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geekhack Community => Keyboards => Topic started by: laptopleon on Sun, 22 August 2021, 10:27:58
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I use a desktop computer (Mac Pro 3,1 / 2008) with a metal Apple A1243 full size, (aluminium body) keyboard. I get the needly-pinching type of feeling of electricity from the edges of the keyboard when I use it. It's very annoying. The effect is worse when my hands get slightly sweaty from the warm weather. It only happens when my skin barelt touches the metal.
Most topics are about static electricity. I get that a lot too, in winter, but that's a different phenomena.
I found this answer on geekhack, but it doesn't say how to do something about it:
If by "shock", you actually really mean tingling felt when sliding your finger across the keyboard's case then the case might be connected to the ground wire in the USB cable.
If the keyboard has a USB socket and that socket is in contact with the case, then that could be it.
Does anyone have a solution? Except for the obvious ones like switching to a plastic keyboard etc.
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It sounds like your setup may not be properly grounded. Any hardware store can sell you an electrical outlet tester. Just plug it in where the computer is plugged in and it will indicate several problems if they exist, including a bad ground.
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I had this with an Apple aluminium keyboard I used to use at work.
I eventually switched to a Ducky keyboard with plastic case.
Probably not a solution for all, but at least a bit of sympathy. I used to flick the edge of the keyboard with my finger every time I sat down to discharge the static or whatever it was - seemed to be a sort of work-around.
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It sounds like your setup mat not be properly grounded. Any hardware store can sell you an electrical outlet tester. Just plug it in where the computer is plugged in and it will indicate several problems if they exist, including a bad ground.
This is pretty much the only way to get shocks other than static from a keyboard (without the entire computer being fried).
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https://academic.oup.com/ptj/article-abstract/46/9/968/4637975?redirectedFrom=PDF (https://academic.oup.com/ptj/article-abstract/46/9/968/4637975?redirectedFrom=PDF)
TL;DR "current between 100 and 200 milliamperes can be lethal"
note - USB standard is 500 mA
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https://academic.oup.com/ptj/article-abstract/46/9/968/4637975?redirectedFrom=PDF (https://academic.oup.com/ptj/article-abstract/46/9/968/4637975?redirectedFrom=PDF)
TL;DR "current between 100 and 200 milliamperes can be lethal"
note - USB standard is 500 mA
usb 2.0 standard is 500mA, it went up later, although at 5V 500mA can't flow though your body, so it is safe, and ground leakage trough the power supply will either apply to both (so the relative is still 5V even though you take a shock, because you are relative to the ground and the USB is not) or likely fry the PC, it will not count toward the USB power limit. current is function of resistance and voltage, if your resistance is high and voltage low you will get low current too I=V/R (if i remember my physics lessons correctly, been a few years)
tl;dr: USB is safe because I=V/R and 5V is very low and the human skin has a resistance of at least 1kohm, so at best 5mA can go through at 5V
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Meanwhile, I tested the keyboard's power usage / desktop computers' usb-port by putting a usb metering device between them. Nothing out of the ordinairy: 5 Volt, 0.04A so about 40mA, assuming this device is somewhat accurate.
The back of the keyboard reads […] rated 5V DC, 1A max. […]
(https://beeldbuijs.nl/0/usb-toetsenbord-test.jpg)
I don't experience it all the time. Today, so far no pricklings.
I don't have an outlet tester (yet…) but I should be able to test whether the outlet ground is connected properly.