getting lots of electric shocks

emujuice

man, maybe it is ghosts! had an interesting evening. i got my dad round to have a look. he's doesn't pretend to be an expert, but he knows a fair bit. basically he kept saying it's not the wiring...then couldn't make his mind up.
the situation is: if i have my shoes on (trainers say) i don't get shocked. if i take them off and stand on the carpet i get constant shocks. this is to my mp3 player, which is plugged in in a seperate socket to the otehr stuff. it has a transformer. so basically my dad kept saying it can't be the wiring coz of the transformer, it must be static discharging into the player. BUT - i don't get shocks unless it's plugged into the mains. touching the lead (not the mp3 player) also gives me shocks. but again, not if i have my shoes on. so i'm obviously making a circuit some how.
another but, is that plugging it in at the other end of the room i get a much smaller shock, which discharges, and isn't constant.
this is on the same ring as the other socket used.
the flat is very damp and the carpet is some kind of acrilic or something.
we didn't really come to any conclusions, just that it wasn't going to kill me, and to wear shoes when dealing with electrics...
i think we're just going to move out. hte house is riddled iwth little problems and i've had enough. only 2 months left on the contract....

Cagey

Strange one this. You would normally only get static shocks if you discharge to an earthed source. As there is no earthed parts on an mp3 or any equipment supplied by a transformer. By the same token there is no way you should get an electric shock from equipment supplied by a transformer.

Can`t wait to hear what you find.

Raptorman_2

Cagey wrote:

Strange one this. You would normally only get static shocks if you discharge to an earthed source. As there is no earthed parts on an mp3 or any equipment supplied by a transformer. By the same token there is no way you should get an electric shock from equipment supplied by a transformer.

Can`t wait to hear what you find.

Hi,

I disagree slightly with this one. Suppose the output of your transformer is normally 9V. your equipment is supplied by 2 cores from the transformer, 0V and 9V so the MP3 player sees a potential of 9V minus 0V = 9V. However, if there's a problem with the earth the transformer may be floating at a different potential giving 240V where 9V should be and 231V where 0V should be. So the MP3 player is still seeing a power supply of 240V-231V = 9V therefore it would still work... but.... if you were to touch the output of the tranformer you would bridge the potential of 240V from the floating output of the tranformer and 0V (earth) on your bare feet. However, if you were wearing insulating shoes, you would not be earthed and therefore would not connect to the ground (earth). The above is an over exaggeration, but you see my point.
It may be nothing to do with the above, but seems possible!!

Interesting to see the outcome!!

Rap

emujuice

thanks for the help guys. my dad seems to agree with you about the earth being dodgy and creating a circuit. i'm not sure there is a solution. my dad is completely puzzled, and finding it facinating, but not too worrying.
if he comes up with an answer i'll let you know. raptorman i think you're winning so far!

djohn2002uk

Raptorman wrote:

Hi,

I disagree slightly with this one. Suppose the output of your transformer is normally 9V. your equipment is supplied by 2 cores from the transformer, 0V and 9V so the MP3 player sees a potential of 9V minus 0V = 9V. However, if there's a problem with the earth the transformer may be floating at a different potential giving 240V where 9V should be and 231V where 0V should be. So the MP3 player is still seeing a power supply of 240V-231V = 9V therefore it would still work... but.... if you were to touch the output of the tranformer you would bridge the potential of 240V from the floating output of the tranformer and 0V (earth) on your bare feet. However, if you were wearing insulating shoes, you would not be earthed and therefore would not connect to the ground (earth). The above is an over exaggeration, but you see my point.
It may be nothing to do with the above, but seems possible!!

Interesting to see the outcome!!

Rap

How do you get 240v from the secondary winding of a transformer? The ONLY way that could happen is if the ratio of the primary to secondary was 1 : 1. If that were the case her mp3 player would have been long gone.

Also you don't get 9v and 0v out of a transformer. Transformers only work on AC and both poles of the output are constantly changing 50 times a second between positive and negative at values depending on the ratio of the Primary and Secondary windings. In this case from -4.5v to +4.5v.

On some types of small transformer you may see outputs of, for example 9v--0v--9v and this is purely 2 seperate secondary windings where you can use the 9v and 9v connections to get 18v, but if you were to measure between the 3 connections you would find a meter would read one as -9v and the other as +9v.

Raptorman_2

djohn2002uk wrote:

How do you get 240v from the secondary winding of a transformer? The ONLY way that could happen is if the ratio of the primary to secondary was 1 : 1. If that were the case her mp3 player would have been long gone.

Also you don't get 9v and 0v out of a transformer. Transformers only work on AC and both poles of the output are constantly changing 50 times a second between positive and negative at values depending on the ratio of the Primary and Secondary windings. In this case from -4.5v to +4.5v.

On some types of small transformer you may see outputs of, for example 9v--0v--9v and this is purely 2 seperate secondary windings where you can use the 9v and 9v connections to get 18v, but if you were to measure between the 3 connections you would find a meter would read one as -9v and the other as +9v.

Apologies djohn2002uk, I blame my Father for his terminology when I was young i.e. "plug the transformer in" would mean any power supply that you plugged into the mains, whether or not it had a transformer in or not. Sometimes I come out with the same wrong terminology out of habbit!
Anyhow, you were missing the point some what. Assume that the output of the power supply was 9V DC regulated, What I was trying to point out was that in some cases the 0V and 9V can float together if the 0V is not tied in some way to the Earth on the mains side of things. Obviously not all power supplies are built like this, but a fair few are. When I say float I mean the following. If the 0V is not tied to Earth in a power supply that requires it to be, although the MP3 player will see a potential difference of 9V on its power supply, and still work, if you then put a volt meter between 0V on the power supply output and the Earth on the Mains side, you could get a potential difference of say 100V (random plucked out of the air figure). In this case the potential difference between then 9V output and Earth would be 109V. So, the MP3 player would still work because it only saw the 9V difference, but if you touched the MP3 player and earth yourself, you could have a potential between your hand holding the MP3 player, and your foot on the floor of 100V, hence the shock. Whether or not it would be 100V would be dependent on the power supply, and how much the output had floated away from the Earth.
Another way in which earths can float is if you think of some poor designs of Mains suppression techniques. Place a capacitor between live and earth, and neutral and earth should be okay, BUT remove the earth connection in the plug and all of a sudden you have a potential divider between live and neutral. i.e. a capacitor from live to earth, and earth to neutral. Therefore you end up with an AC voltage on what should be earth of +- 120V. It will be tiny current, but enough to shock you.
Working for a major mobile phone company, I've seen some interesting charger designs. One charger was such a poor design and had some of the things mentioned above, and eveytime you spoke to someone on the phone when the charger was plugged in, you would get a shock on your ear (the chassis of the phone was metal). On another design the current through some of the caps on the mains side of things was high enough to slowly heat it so after a couple of days it exploded.... nice!!

emujuice

woah! i'm hoping nothing is going to explode. i think i'm begining to lose the gist of things, but i do appreciate all your help. the landlord has agreed to have a electrician come, unfortunately he's coming this weekend when we're not around. i'm hoping i can persuade him to take his shoes off over the phone...also i brought the mp3 player with me, so i'll have to hope the other equiptment is still giving shocks (if you know waht i mean), but my dad had rearranged stuff to improve it (ie stopping diff equiptment touching each other).
anyway, i'll let you know what he finds...

irnbru_2

emujuice wrote:

the landlord has agreed to have a electrician come, unfortunately he's coming this weekend when we're not around.

Did the electrician fix it?

rygon

If its a new installation (done this year) then by law it has to be inspected and tested by a competent person (under Part P)
A competent person must be registered (a bit like the corgi register).
If so ask for a copy of the inspection. If he hasnt got one its more than likely its done by a cowboy and is also illegal (although Part P was only introduced this year so if it was done a few yrs back they wouldnt have needed one)