookie

    Expert

    Jul 17, 2007
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    It also guarantees a current path through your heart. :eek:
     
  12. t06afre

    AAC Fanatic!

    May 11, 2009
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    I would not worry about it. It is a folklore myth. On my workplace we have conducting floor and conducting "ESD" shoes. Even in operating theatre in hospital they use this approach. Besides it is common for the manufacturer to put a 1M protection resistor usually in the cable that connect to the grounding strap. This is done for safety. You do not which way the current will take. So I will still use use my foot/ankle with and relax.
    Ps If you do not have 1M resistor somewhere in your strap system you should put it in for safety. Just ohm your strap+cable system
     
    Last edited: Nov 11, 2009
  13. wr8y

    Active Member

    Sep 16, 2008
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    I have been doing that for 30 years (got into the habit when working on tube-type ham stuff and broadcast transmitters.) :cool:
     
  14. foolios

    Thread Starter Active Member

    Feb 4, 2009
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    Ya know what, I realize now I had to remove the original cable from the wrist strap since it was breaking at multiple points. I didn't realize they had this built into the attachment to the strap. I will have to work this into my wire somehow.

    So this 1MegaOhm resistor will prevent large voltages and current but will allow the little static that builds up to go to ground easily right?
     
  15. BMorse

    Senior Member

    Sep 26, 2009
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    Definitely one of my pet peeves, when ever I am training new techs, I always insist on it just for safety especially when trouble shooting live circuits, or wear 2 wrist straps, so each hand is grounded at the wrist...(still painfull to divert current through your wrist but better than having it go through your body with a grounded floor mat, which does not do you any good if you are wearing rubber soled shoes anyway :rolleyes:....)

    1 of my service techs keeps his pinky of the hand he is working with touching the metal chasis of the electronic enclosures we work on, and one day he was working on a CRT monitor and accidentally touched part of the flyback circuit and whalla! he had a hole around 1/8" burnt/blown through his pinky :eek:! Better than his cardiac system I guess;)....

    Always! Safety first! Not just protecting equipment or components, but especially yourself and others.....
     
  16. rjenkins

    AAC Fanatic!

    Nov 6, 2005
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    You should never use a DIRECT ground cable for anti-static gronding, it is extremely dangerous...

    Put a high-value resistor in series with your ground cable - 100K Ohms or more.
    This provides anti-static grounding but limits currents to a reasonable level if you accidentally touch a live connection.

    Also, remember the key to working with static sensitive components is not grounding but equalising potentials.
    Touching a component that is not grounded when you are grounded is as bad as you not being grounded - there can still be a voltage difference that it equalised by the contact, so WHERE you touch an item is important.

    Grounds are OK in production environments, where the floor mats, bench tops and storage all have earth leak resistors but for DIY you are better off developing the correct habits:

    Always touch a chassis point or (power) ground on any item before picking it up, to equalise voltage with you body before touching signal pins.

    Touch the circuit board ground or anti-static/metal container etc. before putting a component into it after picking it up.

    If you always equalise voltages at none-sensitive points before allowing contact by possibly sensitive parts, you will not have problems, even without grounding.
     
  17. foolios

    Thread Starter Active Member

    Feb 4, 2009
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    Thanks all for that valuable insight. You may have just saved my arse some day.
     
  18. t06afre

    AAC Fanatic!

    May 11, 2009
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    Rjenkkins has made a very good point. On my workbench home I have a conducting table mat, connected to ground. And I also ground my self. This will give god enough protection against ESD. At least for the hobbyist. The cost is small. I can not remember the last time I zapped a component
     
  19. foolios

    Thread Starter Active Member

    Feb 4, 2009
    160
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    Just to make sure I'm setting this up right.

    The resistor I have is brown/black/green = 1/0/00000 = 1,000,000 ohms = 1MegaOhm

    I used my multimeter on the 2000k ohms setting to measure the resistor just to make sure I didn't read the color band wrong.
    It gave me a reading of 1000, of which I am assuming that that means 1000k since there are no other indicators on my mm and the range I had selected was 2000k. If I go to the next lower range of 20k then I'll get the 1(or in other words the OL).

    I'm gonna solder it together right now and then do a continuity test after I'm done.
     
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