Grounding and Static Electricity FAQ

Discussion in 'General Hardware' started by RHochstenbach, Mar 2, 2009.

  1. RHochstenbach

    RHochstenbach Administrator Staff Member

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    Grounding and Static Electricity FAQ

    One of the most common dangers to computer hardware is caused by static electricity. If your body is loaded with static electricity, it can severely damage the hardware components of your computer when performing maintenance. It is important to ground yourself, so the electricity can flow away from your body. This topic appears to be quite frustrating, so I'll take some time to write this down.

    What is Static Electricity?
    Static Electricity is caused by the friction of two different non-conductive materials. The friction causes electrons from one object to move to the other object. Because these are non-conductive, the electrons can't flow away from the object. This also happens when you walk on a carpet with your shoes on. But also by the friction of your body and clothes. The shoes isolate you from the ground, and the electrons can't flow to the ground.

    What are the dangers of Static Electricity to computer hardware?
    When your body has a static charge, it could reach up to 400 Volts or even more! If you would touch an electrical component of your computer, you transfer a high amount of electricity to that component. And as a result, you could damage that component. To prevent this, you need to ground yourself while working on the hardware components of your computer.

    I just have to touch the chassis of the computer to ground myself, right?
    This is not entirely true. All components of your computer are connected to each other by a wire or line called GND. This line acts as a ground and also as the minus-pole in the electronic circuit. The chassis of the computer and the ground wire of the AC-cable are also connected to that wire. This means that you can ground yourself by holding the chassis or any other wire of your computer that is connected to the grounding of the circuits.

    The electricity needs to flow to the ground, so it's only possible to ground yourself to the chassis when the AC plug is connected to the power outlet, as the grounding system of your house lets the electricity flow to the ground. Just touching an unplugged computer chassis will not ground you in any way! That is also the reason why some people feel electric shocks when touching a laptop with just 2 AC pins and no ground.

    How can I make sure that my computer connects to the grounding system of my house?
    In order for your computer to connect to the grounding system, you'll need ground wires in the AC cable, and a ground connector in your AC wall socket.

    An AC cable with grounding wires usually look like this:

    Europe
    [​IMG]

    UK
    [​IMG]

    USA and Canada
    [​IMG]

    Furthermore you should check if the AC socket has ground leads (especially European people should check this):

    Europe
    [​IMG]

    UK
    [​IMG]

    USA and Canada
    [​IMG]

    There should be three different color-coded wires connected to the back of the socket (the grounding wire is in most cases coded green/yellow).

    I need both hands or I'm not comfortable when the computer is connected to AC power
    The best way to ground yourself is to use an ESD wrist strap, as shown in the following image:
    [​IMG]

    You put the strap around your wrist, and connect the other end to the ground lead of your AC socket (the locations shown in the images above). This way you can use both your hands and you don't need to connect the computer to the AC power. You could also connect it to the chassis of a different grounded computer or to an unpainted part of a radiator.

    You can also connect a Wrist Strap to another grounded computer by connecting a USB cable to that computer, and connecting the wrist strap to the outer part of the USB plug at the side that is not plugged in.
    [​IMG]
    [​IMG]

    There is also an alternative to the wrist strap that could be useful when you don't have a wrist strap at the moment and you need both hands. Get a long flexible conducting wire (copper preferred), and use your imagination to connect it to a grounded object. Then wrap the other end of the wire around your wrist.

    Do I need to have a motherboard seated in order for the case to be grounded?
    No, the chassis of the power supply is also grounded, and therefore the chassis of the computer is also grounded (when connected to a grounded AC socket).

    I haven't yet seated a power supply in my new computer. Can I just hold the chassis to discharge myself?
    No. The electric charge needs to flow to the grounding system of your house. If there is no way to reach this, then the chassis of the computer is not grounded either. In this case, connect an ESD strap to the ground leads of an AC socket, to the chassis of another grounded computer or to an unpainted part of a radiator.

    Why don't others say that you need to connect the computer to the AC socket? Are they all wrong?
    No not really. If you would touch a conductive material when you have a static charge cause the electrons to flow away from your body. However this can't guarantee that you're 100% static free. It will mostly give the same results as standing in a bucket of water while working on your hardware. When touching a grounded object, all static electricity will leave your body within a second. So an ESD Wrist Strap is always the best solution.

    If you have any questions or comments, just leave 'em here :)
     
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  2. henry222

    henry222 Geek

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    Much of what you say is good sense,
    - but I do query the connection between the ac supply and the PC chassis Ov, However, I don't think it really matters.
    Provided modders are fitting parts into a case then being connected to the case (via a wrist-strap you suggest) is quite sufficient. ((However, a copper wire alternative is NOT a good idea becuse of electrocution risk, wrist-straps are quite high resistance for this reason)). Some care needs to be taken when removing new bits from their packing and using a grounding sheet on the table/bench is quite a good idea. I believe a newspaper which is under the chassis is quite suffient since any charge can be disapated. This is because newspaper is partially conductive by the fibres which absorb moisture.


    ((I've heard of folks using aluminium foil, but in my opinion this is risky...1) it conduct any charge too quickly and 2) it presents a risk to you of electrocution should you connect to something live (very unlikley) - but reason 1) is enough.
    You mention the generation of static - but those who are worried can help themselves by working on their PC when it's raining and avoiding dry conditions such as created by central heating and snow - these both take moisture from the air, increasing the likelyhood of static build-up. Conversely using a water-spray will also assist in reducing the likelyhood of static for a hour or so. ((I am NOT suggesting spray the computer, rather the air in the room!))

    Back to that ground-issue. IMHO static can only cause damage when there is a sudden change in electric potential. No one worries if the components get hit by lightning (eg during airfreight) because the whole part rises/falls together. There is also the matter of "Faraday Cage" whereby static charges exist only on the outside . . . but if you are fitting some new kit, better safe than sorry.
    Largely it's a matter be taking care......on a subject that is well worth airing here.

    Also, I should warn against a secondary issue - that used to be known as "wounding" whereby mishandling doesn't kill the electronics - so some folk will say "it doesn't matter anymore" - but there is some suggestion that parts can fail later for some unexplainied reason......if you are reasonably sure your component parts have been handled "safely" then this secondary falilure is most unlikley. A good maxim may be that "Prevention is better...." - except there is no cure, other than to replace said bits.
    Being "static safe and static aware" need not be expensive, just a few precautions before you do anything.
     
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  3. FEC_80

    FEC_80 Geek Trainee

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    using my sellar (should be a nice hub) to conduct my preparations, reperations etc.it has all the things.
     

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