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electric shock
I was working on a 55VAC line-powered TV system the other day and I
could feel the power through dry fingers. I got the impression 55V could be quite nasty with wet hands and a good earth. It was interesting to feel this attenuated mains. The individual cycles can be felt quite clearly. It made me wonder if the feeling of touch has less persistence than vision. Of course the ears would turn the 50Hz into a note. Bill |
electric shock
On Fri, 18 May 2012 16:06:31 +0100
Bill Wright wrote: I was working on a 55VAC line-powered TV system the other day and I could feel the power through dry fingers. I got the impression 55V could be quite nasty with wet hands and a good earth. It was interesting to feel this attenuated mains. The individual cycles can be felt quite clearly. It made me wonder if the feeling of touch has less persistence than vision. Of course the ears would turn the 50Hz into a note. Bill The 'nasty' value would also depend on the available current flow, surely? 20 Amps would do serious damage, even 2 will kill you. -- Davey. |
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Now here is a thing. We have some pylons near here, if I walk under the
lines , thn hold my white cane up in the air, I can feel the 50 hertz as i gently run my finger over any exposed aluminium exposed area on the cane. Brian -- From the Sofa of Brian Gaff Reply address is active "Bill Wright" wrote in message ... I was working on a 55VAC line-powered TV system the other day and I could feel the power through dry fingers. I got the impression 55V could be quite nasty with wet hands and a good earth. It was interesting to feel this attenuated mains. The individual cycles can be felt quite clearly. It made me wonder if the feeling of touch has less persistence than vision. Of course the ears would turn the 50Hz into a note. Bill |
electric shock
Its of course across the heart you need to watch out for. Some people like
the effect of electric shocks, but obviously there are limits! Brian -- From the Sofa of Brian Gaff Reply address is active "Davey" wrote in message ... On Fri, 18 May 2012 16:06:31 +0100 Bill Wright wrote: I was working on a 55VAC line-powered TV system the other day and I could feel the power through dry fingers. I got the impression 55V could be quite nasty with wet hands and a good earth. It was interesting to feel this attenuated mains. The individual cycles can be felt quite clearly. It made me wonder if the feeling of touch has less persistence than vision. Of course the ears would turn the 50Hz into a note. Bill The 'nasty' value would also depend on the available current flow, surely? 20 Amps would do serious damage, even 2 will kill you. -- Davey. |
electric shock
"Bill Wright" wrote in message
... I was working on a 55VAC line-powered TV system the other day and I could feel the power through dry fingers. I got the impression 55V could be quite nasty with wet hands and a good earth. It was interesting to feel this attenuated mains. The individual cycles can be felt quite clearly. It made me wonder if the feeling of touch has less persistence than vision. Of course the ears would turn the 50Hz into a note. Bill In my younger days I managed to get 'stuck' on the 240V mains (picked up a live electrical item I was working on, forgetting the bottom cover was removed). I reckon I was connected for about five seconds before the power was removed. I can testify you can REALLY feel the cycles! Seriously scary moment when realised couldn't do anything about it. Arm muscles were near unusable for days afterwards. Over twenty years on you can still see the marks on my hands where the skin melted. |
electric shock
Davey wrote:
On Fri, 18 May 2012 16:06:31 +0100 Bill Wright wrote: I was working on a 55VAC line-powered TV system the other day and I could feel the power through dry fingers. I got the impression 55V could be quite nasty with wet hands and a good earth. It was interesting to feel this attenuated mains. The individual cycles can be felt quite clearly. It made me wonder if the feeling of touch has less persistence than vision. Of course the ears would turn the 50Hz into a note. Bill The 'nasty' value would also depend on the available current flow, surely? 20 Amps would do serious damage, even 2 will kill you. A lot less than 2A across your chest will kill you. Bill |
electric shock
In article ,
Bill Wright wrote: The individual cycles can be felt quite clearly. It made me wonder if the feeling of touch has less persistence than vision. Of course the ears would turn the 50Hz into a note. Presumably you feel it as 100Hz, since all you can detect is the magnitude. -- Richard |
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On 18/05/2012 16:09, Davey wrote:
On Fri, 18 May 2012 16:06:31 +0100 Bill wrote: I was working on a 55VAC line-powered TV system the other day and I could feel the power through dry fingers. I got the impression 55V could be quite nasty with wet hands and a good earth. It was interesting to feel this attenuated mains. The individual cycles can be felt quite clearly. It made me wonder if the feeling of touch has less persistence than vision. Of course the ears would turn the 50Hz into a note. Bill The 'nasty' value would also depend on the available current flow, surely? 20 Amps would do serious damage, even 2 will kill you. Actually anything greater than 20mA can induce cardiac fibrillation. This is why most RCDs are rated at 20mA leakage current. Rob. |
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On Fri, 18 May 2012 17:49:13 +0200, Martin wrote:
On Fri, 18 May 2012 16:16:14 +0100, "Brian Gaff" wrote: Its of course across the heart you need to watch out for. Some people like the effect of electric shocks, but obviously there are limits! Brian In one of today's newspapers there is a photo of a paraplegic guy who has just swum between two of the Indonesian islands using special attachments to what is left of his legs. It says he was electrocuted whilst removing a TV aerial You can't be electrocuted and live to tell the tail. By definition the word means a fatal electric shock. It was coined at the time of the first electric chair, a contraction of "electric execution". -- Graham. %Profound_observation% |
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On Fri, 18 May 2012 18:09:40 +0100, Graham. wrote:
On Fri, 18 May 2012 17:49:13 +0200, Martin wrote: On Fri, 18 May 2012 16:16:14 +0100, "Brian Gaff" wrote: Its of course across the heart you need to watch out for. Some people like the effect of electric shocks, but obviously there are limits! Brian In one of today's newspapers there is a photo of a paraplegic guy who has just swum between two of the Indonesian islands using special attachments to what is left of his legs. It says he was electrocuted whilst removing a TV aerial You can't be electrocuted and live to tell the tail. By definition the word means a fatal electric shock. It was coined at the time of the first electric chair, a contraction of "electric execution". Tale, not tail. Sory. -- Graham. %Profound_observation% |
electric shock
In article ,
Davey wrote: I was working on a 55VAC line-powered TV system the other day and I could feel the power through dry fingers. I got the impression 55V could be quite nasty with wet hands and a good earth. It was interesting to feel this attenuated mains. The individual cycles can be felt quite clearly. It made me wonder if the feeling of touch has less persistence than vision. Of course the ears would turn the 50Hz into a note. Bill The 'nasty' value would also depend on the available current flow, surely? 20 Amps would do serious damage, even 2 will kill you. It's the current flow through the body that matters - and pretty well anything you are likely to touch will be capable of supplying the 20 mA or so needed to kill you. Even a small battery. But then it needs enough volts to produce that current where it matters in the body. The most likely and shortest path is between both hands. It used to be thought less than about 50 volts was safe under those conditions, but many reckon 30 now. -- *I am a nobody, and nobody is perfect; therefore I am perfect* Dave Plowman London SW To e-mail, change noise into sound. |
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Martin wrote:
In one of today's newspapers there is a photo of a paraplegic guy who has just swum between two of the Indonesian islands using special attachments to what is left of his legs. It says he was electrocuted whilst removing a TV aerial This is typical of wiring in parts of Indonesia's capital Jakarta: http://tinyurl.com/7ro8dcr So if he was attending to an aerial above a shop front, say, then it might well have been amongst something like that. |
electric shock
On Fri, 18 May 2012 18:09:40 +0100, Graham. wrote:
On Fri, 18 May 2012 17:49:13 +0200, Martin wrote: On Fri, 18 May 2012 16:16:14 +0100, "Brian Gaff" wrote: Its of course across the heart you need to watch out for. Some people like the effect of electric shocks, but obviously there are limits! Brian In one of today's newspapers there is a photo of a paraplegic guy who has just swum between two of the Indonesian islands using special attachments to what is left of his legs. It says he was electrocuted whilst removing a TV aerial You can't be electrocuted and live to tell the tail. By definition the word means a fatal electric shock. It was coined at the time of the first electric chair, a contraction of "electric execution". Yes. However, it was soon also used to refer to non-lethal "electrocution" as seen in this example from the OED: 1899 Times 11 Apr. 1/4 Continuation of the Monster Holiday Show. Marvellous performances... See to-day, at 3 and 8, Dr. Walford Bodie electrocute a man. -- Peter Duncanson (in uk.tech.digital-tv) |
electric shock
On Fri, 18 May 2012 18:09:40 +0100
Graham. wrote: On Fri, 18 May 2012 17:49:13 +0200, Martin wrote: On Fri, 18 May 2012 16:16:14 +0100, "Brian Gaff" wrote: Its of course across the heart you need to watch out for. Some people like the effect of electric shocks, but obviously there are limits! Brian In one of today's newspapers there is a photo of a paraplegic guy who has just swum between two of the Indonesian islands using special attachments to what is left of his legs. It says he was electrocuted whilst removing a TV aerial You can't be electrocuted and live to tell the tail. By definition the word means a fatal electric shock. It was coined at the time of the first electric chair, a contraction of "electric execution". Fair enough. But what is the correct word for the survived equivalent, then? -- Davey. |
electric shock
On Fri, 18 May 2012 19:26:35 +0100, Davey
wrote: On Fri, 18 May 2012 18:09:40 +0100 Graham. wrote: On Fri, 18 May 2012 17:49:13 +0200, Martin wrote: On Fri, 18 May 2012 16:16:14 +0100, "Brian Gaff" wrote: Its of course across the heart you need to watch out for. Some people like the effect of electric shocks, but obviously there are limits! Brian In one of today's newspapers there is a photo of a paraplegic guy who has just swum between two of the Indonesian islands using special attachments to what is left of his legs. It says he was electrocuted whilst removing a TV aerial You can't be electrocuted and live to tell the tail. By definition the word means a fatal electric shock. It was coined at the time of the first electric chair, a contraction of "electric execution". Fair enough. But what is the correct word for the survived equivalent, then? How about the subject line of this thread, perhaps qualified by "severe", "very dangerous" etc. -- Graham. %Profound_observation% |
electric shock
On 2012-05-18, Graham wrote:
On Fri, 18 May 2012 19:26:35 +0100, Davey Fair enough. But what is the correct word for the survived equivalent, then? How about the subject line of this thread, perhaps qualified by "severe", "very dangerous" etc. I'm not sure "the severe subject line of this thread" has quite the same ring to it... -- David Taylor |
electric shock
Dave Plowman (News) wrote:
It's the current flow through the body that matters - and pretty well anything you are likely to touch will be capable of supplying the 20 mA or so needed to kill you. Even a small battery. But then it needs enough volts to produce that current where it matters in the body. But really it's about skin resistance. Yes, 50V might be able to push 30mA through your body, but your body would need to present a resistance of about 1.7k or less to drive that much current. I've just been downstairs, mixed up some strong brine and thoroughly soaked both my hands in it. With both hands still wet I gripped the probes of my multimeter as hard as I could. By altering my grip and trying really hard, I can just about get the reading down to 30k. Yes, I know this is not scientific and perhaps non-linear effects might arise with a higher voltage. But it's an indication. I reckon you'd be really hard pressed to drive 20mA through your body from 50V. -- SteveT |
electric shock
In article , Dave Plowman (News)
scribeth thus In article , Davey wrote: I was working on a 55VAC line-powered TV system the other day and I could feel the power through dry fingers. I got the impression 55V could be quite nasty with wet hands and a good earth. It was interesting to feel this attenuated mains. The individual cycles can be felt quite clearly. It made me wonder if the feeling of touch has less persistence than vision. Of course the ears would turn the 50Hz into a note. Bill The 'nasty' value would also depend on the available current flow, surely? 20 Amps would do serious damage, even 2 will kill you. It's the current flow through the body that matters - and pretty well anything you are likely to touch will be capable of supplying the 20 mA or so needed to kill you. Even a small battery. But then it needs enough volts to produce that current where it matters in the body. The most likely and shortest path is between both hands. It used to be thought less than about 50 volts was safe under those conditions, but many reckon 30 now. As its said; "Its the volts that jolts, but its the mill's that kills".. You need sufficient volts to push the mills... I do think that unless you have possibly bare skin thats soaked in a contact solution of sufficient area and applied to the right places you'd be hard pressed to kill anyone with say 30 volts... -- Tony Sayer |
electric shock
In article , Brian Gaff
scribeth thus Now here is a thing. We have some pylons near here, if I walk under the lines , thn hold my white cane up in the air, I can feel the 50 hertz as i gently run my finger over any exposed aluminium exposed area on the cane. Yes its called "leakage" Many years ago we used old fluorescent tubes to demonstrate this. We used to ride around in an old transit van which one of those long fibreglass aerials on the top, the sparks you could pull off the aerial lead were very impressive on wet nights;).. If you have a railway station thats on an electrified line you can get similar things, the volts are lower but so are the distances.. Not that I'd advise you too wave that too high of course;)... Brian -- Tony Sayer |
electric shock
In article , The Hemulen
scribeth thus "Bill Wright" wrote in message ... I was working on a 55VAC line-powered TV system the other day and I could feel the power through dry fingers. I got the impression 55V could be quite nasty with wet hands and a good earth. It was interesting to feel this attenuated mains. The individual cycles can be felt quite clearly. It made me wonder if the feeling of touch has less persistence than vision. Of course the ears would turn the 50Hz into a note. Bill In my younger days I managed to get 'stuck' on the 240V mains (picked up a live electrical item I was working on, forgetting the bottom cover was removed). I reckon I was connected for about five seconds before the power was removed. I can testify you can REALLY feel the cycles! Seriously scary moment when realised couldn't do anything about it. Arm muscles were near unusable for days afterwards. Over twenty years on you can still see the marks on my hands where the skin melted. I had a similar thing happen with an old metal cased electric drill years ago, the earth in the house that I was working in wasn't earth at all. That was disconnected at the fuse board and the cable in those days was lead covered rubber;!. Drill in one hand earthed metal ladder rung in the other!.... Didn't quite have burns, but the doc said if it had gone on for much longer it wouldn't have been a very good outcome;(.,. -- Tony Sayer |
electric shock
On Fri, 18 May 2012 19:35:27 +0000 (UTC)
David Taylor wrote: On 2012-05-18, Graham wrote: On Fri, 18 May 2012 19:26:35 +0100, Davey Fair enough. But what is the correct word for the survived equivalent, then? How about the subject line of this thread, perhaps qualified by "severe", "very dangerous" etc. I'm not sure "the severe subject line of this thread" has quite the same ring to it... Try "Quite the same Tingle", and we're getting closer. Still not there, though. -- Davey. |
electric shock
Martin wrote:
In one of today's newspapers there is a photo of a paraplegic guy who has just swum between two of the Indonesian islands using special attachments to what is left of his legs. It says he was electrocuted whilst removing a TV aerial What, removing it from the top of a 132kV pylon? Bill |
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Richard Tobin wrote:
In article , Bill Wright wrote: The individual cycles can be felt quite clearly. It made me wonder if the feeling of touch has less persistence than vision. Of course the ears would turn the 50Hz into a note. Presumably you feel it as 100Hz, since all you can detect is the magnitude. -- Richard I have very bad skin. It only conducts one way. Bill |
electric shock
They must have some strange ideas of how to power mast head amplifiers over
there then. What i mean is that you can still get devices that create electric shocks. tens devices and these are not lethal, some find them very pleasent. Brian -- From the Bed of Brian Gaff. The email is valid as Blind user. "Martin" wrote in message ... On Fri, 18 May 2012 16:16:14 +0100, "Brian Gaff" wrote: Its of course across the heart you need to watch out for. Some people like the effect of electric shocks, but obviously there are limits! Brian In one of today's newspapers there is a photo of a paraplegic guy who has just swum between two of the Indonesian islands using special attachments to what is left of his legs. It says he was electrocuted whilst removing a TV aerial -- Martin |
electric shock
In message , Bill Wright
writes Richard Tobin wrote: In article , Bill Wright wrote: The individual cycles can be felt quite clearly. It made me wonder if the feeling of touch has less persistence than vision. Of course the ears would turn the 50Hz into a note. Presumably you feel it as 100Hz, since all you can detect is the magnitude. -- Richard I have very bad skin. It only conducts one way. You ought to see a dermatologist and see if he can rectify the problem. -- Ian |
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Ian Jackson wrote:
You ought to see a dermatologist and see if he can rectify the problem. Yay! :-) -- SteveT |
electric shock
In one of today's newspapers there is a photo of a paraplegic guy who
has just swum between two of the Indonesian islands using special attachments to what is left of his legs. It says he was electrocuted whilst removing a TV aerial What, removing it from the top of a 132kV pylon? Metal ladder met powerline. And he is "limbless" (4 amputations) rather than paraplegic. http://www.bbc.co.uk/news/world-asia-18100850 -- Robin reply to address is (meant to be) valid |
electric shock
On Fri, 18 May 2012 16:16:14 +0100, "Brian Gaff"
wrote: Its of course across the heart you need to watch out for. Some people like the effect of electric shocks, but obviously there are limits! Brian A good shock is also used to start the heart! About 50 years ago when I was an apprentice TV engineer I often "showed off" by producing a blue arc with my finger from the EHT. It was quite safe because the current was very low. Years later I was working on Ampex computer tape decks and accidentally touched a motor servo drive. That was a releatively low voltage but high current - I almost did a somersault! Steve -- Neural Network Software. http://www.npsl1.com EasyNN-plus. Neural Networks plus. http://www.easynn.com SwingNN. Forecast with Neural Networks. http://www.swingnn.com JustNN. Just Neural Networks. http://www.justnn.com |
electric shock
On Saturday, May 19th, 2012, at 12:06:22h +0100, Stephen Wolstenholme wrote:
A good shock is also used to start the heart! Oftentime it is a shock (not necessarily an electric one) which causes it to stop. Incidentally, if you are interested in the role of electric currents in developmental biology, you may like to listen to the first segment on this week's edition of "Life on Earth", from PRI (Public Radio International). http://www.loe.ORG/shows/segments.html?programID=12-P13-00020&segmentID=1 |
electric shock
On Sat, 19 May 2012 13:29:38 +0200
Martin wrote: On Sat, 19 May 2012 12:06:22 +0100, Stephen Wolstenholme wrote: On Fri, 18 May 2012 16:16:14 +0100, "Brian Gaff" wrote: Its of course across the heart you need to watch out for. Some people like the effect of electric shocks, but obviously there are limits! Brian A good shock is also used to start the heart! About 50 years ago when I was an apprentice TV engineer I often "showed off" by producing a blue arc with my finger from the EHT. It was quite safe because the current was very low. Years later I was working on Ampex computer tape decks and accidentally touched a motor servo drive. That was a releatively low voltage but high current - I almost did a somersault! LOL I did the same thing. I also picked up a plug of a Honeywell line printer. A capacitor discharged through me knocking me off my chair. I have had a few car ignition spark shocks, and at work, one or two 6,000 volt industrial ignition transformer shocks. The common brand used half of the sine wave, but the Honeywell transformer used both parts, or something, and produced 15,000 volts. That hurt. -- Davey. |
electric shock
Brian Gaff wrote:
They must have some strange ideas of how to power mast head amplifiers over there then. What i mean is that you can still get devices that create electric shocks. tens devices and these are not lethal, some find them very pleasent. Brian I have a 200 year old device intended to cure neuralgia by means of electrodes and a small dynamo. Bill |
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Martin wrote:
The printer had been switched most of the day, when somebody asked me to pass him the plug. The mains plug? How did that work, then? If it were an SMPS the storage capacitor would have to discharge "backwards" through a bridge rectifier. Interesting! -- SteveT |
electric shock
On Sat, 19 May 2012 18:48:09 +0100, Steve Thackery
wrote: Martin wrote: The printer had been switched most of the day, when somebody asked me to pass him the plug. The mains plug? How did that work, then? If it were an SMPS the storage capacitor would have to discharge "backwards" through a bridge rectifier. Interesting! Quite common, it's the capacitors in the EMC filter that remain charged up when the power is turned off mid cycle. -- Graham. %Profound_observation% |
electric shock
On Sat, 19 May 2012 18:08:07 +0100, Bill Wright
wrote: Brian Gaff wrote: They must have some strange ideas of how to power mast head amplifiers over there then. What i mean is that you can still get devices that create electric shocks. tens devices and these are not lethal, some find them very pleasent. Brian I have a 200 year old device intended to cure neuralgia by means of electrodes and a small dynamo. Bill My Dad was a physiotherapist, and our front room was his treatment room in the late 50s - early 60s. The electroheropy console was bigger than me, and my dad would talk about galvanism and faradism and also shortwave diathermy (although I don't think he had a machine for that) He also had a poweful UVA lamp that I had until comparativly recently. It eas great for curing Loctite Glass-Bond when there was no sun. -- Graham. %Profound_observation% |
electric shock
Graham. wrote:
Quite common, it's the capacitors in the EMC filter that remain charged up when the power is turned off mid cycle. Ah! Thank you. -- SteveT |
electric shock
"Davey" wrote in message ... On Fri, 18 May 2012 16:06:31 +0100 Bill Wright wrote: I was working on a 55VAC line-powered TV system the other day and I could feel the power through dry fingers. I got the impression 55V could be quite nasty with wet hands and a good earth. It was interesting to feel this attenuated mains. The individual cycles can be felt quite clearly. It made me wonder if the feeling of touch has less persistence than vision. Of course the ears would turn the 50Hz into a note. Bill The 'nasty' value would also depend on the available current flow, surely? 20 Amps would do serious damage, even 2 will kill you. Quoting figures like "20A" is pointless - a few tens of mA can kill, but you have to have enough voltage to develop the current through the resistance. With dry unbroken skin the resistance can be as high as a few hundred k Ohms - some people can survive mains voltage for a short while. With wet skin mains shocks are frequently fatal and with broken skin, the 55V might be enough to do the job. With 55V, the sensation it causes might be enough to cause an increase in perspiration - then you have wet skin. That may lead to passing enough current to damage the epidermus, and then you're down to broken skin! |
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In message , Steve Thackery
writes Graham. wrote: Quite common, it's the capacitors in the EMC filter that remain charged up when the power is turned off mid cycle. Ah! Thank you. There should, of course, be a law which requires that there be a (say) 100k bleed resistors across each EMC capacitor. -- Ian |
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On 19/05/2012 23:00, Ian Jackson wrote:
There should, of course, be a law which requires that there be a (say) 100k bleed resistors across each EMC capacitor. There is, in effect. The two main safety standards, viz. EN 60065 for AV & similar equipment and EN 60950 for IT equipment both have requirements in this respect: - EN 60065:2010 (clause 9.1.6) requires that 2 s after withdrawal of the mains plug the voltage at its pins shall be less than that defined as 'hazardous live' - essentially 60 V DC; - EN 60950:2006 (2.1.1.7) expresses it in terms of the discharge time constant, which has to be 1 s (or 10 s if the mains plug is an industrial IEC 60309 type); - in both cases if the capacitance is less than 100 nF you don't have to worry. Since compliance with a harmonised standard is the usual way of meeting the LVD requirements (implemented as the Electrical Equipment Safety Regulations in the UK), the above is effectively a legal requirement. -- Andy |
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Ian Jackson wrote:
In message , Bill Wright writes Richard Tobin wrote: In article , Bill Wright wrote: The individual cycles can be felt quite clearly. It made me wonder if the feeling of touch has less persistence than vision. Of course the ears would turn the 50Hz into a note. Presumably you feel it as 100Hz, since all you can detect is the magnitude. -- Richard I have very bad skin. It only conducts one way. You ought to see a dermatologist and see if he can rectify the problem. Oh God here we go.... OK. "I have considerable resistance to the idea." Bill |
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