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

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.

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

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

[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.

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.

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.

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: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.

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.

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

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.

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.