Ravichandra
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Getting shock from micro hdmi port when connected to tv hdmi port

Wed Jun 17, 2020 11:06 am

Getting shock from micro hdmi port and sometimes from USB port .I connected original raspberry Pi 4 charger .

jowage
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Re: Getting shock from micro hdmi port when connected to tv hdmi port

Wed Jun 17, 2020 12:34 pm

first thing that comes to mind is: do you walk much on carpets? can you replicate the shock by touching other things known to be earthed?

drgeoff
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Re: Getting shock from micro hdmi port when connected to tv hdmi port

Wed Jun 17, 2020 12:41 pm

Frequently to do with switch mode power supplies having small value capacitors from the AC mains side to the output side. Not dangerous but one of the reasons that operating manuals for TVs, set top boxes etc invariably tell you to connect all pieces og a system together before plugging any of them into the AC sockets.
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Heater
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Re: Getting shock from micro hdmi port when connected to tv hdmi port

Wed Jun 17, 2020 3:46 pm

When you say "shock" do you mean an electric jolt that gripped all your muscles and threw you across the room, only to regain consciousness some time later and wonder: "WTF happened"?

Or do you mean that little "tick" one gets from normal bodily discharges of static electricity?
Last edited by Heater on Thu Jun 18, 2020 9:32 am, edited 1 time in total.
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mahjongg
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Re: Getting shock from micro hdmi port when connected to tv hdmi port

Wed Jun 17, 2020 4:12 pm

This is the common problem of half the mains voltage ending up on the GND (ground) wire of the HDMI cable when the TV is not plugged into a grounded outlet. It is not a case of static electricity! it is mains voltage leaking to the GND wire of the HDMI cable!

This because the switching power supply in the TV has filter caps between both mains wires and the GND of the TV, and by extension the GND of the HDMI cable.

As both capacitors have the same value, the voltage between the "hot" mains wire and the "cold" mains wire is split in two by this capacitive divider.
The caps are only a few nanofarad, so only a small current is leaking through them, so touching the divided voltage does not give you a fatal shock, but you should connect the GND of theTV to earth, by plugging the TV into a grounded outlet.

Not the that a PI is not connected to earth normally, so any voltage between GND (of TV and RPI) relative to earth does not leak away, and you can still feel a "tingle" from it.

Be safe, and ground your TV!

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Re: Getting shock from micro hdmi port when connected to tv hdmi port

Wed Jun 17, 2020 4:44 pm

Heater wrote:
Wed Jun 17, 2020 3:46 pm
.... all your mussels ........
And all your cockles too!
Quis custodiet ipsos custodes?

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Re: Getting shock from micro hdmi port when connected to tv hdmi port

Wed Jun 17, 2020 5:09 pm

drgeoff wrote:
Wed Jun 17, 2020 4:44 pm
Heater wrote:
Wed Jun 17, 2020 3:46 pm
.... all your mussels ........
And all your cockles too!
and why are we throwing random seafood across the room anyways? Inquiring minds want to know. Seems wasteful and messy

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Re: Getting shock from micro hdmi port when connected to tv hdmi port

Wed Jun 17, 2020 6:55 pm

bjtheone wrote:
Wed Jun 17, 2020 5:09 pm
and why are we throwing random seafood across the room anyways? Inquiring minds want to know. Seems wasteful and messy
Well something has to come before Raspberry Pie. :lol:
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wh7qq
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Re: Getting shock from micro hdmi port when connected to tv hdmi port

Wed Jun 17, 2020 7:12 pm

Old practice in TV set design was to put the bottom of the single winding transformer to the chassis...all fine until someone cut off the extra wide part of the plug blade to reverse it or plugged into a mis-wired receptacle or used a "cheater" plug or used a coat-hanger antenna pushed blindly down the old hole for the missing rabbit ear antennas. I am not current on flat screen TV design but is that a possibility here...the use of single winding transformers to save $$$? Considering all the dirt cheap TVs that are flooding the market, one wonders.

Many so-called "electricians" used to believe that there was no difference between line and neutral (black and white) lines so it didn't matter how you wired an outlet or plug. One of those "hot-chassis" TV sets could kill under the right circumstances. One hopes that it is not the case today.

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Re: Getting shock from micro hdmi port when connected to tv hdmi port

Wed Jun 17, 2020 7:29 pm

wh7qq wrote:
Wed Jun 17, 2020 7:12 pm
Many so-called "electricians" used to believe that there was no difference between line and neutral (black and white) lines so it didn't matter how you wired an outlet or plug.
On some supplies, that is true. Just not true for most. It is also the case that many two-pin (unearthed) mains sockets around the world are not polarised anyway, so unearthed equipment should be designed to cope with swapped neutral and line.
Most hot chassis designs ran the chassis at half-mains to overcome that problem. So if exposed they were always semi-lethal, instead of truly lethal half the time. :shock:
wh7qq wrote:
Wed Jun 17, 2020 7:12 pm
One of those "hot-chassis" TV sets could kill under the right circumstances. One hopes that it is not the case today.
A live chassis in a properly designed and undamaged case should not be dangerous. (I am NOT advocating the practise!!) Danger arose when some clever person decided to add a video input, or sound output, with the ground connected to the chassis -- instant big problem. Note that the aerial input on such TVs should have had an (internal) isolating transformer, removing this would also be highly dangerous.
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Re: Getting shock from micro hdmi port when connected to tv hdmi port

Thu Jun 18, 2020 8:23 am

davidcoton wrote:
Wed Jun 17, 2020 7:29 pm
wh7qq wrote:
Wed Jun 17, 2020 7:12 pm
Many so-called "electricians" used to believe that there was no difference between line and neutral (black and white) lines so it didn't matter how you wired an outlet or plug.
On some supplies, that is true. Just not true for most. It is also the case that many two-pin (unearthed) mains sockets around the world are not polarised anyway, so unearthed equipment should be designed to cope with swapped neutral and line.
Most hot chassis designs ran the chassis at half-mains to overcome that problem. So if exposed they were always semi-lethal, instead of truly lethal half the time. :shock:
wh7qq wrote:
Wed Jun 17, 2020 7:12 pm
One of those "hot-chassis" TV sets could kill under the right circumstances. One hopes that it is not the case today.
A live chassis in a properly designed and undamaged case should not be dangerous. (I am NOT advocating the practise!!) Danger arose when some clever person decided to add a video input, or sound output, with the ground connected to the chassis -- instant big problem. Note that the aerial input on such TVs should have had an (internal) isolating transformer, removing this would also be highly dangerous.
It was standard practice that valved UK monochrome TVs had chassis connected directly to one side of the mains. Other side of mains input went through the on/off switch to two places. One was a diode valve acting as half wave rectifier to provide the H.T. supply. The other was the chain of all the valve heaters in series (and a dropper resistor).

The aerial input had a low value capacitor in series with each of the inner and outer of the coax socket. As the lowest input frequency was 40 MHz there was negligible loss to the RF input but enough impedance at 50Hz to limit current to a safe value even if the chassis was live.
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Heater
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Re: Getting shock from micro hdmi port when connected to tv hdmi port

Thu Jun 18, 2020 9:39 am

drgeoff wrote:
Wed Jun 17, 2020 4:44 pm
Heater wrote:
Wed Jun 17, 2020 3:46 pm
.... all your mussels ........
And all your cockles too!
Dammit.

Seafood and electricity do not mix. As Molly Malone found out:

"Cockles and mussels alive, alive oh!"
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Re: Getting shock from micro hdmi port when connected to tv hdmi port

Thu Jun 18, 2020 9:59 am

drgeoff wrote:
Thu Jun 18, 2020 8:23 am

It was standard practice that valved UK monochrome TVs had chassis connected directly to one side of the mains. Other side of mains input went through the on/off switch to two places. One was a diode valve acting as half wave rectifier to provide the H.T. supply. The other was the chain of all the valve heaters in series (and a dropper resistor).

The aerial input had a low value capacitor in series with each of the inner and outer of the coax socket. As the lowest input frequency was 40 MHz there was negligible loss to the RF input but enough impedance at 50Hz to limit current to a safe value even if the chassis was live.
I stand corrected. Thanks drgeoff.
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Re: Getting shock from micro hdmi port when connected to tv hdmi port

Thu Jun 18, 2020 10:03 am

@OP
1. disconnect the RPi from the TV.... power on the RPi setup...do you get shocks from the HDMI and or USB port?
2. remove the HDMI cable from the RPi and connect that HDMI cable to your TV... power ON the TV.... do you get shocks from the HDMI cable?

if NO on #1 and YES on #2, your TV is not safe.... and might kill you! get a better (electrically isolated and safe) TV

if YES on #1, change your charger! its not safe! it might kill you! get a proper PSU!

one cannot negotiate with electrical shocks!
its your safety.....YOU DECIDE!
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Come to me with 'problems' and I'll help you find solutions"

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drgeoff
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Re: Getting shock from micro hdmi port when connected to tv hdmi port

Thu Jun 18, 2020 10:30 am

Does the OP know the differences between:

1. The brief zap from a static discharge eg touching earthed metalwork after walking across a carpet or touching the bodywork of a car after getting out of it on a hot dry day.

2. The continuous mild tingle caused by the capacitors discussed above.

3. A full blooded shock arising from accidentally coming into contact with live AC mains.

1 and 2 may be unpleasant but nothing to be overly concerned about.

3 is to be avoided.
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Heater
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Re: Getting shock from micro hdmi port when connected to tv hdmi port

Thu Jun 18, 2020 10:32 am

We still don't know what "shock" is meant here.

Could be that cockles and mussels getting thrown across the room kind of shock.

Could be that kind hint of "electric vibration" one can often feel when gently rubbing a finger over a non-grounded chassis. Like my Microsoft Surface Pro.

Could be the little "ticks" of static discharge.

Some of these might kill your Pi or other static sensitive electronics. Others might kill you. Others are just, meh.
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Re: Getting shock from micro hdmi port when connected to tv hdmi port

Thu Jun 18, 2020 11:03 am

drgeoff wrote: Does the OP know the differences between:

1. The brief zap from a static discharge eg touching earthed metalwork after walking across a carpet or touching the bodywork of a car after getting out of it on a hot dry day.

2. The continuous mild tingle caused by the capacitors discussed above.

3. A full blooded shock arising from accidentally coming into contact with live AC mains.

my bet is on #3
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Come to me with 'problems' and I'll help you find solutions"

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Heater
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Re: Getting shock from micro hdmi port when connected to tv hdmi port

Thu Jun 18, 2020 12:02 pm

LTolledo wrote:
Thu Jun 18, 2020 11:03 am
my bet is on #3
Why?

Seems really unlikely with modern consumer monitors and such. Was never a common issue with such thing even decades ago. Unless our OP has been hacking on something we don't know about yet.
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Re: Getting shock from micro hdmi port when connected to tv hdmi port

Thu Jun 18, 2020 12:27 pm

Well, if the OP does not responsibly return back (in 3 days lets make it 5 days) to "satisfy our curiosity" on the matter

then we've all been "spammed"

best that the topic be "quarantined and locked" before it "corrodes"
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Come to me with 'problems' and I'll help you find solutions"

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drgeoff
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Re: Getting shock from micro hdmi port when connected to tv hdmi port

Thu Jun 18, 2020 3:30 pm

LTolledo wrote:
Thu Jun 18, 2020 12:27 pm
Well, if the OP does not responsibly return back (in 3 days lets make it 5 days) to "satisfy our curiosity" on the matter

then we've all been "spammed"

best that the topic be "quarantined and locked" before it "corrodes"
Or he decided to try it again to identify which of the 3 types I posted and it really was the third one. :(
Quis custodiet ipsos custodes?

Heater
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Re: Getting shock from micro hdmi port when connected to tv hdmi port

Thu Jun 18, 2020 3:37 pm

drgeoff wrote:
Thu Jun 18, 2020 3:30 pm
Or he decided to try it again to identify which of the 3 types I posted and it really was the third one. :(
I thought that was the 3 types "we" posted.

Oh dear, what have we done?

Perhaps we should include a hazard warning and disclaimer in our sigs?
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RaspbianUser1
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Re: Getting shock from micro hdmi port when connected to tv hdmi port

Thu Jun 18, 2020 3:38 pm

First and last post, do all of the people that do this touch their nearest plug with a fork :lol:

Just kidding, not meaning mean :?


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Re: Getting shock from micro hdmi port when connected to tv hdmi port

Thu Jun 18, 2020 3:40 pm

Heater wrote:
Thu Jun 18, 2020 3:37 pm
drgeoff wrote:
Thu Jun 18, 2020 3:30 pm
Or he decided to try it again to identify which of the 3 types I posted and it really was the third one. :(
I thought that was the 3 types "we" posted.

Oh dear, what have we done?

Perhaps we should include a hazard warning and disclaimer in our sigs?
"☠ Warning do not put fork in outlet ☠ "
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Overclocked at 2200MHz CPU and 700 MHz GPU with a over voltage of 7
Think before you delete something a stranger on the internet told you to.

drgeoff
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Re: Getting shock from micro hdmi port when connected to tv hdmi port

Thu Jun 18, 2020 4:08 pm

Heater wrote:
Thu Jun 18, 2020 3:37 pm
drgeoff wrote:
Thu Jun 18, 2020 3:30 pm
Or he decided to try it again to identify which of the 3 types I posted and it really was the third one. :(
I thought that was the 3 types "we" posted.
Merely specifying the list I posted, otherwise "the third one" would be ambiguous.
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Re: Getting shock from micro hdmi port when connected to tv hdmi port

Fri Jun 19, 2020 4:30 pm

P.S. the Type 2 "tingles" is actually very common, seen as many people don't plug their TV or Monitor in a grounded outlet.
alsmost all RPI's out there have a permanent 110V (for europe) or 55V (for US etc) AC voltage relative to earth on them, and almost nobody notices this, as the current flow is so low. But you have to keep this in mind when you interface stuff with long cables etc, as it might cause disturbances. :mrgreen:


If you don't believe me, use a multimeter set to AC Volt, and measure the voltage between any metal part of the PI, and a local ground point, that is water faucet, or anything else electrically connected to earth, like a CV radiator, or the ground pole of an electrical outlet. or just you finger for that matter, as long as you are not wearing dry plastic shoes, you should be "grounded".... :mrgreen:

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