Is it unsafe to rest tower on a carpeted floor?

[xMax]

I've always had my computer towers resting on carpet flooring and never once had a problem with electrostatic discharge frying any of the components inside.

But a friend of mine recently told me that he always uses a wooded surface to rest his tower on and never uses a carpeted floor.

Is here right or over cautious?

 

[potato28]

Depends... Your case is grounded by the PSU cable. The only time you do this is if you have an acrylic case.

 

[xMax]

What do you mean 'my case is grounded by the PSU cable'?

Are you saying that the PSU cable should be touching the carpet?

Im not sure i understand.

 

[JM Aggie08]

hasn't given me any problems yet, just dont rub your foot on the carpet madly and kick the case

 

[xMax]

Hmm..

The question is this: Are computer towers, with the case and the power supply in particular, built with some kind of a defence mechanism against electrostatics?

I say this because the box that my tower comes in is filled with electrostatic charge from the Styrofoam that holds the case. So everytime i take my tower out of the box, with all the computer components inside the tower, i just cant help but wonder how all the dissipating charge on the tower from the styrofoam doesn't damage the components inside the tower. My only guess would be that the case and PSU have defensive mechanisms or because the tower is not turned on.

I think its because its not turned on.

 

[GalvanizedYankee]

What potato is saying is you really should use a grounded wall plug for the comp.
No static charge off the rug will hurt you rig BUT your case will need cleaning MUCH less ofter IF it is atleast 8" off the floor. Dust and grit live 6" off the floor and your comp will become a dust buster on the floor.
Many keep the box on the floor, I won't.


...Galvanized

 

[xMax]

But what is a 'grounded wall plug'?

All i have is my computer and monitor hooked up to a surge protector, with the surge protector going into the wall.

I don't understand.

 

[mra]

Components aren't damaged by even lightning-level electrical charges. They are damaged when these charges travel THROUGH them. Since they are in the case the whole thing can become electrically charged (not even possible when it's plugged in and your house is wired with a proper ground), but there will never be current flowing through the components.

The reason to keep computers off the carpet is to help keep them cool.

 

[imported_Seer]

a grounded wall plug is a 3 pin plug...2 regular, rectangular prisms and one cylindrical plug. The cylinder is the ground. a non grounded outlet only has 2 plugs.

 

[Zepper]

I second raising systems off the floor for minimizing dust intake.

.bh.

 

[xMax]

Understood!

Thanks a bunch guys.

 

[cretinbob]

It's not so much the electrostatics you need to worry about, it's all the dust and fibers and crap that gets into it. all of that falls to the floor, so if you can keep it on a desk, I would do so.

 

[xMax]

Unfortunately there isn't really much space on my desk for my tower.

 

[JeffMD]

You can allways mod your case or buy a case that has filters over the fan intakes. Other then that, the floor is perfectly fine. You can set it on a stool too.

As for static electricity and grounding, the 3rd round pin on the bottem of plugs is the grounding plug. Some appliances dont have it but PC's and the outlets you plug them into must have this, PCs are easy prey if they cant get rid of stray charges. That said, YES your case (atleast the frame, the doors facing out are probably covered in a non conductive paint) is grounded as well. It is touching the power supply casing (also the screws going form the case frame to the power supply help as contacts) and that is grounded. This is also why they tell you not to disconnect the power cord when working on your pc, cause then you can touch the case to get rid of any static charges you accumulate while touching the electronics inside.

 

[Navid]

Originally posted by: JeffMD
This is also why they tell you not to disconnect the power cord when working on your pc, cause then you can touch the case to get rid of any static charges you accumulate while touching the electronics inside.

That can be quite dangerous. You should really disconnect any equipment from the live grid before opening and working on it to be on the safe side.

ESD damage occurs because electrostatic charge is dumped on to a sensitive component resulting in a current flow that damages the component.
To avoid that, you touch the case! Yes, even if the PSU is disconnected from the wall!

The ground plane of the motherboard is the large metallic plate that you see on the board. It is the (electrical) point of reference for any component on the motherboard. When you touch the case, if your body is charged, the charge will be dumped on the ground plane. The ground plane will then be slightly charged. Since the ground plane is physically large, it has a relatively large parasitic capacitance. The charge dumped on it will not cause its voltage to dramatically rise because of its high capacitance.

Even if its voltage rises, it will still be at the same voltage (potential) as your body. So, if you then touch a sensitive component, there will be no reason for a current flow since the relative voltage is 0.

Even if your PSU is plugged to the wall, you must still always touch the case first before touching anything else. If you don't and you touch a sensitive component and your body is charged, you will be placing a large voltage on the component. The ground plane is at 0 Volts. That difference in voltage is enough to cause a large current to flow through the component and damage it.

REMEMBER:
When working with ESD sensitive devices, always touch the ground plane of the device first. For example when you handle a sound card or graphics card, handle it by holding the metallic part (frame used for mounting) and the corner of the board. Usually, the corner of these boards is either blank or has its ground plane.

 

[xMax]

I definitely think having filters over the fan intake built into the case is cool. Although it could be over kill if your tower is resting up high on a desk or anywhere that is away from the ground. Nontheless, with my system completely built, i will not consider this as an option right now. Maybe for my next RIG.

Now as far as touching the case goes, i could say that i understood clearly to touch the case before any other component, and to touch the ground plane on any device before putting it into the case. But im not sure about this thing with having the main power plug plugged or unplugged into the wall when working on my PC.

Originally posted by: JeffMD
This is also why they tell you not to disconnect the power cord when working on your pc, cause then you can touch the case to get rid of any static charges you accumulate while touching the electronics inside.

Originally posted by: Navid
That can be quite dangerous. You should really disconnect any equipment from the live grid before opening and working on it to be on the safe side.

Unless im mistaken, isn't that a contradiction.

Clearly the computer should be off when working on it. But should it remain plugged into the wall unit or not?

 

[Navid]

Originally posted by: xMax

Originally posted by: Navid
That can be quite dangerous. You should really disconnect any equipment from the live grid before opening and working on it to be on the safe side.

Unless im mistaken, isn't that a contradiction.

120 Volts can kill you.
Disconnect from the wall, if you can, before working inside your PC (or any other electrically powered equipment).
I assume that you want to live.

Do you see any contradictions in that?

 

[xMax]

Well JeffMD said to keep the power cord plugged into the wall and you said to make sure the power cord is unplugged from the wall. So one of you is correct and ther other is incorrect.

But im guessing that keeping the computer plugged is better for grounding and may be safer for the computer components, but worse for the safety of the human working on the computer.

Of course, i would imagine that unplugging everything makes much more sense since human safety comes first.

 

[Navid]

Originally posted by: xMax
Well JeffMD said to keep power connected, and you said to disconnect power cord. So one of you is correct and ther other is incorrect.

But im guessing that keeping the computer plugged is better for grounding and may be safer for the computer components, but worse for the safety of the human working on the computer.

Although i would imagine that unplugging everything makes much more sense. Regardless of the possibility that keeping the computer plugged will have better grounding.

I believe that as long as you touch the case or the ground plane of the device before touching anything else, having the PSU plugged to the wall is not going to add any advantage.

My reasoning is that it is not the absolute voltage that damages a sensitive component. If your body is charged up to 2,000V (static), you are not going to damage your graphics card by touching it as long as your graphics card is also charged up to 2,000V.

But, you can kill your graphics card if your graphics card is at 0V. It is the relative voltage (potential) that matters.

 

[xMax]

It is the relative voltage (potential) that matters.

I didn't know that. It's rather interesting.

You had mentioned it in your previous reply, but i didn't pick it up.

 

[Navid]

Some reading if you are interested in ESD.
http://www.midwestesd.org/aboutesd.html

 

[AZReDWiNG]

Originally posted by: Navid

Originally posted by: xMax

Originally posted by: Navid
That can be quite dangerous. You should really disconnect any equipment from the live grid before opening and working on it to be on the safe side.

Unless im mistaken, isn't that a contradiction.

120 Volts can kill you.
Disconnect from the wall, if you can, before working inside your PC (or any other electrically powered equipment).
I assume that you want to live.

Do you see any contradictions in that?

WRONG!

Tasers can send 400,000 (! -- not factorial) volts. You don't die (unless you've got a pacemaker, but that's a whole different story). What kills you is CURRENT: the flow of electricity through your body. The more electricity flowing through your body, the higher probability of death. It makes sense, but many people believe that voltage is the electricity flowing into the body.

(I had a longer response about potential difference and why keeping stuff grounded is important, but I saw that you already said that stuff. This makes me ask why you think 120V is lethal.)

ANY voltage is lethal -- so long that there is a current to carry the electricity.

 

[xMax]

You guys can go at it with this one.

All i know is that i was never able to grasp the difference between current, amps, volts, and potential difference.

And i have no interest in learning either.

 

[Navid]

Originally posted by: AZReDWiNG

Originally posted by: Navid

120 Volts can kill you.
Disconnect from the wall, if you can, before working inside your PC (or any other electrically powered equipment).
I assume that you want to live.

Do you see any contradictions in that?

WRONG!

Tasers can send 400,000 (! -- not factorial) volts. You don't die (unless you've got a pacemaker, but that's a whole different story). What kills you is CURRENT: the flow of electricity through your body. The more electricity flowing through your body, the higher probability of death. It makes sense, but many people believe that voltage is the electricity flowing into the body.

(I had a longer response about potential difference and why keeping stuff grounded is important, but I saw that you already said that stuff. This makes me ask why you think 120V is lethal.)

ANY voltage is lethal -- so long that there is a current to carry the electricity.

V = I R

This is Ohm's law. It is a relationship between the voltage across a component, the (effective) resistance of the component, and the current flowing through the component.

The component can be anything (even your body).
If you place 120V across your body for a long enough time, the current flowing through your body will give you a shock. If the current flows through your heart, it may stop.

You need to take everything in the current path into account though. Just because you have thousands of Volts, it does not going to be lethal if you connect it to someone through a large resistor, which is probably how a taser limits its output current to non-lethal levels. But, in that case, the voltage is split between the subject body and the resistance in the path.

You also need to take into account the length of time the voltage is across your body. The taser very likely is a capacitor charged up to the high voltage. But, as you start the current flow through the body of the victim, the capacitor starts to discharge. So, the current decreases rapidly.

Please note that the electric wires in the house do not satisfy either of these two conditions. Those wires have a negligible resistance and the power company provides voltage continuously (very dangerous).

When I say 120V is lethal, I mean that voltage being across your body at a lethal point of entry. If you connect the tip of your little finger to neutral wire and connect the tip of your ring finger (of the same hand) to the hot wire (120V), and isolate every other point of your body, the current will flow through those two fingers only. It is going to be quite painful. But, very likely not lethal since no major organ will be in the path of the current.

But, the same voltage placed between your left hand and your right foot can kill you since it goes right through your heart and can stop it.

Resuscitation is possible. But, I hope you never get to that stage.

So, you are right, it is the flow of current that is the problem. But, don't forget that it is the voltage that causes the current to flow.

If you believe that 120V cannot kill you, I hope that you do some research before you tell this to others or before you yourself put it to the test!
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/shock.html
http://www.electrical-online.com/howtoarticles/safety.htm
http://en.wikipedia.org/wiki/Electric_shock

 

[F1shF4t]

Firstly i wanna know where did people pull out 120v from inside the computer from :S
Human skin has a large resistance as soon as skin is penetrated the resistanse falls below 1000 ohms, as essentially we are a blow of salts dissolved in liquid .
Now when elctricity goes through a human its esentially like short cicuiting the source as our body resistance is low.

There are 2 things which will limit how much currnt will go though our body.

1) The power that the circuit can diliver. V=IR so if u got 100v and 100ohm resistance u will get a current flow of 1A. now what will happen if the power souce can only deliver 50w. power = vI so with 50 watts and voltage of 100 we are limited to only 0.5A of current being able to be delivered.

2) Body resistance.

3) voltage, more of it more current will flow until u get to the limit of power.

What damages the body tissue is essentially not the current or voltage, but the heat generated from the current going through it.
heat dicipated = I^2 * R, so if we take the previous figures of 0.5A and 100ohms u will have 25 joules of evergy dicipated every second at the path of current.
Now if the supply was bigger rated like 400watt the current will be bigger and there will be more damage.

Just for another point 16mA through the heart will desrupt its normal rythm