New Dell Laptops Give Users a Literal Shock

An anonymous reader writes "According to CNET.co.uk, certain new Dell laptops with a brushed-aluminum finish are giving users more than they bargained for. 'We know this because several CNET staff were hit with an electrical charge while using Dell's new XPS M1530 — and we're not the only ones. Dell's forums are littered with user complaints about the shocking experiences they've had with some systems. The problem only seems to occur in Dell laptops that have a brushed-aluminum finish. These include the XPS M1330 and XPS M1530. It's caused by the two-pronged connection between the mains lead and the power adapter, which isn't earthed properly because of its lack of a third pin. The laptop therefore exhibits an electrical potential (voltage) between its exposed metal parts (the brushed aluminum wrist pad) and earth ground. Since there is no earth, the human body basically acts as a wire that can conduct electric current, hence the tingling, jolting sensation.'"

Comments

Forget exploding batteries,

[Anonymous Coward]

This is the new ground breaking experience with laptops!

Re:Forget exploding batteries,

[einhverfr]

Customer's shocked by Dell's high-performance Laptops!

Actually, on one of my trips to Indonesia I had a similar problem with my (three-prong) Compaq Armada. If I touched any exposed metal on the case, I might (or might not, depending on the circumstances) receive an electric shock.

In that case though the problem was not due to the laptop but rather faulty building wiring. My guess is that either the earth ground was not attached to the wall socket properly or somewhere else a lot of electricity was being dumped down the earth ground, changing its electric potential.

Re:Forget exploding batteries,

[Anonymous Coward]

You aren't putting AC into your computer. You are first going to a rectifier which converts it to DC. In an AC system, the third prong is designed to ground the case. In most settings it could effectively be connected to the neutral ground (wide prong) as well but this isn't done because if the neutral prong broke and there was an electrical fault then there would be no protection to the case. Your DC adapter, however, has no choice in this matter. Since the rectified output of your DC adapter is so low voltage, designers haven't felt the need to take the grounding precautions that they have done in higher voltage AC settings, such as grounding the case to the neutral ground or the third prong ground. For this reason, very few DC adapters even have a third prong for the AC side. It would only be useful if you had a fault inside the rectifier unit itself. Since most DC adapters have plastic cases, this isn't an issue.

Re:Forget exploding batteries,

[Anonymous Coward]

There are a couple of things you can do to figure this out. First, you can check if you system ever shocks you when it is not plugged in and running off the battery. If it doesn't, then your fault lies somewhere before the charging circuit in your system (which would be dead when you are running on the battery but live when you are plugged in). Second, you can check the conductivity between your case and the DC ground (outer cylinder in your plug). If it is open, then your case isn't grounded. I haven't seen a three pronged plug for a laptop, but if you somehow have one (which I doubt), then run your conductivity tests on it as well. Third, you can check other potential faults. If your system isn't grounded in any way as I suspect, you might want to check anything else that is plugged into your system and has a separate power supply. Finally, you can open up your adapter and verify that the third AC prong goes nowhere except perhaps the neutral ground connection on the AC side leaving the DC side isolated from the AC side by a transformer.

Re:Forget exploding batteries,

[plover]

Dude! You're getting a shock!

Re:Forget exploding batteries,

[BobNET]

Don't buy metal-clad laptops you dip-shits. Use your brain!

How is encasing your laptop in a brain supposed to help? Wouldn't it be messy?
Mmm... brain-clad laptop... chewy on the outside, crunchy on the inside!

Re:Forget exploding batteries,

[Vihai]

The lack of the earth pin is not a lack of safety. Actually, double-insulation appliances MUST NOT be grounded, thus they miss the earth pin. http://en.wikipedia.org/wiki/Double_insulation If you have a class I power supply and you plug it in an outlet with faulty ground the EMI filters (yes, they are connected between both neutral and line to ground) will induce a mains/2 voltage on the chassis with an impedance high enough to be felt. Thus, if you feel electricity on the chassis of an appliance check that the earthing of all your Class I appliances is good.

Re:Forget exploding batteries,

[TheLink]

Great, the PC manufacturers are copying Apple again.

Ooh,

[Voltageaav]

Where can I get one? I need a presant for my mother in law.

Re:Ooh,

[LrdDimwit]

Better move fast, you'll need to strike while the metal is hot.

Happens on Apples Too.

[jellomizer]

To be fair to Dell this happened on my PowerBook and not so much on my MacBook Pro... But sometime I do get a tingle, in the right condition.

Re:Happens on Apples Too.

[tsotha]

That tingle is from the websites you're visiting.

The real question is...

[MikeyVB]

...what happens when you lick it?

Better or worse than a 9V battery?

Just Dell's friendly way to remind you that...

[BUL2294]

"Dude, you've got a Dell!"

PowerBooks have had this for a while....

[zardie]

The Apple PowerBook G4 aluminium systems have also suffered from this - but only when using the 2-pronged power plug. If I use the actual cable between the power adaptor and the wall (with three pins) then this is no longer an issue.

I believe the MacBook Pros also suffer from this however I haven't tested this.

Re:PowerBooks have had this for a while....

[v1]

I've used a macbook pro and powerbook for some time, always with the two prong pack, and I have yet to get any tingle from the case. One thing that is being overlooked here is that the lack of a ground pin is not the cause. To get a buzz off the case there has to be an original path from the outlet to the computer, to allow your body to be the return path.

Many electronic power packs use "transformers", which use two isolated, closed loops to transform power, magnetically coupled. (to make a trade off of voltage for current, since laptops need 12v and the wall gives 120v) There is no path between the two, and you could start chewing on the power wires if you wanted to, (one at a time I would advise) without getting the slightest buzz.

The only way you could get a buzz off the case is if the case is grounded (via the 3rd pin) and that there is a ground fault in your area of the building (in which case you would get a buzz by sticking a paperclip into the ground pin on the outlet) OR if the pack was a more direct regulated power and was designed poorly. (like connecting the center tap off the 120v side with the center tap on the laptop side)

Devices experiencing a minor short that have a ground pin can cause equipment all over the building to buzz you. Attach a GFCI (ground fault circuit interrupter) power strip and see if it trips where you are seeing the problem. It just might. I've seen cases where when I plugged in a certain power tool and revved it up, it would trip every GFCI outlet in the house. Same effect, caused by the power tool's bad (dangerous really) design.

Re:PowerBooks have had this for a while....

[v1]

I'll see if I can find some more authoritative answer for you. "Ground" only behaves as you expect it to because it's often used as a common. When lightning strikes, it's because there's a charge difference between the ground and the air. If there is no charge difference, electrons will not flow, they have to reason to. That's why they can drop off repairmen on high power lines to work on them via helicopter. In those cases though they do have to equalize the charge with a pole before he hops on the wire but it's not an ongoing issue like the buzz you get off a ground problem.

When ground is not common between two pieces of equipment, there is no return path, and no electrons flow. Most people's view of electricity is relative to their AC power outlets, which DO have a common ground. I have an isolation transformer in the basement, it's a simple 1:1 transformer. I can GRAB the power wires coming out the back (one at a time!) and nothing happens. Nothing, not even a light buzz. That's because the transformer isolates the outgoing lines from ground. This is an excellent lightning deterrent for my servers because lightning simply has no reason to go after my servers since they are isolated from what the lightning wants, to seek out ground.

All power tools have to pass UL, if it's tripping a GFI either it or the GFI is bad.

The power tools I was speaking of, are the type that have either failed, (loose internal wire usually) or are too old for that. Yes they're not supposed to do that.

Let me try to illustrate with water as an example. Water works a lot the same way as electricity. (that's where current got its name actually) Lets imagine water requires a pipe to flow in. As in, if you cut off the end of a water pipe with water in it, nothing comes out. It would behave the same as electricity. At the wall you have a pump that on one port pushes water and the other it pulls. Attach a single pipe and no water flows because the end just terminates, there is no return path. Put a water powered toy at the end of the wire and the toy does nothing. Run a second pipe from the toy and back to the outlet, and now the toy operates. The reason is the water cannot run through the toy no matter what the pressure (voltage) unless it has a return path since it can't just come flying out the other end of the toy and spray around the room. Electricity is the same way, it can't just spray out the end of the wire all over the room.

Water has to come from somewhere. And they provide you with a third port on the outlet to tap into the water reservoir. This is the ground. Now lets run a drip pan below our toy and run that to the common. As long as the toy doesn't leak, no water flows back to the outlet through the ground. Lets for the sake of argument say that around the toy the water can get to the drip pan if it springs a leak. This is why there is a metal shell around your power drill, that's the drip pan. Now lets say the toy springs a leak. (a frayed wire comes loose inside the drill and touches the outer case)

That's a ground fault. Water can now flow from the high pressure line to the ground, as well as the return. Depending on the size of the pipe, energy the toy requires, and size of the fault, this may be a little water or a lot of water. Same with the short in the drill.

This is actually working out well as an example. :) Anyway, the GFCI is a device in the outlet or in the cord to the toy that looks for water to be moving to ground. if it detects any, it slams the valves shut on the outlet because it knows some water is going someplace it shouldn't. It's possible to monitor the two ports on the outlet and compare them and make sure that exactly the same power is going in one as is going out the other, and of there's any difference, trip. Most do this, which is why they can protect you from completing to ground from the appliance by touching the ground of something ELSE that is common grounded, like your refrigerator. O

Re:PowerBooks have had this for a while....

[v1]

yes, though for a consumer electronic, that's probably a really bad idea. I see a lot of older hardware before the 3rd prong era hit, where the center taps on the in/out were tied together.

Please

[Daimanta]

Don't shock me bro!

Which is the better option?

[damn_registrars]

The exploding / burning batteries, or the electric shock?

I think I'll stick to my ThinkPad, thank you much...

xps m1330 owner here

[yourexhalekiss]

I've had an aluminum-brushed XPS m1330 for about four months now, and I've never experienced a "shock" like the article is suggesting. I don't doubt that the CNET editors have experienced this, but I'm certain I would have remembered it if it had happened to me.

I checked, and my 1330 has a grounded three-prong plug going into the wall, and a three-prong plug going in to the power brick. Maybe the UK 1330s/1530s are different than the American ones?

Re:xps m1330 owner here

[Alioth]

They probably are. Having lived in both countries, where most UK devices are almost always properly grounded (the earth pin is not optional in UK power plugs because you physically can't plug something in that doesn't have one - the earth pin opens the shutters in the wall socket), a great number of US appliances lack a ground pin.

Perhaps because 110 volts is seen to be less dangerous than 240v, it gets omitted.

Re:xps m1330 owner here

[RikF]

Heh - check again! The UK plugs may need to have 3 pins but quite often than third pin is plastic and unconnected

Re:xps m1330 owner here

[PeterBrett]

Heh - check again! The UK plugs may need to have 3 pins but quite often than third pin is plastic and unconnected

Only unearthed devices using power-supply protection described as "double-insulating" may substitute a plastic 3rd pin. Typically, these have (very) heavy insulation on the mains side of the power supply, and then use an internal transformer to "float" the device's electrical workings so that any inadvertent contact with a person just changes the circuit's point of reference without causing a shock. They would not exhibit the symptoms described in this article.

Any devices you might own which have a plastic third pin and don't bear the label "Class 2" or the double insulation symbol are unsafe. Get them looked at by someone competent. As a point of reference, a brief poll of the various devices around me here found one Class 2 device -- the LVDC transformer for my desktop speakers. And a hauling out the schematics, yes, the transformer has a floating secondary.

BTW, the reason you see a lot more Class 1 appliances in the UK is because that is the preferred design for any device that uses more than a trivial amount of power. In a Class 1 device an electrical failure cannot bring the chassis to mains potentials without blowing a fuse, whereas in some pathological cases Class 2 devices fail to fail safe (if that makes sense).

The problem discussed in the article has nothing to do with what sort of plugs are in use. Class 1 devices, properly earthed, are safe. Class 2 devices, properly insulated, are safe. The problem in TFA is that the safety features of the electrical system weren't used properly, thus causing a hazard. Much the same as if you have a Class 1 device without a ground connection -- a charge (which would normally be rapidly dissipated to ground) can very slowly build up on the chassis, leading eventually to a shocking result.

Re:xps m1330 owner here

[pcgabe]

It's even worse in Japan. You can't physically plug something in that DOES have an earth pin; the sockets aren't made for them. There's no grounding at all*. I guess 100 volts must be safer than 110v.

(* not entirely true, some outlets have a grounding tab on them, to which you can attach a grounding wire from certain appliances. But not every appliance, nor every outlet. Or even most. Or half. My last apartment had two outlets with grounding tabs on them, total.)

Someone go grab John Connor!

[Kingrames]

The machines have struck the first blow!

two in the junk, one in the trunk

[seanadams.com]

the two-pronged connection between the mains lead and the power adapter, which isn't earthed properly because of its lack of a third pin.

That explanation is over simplified. Tons of metal-encased devices have only two-prong leads and are perfectly safe. My Apple laptop for one, and a lot of stereo equipment as well.

UL allows this if the device is sufficiently isolated. What is sufficient depends on the type of device, the type of power supply, whether the supply is internal or external, and so on. Usually it means that the DC output of the power supply has a very high impedance with respect its input, and also that the metal chassis of the device is floating (with specific distances and or dielectics between it and any possible potential) and/or has a non-conductive finish. I'm not sure but I think even just clear anodizing would meet that requirement. I just tested my MacBook and all the aluminum surfaces are not conductive, suggesting such a finish.

In order for the Dells to be zapping people they must have doubly screwed the pooch: wall wart is putting out a high potential, AND the case is not properly insulated.

Dell's answer to the MacBook Air?

[rainer_d]

It keeps you awake in those meetings that seem to take *forever*.
Just keep in touch with your Dell laptop.

Were they having a fire sale?

[englishb]

I guess you could say that the folks who bought these laptops got a shockingly good deal.

Dell's response...

[d474]

"We deny all charges."

Technically it's bad design...

[Animaether]

...after all, no part of the casing *should* be making contact with the electrical parts at all. The whole thing with making the casing grounded is for the unfortunate event that it does; typically as the result of some manner of physical malfunction within (e.g. a wire coming loose).

That said - my acer laptop has a brushed aluminum finish and has the same problem *if* I don't plug it into a grounded wall outlet (as it currently isn't). It doesn't feel so much like a jolt or a tingle, however, as that the surface feels strange.. almost like it's vibrating at a high frequency; but only when touched very, very lightly.. a firm touch increases contact area and away goes that odd feel.
Surprisingly, the metallic finish (probably aluminum as well) on my USB keyboard has the same thing going on.
Again, though, if plugged into a proper outlet, the problem goes away.

It seems fairly common for the housings of low-power (and yes, a laptop is pretty much low power; although a 'jolt' sounds light it might be otherwise.. high performance gaming laptop sucking 150W+ perhaps?) to not be properly insulated, though.. I can probably walk around the house and find a dozen more appliances that exhibit this.

Re:Technically it's bad design...

[pz]

It doesn't feel so much like a jolt or a tingle, however, as that the surface feels strange.. almost like it's vibrating at a high frequency; but only when touched very, very lightly

Run do not walk away from any situation where this is true. The casing you are touching is not at ground, and you are feeling the 50 or 60 Hz current (that's the high frequency vibration you're feeling) flowing through you. Don't believe me? Next time you experience this, put an AC voltmeter between the pseudo-vibrating chassis and ground. You'll see between 6 and 20 VAC (at least that's the range I've observed). This is the mains current leaking onto the chassis.

There are many reasons for this, but they almost all boil down to poor design of the equipment or inexpert wiring of the mains outlet. Often the fix is to unplug the two-pronged plug and re-plug it in the other way around. This isn't always possible with polarized plugs (which were *supposed* to make this not nearly as much of an issue, but then, that relies upon all outlets being wired correctly and my experience is that only about 80% of them are).

Do not ignore this when you find it. It is a potential danger. If you're in a country where they use 220/240 VAC, it is of particular concern.

Re:Technically it's bad design...

[Skapare]

If you are only getting less than 30 volts between the metal case and a true ground, then it is capacitively coupled to the mains hot wire, or capacitively coupled to the transformer primary. If it were fully connected you would get the full line voltage, 100 to 240 volts depending on where you are. The later is extremely dangerous and could result is big electrical arcs and human corpses. The former is very annoying but not an emergency.

No computer should ever be designed to be operated without the earthing wire used to connect to the case to drain off the capacitively coupled voltage. This big reason, though, is not to eliminate that vibration feeling, but rather, to provide a safety path for electricity to go back to ground should a wire break or whatever and accidentally fully charge the case. That would be a quick short circuit and should throw off the circuit breaker.

If the source of the voltage on the case happens to be capacitive coupling in the transformer primary winding, and if the power is plugged into a 240 volt outlet in the USA (which normally uses 120 volts for most things), then you are likely to not get any vibration feeling at all. This is because 240 volts in the USA comes from a pair of 120 volt wires of opposite phasing. The balance between them is effectively 0 volts relative to ground. Power connections this way (both wires are equal but opposite voltage relative to ground) can also eliminate hum from audio equipment that might have that issue.

In any case, if you get a computer with no earthing pin on its AC mains power connection, you should insist that it be replaced (at least the AC adapter part) with one that has the proper connection to earth/ground.

The 3rd pin isnt much different from the neutral

[Tmack]

Since the "neutral" line is actually ground as well (it ties to the grounding bar at your breaker panel), the "Ground" wire itself is really just an extra protection in case one of the wires goes bad or electricity flows to where it shouldnt. This case of electrical shocks (pun not intended)is due to improper grounding in the power supply brick of the power going from it to the laptop itself, and of the laptop's case against the innards of the machine. If it were just the lack of a 3rd pin on the power brick, then why does my macbook (and why did my powerbook before that) never shock me (both have a 2prong only plug, or 3prong cord, never been shocked with either in use)? It is simply a poor electrical design. And the "tingly" feeling is most likely AC current (dc would just lock your muscles, AC makes you twitch), rather than simple static buildup, meaning the circuits are actually leaking AC current from somewhere to the case, which should never happen since the power brick should only be sending DC to the laptop.

tm

3 things

[sayfawa]

1) It seems as if it's UK only. American ones come with the ground prong on the plug

2) People who complain are getting new plugs with the ground prong and the problem goes away (not that they should have to complain).

3) On the forums linked to in TFA there's a response from "a Dell guy":
To the tingle, you are absolutely correct, it's a grounding thing. Dell product design went from a 3 prong grounded plug at the outlet to a 2 prong "floating ground". The tingle you get is your body feeling the circuit. If you wish to eliminate that sensation, use the system on a solid surface such as a table or put something between the bottom of the system and you that's thicker than typical blue jean or khaki material. If you're more concerned than that the 2 prong adapter can be replaced with a 3 which eliminates it. As full assurance, the voltage you feel is decidely not harmful and there's no risk of electric shock.

Whaa? Even if it's true that it's not dangerous, who the hell wants current running through them all the time? That tingling feeling isn't very pleasant. I know, I've had it from other appliances (and from sticking my tongue on batteries).

Re:3 things

[moosesocks]

1) It seems as if it's UK only. American ones come with the ground prong on the plug

Not possible. A UK socket physically *requires* that a ground pin be present. The ground pin is a bit longer than the live/neutral pins, and is used to open a "shutter" blocking the live/neutral holes when the plug is inserted. When the longer ground pin is inserted, the shutter opens, allowing the plug to be fully inserted.

As an additional safety precaution, every plug is also fitted with a 13A fuse, and all domestic circuits fitted with the connector described above are *explicitly* rated to operate at up to 13 amps. (Additionally every single wall socket also has an individual on/off switch)

The UK/Ireland wiring standard is arguably the safest in the world, and makes the North American NEMA standard seem primitive and dangerous by comparison, as outlets are not shuttered, circuits do not have an explicit amperage rating, and no ground pin is required.

(There's also an older 15A British standard that's still used in some former British colonies and dimmable theatre installations that lacks the fuse and shutter mechanism, and is electrically compatible with the "new" standard with the use of an adapter, despite lacking the newer standard's safety features)

Mind you, the ground pin doesn't actually have to be connected to anything, nor would one expect it to on a laptop, considering that no grounding is possible when the laptop's running off of battery power, nor should AC power ever even enter the laptop's chassis.

Sounds like either Dell screwed up the design, or CNet installed carpeting in their UK office.

This could be...

[Paranatural]

The engineers giving in to the Helpdesk people.

Think of the possibilities!

Tech: Ok, put your mouse over the 'My computer' Icon and right click...
Guy: Why does this have to be so complicated? Why doesn't everything just work right the first time? You Idiots should be shot!
Tech: Well Sir, if you would just...
Guy: I'm tired of you people and your attitudes, why I should...*ZAP* AHHH! WHAT THE HELL WAS THAT?
Tech: Now what did you learn?
Guy: I'M GONNA KILL...*ZAAP* AHHH!
Tech: A bit slow today are we?

Simple fix. (With disclaimer)

[Tavor]

Cut open an unplugged three prog extension cord, exposing the three wires inside.
Cut open Dell power cord, exposing the two wires inside.
Position pieces of heat-shrink tube over the stripped inner wires to be joined.
Connect positive extension cord wire to positive laptop wire and solder.
Connect neg. wire to neg. wire and solder.
Connect the third ground wire to the exterior casing of the laptop with tape as to be removable.
Cover over the sealed three wires with heat shrink or electrical tape for asthetics.

Disclaimer: I'm assuming everyone here knows what they are doing. Mains power can be very hazardous and very deadly. Do NOT attempt this if you are unsure of what you are doing -- call someone more experienced if in doubt. But for those of you who know what you are doing, this should be an easy fix to avoid the shock of you being used for a ground wire.

Re:Simple fix. (With disclaimer)

[Dachannien]

You can also follow this procedure for getting the mains back online:

Enter glass-walled reactor room
Remove shiny tube cover
Hold hands over open end of tube in mysterious fashion while leaning over tube, ensuring maximum irradiation
Replace cover, waddle over to locked door, collapse
Die in dramatic fashion while taking a subtle parting shot at your best friend for his lack of manual dexterity

Optionally, you might consider transferring your katra to someone else beforehand, especially if you've been thinking about directing and would like a shot at it in your next movie.

Re:How the hell did they get it UL listed??

[milsoRgen]

I remember years back watching a Dateline or some such nonsense on UL. Long story short... They are not worth the ink used to print their logo. Just a case of too much to do and too little time. This could of changed by now. But I really put no stock into UL certification.

WRONG!

[seanadams.com]

Neutral is neutral and ground is ground. The fact that they are connected to each other at the service entrance does NOT mean that neutral can be used as a ground reference.

From the device's perspective, neutral must be treated as AC line input, never ever ever as a ground.

Any number of wiring faults could cause the neutral to become hot, and even under normal circumstances it is common to see some potential on neutral relative to ground, because loads on the branch circuit are pulling it towards one phase or the other.

That's different

[EmbeddedJanitor]

Static discharge (what you're experiencing here) is worse if the computer case is earthed because this provides a better path. For this reason those "earthing straps" etc used to protect sensitive equipment should be connected through a high resistance (1 M ohms or so) to limit the discharge current.

Re:Earthed?

[anonymous_echidna]

In Australia we use the terms "earth", "active" and "neutral", coloured respectively green, red and black.
There is no need to be *shocked* that other conventions exist. "Earthed" is not wrong, it's not slang, it's just not standard in the US.

Re:The 3rd pin isnt much different from the neutra

[nbritton]

The "neutral" is connected to the center tap on the transformer in split phase systems. The ground (green) wire has to be connected to the neutral bus or it would be point less (no return path).

* In sub panels the neutral and ground should never be connected (ground loop)!
* The neutral wire has the same amount of energy running through it as the black wire!
* A GFCI outlet will save you from your shitty Dell. Install them!

http://en.wikipedia.org/wiki/Split_phase

Re:Earthed?

[geekoid]

earthed was more commonly used in the US 30+ years ago. Mostly people say grounded.

Since my initial electronic instruction in the 70s was from my grandfather, I will often use the term 'earthed'.

Re:Any electricians in the house? Bad wiring!

[Ignis Flatus]

no, but IAA electrical engineer. it shouldn't matter if ground is missing, 110V vs 220V, or if hot and neutral are swapped. if you are getting shocked from your laptop, it's either bad design, a manufacturing defect, or some other part failure. these people are probably feeling a static charge that has built up on the metal case parts. if there's mains voltage on the case, then you should be able to measure it with a meter.

if there were an actual short to the plate, i'd look somewhere non-obvious. like maybe an inverter used to step up voltage for the display. (and no, i do not have any specific knowledge of the voltages used on modern displays)

You've not tried hard enough - try in the bathtub

[name_already_taken]

Had my Macbook pro for months now and never one gotten a shock.

I too have a Macbook Pro, and I have felt the tingly sensation of voltage alternating at 60Hz on the outer case. The reason you didn't feel it was that you, yourself, were not grounded and so you didn't complete the circuit. You have to be grounded to the earth ground or the neutral conductor to notice the voltage.

It is common to ground the outer case of electronic devices to the ground of the electronics - that way static discharges to the case don't end up going into expensive semiconductors. Normally this ground connection is not an issue; however, leakage currents can make their way through the power adapter and can apply an AC bias to the "ground" voltage on the DC side of the power supply - so effectively what should be 0VDC actually is floating around 60-70VAC. Because it's a leakage current through the very high resistance between the AC side and the DC side of the power adapter, there usually is very little current (a few microamps) available, so if you complete the circuit to ground via your body, you'll usually only feel a tingle at most. It's really not anything to worry about - more of a curiosity than anything else.

Taking this to a little more of an extreme... back when I was a teenager, my room had a concrete floor with linoleum flooring on it, and I had a 1960s-era Hickok vacuum tube tester with a metal front panel and an unpolarized plug. I was sitting on the floor one day testing vacuum tubes, as teenagers are apt to do, and I noticed that whenever I touched the front panel I felt a strong buzzing sensation in my hand. I unplugged the tube tester, and plugged it back in with the plug rotated 180 degrees and the AC voltage on the front panel was gone. I cut the antique power cord off the next day and installed a grounded plug and power cord.

Re:Earthed?

[El_Isma]

In Spanish we say that a device has "tierra" (direct translation: "earth").

Re:Wow!

[Anonymous Coward]

You could just go for http://www.erostek.com/ ;)

Re:I call bullshit

[Knara]

Hey, fanboy. Stop your drooling for a few seconds and re-read that he said it happens with MacBooks. Not *all* Mac Books. It doesn't happen with *all* individual machines in that Dell (or Toshiba, etc) line, either.

There's nothing magical about the components in an Apple laptop (probably using almost the same damn parts) that makes grounding and electricity work differently.

Re:earthed?

[aXis100]

I'm in Australia and we use the term "Earth" interchangably with "Ground", with a preference for "Earth".

On a similar note, alot of people are questioning the use of "Mains". In Australa it referes to the main utility supply - eg the 240V wall socket.

Two Cultures Divided by a Common Language

[John Hasler]

"earthed" is British for "grounded".

Re:Defective design

[Anonymous Coward]

Why, yes, you're clearly not using UL certified forks.

Taser International's stock price plummets.

[^avenger]

"Don't Dell me, Bro !!"

Once when I was nine...

[The Underwriter]

...I had the bright idea of touching a 9 volt battery to my *braces*.

I couldn't tell if the bright white flash/pop that followed came from just in front of my face, or from somewhere inside my head. Painful to say the least.

Can someone explain what happened?

Re:Once when I was nine...

[tic!lock]

  Yeah, you discharged the battery across your metal braces.

  You're lucky the braces didn't heat up enough to burn you or crack a tooth open, and that the battery didn't explode. ;)

tic

Re:Once when I was nine...

[TexNex]

...that was your brain on electrons...any questions?

Re:Once when I was nine...

[TheLink]

You failed as a Darwin Award contender.

Sony batter or two and you would have been in the running, or at least an honorable mention.

Perspective from Dell

[Lionel_Menchaca]

Last year, I posted detailed information on the tingling sensation sometimes associated with leakage current http://direct2dell.com/one2one/archive/2007/04/24/8522.aspx. Since the story, I re-visited the issue with members of our Engineering team. Here's what they had to say: Even though the leakage current is extremely low and well within safety limits, it is perceptible by some people. This perception may be experienced as a mild "tingling" effect. However, if that "tingling" effect is coupled with an electrostatic discharge, such as is experienced when walking on carpet in dry conditions, the total effect can be surprising but not harmful. The primary effect being felt is from the electrostatic discharge (static electricity). Typically the tingling sensation can be eliminated with a three-prong adapter, however a three prong grounded AC adapter will not eliminate the electrostatic discharge. The tingle is not harmful to the users or the system components. Again, more details about the tingle sensation are available here. http://direct2dell.com/one2one/archive/2007/04/24/8522.aspx

Cuba and non-grounded 220v...

[PhotoGuy]

Reminds me of a trip to Cuba last year. The power in the rooms was 220v, with no ground plug. Many consumer electronics, including my wonderful little Toshiba Libretto (now *that's* a sub-notebook, Apple) work fine on 220, the switching power supply just regulates it properly.

However, I had to bend the ground pin out of the way to plug it in. Things charged and worked fine. However, apparently the brushed aluminum case wasn't quite at true ground with this arrangement. It was more than tingly (if your feet were on the ground; if you lifted them, it was fine). I made a point of only using the power supply to charge it, then use it on battery power, for safety's sake.

It was interesting to see the cavalier attitude towards electricity down there. A worker was doing some construction with an electric drill outside our room; the drill obviously only took 120v, as he hooked up a transformer in our *bathroom* (which was near the door) to power his drill. It was connected to the plug with wires jammed into the outlet, and to the drill by wires wrapped around the prongs. Scary stuff. We stayed clear of our room that day. :) Check out the photos.

Re:You've not tried hard enough - try in the batht

[Bluesman]

I was sitting on the floor one day testing vacuum tubes, as teenagers are apt to do

Ah yes, gone are the carefree and reckless days of youth.

Re:Earthed?

[zsau]

Actually, earth is green with a yellow line through it. It was changed years and years ago (before I was born, even) so that colorblind people can see it better. Imported from the European standard, I believe. This is what I was taught during high school years ago, but I'm no electrician.

MOD PARENT UP

[DMUTPeregrine]

He's correct. It's a safety issue.
Also, prolonged contact with (nearly) ANY electrical current that you can feel can become dangerous. While a low voltage won't be able to pass much current through the skin (skin resistance) initially, this situation will change. As voltage flows skin resistance slowly decreases, and can lead to fatal currents if allowed to persist for long enough.

Effects of current through the human body (rough):
0.2 amp - no fibrillation. Severe burning and breathing halted.

0.1 - 0.2 amp is the most dangerous zone, because fibrillation is a faster death and harder to stop than a mere stoppage of the heart as occurs above 0.2 amp.
Skin resistance is about 1kohm for wet skin and 500kohm for dry skin. Internal resistance is 100-500 ohms, so current penetrating the skin is what causes problems. Higher voltages let more current through, so above 240V current easily penetrates the skin. If you touch a wire of 0.02 amps or so your muscles will contract, forcing you to hold onto the wire. Since skin resistance drops over time you will soon find it difficult to breathe and eventually you WILL die.

If you find someone stuck to a wire in this manner, the person WILL die if they are not removed. Do not attempt to touch them uninsulated, since you will likely become stuck yourself. Turn power off, or push them off with a stick or other non-conductive object.

Re:MOD PARENT UP

[p0tat03]

Furthermore, if you ABSOLUTELY must touch something with your bare hand without insulation that you suspect may be electrified, DO IT with the BACK of your hand. This way should your muscles contract, at least you won't have made a death grip on the wire.

That being said... Just don't touch stuff you think is electrified.