Grond and earth tingles

[imstuee123]

Hi all. I have this power supply which is connected to 240v L N E.
It has 244v dc. 12v dc and 5vdc outputs.
I have my nuc pc piggybacked on the 240v terminals as that uses its own psu.
The issue is any casing etc on the unit or arcade controls terminals [usb) all give a tingle.
I did look and see the earth is linked to the gnd too.

Is this right or something wrong. I have 10 of these and all the same.

 

[imstuee123]

Image

 

[Galgso]

If you have a multimeter do a continuity check between the ground screw terminal on the PSU and the earth pin on the mains plug feeding the PSU. You should get low resistance (less than 1Ω). If you do get continuity, check if the USB connector metal shields are also grounded properly using the same technique.

 

[Diver300]

You should connect the power supply ground to the earth for the 24V, 12V and 5V.

The tingles come from at tiny leakage current and if that it grounded there will be no problem.

 

[Nigel Goodwin]

Either the unit isn't actually earthed (so you're getting leakage as if it's acting like a Class II device instead of a Class I), or it IS earthed, and it's you who's charged up, and discharging to earth via the casing.

MANY years ago, a crude and simple earth test for a socket was to have a 60W bulb wired to a plug, from Live to Earth, and when plugged in the bulb should light brightly. This has long since ceased to be possible, due to 'modern' earth leakage trips.

 

[ClydeCrashKop]

Is that a special effect for the arcade game?

 

[schmitt trigger]

To verify Nigel’s theory, you may take the suspect units to a different location and see whether you still receive the tingling.
If not, the wiring in the original location may have issues.

 

[Tony Stewart]

This is a common issue with isolated ACDC SMPS's since the transformer has leakage capacitance between the primary and secondary that conducts the switching frequency (RF) currents modulated at line rates causing the tingle yet considered safe. Check that my assumption was correct with a DMM continuity test between PE and GND is isolated.

Bridging them should eliminate the tingle but expose a risk if the PE ground should ever fault open or worse fault open and reconnect to line. Although low probability, a better way, I suggest, is to use a cap such as 0.01 uF to redirect the leakage RF current to PE. (protective earth.

It also means the shoes worn by the user have enough capacitance thru the floor to "earth" thus making a path with the tingling of ~ <= 100 uA. This can be bypassed with a sufficiently bigger capacitance than the xxx pF of the shoes to floor and earth. Leather shoes have much better conductance than sneakers or rubber boots for leakage capacitance and resistance.

 

[Tony Stewart]

Electrical appliances with a metal case must use the case grounded to PE.

I was not sure if your machine had a metal case or not.

But if your USB controllers were not PE grounded yet the 0Vdc exposed, then you would feel the leakage current when touching between the metal frame and 0Vdc. Thus, connecting PE to floating GND = 0Vdc would eliminate the problem.

If your circuit has a GFCI or equivalent leakage interrupter, that just uses a common mode transformer relay to trip if the line and neutral currents are unbalanced and exceed some low mA differential threshold and thus assume it is leakage current.

 

[Nigel Goodwin]

Electrical appliances with a metal case must use the case grounded to PE.

Sorry, but that's completely untrue - MANY Class II devices have metal cases and no ground - having a metal case doesn't make it a device Class I. Prime examples would be VCR's, STB's, Audio Amplifiers etc. most of which have metal cases but are Class II.

However, as this thread is about arcade machines, I once went to a pub (playing there in a pool league match) and the Fruit Machine was noticeably Live - not the minor tickle from a Class II device, but that from a Class I device with the earth not connected, and possibly even a live wire touching the case?.

Luckily I never touch anything without testing it first, you simply rub the back of your finger on the offending item, and if it's Live then it's like rubbing a piece of sand paper. If it's a Class II device it either feels smooth, or only very slightly rough.

I notified the bar staff, but they didn't seem interested.

 

[Tony Stewart]

Sorry, but that's completely untrue - MANY Class II devices have metal cases and no ground - having a metal case doesn't make it a device Class I. Prime examples would be VCR's, STB's, Audio Amplifiers etc. most of which have metal cases but are Class II.

However, as this thread is about arcade machines, I once went to a pub (playing there in a pool league match) and the Fruit Machine was noticeably Live - not the minor tickle from a Class II device, but that from a Class I device with the earth not connected, and possibly even a live wire touching the case?.

Luckily I never touch anything without testing it first, you simply rub the back of your finger on the offending item, and if it's Live then it's like rubbing a piece of sand paper. If it's a Class II device it either feels smooth, or only very slightly rough.

I notified the bar staff, but they didn't seem interested.

The players might have been well-lubricated to not notice either. FWIW I use the same finger test, although now post-surgical neuropathy feels the same all the time from nerve damage.

TY for my oversight on Class II. Did you agree with my leakage C explanation?

 

[Nigel Goodwin]

The players might have been well-lubricated to not notice either. FWIW I use the same finger test, although now post-surgical neuropathy feels the same all the time from nerve damage.

TY for my oversight on Class II. Did you agree with my leakage C explanation?

I can't say I've ever really thought about?, but if you're getting shocks (other than the tiny leakage of Class II) then there's something wrong, find out what it is.