What could be causing electric current on my laptop case?

In summary, an electric shock from a laptop power supply may be caused by a dirty or worn transformer, lack of grounding, or incorrect wiring. If the shock is not severe, it may be remedied by turning off the power supply and/or unplugging the cord from the wall.
  • #1
DaveC426913
Gold Member
22,432
6,106
TL;DR Summary
Just realized I'm being zapped by my laptop.
I thought there was a tiny metal burr on the corner of the lappie, and I kept scraping my forearm across it.
Then I thought I had a tiny metal shaving in my skin that I kept brushing on the corner as I typed.

Turns out, that little pinprick I'm feeling is electric current. I can only feel it on thin-skinned, areas, such as the undersides of my forearms.

It goes away when I unplug the power cord. (Of course that doesn't mean it stops, it simply means it's not strong enough for me to feel it.)

If I could find my multimeter, I could figure out the voltage and amperage and figure out if it'll kill me.
 
  • Haha
Likes etotheipi
Computer science news on Phys.org
  • #2
If you don't post for a day, we'll call 911 for you. (Just kidding.) :smile:
 
  • Haha
Likes DaveC426913
  • #3
Some laptop bricks can be pretty noisy in common mode (CM), but that's the first I've heard of anybody feeling a shock from one. Is it a name-brand power brick? Did it just start happening? How long have you had that laptop and power brick?

If you ground the laptop, does the effect go away? You can ground it by using a USB cable to some grounded USB accessory, for example
 
  • #5
As far as I know, there are no laptops in the market that are directly fed AC from the mains without an adapter. And the DC voltage should be quite low. Could it be some kind of static charge build-up?

Does your charger have an Earth pin?
 
  • #7
berkeman said:
Is it a name-brand power brick?
Yes. Acer. Original. 19V 3.42A.

berkeman said:
Did it just start happening? How long have you had that laptop and power brick?
Hard to say. I might not normally notice it if I'm not resting my arms right.

It doesn't seem to be doing it now (an hour later), which, frankly, is even stranger.

(Have to do with it having reached being full-charge?)
Wrichik Basu said:
As far as I know, there are no laptops in the market that are directly fed AC from the mains without an adapter. And the DC voltage should be quite low. Could it be some kind of static charge build-up?
It was doing this constantly for at least five minutes, tried both arms.
Wrichik Basu said:
Does your charger have an Earth pin?
Yes, although I can't guarantee the condition of the circuit it's plugged in to. It's plugged into a power bar which is powered from an outdoor outlet. It should be good, having been done just a few years ago by a certified electrician, but I have been having some issues with my backyard circuits futzing out on me.

Other possibly un/related anomalies: for a while the plug into the lappie was futzy. I'd have to twist the plug "just so" to get it to power the lappie. That suggests to me a twisted, worn wire inside. But there is no exposed wiring or anything else amiss, and it seems to be working fine of late.

Argh! Where is that multimeter!
 
Last edited:
  • #8
Trust the charge my young padawan, let your fingers guide you to the right voltage. You have the power within.

emperor.jpg


https://moseisleychronicles.files.wordpress.com/2017/04/emperor.jpg
 
  • Haha
  • Love
Likes etotheipi and Klystron
  • #9
DaveC426913 said:
It's plugged into a power bar which is powered from an outdoor outlet.
Okay, that's even weirder. If it's plugged into an outdoor GFCI outlet, the GFCI should trip before you feel much of a tingle/shock. In addition to checking things with your DVM, do you have one of these with the GFCI test button? Maybe worth the investment...

1590598084486.png
 
  • #10
berkeman said:
do you have one of these with the GFCI test button?
Yeah. It's with the multimeter. :sorry:
 
  • Haha
Likes Wrichik Basu, Klystron and berkeman
  • #11
OK, here's what is probably happening. Your power supply must not be grounded (i.e. 2 prongs, not three). PSs are required to protect the users (output) from electric shock. This is measured as no high voltages (>30Vrms normally), or if high voltages are present, then the leakage current from the output to ground must be less than a specified value. For computers that value (EN-60950-1) is something like 750uA. For medical patient contact equipment it's something like 100uA.

To achieve this safety the PS has an isolation transformer. Let's say your input voltage is 0Vac at the neutral conductor, and 120Vac at the hot conductor (w.rt. Earth ground). Then the average voltage on the input circuitry is 60Vac. This is the average voltage difference across the transformer insulation. That insulation will probably act like a capacitor and let some leakage current through. It could also fail and be resistive. In PSs with a grounded plug, the transformer will usually be constructed with an electrostatic shield between the primary and secondary to divert the leakage current to ground. For loads that are grounded (not your laptop, btw), it doesn't matter, they will divert the leakage current to ground.

For PSs that don't have a ground connection, it is required that they have really good insulation (commonly called "double insulated"). In any case, the leakage voltage and current must be tested on each PS manufactured, as well as having the safety agency approve the design.

In addition, EMI filters are required to keep the PS from interfering with other stuff. Without going into the details, an easy way to filter EMI has the side effect of increasing the leakage current. So designers will sometimes trade one bad thing for another to meet the EMI & safety standards at the lowest cost. This leakage current can be a key specification that people like me look for when choosing a PS. For example, what if you make a system that has multiple PSs, each of which claims to meet the spec? OK, but your system may not meet that spec when you connect them all together.

So, the leakage current problem is sort of fundamental. The safety standards allow some, because, frankly, without a ground to send the leakage current to, there will always be some. The fact that you can feel it slightly doesn't necessarily mean that it's dangerous. Your sensory nerves are, well, sensitive, and located at your skin which is far away (electrically speaking) from your muscles. An interesting diversion, btw: the old US military safety standards (1.5mA I think?) weren't based on what it took to stop your heart, they were based on what they thought it might take to make you fall off of a ladder and smash your skull.

The leakage current that you can feel is often too small to trip a GFCI outlet. They don't want to have "nuisance tripping" that is annoying, and is also a safety hazard, because it encourages people to defeat them. GFCI is to save your life not to keep your fingers from tingling.

But, it's pretty terrible marketing for your PC to make you feel like you're being electrocuted. So, good manufacturers will ensure less leakage than the standards allow. This is often done with a grounded (3-prong) power input. OTOH, ancient houses don't always have grounded outlets, so some go for convenience.

So, if I were you, I would replace that PS. Because 1) it sounds annoying, 2) it may be damaged in ways which could be scary.
 
  • #12
OK, confirmed. I can still get that zap.

It's very minor. Almost hard to tell, unless I'm paying attention. Like a burr on the metal, or a teeny metal sliver in my skin. But it's not a tingle - it's like a needle.

It happens if I ground myself on something, while the power supply is plugged in.
If I don't ground myself it's less noticeable.
If I unplug the power supply, it stops.
 
  • #13
Were you able to try a grounded USB cable shield to see if that gets rid of it?
 
  • #14
berkeman said:
Were you able to try a grounded USB cable shield to see if that gets rid of it?
I have a USB phone recharger. Shall I just plug the USB end in and ... I don't know ... stick some aluminium foil in the other end, and bridge it to my rad? o0)
 
  • #15
So this is outdoors, so I assume you are telecommuting from your patio? :smile:

Anyway, simplest would be to find something that is Earth grounded nearby and use a big cliplead to connect the Type-A USB shield at the other end of the cable to that Earth ground.
 
  • #16
DaveC426913 said:
If I unplug the power supply, it stops.
That proves the problem is due to improper grounding.
DaveC426913 said:
Yes, although I can't guarantee the condition of the circuit it's plugged in to. It's plugged into a power bar which is powered from an outdoor outlet. It should be good, having been done just a few years ago by a certified electrician, but I have been having some issues with my backyard circuits futzing out on me.
Is it possible to test on a different outlet? Plug it in and see whether it still zaps you. If it does, move on to the next experiment. If it doesn't, the outlet that you generally use is faulty and not the charger.

Next, wrap a wire around the Earth pin and ground it manually. If you can still feel the current, it's your charger that is faulty (torn wires inside?). If you don't feel a zap, there is some problem in earthing in your house.
 
  • #17
DaveC426913 said:
It's plugged into a power bar which is powered from an outdoor outlet. It should be good, having been done just a few years ago by a certified electrician, but I have been having some issues with my backyard circuits futzing out on me.
Wrichik Basu said:
That proves the problem is due to improper grounding.
That seems like a reasonable explanation to me. Wrichik Basu's advice to plug the laptop and charger into an indoor circuit would be my next step.
I remember you saying a while back that you were having trouble with an outdoor circuit, but I don't remember the details. In any case, since you were having problems with an outdoor circuit before, and you're again having problems with the (same?) outdoor circuit, it seems to me that the insulation in the "hot" wire is damaged, and coming in contact with either the ground wire or common wire.

If it happened to me, I would use my GFCI device at the outside receptacle. It will tell you whether the receptacle is connected correctly. If it isn't, I would disconnect that outlet where it's connected to the house wiring.

One possibility is that the outdoor receptacle has the hot (black) and common (white) wires switched. Another is that the cable is connected incorrectly to the house wiring.

If neither of these turns out to be the case, I would suspect that the cable insulation is damaged, causing a short between the hot and either the common or ground. It wouldn't be difficult to check that -- get a roll of Romex of the length you need and appropriate to the amperage of the circuit -- 12AWG for a 20 A circuit, and 14AWG for a 15 A circuit. Disconnect both ends of the potentially damaged wire, but attach the new wire to one end, wrapping the connection with electrician's tape. As you pull the old wire out, you will be pulling new wire into replace it. If the old cable is damaged, you might be able to find a worn spot on the outer insulation or a place where it was pinched.
 
  • #18
Don't seem to have the problem on an indoor circuit.
 
  • #19
DaveC426913 said:
Don't seem to have the problem on an indoor circuit.
So your outdoor socket should be faulty.
 
  • #20
DaveC426913 said:
Don't seem to have the problem on an indoor circuit.
Did you ground yourself? Are you well-grounded? :wink:
 
  • #21
I would not recommend that you use yourself as the meter. Instead of being "well-grounded", I would recommend that you remain insulated from the ground while you experiment.
 
  • Like
Likes Nugatory, jedishrfu and berkeman
  • #22
Working outdoors you are probably either physically closer to the Earth or on a concrete slab that is on the earth. Either of these increases your capacitive coupling to Earth Ground. Yes, being on a concrete slab makes it worse because concrete is normally damp internally.

I agree that most of the problem is some small leakage in the power brick. The following assumes that the plug on the power brick is not polarized (both prongs the same size). A temporary work-around is to try reversing the power plug when plugging into the outlet.

If that helps you can mark the plug to always plug it in the same way, or, using solder and some small wire, widen the prong that goes into the wide slot in the outlet strip. The wide slot is the Neutral connection that is eventually connected to Ground via the electrical system.

As @berkeman suggested, it would still be a good idea to use a GFCI tester on that outdoor outlet and outlet strip... even when/if you solve the computer problem.

Please keep us updated.

Cheers,
Tom
 
  • #23
I'm sitting on a wood deck that is on top of a concrete slab. Not fully insulated.

My power brick is 3-pronged. So is the power bar it's plugged into.
 
  • #24
There's sensitive, and there's 'sensitive'...
I used to check continuity of our 'OO' model trains' 2-rail power by gently running a dry finger tip along each rail in turn. These carried bridge-rectified but un-smoothed 12 Volts, should have been below sensitivity threshold. My brother could not feel that 100 Hz 'buzz', I could...
 
  • #25
@DaveC426913 Could you solve the problem? Asking because I am facing the same situation now: my laptop is giving a tingling sensation when the charger is plugged in.
 
  • #26
Wrichik Basu said:
@DaveC426913 Could you solve the problem? Asking because I am facing the same situation now: my laptop is giving a tingling sensation when the charger is plugged in.
Is the power cord 3-prong or 2-prong? Have you used an electrical tester on the outlet? Are you grounded or floating when this happens (electrically, I mean).

1619189908204.png

https://en.wikipedia.org/wiki/Electrical_outlet_tester
 
  • #27
FWIW, I have exactly the same issue with my Apple MacBook Air. The Apple power supply is two prong, so the laptop case is not grounded. As @DaveC426913 said, it is just a very minor tingling. It goes away if I unplug the charger or ground the laptop case with a wire.
 
  • #28
berkeman said:
Is the power cord 3-prong or 2-prong?
3-pin.
berkeman said:
Have you used an electrical tester on the outlet?
I don't have an electrical tester, but I just tested the outlet using my multimeter. According to this WikiHow article, if (Potential difference b/w live and earth) - (Potential difference b/w live and neutral) + (Potential difference b/w neutral and earth) > 2 V, the earthing might be faulty. My readings are as follows:
  • PD b/w live and Earth = 172.5 V
  • PD b/w live and neutral = 218.0 V
  • PD b/w neutral and Earth = 44.5 V
The result is -1. So, the outlet earthing is fine?
berkeman said:
Are you grounded or floating when this happens (electrically, I mean).
The laptop is on a wooden table-top, which has iron legs. My legs are touching the table's legs, so I am electrically grounded when I get the sensation.
 
  • #30
Wrichik Basu said:
PD b/w neutral and Earth = 44.5 V
Yikes! In the US, this would be a red flag, since Neutral and Earth are tied at the house breaker panel. Are they not tied in your country? See the expected low reading from the Wikihow article that you linked to:

1619191149792.png
 
  • Wow
Likes Wrichik Basu
  • #31
berkeman said:
In the US, this would be a red flag, since Neutral and Earth are tied at the house breaker panel. Are they not tied in your country?
They are tied together at the distribution transformer as per this website.
 
  • #32
Wrichik Basu said:
my laptop is giving a tingling sensation
At certain ages, that is considered a feature. :wink:
 
  • Haha
Likes hutchphd, Wrichik Basu and jedishrfu
  • #33
If your laptop takes a generic USB charger, I'd suggest trying that.

Plan_$$ may be an isolation transformer. Besides thwarting 'ground loops' in audio and other equipment, it side-steps that N/E voltage. Care, not cheap...

But, IMHO, you must investigate your Neutral / Earth binding ASAP.
40+ Volts, even at fair impedance ?? That's not healthy.
May be corrosion, may be damaged wire. May be symptom of something dire...

( BIL, a 'Sparky', suggests rats or 'unauthorised electricity abstraction'. Either is 'rung' unto serious fire risk. )
 
  • #34
Wrichik Basu said:
They are tied together at the distribution transformer as per this website.
How far away is your distribution transformer? How many homes does it power?
 
  • #35
Nik_2213 said:
40+ Volts, even at fair impedance ?? That's not healthy.
Yeah. I tested five different outlets (all indoor), and all of them are giving around 45 V.
berkeman said:
How far away is your distribution transformer?
We have a 440V to 220V 3-phase transformer about 100 m from our house, but I am not confident if that is the place where the Earth and neutral are tied together.
berkeman said:
How many homes does it power?
Sorry, no idea.
 
<h2>1. What is electric current and how does it work?</h2><p>Electric current is the flow of electric charge through a conductive material. In the case of your laptop, the current is generated by the flow of electrons through the circuitry, which is powered by the battery or AC adapter. The current is then used to power the components of the laptop, such as the processor and display.</p><h2>2. Why is there electric current on my laptop case?</h2><p>The most likely reason for electric current on your laptop case is a faulty or damaged power supply. This can result in a leakage of current from the circuitry to the metal components of the laptop, causing a shock when touched. It is important to have this issue addressed by a professional to avoid potential damage to your laptop or harm to yourself.</p><h2>3. Can electric current on my laptop case be dangerous?</h2><p>Yes, electric current on your laptop case can be dangerous. While the voltage is typically low, it can still cause an electric shock if touched. In addition, the current could potentially damage the internal components of your laptop. It is important to address this issue as soon as possible to avoid any potential hazards.</p><h2>4. How can I prevent electric current on my laptop case?</h2><p>To prevent electric current on your laptop case, it is important to regularly check and maintain your power supply. Make sure all cords and connections are in good condition and not damaged. It is also important to use the correct power supply for your laptop and avoid using third-party or generic chargers. If you notice any issues with your power supply, have it checked by a professional.</p><h2>5. Is there a way to fix electric current on my laptop case?</h2><p>In most cases, the issue of electric current on your laptop case can be fixed by replacing the faulty or damaged power supply. If the issue persists after replacing the power supply, it is important to have a professional inspect your laptop for any other potential issues. Do not attempt to fix this issue yourself, as it can be dangerous and may cause further damage to your laptop.</p>

1. What is electric current and how does it work?

Electric current is the flow of electric charge through a conductive material. In the case of your laptop, the current is generated by the flow of electrons through the circuitry, which is powered by the battery or AC adapter. The current is then used to power the components of the laptop, such as the processor and display.

2. Why is there electric current on my laptop case?

The most likely reason for electric current on your laptop case is a faulty or damaged power supply. This can result in a leakage of current from the circuitry to the metal components of the laptop, causing a shock when touched. It is important to have this issue addressed by a professional to avoid potential damage to your laptop or harm to yourself.

3. Can electric current on my laptop case be dangerous?

Yes, electric current on your laptop case can be dangerous. While the voltage is typically low, it can still cause an electric shock if touched. In addition, the current could potentially damage the internal components of your laptop. It is important to address this issue as soon as possible to avoid any potential hazards.

4. How can I prevent electric current on my laptop case?

To prevent electric current on your laptop case, it is important to regularly check and maintain your power supply. Make sure all cords and connections are in good condition and not damaged. It is also important to use the correct power supply for your laptop and avoid using third-party or generic chargers. If you notice any issues with your power supply, have it checked by a professional.

5. Is there a way to fix electric current on my laptop case?

In most cases, the issue of electric current on your laptop case can be fixed by replacing the faulty or damaged power supply. If the issue persists after replacing the power supply, it is important to have a professional inspect your laptop for any other potential issues. Do not attempt to fix this issue yourself, as it can be dangerous and may cause further damage to your laptop.

Similar threads

  • Computing and Technology
Replies
7
Views
1K
  • Computing and Technology
4
Replies
123
Views
15K
  • Engineering and Comp Sci Homework Help
Replies
7
Views
586
Replies
5
Views
963
Replies
6
Views
1K
Replies
32
Views
2K
Replies
10
Views
2K
Replies
5
Views
794
Replies
1
Views
944
  • STEM Academic Advising
Replies
27
Views
2K
Back
Top