Author Topic: Why do I feel there's current to my left ear through earphone from tablet?  (Read 6722 times)

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Offline Boris_yoTopic starter

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I am wearing Logitech's earphones connected to chinese tablet. The tablet has power adaptor plugged in mains. Next to my leg is a workshop type of a fan. Whenever I touch it with my bare foot, I feel small current goes through my ear.

How is this possible and why only left ear?
Does this have the potential to damage earphones?

Here's the approximate spot where I feel current:

« Last Edit: July 01, 2014, 05:09:59 pm by Boris_yo »
 

Offline AndyC_772

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Sod your earphones, what you describe has the potential to send a current up your leg and through your heart and your brain.

It sounds like the mains adapter for your tablet has poor isolation. There's a leakage path through the adapter from the mains, into the tablet, through the earphones, then through you, and down to earth via the fan which is (presumably) earthed.

Does the tablet have batteries? If so, try removing its mains adapter to ensure that the problem goes away. Then take the adapter outside, find something nice and solid to use as an anvil, and smash the adapter to unrecognisably small pieces with the biggest hammer you can find.

Offline electronwaster

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I wouldn't be comfortable not knowing either! :o I personally would want to know if it's RF, mains, or switching noise, or whatever.

If you swap the earpieces over with respect to your ears (left to right, right to left) does the feeling move to the other ear?

I would probably try testing the relevant parts for unwanted voltage with a multimeter, also it would be instructive to know if the conductive parts of the earpiece are electrically connected to any of the terminals on the headphone plug.
 

Online sean0118

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It sounds like the mains adapter for your tablet has poor isolation. There's a leakage path through the adapter from the mains, into the tablet, through the earphones, then through you, and down to earth via the fan which is (presumably) earthed.

It's suspected someone in Australia died recently from this sort of defect, OP needs to remove the adapter ASAP.

http://www.theage.com.au/victoria/australian-woman-electrocuted-by-usb-charger-20140627-zsnm7.html
 

Offline Rerouter

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i will probably say that the op should measure first before destroying / replacing a mains adapter, as it is better to identify a clear fault over thinking you have resolved it only to fry yourself later,
 

Offline bookaboo

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Sod your earphones, what you describe has the potential to send a current up your leg and through your heart and your brain.

It sounds like the mains adapter for your tablet has poor isolation. There's a leakage path through the adapter from the mains, into the tablet, through the earphones, then through you, and down to earth via the fan which is (presumably) earthed.

Does the tablet have batteries? If so, try removing its mains adapter to ensure that the problem goes away. Then take the adapter outside, find something nice and solid to use as an anvil, and smash the adapter to unrecognisably small pieces with the biggest hammer you can find.

My first reaction was this too, on reflection I'd send it to your local Trading Standards. Then contact your solicitor and sue the crap out of the importer. Normally I hate claim culture but in this case it's probably the only way you are going to get the industry to listen.
 

Offline AndyC_772

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You write as though "the industry" was one, single entity.

In this case, the entity in question is one single company which, we presume, imported a charger from China. We further presume that the charger is defective and non-compliant by design, rather than simply being faulty.

With that in mind, what, specifically, would you hope to gain by personally taking the seller to court?

By all means report it to the authorities if you have the energy, but I stand by the hammer as being the best course of action.

Offline beretmaster

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I would use the FBH on that! I would imagine its a strange coincidence that its your left ear, but I certainly wouldn't want to risk finding out. Just get rid of that adapter!
 

Online sean0118

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Also I just though, could the fan be the problem? With Op being grounded by the headphones? Maybe unlikely?
 

Offline amyk

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http://www.theage.com.au/victoria/australian-woman-electrocuted-by-usb-charger-20140627-zsnm7.html
That's what came to mind when I read the title too...

Measure with a multimeter on AC range how much voltage there is between the the earphones and the fan, then earphones and ground, and fan and ground; if you get a voltage, see if you can draw any appreciable current between the two points. It could be a fault with the adapter, the fan, the socket wiring, or a harmless (but possibly still perceptible) <250uA as allowed by IEC60950  through an EMI suppression cap. The available current is the important part.
 

Offline bookaboo

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You write as though "the industry" was one, single entity.

In this case, the entity in question is one single company which, we presume, imported a charger from China. We further presume that the charger is defective and non-compliant by design, rather than simply being faulty.

With that in mind, what, specifically, would you hope to gain by personally taking the seller to court?

By all means report it to the authorities if you have the energy, but I stand by the hammer as being the best course of action.

Ok so you take the hammer to it, what about the next guy that's not so observant? As for the authorities, all the rules are there but they are not enforced and government bodies move slow. I still say people should take suppliers of dangerously non-compliant items to book themselves. Once word spreads the importers will might twice about importing cheap tat. That should also help out the responsible importers that do take the time to spec and check their products.
 

Offline beretmaster

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Also I just though, could the fan be the problem? With Op being grounded by the headphones? Maybe unlikely?

I would say its very unlikely, assuming the fan is a grounded device, there would have to be a fault to earth in the fan, and the earth on the fan disconnected. (Otherwise the fan would just blow the fuse in the distribution board)
 

Offline Rigby

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Fans aren't always grounded.  I don't think I have a single fan in my house with a grounding pin on the plug.  About half of them have metal exteriors, though.

Whomever the authority is in your country on these things, notify them. In the US it would probably be the FTC.  It is the government's responsibility to allow or disallow the import of unsafe items such as this.  They need to be made aware.

If they are aware, and they are doing nothing, it is time to start talking to the press.

The other half of me says 'caveat emptor' and 'don't buy cheap shit.'
« Last Edit: June 28, 2014, 08:36:36 pm by Rigby »
 

Online wraper

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That's because of the capacitor between primary and secondary side in the charger. Fan is either grounded or also have small filter capacitor between mains and housing. You eapphone likely also have some contact to the housing. Therefore you become a part of elecric circuit and small AC current flows through you  >:D. There are no any faults, of course it does not mean that Chinese charger is designed safely.
 

Offline Psi

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As said above,

It's not uncommon to get small currents between an appliances and ground, especially devices that have no earth pin.
You can sometimes even see tiny sparks when connecting a metal connector from the no earth device to an earthed metal connector, like you might do plugging audio RCA from tablet to stereo (where stereo rca shield is mains earth)

It's usually safe in that it wont kill you but always a sign of bad product design.
« Last Edit: June 28, 2014, 10:04:47 pm by Psi »
Greek letter 'Psi' (not Pounds per Square Inch)
 

Online wraper

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It's usually safe in that it wont kill you but always a sign of bad product design.
I won't fully agree with this part. At least if not considering most of the double insulated products as a bad design. This capacitor quiet often is a must to suppress HF noise (on higher power SMPS). In this case it is needed so touch screen works properly, otherwise it will be register false presses. On branded mobile phone/tablet chargers there are often no capacitor. They use more expensive transformer construction with shield between primary and secondary to suppress the noise.
 

Offline ejeffrey

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It's usually safe in that it wont kill you but always a sign of bad product design.
I won't fully agree with this part. At least if not considering most of the double insulated products as a bad design. This capacitor quiet often is a must to suppress HF noise (on higher power SMPS). In this case it is needed so touch screen works properly, otherwise it will be register false presses. On branded mobile phone/tablet chargers there are often no capacitor. They use more expensive transformer construction with shield between primary and secondary to suppress the noise.

If a double insulated design has enough leakage current through the class XY capacitors to exceed the sensory threshold they are bad design, and I don't care why they have to.  It is extremely common, but it is bad design and there is simply no excuse for it.

Of course getting cheap "Chinese Export" goods to comply with the rules that actually exist is apparently already impossible, so I don't know what you can do about it. 
« Last Edit: June 29, 2014, 01:42:08 am by ejeffrey »
 

Online wraper

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through the class X capacitors
Class Y. Class X are higher capacitance and are used between phase and neutral. Class Y goes to ground or secondary and comply with rules very well.
 

Offline Boris_yoTopic starter

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You can sometimes even see tiny sparks when connecting a metal connector from the no earth device to an earthed metal connector, like you might do plugging audio RCA from tablet to stereo (where stereo rca shield is mains earth)

I have often spark when connecting charger which is already connected to the tablet to mains. It reminds me if spark I get to see when connecting iron to mains. In both cases appliances have adapters with 2 prongs.
 

Offline Richard Crowley

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In both cases appliances have adapters with 2 prongs.
In that case BOTH the mains adapter AND the fan are suspect.  If EITHER of them were properly isolated, you wouldn't be experiencing this symptom. Is it  possible that the fan metal-work is "accidentally" grounded even if it has only a 2-prong plug?

I would put a proper 3-wire grounded power cord on the fan, and replace the mains adapter with something more properly isolated (or 3-wire grounded).
 

Offline XOIIO

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You know, I even had a big box fan (and still do somewhere, need to put it back together) I've never seen a grounded fan personally.

Offline Stonent

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How is this pissible



 :-DD

(Reference might not make sense unless you watch 80s Brit-Coms)
The larger the government, the smaller the citizen.
 

Offline sfiber

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actually its not a current.its just a spark.I use gionee e3 and I lived this situaton once a time then I never listen with earphones when its phone was plugged.I think its all about its manufacturing quality.
 

Online wraper

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actually its not a current.its just a spark.I use gionee e3 and I lived this situaton once a time then I never listen with earphones when its phone was plugged.I think its all about its manufacturing quality.
No, it's not just a spark. Spark appears because capacitor(s) discharges at the connection moment. As it was charged to some voltage, and then small AC current flows. Attach multimeter with AC uA or even mA range, you'll be able to measure some current.
 

Offline Monkeh

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How is this pissible



 :-DD

(Reference might not make sense unless you watch 80s Brit-Coms)

Listen very carefully, I shall say this only once.
 


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