Fix "pulsing" sensation when charging MacBook | Hacker News Reader

Fix "pulsing" sensation when charging MacBook

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This is a widespread and well documented phenomenon.

https://www.reddit.com/r/AskElectronics/wiki/why#wiki_tingli...

> Apple support are utterly fucking useless and don't know about this.

That particular support person/bot may not have but the company absolutely does

I've never had this happen with a laptop but as a musician I've been zapped by a microphone a bunch... not an infrequent occurrence if you play electric guitar and sing at the same time. Twice in the past year I've been hit during soundcheck at a gig because of bad grounding at a venue. Last time my solution was to plug everything into the same outlet via a power strip but I invariably end up off-kilter for a few minutes after being electrocuted through my mouth as I'm about to play :-(

This also happens with iPhones. And under the right circumstances you can feel the same tingling sensation on skin contact as well if the other person is holding a plugged in iPhone.

I'm startled they put a metal earth pin on the type-G adapter for that plug that does nothing.

That's additional cost just to make it look like it's grounded when it's not.

They didn't. The one that's ungrounded is a plastic pin. It's just there because the UK plugs require it to mechanically open the live and neutral connections, allowing you to actually plug the thing.

I saw the silvery colour in the photo and made an incorrect assumption, I guess.

I think there's some confusion going on here. The "earth" pin on the duck head is black plastic.

The metal pin on the actual PSU is an earth pin, but the duck head isolates it since the sleeve part that fits around it is all plastic.

The extension cord, on the other hand, has metal in the sleeve and has a proper metallic ground pin on the mains plug.

Shouldn't this be a UL/CE certification issue?

I have no expertise in this: but it could be one of the cells in the battery is performing worse than the rest. The way charging works in a pack is that it measures all 4 cells for instance, and if one is higher than the others it discharges that one only, then continues on charging them all at once, then periodically checks again

I get this sometimes, but not all of the time on my newish (6 month) Asus 14 laptop with a UK 3-pin to mains power supply. And I've had it with other laptops in the UK. It's mysterious, but don't think it is going to kill you.

It won't kill you right up until you plug it into an outlet with a unbalanced neutral.

Granted a couple things have to go wrong for that to happen but they do happen.

> unbalanced neutral

So, what's that? And how to know, in the UK, if I have it, or don't want it. Because I have had the same throbbing experience with several metal shell laptops plugged in to power in at least three houses in the UK.

There are a series of things that can be wrong both with the hardware you plug in and with the plug itself. Things can straight up be wired in the wrong order, grounding can be done incorrectly so there's more than one path to ground which among other things causes there to be a voltage difference between the neutral wire and the ground wire, corrosion or bad connections can cause similar issues.

The first cheap test you can do is buy one of these plug testers that diagnose some of the more direct problems you could be having for about £10, don't necessarily buy the one I linked, but do a little research and pick something that seems right.

https://www.amazon.co.uk/QUILLE-Socket-Display-Neutral-Testi...

If you're having those kinds of problems, it wouldn't hurt to contact a local electrician and quickly describe the issue and ask what it would cost to diagnose.

Well, it is not so much of a problem as just strange. I have had my brother, who knows a bit about power circuits, do some testing on my current house, and it seems OK. But sometimes, and only sometimes, metal shell things plugged into the UK mains via 3-pin UK plugs will do the throbbing stuff. And as I said, this happened in multiple houses, with multiple PSUs and laptops and other stuff.

I dunno.

I'm not familiar with the UK wiring standards. However an easy first step that I would imagine also applies there is losing the bonding jumper between neutral and ground at the main circuit breaker panel.

In Canada and USA with our split phase residential system a decent next step is to overload 1 phase causing the neutral to start drifting from 0V.

In the UK with single phase supply I imagine the next best thing would be to also break the neutral return to the pole which should generate at least 100V on the neutral (and also stop all appliances from working), fortunately for you (I think) the UK mandates GFCIs (RCDs) on all residential circuits which would also prevent that from actually killing you.

In summary, I'm going to guess that touching neutral in the UK is a healthier past time then it is in the US or CA. Still not healthy, but at least healthier.

The laptop is DC powered. This isn't a 1950s TV with a hot chassis. You're not exposed to the AC side.

Sure, but DC relative to what? Can't be ground since that connection isn't there, so that leaves neutral.

I've got half an alligator clip on my workbench, the other half disappeared when I connected it to the floating ground of a 5VDC system. It just so happens the ground was floating on top of 120VAC. The ATmega didn't care, it only ever saw 5V between its Vcc and Vee, however once I made the mistaken of connecting its "ground" to an actual ground sparks flew.

The DC side is fully isolated except through a capacitor that is there to reduce EMI interference and is specifically built to "fail safe", except for the cheapest no-name imported power supplies. (https://www.pcbaaa.com/y1-capacitors-function-application-an...)

A Y capacitor prevents the neutral from shorting to ground, in this case Apple has cleverly avoided the issue by not having a ground whatsoever.

I am however curious about your design for a galvanically isolated AC-DC power supply.

That's not what the Y capacitor is doing here. All Y means is "high voltage withstand, will fail open, and we have receipts". Here, it's not line-to-ground, but primary-to-secondary.

Isolated ACDC converters are very common these days. Companies like Traco will sell you modules: https://www.tracopower.com/isolated-power-supplies

You'd use X for L to L/N, Y is for N to Ground. Those isolated power supplies are definitley grounded, definitely not what Apple is using, and will probably shut themselves off if they lose their ground connection (or at least signal a fault to the operator)

Unlikely, since you can quite happily buy two-prong power supplies.

And most packaged modules don't even have ground connections, e.g. https://www.tracopower.com/sites/default/files/products/data...

You're also confusing the Y designation, which relates to the capacitor properties, to the application. Not all Y capacitors are used for line-to-ground applications. However any application where a failure to a closed state would result in a shock hazard must use Y-rated capacitors.

> Sure, but DC relative to what?

What are an AA battery's terminals relative to when you hold the thing up in the air?

Irrelevant as what it isn't relative to is any part of your household wiring.

Neither is the output of an isolated power supply. That's the whole point. There is an enormous amount of resistance between the output side and the household wiring in the input side, just like the battery scenario. The difference between gigaohms (like you might see in between the windings of the SMPS transformer) and exaohms or whatever the airgap between the battery and the nearest outlet is is negligible for any practical purposes.

You may see AC leakage due to the capacitance between the windings and also that of the Y capacitor (this leakage is the source of the sensation in the article), but that's also tiny and it won't be blowing up any crocodile clips. If you did have that happen, your power supply wasn't isolated somehow.

The problem is at least a decade old and they sold hundreds of millions of unit since then, where are the deaths?

My frustratingly rubbish M1 Air does this, amongst many other odd and annoying things. But hey... what are the alternatives?

This is why I avoid aluminum laptops. Too many plugs aren't properly grounded and the tingling annoys me to no end.

I don't notice this in North America but I did notice it in Europe. Using the 2 prong in both places.

I’ve always felt it in North America. Especially if you slide your hand/finger. My iPad does it as well (if it’s on a charger).

Yeah, I've haven't had it in the USA with two prong, but then 110/120V(?) would be presumably harder to notice?

At home with 240V I use 3 prong so presumably I'm properly grounded as this would be an ongoing annoyance I'd definitely notice.

Noticed it in Asia but Not Japan. Always knew it was a grounding issue.

i have had this issue and realized i was basically getting a low key elec shock every time i had the power plugged into my mac; turned out it was the apple wall wart power brick; using a different one ended the constant elec pulse shocking effect. (at first i thought it was the shitty fraying usb-c cables apple provides which turn yellow and the plastic breaks apart after 6months to a year - nope! that thing is fine).

it’s a design decision because some people like myself actually like the light throbbing

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