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How can I avoid my MacBook Pro giving me minor shocks?

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Re: How can I avoid my MacBook Pro giving me minor shocks?

#121

Post by amatix »

jordwest wrote: post #18

What's fascinating to me about this phenomenon is that you can actually feel the 60Hz AC by running your hand across the lid. It feels as if the surface is slightly bumpy, but the width of the bumps changes as you adjust the speed your finger moves. Unplug from mains, and the surface becomes smooth. As the answer notes, this only happens when using the two-prong adapter without earthing. It also seems to be more noti…

Easy way to cause it -- connect something that's got it's own cheapo AC power supply (eg. phone charger, speakers) to your computer via USB. The DC grounds are linked via USB, but the different power supplies end up with a wildly different DC ground wrt AC ground from each other, which can cause buzzing noises or the surface feel you're talking about.

Bring back transformers! (ok, don't, but...)

Re: How can I avoid my MacBook Pro giving me minor shocks?

#122

Post by kalleboo »

Teever wrote: post #88
kalleboo wrote: post #78

Earlier quoted context omitted.

I don't think I've ever seen a three-prong outlet in Japan (maybe only new installations?), but "earth screws" are quite common (any room prepared for an air conditioner will have one at least) http://www.hakusui-trading.co.jp/safety/img/img02.jpg

What? That's crazy looking! Why not just put the third prong in there if it's wired up to handle a screw? What's the point?

And the cable on the left here is what the included Apple MacBook power cable looks like, with the little earth wire sticking out to screw on http://rinare.com/wp-content/uploads/image_archive/110801_2....

I think it's just a legacy thing - historically, the only things that needed grounding were static appliances like fridges, washing machines and air conditioners. The manual in our fridge has this instruction for earthing http://mayoyo.tokyo/jIe.jpg

I need to revise my comment that "I don't think I've ever seen a three-prong outlet in Japan", because now that I have power sockets on my mind, I just saw a three-prong outlet at my gym. So I guess newer buildings have them.

Re: How can I avoid my MacBook Pro giving me minor shocks?

#123

Post by spyder »

jordwest wrote: post #18

What's fascinating to me about this phenomenon is that you can actually feel the 60Hz AC by running your hand across the lid. It feels as if the surface is slightly bumpy, but the width of the bumps changes as you adjust the speed your finger moves. Unplug from mains, and the surface becomes smooth. As the answer notes, this only happens when using the two-prong adapter without earthing. It also seems to be more noti…

This effect can be used for tactile feedback on touchscreens:

TeslaTouch: Electrovibration for Touch Surfaces:

http://www.ivanpoupyrev.com/e-library/2010/teslatouchUIST201...

Video: https://www.youtube.com/watch?v=FiCqlYKRlAA

Re: How can I avoid my MacBook Pro giving me minor shocks?

#124

Post by mavhc »

creshal wrote: post #107
Hydraulix989 wrote: post #87

Earlier quoted context omitted.

Like I said, it was otherwise, an excellent vacuum. Any how, I know about Lenovo's Superfish and recently its attempts to block Linux installs, but I am still a die-hard Thinkpad user because these are very large organizations where all it takes is one single person's oversight to cause a mistake.

They didn't "attempt to block Linux", they just shipped hardware without a Linux driver. And later released a workaround to make the hardware work in a slower, more power consuming backwards compatibility mode so Intel can continue not properly supporting the hardware in Linux. But sure, it was totally "Lenovo blocking Linux".

How come Intel is one of the top contributors to linux, but doesn't ship drivers for all their hardware?

Re: How can I avoid my MacBook Pro giving me minor shocks?

#125

Post by jimboj »

jordwest wrote: post #18

What's fascinating to me about this phenomenon is that you can actually feel the 60Hz AC by running your hand across the lid. It feels as if the surface is slightly bumpy, but the width of the bumps changes as you adjust the speed your finger moves. Unplug from mains, and the surface becomes smooth. As the answer notes, this only happens when using the two-prong adapter without earthing. It also seems to be more noti…

This doesn't only happen with the two-prong adapters, I have noticed this on a few MacBooks, plugged in using the standard 3-prong UK plugs (sometimes with my phone too). An even weirder feeling is when someone else is touching the laptop, if you run your finger over their arm you'll notice the same bumpy feeling.

Re: How can I avoid my MacBook Pro giving me minor shocks?

#126

Post by riprowan »

jordwest wrote: post #18

What's fascinating to me about this phenomenon is that you can actually feel the 60Hz AC by running your hand across the lid. It feels as if the surface is slightly bumpy, but the width of the bumps changes as you adjust the speed your finger moves. Unplug from mains, and the surface becomes smooth. As the answer notes, this only happens when using the two-prong adapter without earthing. It also seems to be more noti…

My old 2011 MBP and MBA do this when plugged into European 240V power

Re: How can I avoid my MacBook Pro giving me minor shocks?

#127

Post by snarfy »

I'm curious if this would trip a GFCI when you touched the lid.

People often judge whether they will get shocked based on resistance, but humans are also capacitors. The casing of a macbook is a machined aluminum frame which will act as one plate in a capacitor. Your hand is the other plate. Unlike DC, AC passes through capacitors.

Re: How can I avoid my MacBook Pro giving me minor shocks?

#128

Post by zymhan »

jimboj wrote: post #125
jordwest wrote: post #18

What's fascinating to me about this phenomenon is that you can actually feel the 60Hz AC by running your hand across the lid. It feels as if the surface is slightly bumpy, but the width of the bumps changes as you adjust the speed your finger moves. Unplug from mains, and the surface becomes smooth. As the answer notes, this only happens when using the two-prong adapter without earthing. It also seems to be more noti…

This doesn't only happen with the two-prong adapters, I have noticed this on a few MacBooks, plugged in using the standard 3-prong UK plugs (sometimes with my phone too). An even weirder feeling is when someone else is touching the laptop, if you run your finger over their arm you'll notice the same bumpy feeling.

Oh my god, this is the feeling my ex and I could never figure out. One of us would touch the other, and there was a weird vibrating sensation as one would move their hand along the other's skin. I can't believe I never thought that it might be the laptop.

Re: How can I avoid my MacBook Pro giving me minor shocks?

#129

Post by dsfyu404ed »

pmoriarty wrote: post #51
jordwest wrote: post #18

What's fascinating to me about this phenomenon is that you can actually feel the 60Hz AC by running your hand across the lid. It feels as if the surface is slightly bumpy, but the width of the bumps changes as you adjust the speed your finger moves. Unplug from mains, and the surface becomes smooth. As the answer notes, this only happens when using the two-prong adapter without earthing. It also seems to be more noti…

I felt this on an Apple laptop in California a couple of years ago, in an apartment with only two-prong outlets in it. I'd describe the feeling more like the laptop cover was vibrating, rather than bumpy. The feeling went away and the laptop cover became smooth and normal if I lifted my feet off of the ground. Once all the outlets were rewired to be three-prong, with ground, I used a three-prong power cord and the pr…

120v isn't going to hurt you, just scare you. You have too much resistance.
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