tvvignesh
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Very high shock in raspberry PI 2 Model B

Wed Feb 25, 2015 1:49 pm

I recently bought the latest Raspberry PI 2 Model B and I am getting very high shock whenever I touch the PI which was not the case with my old PI (Raspberry PI Model B).
Is there any reason behind this? Can this be fixed? If the PI which I got is faulty, does the foundation accept returns?
Thanx in advance.

Joe Schmoe
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Re: Very high shock in raspberry PI 2 Model B

Wed Feb 25, 2015 1:54 pm

(I hope I am interpreting your post correctly. It sounds like you are saying that you got an electrical shock from handling the board… Is that correct?)

Yeah, most people will say that you (and subsequently, me as well) are imagining things, but I'm pretty sure that I received a shock the other day from handling my board (when it was plugged in and running) as well. I was more than a little surprised at this. It wasn't a big deal - nothing major - but I did feel a tingle.
And some folks need to stop being fanboys and see the forest behind the trees.

(One of the best lines I've seen on this board lately)

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RaTTuS
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Re: Very high shock in raspberry PI 2 Model B

Wed Feb 25, 2015 1:59 pm

as to returns - see the place where you got it from

dunno about shocks
Last edited by RaTTuS on Wed Feb 25, 2015 3:13 pm, edited 1 time in total.
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tenochtitlanuk
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Re: Very high shock in raspberry PI 2 Model B

Wed Feb 25, 2015 2:51 pm

My experience with USB power supplies is that they 'float', ie resistive & capacitive leakage means that their 'stable 5V' may be oscillating on top of tens of volts or more at 50Hz relative to house mains ground.. Luckily the source impedance of this ripple is high. But I've lit a high-brightness LED visibly with one side on a GPIO pin and the other in my hand- exactly like a mains-tester Neon screwdriver. And the Pi was merrily working, since it sees only the voltage across its 5V and zeroV lines!

However, if you felt a shock it implies a lower impedance than there should be for any such leakage.
If you have access to a CRO ( oscilloscope) see whether there is such a voltage by connecting one side to your 5V line and one to the local earth. The Pi CANNOT itself generate a >5V voltage between your hand and local earth...

obcd
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Re: Very high shock in raspberry PI 2 Model B

Wed Feb 25, 2015 3:12 pm

The Pi is powered with 5V. A voltage that low shouldn't bite you.
The problem is usually the power adapter. Those are most of the time not having a ground connection.
This means that the secundary ground can carry some mains voltage in reference to earth. If you touch that, it will cause a current flow between your body toward earth. You can check if you have such a voltage with a simple digital meter. Set it to AC. Connect one probe to a metal part of your pi and the other to a grounding point. This can be a metal water pipe, or the ground pin in your mains outlet. Even taking it between your fingers could work. You might make them wet for better conduction.
It wouldn't suprise me you will see some voltage ranging from 20 - 80V.
Is this dangerous? Yes and No. The current of that voltage is very limited (at least it should be) The voltage however is high enough to damage the Pi and other electronics in some cases. For instance, if you connect your TV hdmi plug, and the connected pin's aren't ground first, you will super impose that AC voltage on the inputs, and this might cause ESD damage. Same, if you connect something "non ground" on your Pi, you will add the AC voltage to that point, and that could cause damage. So, basically, it's good practice to have your Pi in a box and to always connect the power adapter as last device, after all other connections are made. Some modern TV sets don't have a ground connection either, so it's possible that the AC voltage comes from that device instead of your pi power adapter. If you ever touched the case of a PC that wasn't grounded, you will know what I am talking about. It's also for tha reason that PCMIA connectors have longer power and ground pins to ensure that those make contact first, in case of a hotplug.

tvvignesh
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Re: Very high shock in raspberry PI 2 Model B

Wed Feb 25, 2015 5:58 pm

Thanks a lot guys for all your fast replies. I wrote this post cause I am pretty sure it was an AC shock since I am well aware of the shock that the 5V DC may give me and it is certainly not that and I get it only when my TV's HDMI is connected to the PI which does not happen in the older PI version. And as you guys suggested, I will measure the voltage and see the magnitude.
After a bit of research, I noticed a small insulation above the old PI's HDMI plug which is absent in the latest version but I am not sure if that will be the reason.

drgeoff
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Re: Very high shock in raspberry PI 2 Model B

Wed Feb 25, 2015 6:34 pm

As others have said, the RPi is not the culprit. That will be the PSU or the display.

And there is no reason that the RPi2 will give you more of a shock than your previous one. What you feel depends on what resistance you present between your hand (touching metal of the RPi) and ground. That varies with things like what footwear you are wearing, what you are standing on and how damp or sweaty your fingers are.

fichtennadel
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Re: Very high shock in raspberry PI 2 Model B

Tue Mar 31, 2015 9:42 am

tvvignesh wrote:I recently bought the latest Raspberry PI 2 Model B and I am getting very high shock whenever I touch the PI which was not the case with my old PI (Raspberry PI Model B).
I can confirm getting an electrical shock sometimes.

It just happened to me when I lifted my PI 2, even though it is in a case: I accidentially touched the HDMI port and got an electrical shock. Not heavy, just enough to make me drop my PI in wonder. I checked the PI, no harm done (and no harm done on me, checked in that order ;-)).

The PI is connected to my old TV by the audio/video jack and the TV has no ground, so reading the explanations here in the thread, I guess that's where it picked up the voltage.

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