4 ms·

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

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.

zabzonk 1y ago
> 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.
- colechristensen 1y ago
  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-Testing/dp/B07GNPKHQ9 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.
  - zabzonk 1y ago
    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.
- MadnessASAP 1y ago
  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.
theodric 1y ago
The laptop is DC powered. This isn't a 1950s TV with a hot chassis. You're not exposed to the AC side.
- MadnessASAP 1y ago
  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.
  - moqmar 1y ago
    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-and-comparison/ https://www.pcbaaa.com/y1-capacitors-function-application-an...)
    - MadnessASAP 1y ago
      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.
      - grues-dinner 1y ago
        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 https://www.tracopower.com/isolated-power-supplies
lm28469 1y ago
The problem is at least a decade old and they sold hundreds of millions of unit since then, where are the deaths?

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.

zabzonk 1y ago

> 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.

colechristensen 1y ago
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-Testing/dp/B07GNPKHQ9 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.
- zabzonk 1y ago
  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.
MadnessASAP 1y ago
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.

theodric 1y ago

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

MadnessASAP 1y ago
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.
- moqmar 1y ago
  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-and-comparison/ https://www.pcbaaa.com/y1-capacitors-function-application-an...)
  - MadnessASAP 1y ago
    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.
    - grues-dinner 1y ago
      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 https://www.tracopower.com/isolated-power-supplies

lm28469 1y ago

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