USB electric shock?

GodAtum · 16 Sep 2018 at 19:52

I have an Intel NUC with a USB A-B cable. When plugged into power but off, when I touch the USB cable to to my metal simulator frame, there is a very small electric bolt.

When plugging the same USB cable into a desktop PC, there is nothing.

So what's wrong, the NUC, cable or metal simulator frame?

lord filbuster · 16 Sep 2018 at 20:45

If it's just a tingling sensation rather than a proper shock, I'd say there's nothing wrong with it.

You can get a mild shock from switching power supplies, it just depends on the components it's made from.

LuckyBenski · 16 Sep 2018 at 21:49

I've heard of NUCs having leakage. They're not grounded so charge can build up on them which then jumps to anything grounded or with low potential.

Rannoch · 16 Sep 2018 at 21:51

Had the old style NUC do this to me a few times.

GodAtum · 16 Sep 2018 at 22:14

Is this a bad or dangerous thing then? It seems to have broken mu joystick that the USB was connected to.

EsaT · 17 Sep 2018 at 08:51

Joystick shouldn't be grounded, so there shouldn't be any grounding current through it.
Though charge can equalize, when connecting something also "floating"/not connected to ground.

lord filbuster said:
You can get a mild shock from switching power supplies, it just depends on the components it's made from.

There aren't any shocks from properly built SMPS.
Only thing which causes it is lack of ground causing slight "misfunction" of input filtering components.
And SMPS lacking those is likely safety failure garbage anyway, because SMPS is by its nature EMI source and EMC requirements demand them to have filtering to stop that EMI from spreading.

GodAtum · 17 Sep 2018 at 13:27

EsaT said:
Joystick shouldn't be grounded, so there shouldn't be any grounding current through it.
Though charge can equalize, when connecting something also "floating"/not connected to ground.

When i connect it up, it crackles and the lights on the joystick flix on and off. maybe its ground with a loose wire or screw?

I keep it on a metal shelf which shocks me everytime I touch it.

LuckyBenski · 17 Sep 2018 at 17:51

If a device is connected to a USB port then it can be grounded through the cable's shielding/sleeve.

GodAtum · 17 Sep 2018 at 18:24

LuckyBenski said:
If a device is connected to a USB port then it can be grounded through the cable's shielding/sleeve.

How do I do that? Or how do i ground the NUC itself?

LuckyBenski · 17 Sep 2018 at 18:41

GodAtum said:
How do I do that? Or how do i ground the NUC itself?

Well I mean that like it or not, you may find your device is grounded.

If the NUC isn't grounded then its USB ports aren't either.

I would investigate more before grounding anything, it sounds like you might be building up charge from your carpet, clothes, because of shoes etc.

GodAtum · 17 Sep 2018 at 18:58

everything is on a wooden floor. powering on only the NUC it still sparks. Do I need a anti-static matt to put it on?

GodAtum · 18 Sep 2018 at 18:35

LuckyBenski said:
Well I mean that like it or not, you may find your device is grounded.

If the NUC isn't grounded then its USB ports aren't either.

I would investigate more before grounding anything, it sounds like you might be building up charge from your carpet, clothes, because of shoes etc.

Would it help if I get an earthing plug and anti-static wristband to clip onto the NUC?