
My Laptop Bit Me – The Shocking Truth (2012) - tomduncalf
http://enclydion.blogspot.com/2012/04/my-laptop-bit-me-shocking-truth.html
======
CalChris
This happened to me in around 2005. I was constantly getting shocked when I
opened my MacBook. So I took it the Apple store in Berkeley and they
harrumphed and said it was within spec. Still getting shocked. So I took a
multimeter and measured the current and showed _that_ to them. They harrumphed
again and said that service would look at it and probably wouldn't fix it. But
they fixed it.

~~~
vertline3
Yeah their "genius bar" left a lot to be desired, I switched away for that
reason. At first they were great, but over the years the one I went to just
stopped really trying and instead shifted more to sales.

~~~
dontbenebby
I hate that there is no literal "genius bar" anymore - now you have to fight
for table space like it's a SoMa coffee shop.

~~~
crooked-v
Every Apple store I've been to in the last five years seem to have been
designed for half the number of occupants they actually have.

~~~
saagarjha
I mean, it's not surprising why: they were likely designed before Apple was as
popular as it is today.

------
mjlee
I've noticed that even with an earthed power supply I still have the problem
with the newer USB-C MacBooks. I find it rather uncomfortable on my wrists.

A MacBook I had quite a few years ago had a cracked chassis - touching that
when using a non-earthed power supply was enough to be a little bit painful.

~~~
krisrm
Mildly off-topic: is "earthed" a European-ism? I've only ever heard "grounded"
until reading through this article and thread.

~~~
Sujan
Maybe also a translation thing, in German "grounding" is translated to "erden"
which means "putting into or connecting to the ground", but "Erde" is also the
substantive meaning "earth".

~~~
gowld
Words take on a range of meaning. "ground" and "earth" have overlapping
meanings.

~~~
iforgotpassword
Sure. In English though it's fine to refer to e.g. the street as "ground",
like when you drop your ice cream outside. In German, "Grund" would be
something like the ground of a lake, your ice cream would drop on the "Erde".
So they have the same meaning but in the overlapping area English is biased
towards ground and German towards earth. Or something like that.

------
bcaa7f3a8bbc
The real question is, if the common wisdom is to ground the chassis when
possible, and even the induced voltage on the chassis is harmless, they are
seen as a widely recognized annoyance. So, my _(Question 1) then why does the
hardware designers keep using ungrounded design in the first place_? Just
because they think the output through a isolated transformer is safe enough
(also can meet safety regulations), so they want to then omitting the
Protective Earthing to simply make the power supply smaller and they think
it's okay to give the users some small shocks? Or it's something else?

And here's another question I don't understand. When a piece of electronics
don't have a Protective Grounding connection, the common explanation is: the
low voltage is created by a SMPS, and an isolation transformer at the output
side of the SMPS makes the voltage no longer being Earth-referenced, so in the
worst possibly scenario, if a grounded person touches the "hot" output wire,
nothing would happen. But if you ground the chassis to the Protective Ground
(often the ground of the PCB is connected to the chassis), the output becomes
Earth-referenced again and loses the protection of isolation. This is why an
isolation transformer has a unconnected Protective Ground at its output side,
and many SMPS-based appliances don't use the Protective Ground.

So my _Question 2_ , according to the common wisdom and many regulations, most
appliances should be grounded, but from the principle of isolated power
supply, it should not be grounded. And in real life, we clearly see lots of
laptops use DC power supply without the ground connector, and others with the
ground connector. And to further complicated the issue, some DC power supplies
only use the ground internally for the EMI filter circuity and/or its own
enclosure, but the DC output itself is isolated and is not ground referenced.
Then how can an isolated power supply with the ground plug help stopping the
induced voltage on a laptop's enclosure, if the output is isolated? Something
related to the leakage current of the X/Y capacitors? It seems there's lots of
inconsistency here. Just why?

~~~
gumby
> So, my (Question 1) then why does the hardware designers keep using
> ungrounded design in the first place?

Ungrounded sockets are still very common (just off the top of my head, in
Japan, Philippines, Australia, all through Europe, India...). Even as building
codes change it takes many decades for the housing tock to upgrade. Even when
the code requires upgrades to commercial buildings it rarely will of
residential.

If the leakage is harmless (or "harmless) why risk the user buying a product,
getting home, and then being unable to use it. The OOBE is terrible and
possibly fatal.

This is also why the "international travel kit" for Apple power supplies
contains non-grounded plugs.

The authors final and correct point about Apple is fortunately now obsolete as
since it was written Apple has switched to standard Type C connectors. On the
other hand they no longer ship grounded connectors by default (in the USA at
least).

~~~
fzzzy
They do ship grounded connectors still, but it is underneath the molded
plastic piece at the bottom of the box which is hard to get out.

~~~
thomas-st
That's a false rumor. [https://forums.macrumors.com/threads/macbook-
pro-16-17-comes...](https://forums.macrumors.com/threads/macbook-
pro-16-17-comes-with-extension-cable-in-a-hidden-compartent.2097081/)

~~~
fzzzy
Hmm. Thanks!

------
katsura
I have the same problem with my Asus Vivobook. It has aluminimum body, and
sometimes can be quite uncomfortable on my wrists as I get the constant
buzzing feeling. I've been wondering if I could just buy a plastic skin that
would protect me, because where I live, I can't really change the plugs.

~~~
adrianN
A coat of lacquer should do it?

~~~
taneq
Or a properly earthed power supply, maybe?

~~~
adrianN
> because where I live, I can't really change the plugs.

~~~
taneq
In most of the world "changing the plugs" isn't really a thing, the problem is
the design of the power supply (hence my comment.)

To clarify: Floating switchmode power supplies that aren't isolated from a
separately earthed conductive shell are a bad thing.

------
gnode
It's not just an issue for humans. I often have the problem that touching my
single board computer (ODROID-UX4) or plugging another mains powered device
into it like a screen zaps it and causes it to fault and reset.

I wonder if this is because it has a Chinese wall wort power supply with a UK
adapter. Particularly, the Chinese two prong plug is symmetrical and fits the
UK adapter in two orientations, so live and neutral are not differentiated.

~~~
NullPrefix
>Chinese wall wort power supply

What did you expect?

------
mindslight
Does this ever get bad enough to feel without touching something else to
directly complete the circuit?

I would predictably get this when using laptop (on lap) and resting my arm on
a metal heater next to me. I ended up returning a few AC adapters because the
leakage was too damn high, and eventually they offered me a three prong
version that came with many more regulatory marks.

The problem with two prong devices is that a designer has to assume either
wire could be hot, because it could be plugged in backwards. I've got to
wonder if a change in the regulations that would allow for a single cap to the
probable neutral could solve this. It would double the leakage current if the
thing were actually plugged in backwards, but as long as it was just more
uncomfortable rather than dangerous this would be a win.

Also there are a few handwavey things at the bottom of the post that just
leave me scratching my head:

> _Even though the MagSafe power supply itself is not connected to the mains
> earth, there is just enough inductance leakage for the floating charge to
> dissipate through the plastic sheath of the mains cable._

There could be something to what is being said, but if there is he's not
describing it well.

> _It 's worth noting that the fuzzy-electronics effect can be felt if you use
> an earthed power point but the power point's Active and Neutral are wired
> back to front_

That's an odd diagnosis, because three prong means the output is being
directly grounded. Instead, I would infer that the ground (EGC) was
disconnected (like say an old home where someone improperly changed two prong
to three prong outlets when remodeling).

------
thedanbob
I felt this effect for the first time when I was living in Israel for a few
months. I couldn't rest my wrists on my MBA while it was plugged in because of
how painful it was. People said the power was "dirtier" over there than in the
US (lots of voltage spikes? rougher waveform? not sure) so maybe that made it
worse.

~~~
jseutter
Assuming you're coming from North America, I found across Europe when my
laptop was plugged into 240V I would get this, while 120V in North America was
fine. It would also vary depending on the power draw - when the battery was
recharging it would be worse (I think).

I ended up unplugging and running off battery as much as possible, and
eventually buying a smallish bluetooth keyboard and mouse to take on trips.

------
wongarsu
> It's worth noting that the fuzzy-electronics effect can be felt if you use
> an earthed power point but the power point's Active and Neutral are wired
> back to front.

That's an interesting issue, since in continential Europe (and a lot of the
rest of the world) the plugs are symmetrical and don't distuingish between
active and neutral. I guess if this happens to me with a three-pronged plug I
should try flipping it.

~~~
dsfyu404ed
>That's an interesting issue, since in continential Europe (and a lot of the
rest of the world) the plugs are symmetrical and don't distinguish between
active and neutral.

It really doesn't matter much with A/C since the voltage is always flip
flopping. You're basically a bird on a wire at all times but that wire is the
earth itself. I can't think of any situation where a properly manufactured
device would care which contact is neutral and which one is power. Ground is
(in theory) always separate from neutral on the device (it should go without
saying that it's separate from the line otherwise you have a short to ground).
Plugs in the US used to be symmetrical too.

Edit: Since apparently I'm Wrong(TM) does anyone want to tell me why?

~~~
gowld
(1) Your advice could kill people, and (2) it's not reasonable to claim that
decades of expensive electrical mains and appliance design&manufacturing was
done for no benefit.

The ground wire connects to non-electrified portion of the device, as a
protection against accidental electrification.

Neutral closes the mains circuit _also_ is grounded, protecting the
electrified portion against accidental activation.

[https://en.wikipedia.org/wiki/Ground_and_neutral](https://en.wikipedia.org/wiki/Ground_and_neutral)

That article also has a section about how mechanized-farm cow milk production
is harmed by the issue discussed in the OP

~~~
dsfyu404ed
Of course you don't want to use the ground as your neutral. In normal wiring
it's not designed to do that job so it sucks at it. I'm talking about the
polarity of the line and the load as it relates to the device being powered.
Your comment seems like a complete and total non-sequitur to that. I'm talking
about a directional plug here.

> Your advice could kill people,

I am not giving any advice. I'm saying that unless you're doing something
complex involving the neutral and ground no technical reason the neutral and
the hot contacts on any given device are not interchangeable because the
electrons are going both directions anyway.

> it's not reasonable to claim that decades of expensive electrical mains and
> appliance design&manufacturing was done for no benefit.

You can still get devices in 2019 that are not grounded (common) and do not
have a directional plug (rare).

>Neutral closes the mains circuit also is grounded, protecting the electrified
portion against accidental activation.

How is this related to what I said? Yes neutral and ground are both "grounded
to the ground" at some point (usually the panel) but the device being plugged
in doesn't know the difference between the neutral and the live wire because
its getting its electrons from both (because AC).

~~~
pgeorgi
> and do not have a directional plug (rare).

[https://upload.wikimedia.org/wikipedia/commons/thumb/5/50/Sc...](https://upload.wikimedia.org/wikipedia/commons/thumb/5/50/Schuko_%28CEE_7-3%29_socket-
outlets%2C_with_and_without_shutters.jpg/800px-Schuko_%28CEE_7-3%29_socket-
outlets%2C_with_and_without_shutters.jpg)

What would a directional plug for this socket look like?

~~~
dsfyu404ed
I don't know. A non-directional/non-polarized plug would just omit the
features that engage the key-ways on the side enabling you to plug it in
whichever way you want. If you want to make it directional/polarized just
engage the key-ways so the user can only plug it in one way.

In North America we have these[1] for things that don't have a metal case and
on cheaper devices both blades are often the same size allowing you to plug it
into an outlet whichever way you want.

[1][https://cdn.sparkfun.com/assets/5/1/0/d/c/51154c1cce395f903d...](https://cdn.sparkfun.com/assets/5/1/0/d/c/51154c1cce395f903d000001.jpg)

~~~
wongarsu
What parent is getting at is that Socket Type F "Schuko", one of the most
popular socket types, is completely symmetrical and inherently non-polarized.
Since any plug compatible with Schuko is non-directional calling non-
directional plugs rare is factually wrong (if we talk globally). It also
proves your point that the difference between life and neutral largely doesn't
matter, since in about half the world wall sockets don't care about the
difference.

------
nonfamous
I wonder is this is related to an issue with my Surface Book: when it’s
plugged in to some (but not many) power outlets, the trackpad becomes unusable
(the cursor skips all over the screen when you touch it). I’ve noticed it in a
couple of hotels, and unplugging it and using battery eliminates the problem.
I wonder if it’s related to this surface (pun not intended) charge caused by
bad grounding?

------
elektriker99
Are there alternative solutions to this problem, that are not interesting for
industry, but feasible for hackers?

E.g.: remove those two capacitors that bridge the primary and secondary sides
of the power supply. Tingle is now gone, but the supply is now emitting a lot
of EMF noise. How about arresting that with some bulky ol' ferrite cores?

------
julianlam
That's quite interesting! I always wondered why there was a "tingliness" when
I ran my fingers lightly over the top of my laptop when it was plugged in,
good to know.

It is a little concerning that this was with my Asus Zenbook, which comes with
a 3-prong power adapter...!

~~~
andrelaszlo
Are your outlets properly grounded?

------
abledon
Electric exposure is such a new phenomenon in terms of human evolution...
like, humans have had their hands on small charged devices for like less than
100 years.

I wonder if an overweight person feels less of the electricity since they have
more fat shielding their nervous system?

~~~
fpgaminer
We've been exposed to static electricity through all of our history.

~~~
abledon
i think a hand rubbing against a wool sweater making a little shock is
different than having a laptop over my nuts for 10 hours a day!

------
cmsj
I've had this on lots of laptops, but the worst was a thinkpad, whose only
exposed metal was a little fingerprint reader that lined up perfectly with the
softest, most sensitive skin of my wrist. I hated the little shocks from that
thing.

~~~
pflanze
I had the same experience with a T61 I owned, and used to just tape a bit of
plastic foil over the reader (I wasn't using it).

------
blunte
I never felt a buzz through my laptops when I lived in the US, but I feel it
fairly often in Netherlands.

What is really strange is that occasionally I could feel the buzz while gently
moving my fingertips across my girlfriend's shoulder while in bed. It was not
an imagined sensation - it was exactly like with the laptop. We were on a
waterbed, but I don't think that could have anything to do with it. The laptop
mystery is solved, but this one is still a curious mystery.

------
samdung
I had (still have lying around) a Toshiba Portege purchased way back in 2012.
It had quite sharp edges that gave out a shock whenever my elbows grazed them.
The shock was mild but very discomforting and made me very conscious when
using the laptop. Over time i discovered that using a 3 pin plug avoided the
shock. In 2015 i switched to a macbook pro which also has this issue. Thanks
to this article i know whats happening.

------
jlokier
I've felt that uncomfortable tingling and occasional shocks on a number of
laptops, be they metal chassis (Macbook) or plastic. Some friends report being
zapped by their Macbooks.

The weirdest for me was my first laptop. I kept getting shocks from the palm
rest, even though it was all plastic and presumably a good insulator.

I didn't understand how a shock could reach me through solid plastic.

------
IshKebab
> It's current that kills, not volts.

I wish people wouldn't say that, it's a complete mischaracterisation of how
voltage and current work.

~~~
LeonM
When it comes to lethality, time is also an important factor. A very short
burst of high current is not lethal.

So if you really want to be correct, it's electrical charge that kills.

edit: typo

~~~
magduf
No, this isn't true either. The way that most people die of electrocution is
from heart fibrillation, not from having their arms blown off by extreme
voltage and current levels. It doesn't take much current to cause your heart
to fibrillate; only about 100mA across your heart. So getting a shock that
conducts that much current through your foot or hand probably won't hurt you,
but getting a shock that conducts that current across your heart can. In
short, it's more complicated than anything being said here.

~~~
MrBuddyCasino
Even if the heart muscle doesn't kill you, you can still die from the chemical
imbalance caused by subjecting to your whole body to electrolysis. So if you
got shocked, visit a hospital immediately! You can still die hours later.

~~~
magduf
Citation needed. We were taught about electrical safety and its effect on the
human body in college EE classes, and there was nothing said of this.

~~~
MrBuddyCasino
Fair enough. I've read in an interview of a hospital staff doctor, not sure if
I can dig up the source.

Edit: so the way this works if current is flowing through your body your blood
is undergoing electrolysis, and as a consequence your Kalium balance can get
disturbed. This can result in severe heart rythm issues, even hours after the
shock. A doctor can test this and fix it with an infusion.

Not my original source, but says the same. Should be understandable with
Google Translate: [https://derstandard.at/1343744823640/Wenn-scheinbar-
harmlose...](https://derstandard.at/1343744823640/Wenn-scheinbar-harmlose-
Stromschlaege-das-Leben-gefaehrden)

------
maxxxxx
When I took my MacBook to France I noticed this too. It was enough to make me
really nervous. Never noticed the tingly feeling in the US.

------
gambiting
So that's why I always have this tingly feeling under my fingertips whenever I
use my macbook! I always wondered what that was.

------
floatingatoll
Note that using an Apple laptop charger with its included three-prong charger
cord will provide a grounded charge (no buzz), as opposed to Apple’s or any
two-prong connector (or a third-party three-prong that’s missing the female
grounding connector inside the charger-side plug).

------
mrguyorama
I have experienced this in a very weird but completely reproducible manner. My
Logitech G27 steering wheel has a power plug to run the force feedback system.
If you connect the peripheral to power but not to the computer, touching the
metal pedals causes strong burning sensations.

------
VibrantClarity
I had an old Acer laptop, the C710 i think, where the touchpad would only work
if you grounded it. Only the whole chassis was plastic so you could only
operate it with one hand because the other had to touching the little band of
metal around the VGA port.

------
okmokmz
When my old macbook air is plugged in I can feel the electricity in my palms
resting on the aluminum while typing. It was kind of like those old prank
shock pens, but less intense

------
dmitrygr
The description of how SMPS works in thei article is _shockingly_ inaccurate!

    
    
      > To simplify, an SMPS essentially
      > takes the AC input and turns it on
      > and off very quickly (between 10,000
      > and 20,000 times per second), with
      > the output voltage being determined
      > by the duty cycle - the amount of
      > time it is on for each flipflop. The
      > shorter it is on, the lower the
      > voltage. This is fed into regulators
      > and capacitors to produce a stable
      > AC voltage, which is then converted
      > into DC.
    

Literally no part of that is accurate. SMPSs generally rectify first,then PWM,
then smooth

~~~
Animats
Right. But not the real issue. See [1][2]. Most switching power supplies have
a small capacitor between the AC line and output sides of the transformer, to
provide a somewhat tenuous path to ground for RF noise on the output side.
That's a fundamentally bad idea, but cheap. Better approaches involve either a
real ground, with a 3-prong plug, or some new designs which handle RF noise in
a way that doesn't need a path to ground.[3] Here's a patent (in Chinese) for
a solution without a bypass capacitor.[4]

[1] [https://i.stack.imgur.com/fV15S.png](https://i.stack.imgur.com/fV15S.png)
[2]
[https://electronics.stackexchange.com/questions/216959/what-...](https://electronics.stackexchange.com/questions/216959/what-
does-the-y-capacitor-in-a-smps-do) [3]
[https://ieeexplore.ieee.org/document/7488992](https://ieeexplore.ieee.org/document/7488992)
[4]
[https://patents.google.com/patent/CN202818110U/en](https://patents.google.com/patent/CN202818110U/en)

------
menacingly
I thought this would be about how an XPS 13 will literally bite you with its
hinge. I got a few blisters having my finger in the wrong place when I open
the lid.

------
stordoff
I've noticed this a few times - it's usually what e when a stray Lightning/USB
cable is touching another part of my body.

------
jayalpha
I had this with a Dell XPS in India but it was connected somehow to the power
supply. Maybe some voltage crept to the ground wire. Dunno.

------
teekert
I already noticed that I didn't have this with an earthed (grounded) wall
socket, very nice to finally see the explanation!

------
mcguire
VGA external monitors were also susceptible to this, resulting in a wavy
interference pattern.

------
earthboundkid
2012.

~~~
idlewords
The unchanging laws of electricity still make this article...

...current

~~~
dhimes
This isn't about the laws of electricity but about how the power supply is
designed. I was surprised recently when my Mac-using colleague needed a three-
pronged extension cord. I don't carry those around in my backpack because
everything _I_ need is two-pronged. I thought it was silly that Apple would
force this on their users. With a regular transformer/diode bridge/capacitor
power supply this isn't needed.

The traditional use of a ground-plug in these situations is to protected the
user against electric shock should "hot" a wire get loose and touch the metal
case. But when the voltage is dropped to non-lethal amounts (or if you have a
plastic case) this is unnecessary. In fact, most "third wires" don't even make
it to the device- they terminate in the transformer box. So the Mac plug was
truly a bit perplexing.

But now I know why.

