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Static Discharge when building a pc


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#1 itsbobbaayy

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Posted 29 August 2015 - 09:34 PM

If I am wearing an anti-static wrist strap that is connected to my pc case that is not grounded. I will have achieved zero potential with the pc case but as soon as I touch a new component after unboxing will I give it an esd because it has a lower potential?



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#2 czarboom

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Posted 29 August 2015 - 10:29 PM

No, why would the component have a lower potential?  By attaching your wrist strap to the case you are creating a floating ground.  You skin has a higher potential for resistance than the strap does.  They only way this would change are if you have a something that carried or lowered the skins potential, such as water.

 

I used floating grounds for year in all types of environments with no issues.  Unless you are in a clean room, or have something that is below the 2mV level then there is no worry. 

 

Also, cardboard is not a conductor of ESD, so again no worries there? 

Or am I missing what you're saying?

 

cz


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"Never Stop Asking Questions, Question Your Environment, Question Your Government, above all Question Yourself.  We all lose when you Stop asking Why?

#3 itsbobbaayy

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Posted 29 August 2015 - 10:48 PM

Idk maybe I am just confused. Lets say I had a higher potential then my pc case so when I used my strap I became zero potential with the pc case. Then there was a component on the table that I picked up that has a lower potential. Wouldn't I give the component an esd because even though the pc case and myself are zero potential we still have a higher potential than the component thus giving it an esd?



#4 czarboom

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Posted 29 August 2015 - 11:19 PM

Hello again,

Short answer is NO, you will not.  Your potential and resistance are backwards.  Meaning your body has a higher resistance via your skin then the object you could hit with an ESD.  That you got right.  BUT... your strap has a lower resistance than both your body and the object you’re touching.  E.g. a PCB or memory etc. 

 

Your strap will then carry the current to your floating ground, and not your object because electricity is lazy.  And ESD is a kinetic action meaning the field is due to movement and not just there because it’s there. 

 

BUT, just in case make sure you use these best practices:

  • Make sure your wrist strap is tight on your wrist and correctly worn.
  • Attach the alligator clip to another METAL only object. (Not plastic or wood)
  • Before you touch whatever you’re concerned with zapping touch your computer case, or something else that is metal to release any static charge you might have.  Then touch the object you want to grab.
  • ALWAYS use the one hand rule when you can. (One hand rule is only use one hand to grab a part, and the other hand should not be touching anything else.)

So in review, higher the resistance the greater protection from ESD.  Also remember your wrist strap offers the lowest resistance of anything you touch thus the ESD will drain to it.

 

Make sense?  If not I got a link I can give you.  Just remember, attach strap to wrist, then to metal on case (outside or at a ground post), touch the case or another metal object BEFORE you touch the item of concern, and you should be 99% fine and in the clear.

 

Good luck

cz


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"Never Stop Asking Questions, Question Your Environment, Question Your Government, above all Question Yourself.  We all lose when you Stop asking Why?

#5 itsbobbaayy

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Posted 30 August 2015 - 01:01 AM

Okay so the only reason a static discharge doesn't happen is because the strap has lower resistance than if my skin touched a component without the strap? Yet, even if my skin is of higher resistance won't it still give the component a static shock because it needs to equalize the potential? Also so the charge goes to the pc case, then wouldnt the case give the component a static discharge when you place it in there?

Edited by itsbobbaayy, 30 August 2015 - 04:47 AM.





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