8 ms·

Why is there a voltage on my HDMI and coaxial cables?

156 points by jasonhansel 4y ago

hedora 4y ago
Would this explain all apple devices shocking me while charging? (But to varying degrees, depending on the day, and not if I use a three prong plug for the USB power source.)
- askvictor 4y ago
  Are you talking about the bumpy feeling when moving your hand along the chassis? I get that on a metal-body Dell sometimes too. And it doesn't seem to happen if I press hard while moving my hand.
  - HeavyFeather 4y ago
    > it doesn't seem to happen if I press hard I would assume that's because you're increasing the contact area and therefore more of your nerve endings are getting a lower voltage, pushing it below the detectable range.
    - lolc 4y ago
      In my case it's not just nerves that feel it. I can get my fingers to vibrate at presumedly 50 hz by stroking the laptop lid. There is an audible hum. It happens with just one charger I have. The other charger just went out with a bang that tripped the fuse. So guess which one I use now.
  - pizzeys 4y ago
    Wait until you're using it on your chest in bed and accidentally poke your lips with the corner! It's a surprisingly good zap for an allowed amount of stray Not that I've ever done that
- user_7832 4y ago
  No, that's a different (and often "officially allowed") thing. I believe it has to do with stray capacitance. A lot of 2-prong devices are doubly insulated (the symbol on the charger is 2 concentric squares). Weirdly though I have noticed that "tingly" feel even with my 3-pronged laptop charger.
  - heywhatupboys 4y ago
    wow, to a Dane the US electricity rules are something out of a 3rd world country!!
    - user_7832 4y ago
      I assuming that you’re taking what I wrote as US electricity rules but the devices/rules I mentioned were for European products. My iPad that gives me a slight tingle was purchased from the Apple store in The Hague so it’s EU compliant. (I’m Indian and I believe India too has similar rules. Double insulation is generally pretty safe, if a little annoying.)
    - _fizz_buzz_ 4y ago
      The issue they are talking about can (but shouldn't) also happen with the "Europlug" which is also used in Denmark: https://en.wikipedia.org/wiki/Europlug https://en.wikipedia.org/wiki/Europlug
    - lioeters 4y ago
      > US electricity rules are something out of a 3rd world country If you read about the CEE 7 standard that aims to unify power plugs and sockets in European countries [1], which includes the "Europlug" [2] mentioned in a sibling comment, you'll see that the situation is not any better than in the US. For example, about the CEE 7/7 plug which bridges the difference between socket types in Germany (2-pronged - also in Denmark, Spain, etc.) and France (3-pronged - also in Belgium, Czechia, Poland), it mentions: > This plug can be inserted into a Danish Type K socket, but earthing is not enabled. [1] https://en.wikipedia.org/wiki/CEE_7_standard_AC_plugs_and_sockets https://en.wikipedia.org/wiki/CEE_7_standard_AC_plugs_and_so... [2] https://en.wikipedia.org/wiki/Europlug#Compatibility https://en.wikipedia.org/wiki/Europlug#Compatibility
- slow_typist 4y ago
  You already nailed it. Use the three prong plug. If you don’t, stray voltages can occur on the metal casing of your device. I also learned that some usb-c cables connect ground to your device (via the charger) and some don‘t. It‘s not as universal as it is marketed. EDIT: Your neutral is probably ok.
  - chinaman425 4y ago
    [dead]
  - derefr 4y ago
    I’ve been annoyed for the longest time that Apple in North America only sticks grounded plugs on their 1m+ power cables. Very inconvenient for travel. I don’t want to bring an extra 1m cable in my carry-on. I want the little two-prong “duck head” adapter—just with three prongs. Turns out there’s one third party making them now! (Sadly, their jack doesn’t fold flat like the two-prong ones do, but I’m willing to take that compromise.) https://www.amazon.com/Grounded-Duckhead-Apple-Mac-Adapter/dp/B0B452LS67/ https://www.amazon.com/Grounded-Duckhead-Apple-Mac-Adapter/d...
rysertio 4y ago
I have a similar issue with my VGA cables and I'm yet too find a solution.
junon 4y ago
Fascinating, I never knew this is how it worked. I feel like I've run into this before at friends or family's houses and shrugged it off as bad house wiring or the like.
js2 4y ago
Edit: nope. See reply. Klein Tools RT210 Outlet Tester, $13, would've detected this in a jiffy. https://www.kleintools.com/catalog/electrical-testers/gfci-outlet-tester https://www.kleintools.com/catalog/electrical-testers/gfci-o... (If I ever have more money than I know what to do with, one of the things I'll do with it is buy Klein's entire catalog of tools. Just because.)
- jcalvinowens 4y ago
  No it wouldn't. The neutral was cut, that tool can't reliably identify that problem. The tester will see a voltage that depends on the other loads in the house, which might be lower or higher than normal. Your tester would also still show the outlet as grounded, because it just checks for continuity from neutral to ground at the outlet, which exists even when the utility neutral is broken because of the neutral-ground bond at the service entrance. A common misconception is that the neutral-ground bond at the service entrance is what makes the system grounded. That is not true: it is the neutral-ground bond at the transformer that makes the system grounded. If you break the utility neutral wire, the ground (earth) is too bad a conductor to work in its place, even if the transformer and panel both have intact neutral-ground bonds.
  - js2 4y ago
    You're right. That makes sense.
  - mindslight 4y ago
    > A common misconception is that the neutral-ground bond at the service entrance is what makes the system grounded. That is not true: it is the neutral-ground bond at the transformer that makes the system grounded Er, what? It's any/all of the neutral-ground bonds that make the system grounded. The more ground connections, the more redundancy and lower impedance. ... which is probably why the plumber didn't worry too much about disrupting the building's ground connection. If everything else is wired up right it's not going to be that big of a deal - perhaps a few volts on the building's grounding conductor versus actual earth, due to the current on the service neutral.
madmod 4y ago
I now know why I got shocked by the ground at my grandparents house
- I_complete_me 4y ago
  Do they by any chance live on Electric Avenue?
londons_explore 4y ago
This sort of problem is a big moneymaker for electricians. They look at it and say "yeah, it's fucked. You need a full rewire, $20k". When the reality is that with a bit of measurement and testing you can find the missing or broken neutral or incorrect grounding, and fix it for a couple of hours work. Nearly all electrical fires are caused by newly modified electricals anyway, so 'just rewire it all' is probably making your property less safe rather than more safe, at least in the short term.
- bobmaxup 4y ago
  > Nearly all electrical fires are caused by newly modified electricals This seems like an extraordinary claim, that doesn't seem to be supported by this publication: https://nfa.usfa.fema.gov/downloads/pdf/statistics/v8i2.pdf https://nfa.usfa.fema.gov/downloads/pdf/statistics/v8i2.pdf Or this: https://www.electricalsafetyfirst.org.uk/what-we-do/our-policies/westminster/statistics-england/ https://www.electricalsafetyfirst.org.uk/what-we-do/our-poli...
- flandish 4y ago
  > newly modified electrical Anecdotally, as a firefighter for almost 20 years, the ones in my area have been overloading of old wiring, or stupidity. (Jamming a breaker open, etc.)
  - londons_explore 4y ago
    I wonder where you live if one can jam a breaker... All the breakers round me have a mechanism so you cannot hold them 'on'. Sure, the bit in your hand will be pointing towards on, but the electrical switch internally trips and flips to off.
    - flandish 4y ago
      I have seen them jammed. Replaced with straight wire, etc. Also where I live has houses that predate electricity - in my area of the northeast US, for instance. So some of the wiring is, most definitely, old. Heck, some old fuse systems have been known to be the perfect size for coins. ;)
nly 4y ago
I moved in to a newly renovated Victorian house here in England in December, which we bought from a property developer. It was completely rewired, with everything signed off and certified by a qualified electrician, as per legal requirements. Most properties in the UK have common earth/ground and neutral wiring (they're the same wire, the "earth" just bypasses your main board... there's no earth spike). Anyway, I bought a socket tester after noticing an outlet or two didn't work. Went around and tested the whole house... half of the 30 electrical outlets in the house were defective, and at least 4 were wired incorrectly such that they were live on the neutral pin (which means they're live when the switch is off). Some had earthing issues. Fortunately the RCBO's work as advertised. Don't risk your life with this stuff, test it all yourself. A tester will cost you $10
- tblt 4y ago
  I've seen houses with ground bonded to the copper water/gas pipes...and upon further inspection they were supplied with plastic piping outside of their property boundary. Yikes. My understanding is that neutral goes to ground at the substation
  - mattpallissard 4y ago
    > My understanding is that neutral goes to ground at the substation Close. It's at the transformer. North American "split phase" power has the neutral center tapped into the transformer winding. The two 120v lines are phased 180° from each other with respect to neutral. Line to line gets you 240v, line to neutral is half that, 120v. Downstream in the breaker panel itself, the grounding conductor (ground) and grounded conductor (neutral) are bonded at the panel. The ground wire is basically just an alternate path back to the box.
  - brewtide 4y ago
    They are bonded to ground so that if a hot happens to run or chaff up against them, you don't have hot water or gas lines conducting in your house -- a dead short to ground will trigger a breaker overload (near) immediately assuming they are working correctly. If these pipes were not grounded, they are just pretty scary conductive pieces of metal strewn throughout walls and ceilings, and usually terminating at a place where people physically contact, as well.
zenexer 4y ago
> I even checked my electricity 'pen' reader on an HDMI at work to see if it was the reader. It's not the pen. It's my wires. Ah… there it is. Stop using those; use an actual multimeter. See, the problem with measuring voltage is that you really need two points of reference: you’re really measuring the voltage potential between two separate points. When you say your HDMI is live, what does that mean? Relative to what? Are you talking about the grounded shielding, or one of other conductors? This individual is waving around a no-contact A/C voltage detector. These can be useful indicators in the right hands, but they’re just estimation devices. They’re prone to false positives and negatives. If you wave one near an HDMI or coax cable, there’s a good chance it’s going to beep and turn red. That being said, if you see your lights getting brighter on the regular (rather than dimmer), your neutral is probably going bad, and that can be quite dangerous. Call your electric company and/or an electrician if you see that. It’s not going to stop your coax and HDMI from showing as live when you wave a death stick near it, though; they are live, at least from the perspective of a no-contact voltage tester.
sebazzz 4y ago
Is this more prevalent in split-phase countries than three-phase or one-phase systems?

156 points by jasonhansel 4y ago

Would this explain all apple devices shocking me while charging? (But to varying degrees, depending on the day, and not if I use a three prong plug for the USB power source.)

askvictor 4y ago
Are you talking about the bumpy feeling when moving your hand along the chassis? I get that on a metal-body Dell sometimes too. And it doesn't seem to happen if I press hard while moving my hand.
- HeavyFeather 4y ago
  > it doesn't seem to happen if I press hard I would assume that's because you're increasing the contact area and therefore more of your nerve endings are getting a lower voltage, pushing it below the detectable range.
  - lolc 4y ago
    In my case it's not just nerves that feel it. I can get my fingers to vibrate at presumedly 50 hz by stroking the laptop lid. There is an audible hum. It happens with just one charger I have. The other charger just went out with a bang that tripped the fuse. So guess which one I use now.
- pizzeys 4y ago
  Wait until you're using it on your chest in bed and accidentally poke your lips with the corner! It's a surprisingly good zap for an allowed amount of stray Not that I've ever done that
user_7832 4y ago
No, that's a different (and often "officially allowed") thing. I believe it has to do with stray capacitance. A lot of 2-prong devices are doubly insulated (the symbol on the charger is 2 concentric squares). Weirdly though I have noticed that "tingly" feel even with my 3-pronged laptop charger.
- heywhatupboys 4y ago
  wow, to a Dane the US electricity rules are something out of a 3rd world country!!
  - user_7832 4y ago
    I assuming that you’re taking what I wrote as US electricity rules but the devices/rules I mentioned were for European products. My iPad that gives me a slight tingle was purchased from the Apple store in The Hague so it’s EU compliant. (I’m Indian and I believe India too has similar rules. Double insulation is generally pretty safe, if a little annoying.)
  - _fizz_buzz_ 4y ago
    The issue they are talking about can (but shouldn't) also happen with the "Europlug" which is also used in Denmark: https://en.wikipedia.org/wiki/Europlug https://en.wikipedia.org/wiki/Europlug
  - lioeters 4y ago
    > US electricity rules are something out of a 3rd world country If you read about the CEE 7 standard that aims to unify power plugs and sockets in European countries [1], which includes the "Europlug" [2] mentioned in a sibling comment, you'll see that the situation is not any better than in the US. For example, about the CEE 7/7 plug which bridges the difference between socket types in Germany (2-pronged - also in Denmark, Spain, etc.) and France (3-pronged - also in Belgium, Czechia, Poland), it mentions: > This plug can be inserted into a Danish Type K socket, but earthing is not enabled. [1] https://en.wikipedia.org/wiki/CEE_7_standard_AC_plugs_and_sockets https://en.wikipedia.org/wiki/CEE_7_standard_AC_plugs_and_so... [2] https://en.wikipedia.org/wiki/Europlug#Compatibility https://en.wikipedia.org/wiki/Europlug#Compatibility
slow_typist 4y ago
You already nailed it. Use the three prong plug. If you don’t, stray voltages can occur on the metal casing of your device. I also learned that some usb-c cables connect ground to your device (via the charger) and some don‘t. It‘s not as universal as it is marketed. EDIT: Your neutral is probably ok.
- chinaman425 4y ago
  [dead]
- derefr 4y ago
  I’ve been annoyed for the longest time that Apple in North America only sticks grounded plugs on their 1m+ power cables. Very inconvenient for travel. I don’t want to bring an extra 1m cable in my carry-on. I want the little two-prong “duck head” adapter—just with three prongs. Turns out there’s one third party making them now! (Sadly, their jack doesn’t fold flat like the two-prong ones do, but I’m willing to take that compromise.) https://www.amazon.com/Grounded-Duckhead-Apple-Mac-Adapter/dp/B0B452LS67/ https://www.amazon.com/Grounded-Duckhead-Apple-Mac-Adapter/d...

rysertio 4y ago

I have a similar issue with my VGA cables and I'm yet too find a solution.

junon 4y ago

Fascinating, I never knew this is how it worked. I feel like I've run into this before at friends or family's houses and shrugged it off as bad house wiring or the like.

js2 4y ago

Edit: nope. See reply. Klein Tools RT210 Outlet Tester, $13, would've detected this in a jiffy. https://www.kleintools.com/catalog/electrical-testers/gfci-outlet-tester https://www.kleintools.com/catalog/electrical-testers/gfci-o... (If I ever have more money than I know what to do with, one of the things I'll do with it is buy Klein's entire catalog of tools. Just because.)

jcalvinowens 4y ago
No it wouldn't. The neutral was cut, that tool can't reliably identify that problem. The tester will see a voltage that depends on the other loads in the house, which might be lower or higher than normal. Your tester would also still show the outlet as grounded, because it just checks for continuity from neutral to ground at the outlet, which exists even when the utility neutral is broken because of the neutral-ground bond at the service entrance. A common misconception is that the neutral-ground bond at the service entrance is what makes the system grounded. That is not true: it is the neutral-ground bond at the transformer that makes the system grounded. If you break the utility neutral wire, the ground (earth) is too bad a conductor to work in its place, even if the transformer and panel both have intact neutral-ground bonds.
- js2 4y ago
  You're right. That makes sense.
- mindslight 4y ago
  > A common misconception is that the neutral-ground bond at the service entrance is what makes the system grounded. That is not true: it is the neutral-ground bond at the transformer that makes the system grounded Er, what? It's any/all of the neutral-ground bonds that make the system grounded. The more ground connections, the more redundancy and lower impedance. ... which is probably why the plumber didn't worry too much about disrupting the building's ground connection. If everything else is wired up right it's not going to be that big of a deal - perhaps a few volts on the building's grounding conductor versus actual earth, due to the current on the service neutral.

madmod 4y ago

I now know why I got shocked by the ground at my grandparents house

I_complete_me 4y ago
Do they by any chance live on Electric Avenue?

londons_explore 4y ago

This sort of problem is a big moneymaker for electricians. They look at it and say "yeah, it's fucked. You need a full rewire, $20k". When the reality is that with a bit of measurement and testing you can find the missing or broken neutral or incorrect grounding, and fix it for a couple of hours work. Nearly all electrical fires are caused by newly modified electricals anyway, so 'just rewire it all' is probably making your property less safe rather than more safe, at least in the short term.

bobmaxup 4y ago
> Nearly all electrical fires are caused by newly modified electricals This seems like an extraordinary claim, that doesn't seem to be supported by this publication: https://nfa.usfa.fema.gov/downloads/pdf/statistics/v8i2.pdf https://nfa.usfa.fema.gov/downloads/pdf/statistics/v8i2.pdf Or this: https://www.electricalsafetyfirst.org.uk/what-we-do/our-policies/westminster/statistics-england/ https://www.electricalsafetyfirst.org.uk/what-we-do/our-poli...
flandish 4y ago
> newly modified electrical Anecdotally, as a firefighter for almost 20 years, the ones in my area have been overloading of old wiring, or stupidity. (Jamming a breaker open, etc.)
- londons_explore 4y ago
  I wonder where you live if one can jam a breaker... All the breakers round me have a mechanism so you cannot hold them 'on'. Sure, the bit in your hand will be pointing towards on, but the electrical switch internally trips and flips to off.
  - flandish 4y ago
    I have seen them jammed. Replaced with straight wire, etc. Also where I live has houses that predate electricity - in my area of the northeast US, for instance. So some of the wiring is, most definitely, old. Heck, some old fuse systems have been known to be the perfect size for coins. ;)

nly 4y ago

I moved in to a newly renovated Victorian house here in England in December, which we bought from a property developer. It was completely rewired, with everything signed off and certified by a qualified electrician, as per legal requirements. Most properties in the UK have common earth/ground and neutral wiring (they're the same wire, the "earth" just bypasses your main board... there's no earth spike). Anyway, I bought a socket tester after noticing an outlet or two didn't work. Went around and tested the whole house... half of the 30 electrical outlets in the house were defective, and at least 4 were wired incorrectly such that they were live on the neutral pin (which means they're live when the switch is off). Some had earthing issues. Fortunately the RCBO's work as advertised. Don't risk your life with this stuff, test it all yourself. A tester will cost you $10

tblt 4y ago
I've seen houses with ground bonded to the copper water/gas pipes...and upon further inspection they were supplied with plastic piping outside of their property boundary. Yikes. My understanding is that neutral goes to ground at the substation
- mattpallissard 4y ago
  > My understanding is that neutral goes to ground at the substation Close. It's at the transformer. North American "split phase" power has the neutral center tapped into the transformer winding. The two 120v lines are phased 180° from each other with respect to neutral. Line to line gets you 240v, line to neutral is half that, 120v. Downstream in the breaker panel itself, the grounding conductor (ground) and grounded conductor (neutral) are bonded at the panel. The ground wire is basically just an alternate path back to the box.
- brewtide 4y ago
  They are bonded to ground so that if a hot happens to run or chaff up against them, you don't have hot water or gas lines conducting in your house -- a dead short to ground will trigger a breaker overload (near) immediately assuming they are working correctly. If these pipes were not grounded, they are just pretty scary conductive pieces of metal strewn throughout walls and ceilings, and usually terminating at a place where people physically contact, as well.

zenexer 4y ago

> I even checked my electricity 'pen' reader on an HDMI at work to see if it was the reader. It's not the pen. It's my wires. Ah… there it is. Stop using those; use an actual multimeter. See, the problem with measuring voltage is that you really need two points of reference: you’re really measuring the voltage potential between two separate points. When you say your HDMI is live, what does that mean? Relative to what? Are you talking about the grounded shielding, or one of other conductors? This individual is waving around a no-contact A/C voltage detector. These can be useful indicators in the right hands, but they’re just estimation devices. They’re prone to false positives and negatives. If you wave one near an HDMI or coax cable, there’s a good chance it’s going to beep and turn red. That being said, if you see your lights getting brighter on the regular (rather than dimmer), your neutral is probably going bad, and that can be quite dangerous. Call your electric company and/or an electrician if you see that. It’s not going to stop your coax and HDMI from showing as live when you wave a death stick near it, though; they are live, at least from the perspective of a no-contact voltage tester.

sebazzz 4y ago

Is this more prevalent in split-phase countries than three-phase or one-phase systems?