Why do I feel there's current to my left ear through earphone from tablet? - Page 1
Forum section: electronics / beginners

author: Boris_yo
author_rank: Frequent Contributor
timestamp: June 28, 2014, 09:11:34 am
content: 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:

author: AndyC_772
author_rank: Super Contributor
timestamp: June 28, 2014, 09:18:11 am
content: 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.

author: electronwaster
author_rank: Regular Contributor
timestamp: June 28, 2014, 09:22:55 am
content: I wouldn't be comfortable not knowing either!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.

author: sean0118
author_rank: Frequent Contributor
timestamp: June 28, 2014, 09:51:43 am
content: Quote from: AndyC_772 on June 28, 2014, 09:18:11 amIt'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

author: Rerouter
author_rank: Super Contributor
timestamp: June 28, 2014, 10:08:23 am
content: 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,

author: bookaboo
author_rank: Frequent Contributor
timestamp: June 28, 2014, 10:26:47 am
content: Quote from: AndyC_772 on June 28, 2014, 09:18:11 amMy 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.

author: AndyC_772
author_rank: Super Contributor
timestamp: June 28, 2014, 10:32:37 am
content: 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.

author: beretmaster
author_rank: Newbie
timestamp: June 28, 2014, 11:01:39 am
content: 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!

author: sean0118
author_rank: Frequent Contributor
timestamp: June 28, 2014, 11:16:46 am
content: Also I just though, could the fan be the problem? With Op being grounded by the headphones? Maybe unlikely?

author: amyk
author_rank: Super Contributor
timestamp: June 28, 2014, 12:00:52 pm
content: Quote from: sean0118 on June 28, 2014, 09:51:43 amThat'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 IEC60950through an EMI suppression cap. The available current is the important part.

author: bookaboo
author_rank: Frequent Contributor
timestamp: June 28, 2014, 12:44:07 pm
content: Quote from: AndyC_772 on June 28, 2014, 10:32:37 amOk 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.

author: beretmaster
author_rank: Newbie
timestamp: June 28, 2014, 08:19:40 pm
content: Quote from: sean0118 on June 28, 2014, 11:16:46 amI 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)

author: Rigby
author_rank: Super Contributor
timestamp: June 28, 2014, 08:31:22 pm
content: 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.'

author: wraper
author_rank: Unknown
timestamp: June 28, 2014, 09:56:51 pm
content: 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. There are no any faults, of course it does not mean that Chinese charger is designed safely.

author: Psi
author_rank: Super Contributor
timestamp: June 28, 2014, 10:02:48 pm
content: 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.

author: wraper
author_rank: Unknown
timestamp: June 28, 2014, 10:14:12 pm
content: Quote from: Psi on June 28, 2014, 10:02:48 pmI 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.

author: ejeffrey
author_rank: Super Contributor
timestamp: June 28, 2014, 10:21:59 pm
content: Quote from: wraper on June 28, 2014, 10:14:12 pmIf a double insulated design has enough leakage current through the classXY 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.

author: wraper
author_rank: Unknown
timestamp: June 28, 2014, 10:42:43 pm
content: Quote from: ejeffrey on June 28, 2014, 10:21:59 pmClass 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.

author: Boris_yo
author_rank: Frequent Contributor
timestamp: June 29, 2014, 04:28:44 pm
content: Quote from: Psi on June 28, 2014, 10:02:48 pmI 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.

author: Richard Crowley
author_rank: Super Contributor
timestamp: June 29, 2014, 04:44:22 pm
content: Quote from: Boris_yo on June 29, 2014, 04:28:44 pmIn 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).

author: XOIIO
author_rank: Super Contributor
timestamp: June 29, 2014, 04:52:17 pm
content: 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.

author: Stonent
author_rank: Super Contributor
timestamp: June 29, 2014, 08:27:42 pm
content: Quote(Reference might not make sense unless you watch 80s Brit-Coms)

author: sfiber
author_rank: Regular Contributor
timestamp: June 29, 2014, 08:49:04 pm
content: 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.

author: wraper
author_rank: Unknown
timestamp: June 29, 2014, 10:10:57 pm
content: Quote from: sfiber on June 29, 2014, 08:49:04 pmNo, 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.

author: Monkeh
author_rank: Super Contributor
timestamp: June 29, 2014, 11:09:53 pm
content: Quote from: Stonent on June 29, 2014, 08:27:42 pmListen very carefully, I shall say this only once.

author: Boris_yo
author_rank: Frequent Contributor
timestamp: July 01, 2014, 05:13:10 pm
content: Quote from: Monkeh on June 29, 2014, 11:09:53 pmMy misspelling amused you?

author: G7PSK
author_rank: Super Contributor
timestamp: July 01, 2014, 05:45:25 pm
content: If there is one lesson to be learned from this and the story on the thread it's never ever use headphones with any exposed metal in them, plastic all over is the order of the day.

author: pickle9000
author_rank: Super Contributor
timestamp: July 01, 2014, 06:01:12 pm
content: Plastic blades /cage on ungrounded fan can make a fair bit of static charge.

author: SeanB
author_rank: Super Contributor
timestamp: July 01, 2014, 06:17:38 pm
content: Quote from: G7PSK on July 01, 2014, 05:45:25 pmI would not trust the plastic to be insulated to 300V either, I would suggest not using headphones when the device is plugged into the charger, and get some external speakers instead. Used PC amplified speakers are cheap, or free if you look around a little. not going to be anything close to Hi Fi, but then again with low bitrate mp3..............