New Dell Laptops Give Users a Literal Shock 383
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.'"
Happens on Apples Too. (Score:5, Informative)
PowerBooks have had this for a while.... (Score:5, Informative)
I believe the MacBook Pros also suffer from this however I haven't tested this.
My Insipiron 1720 Shocks me sometimes (Score:1, Informative)
Another shocking aspect is how well it runs linux! Everything worked
xps m1330 owner here (Score:5, Informative)
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?
two in the junk, one in the trunk (Score:5, Informative)
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.
3 things (Score:4, Informative)
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:xps m1330 owner here (Score:5, Informative)
WRONG! (Score:5, Informative)
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 (Score:3, Informative)
Re:PowerBooks have had this for a while.... (Score:5, Informative)
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:Earthed? (Score:5, Informative)
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:Forget exploding batteries, (Score:2, Informative)
Re:xps m1330 owner here (Score:5, Informative)
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:The 3rd pin isnt much different from the neutra (Score:3, Informative)
* 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 [wikipedia.org]
Re:Earthed? (Score:3, Informative)
Since my initial electronic instruction in the 70s was from my grandfather, I will often use the term 'earthed'.
Re:Forget exploding batteries, (Score:3, Informative)
Re:Any electricians in the house? Bad wiring! (Score:4, Informative)
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 (Score:3, Informative)
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? (Score:2, Informative)
Re:Wow! (Score:2, Informative)
Re:earthed? (Score:4, Informative)
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.
Re:3 things (Score:5, Informative)
Not possible. A UK socket [wikipedia.org] 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.
Two Cultures Divided by a Common Language (Score:3, Informative)
Re:Forget exploding batteries, (Score:5, Informative)
Re:PowerBooks have had this for a while.... (Score:4, Informative)
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.
Re:PowerBooks have had this for a while.... (Score:3, Informative)
Re:Technically it's bad design... (Score:1, Informative)
If you don't have a grounded system, as a stopgap measure, electricians USED to install a GFCI, since it will provide shock protection if it senses an imbalance between hot and neutral (doesn't need a ground). If you can't use a grounded outlet, consider buying a GFCI extension cord so you can still have the protection. There's a good reason why there's a ground pin!
Or, you can buy an isolation transformer. But that will probably cost too much and take too much time to find...
Perspective from Dell (Score:5, Informative)
Re:Earthed? (Score:4, Informative)
Re:Once when I was nine... (Score:3, Informative)
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:Technically it's bad design... (Score:5, Informative)
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.
MOD PARENT UP (Score:5, Informative)
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:Technically it's bad design... (Score:4, Informative)
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.
Re:Technically it's bad design... (Score:1, Informative)
Neutral has to be grounded at the panel, or in some countries, at the utility. Even if it isn't grounded anywhere (the only case I can think of is an isolating transformer fed supply, or perhaps some sort of generator that isn't grounded), it shouldn't matter, because in that case, you can't receive a shock by touching only one conductor, assuming your body is at "ground" potential (there is no circuit present, therefore no current).
However, a GFCI measures the amount of current being used on two conductors, one of which is live (phase), and the other of which is the return (neutral, or "identified"). Electrical wiring the world over is done like this, except in the case of multiphase wiring (a properly designed GFCI would still work in this case, though, but you'd probably be hard pressed to find one rated for it). Neither _has_ to be grounded, although the code states it does. If one conductor has more current than the other (indicating more current leaving the circuit than being returned, ie: another path to return current through than intended) the GFCI trips. The only way I can see a circuit with two wires allowing a GFCI not to trip is if you were to simultaneously touch both phase and neutral at the same time while jumping in the air (a decidedly unlikely practice).
So a GFCI would not trip if fed from an isolation transformer and a fault to earth occurred. Of course, this doesn't matter since no shock is possible as there is no return path. So it doesn't matter...
A caveat: On circuits that have more than one phase _and_ use a neutral will require all wires be connected to a GFCI (even if they don't, they would, but a two phase, no neutral supply [like a permanent A/C] would only have two wires anyways, plus ground). Since this makes GFCIs expensive, and since in Canada now all outlets near kitchen sinks require a GFCI (they didn't) Canada no longer has this sort of wiring. I expect this type of wiring was somewhat unique to our country, though, and it's sad to see it go, since it's more efficient than standard wiring (okay, not by much, but what the hell). For those wondering what the hell I'm talking about, kitchens plugs here were wired so in a duplex outlet (the standard) the top plug was wired to phase 1 + neutral (and ground), and the bottom plug wired to phase 1 + neutral (and ground). The neutral was shared. A GFCI would have to measure currents on all three wires and ensure that the sum phase 1 - phase 2 - neutral = 0. As you can imagine, that means more $$$ in design. Oh well...
If you don't trust me about the ground not affecting the ability of a GFCI to protect, feel free to open one up. You'll find the phase and neutral are wired internally to the GFCI circuit, while the ground is directly wired to the plug without being involved in the circuit at all. That's not to say that the GFCI invalidates the benefit of a ground, but it is to say it will work 100% as well even if there isn't one.
Re:MOD PARENT UP (Score:5, Informative)
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.