I agree that the title of the thread is daft, but! electrical safety is paramount to DIY audio if you are building projects that are going to work of the mains. It may sound daft, but atleast if in these threads if some basic electrical safety is discussed then it could save peoples lives. Id rather have a daft thread if it meant less death, so i dont see the problem however stupid they may seem.
I think however that listing specs of what it takes to kill is a pointless excercise. Yes under the rite conditions a 9v PP3 could kill but I doubt you will find them whilst bread boarding with opamps etc. If there is anything that has a high current output, ie mains, rectified mains, even if its just 12v 1A regulated or whatever, always er on the side of caution, putting on hand behind your back.
I think however that listing specs of what it takes to kill is a pointless excercise. Yes under the rite conditions a 9v PP3 could kill but I doubt you will find them whilst bread boarding with opamps etc. If there is anything that has a high current output, ie mains, rectified mains, even if its just 12v 1A regulated or whatever, always er on the side of caution, putting on hand behind your back.
wristwatch bands
OK, metal man suits won't work if you use car batteries for filament supplies, but you gave me another idea. Just get four metal watch bands, put them around just above the elbows and around the ankles. Connect all of them with a flexible insulated wire. No grounding strap. Now if you get your hands on something hot (HV) you just get a shock up the arms or feet. The rest of your body is equipotentialed by the shorting strap, so your vitals are protected. Cheap to build too. Don't make them too tight or you will cut off circulation however.
OK, metal man suits won't work if you use car batteries for filament supplies, but you gave me another idea. Just get four metal watch bands, put them around just above the elbows and around the ankles. Connect all of them with a flexible insulated wire. No grounding strap. Now if you get your hands on something hot (HV) you just get a shock up the arms or feet. The rest of your body is equipotentialed by the shorting strap, so your vitals are protected. Cheap to build too. Don't make them too tight or you will cut off circulation however.
Re: metal man suits
The woven metal suits that linemen wear are not meant to protect against electricution, but instead to shield them against the extremely powerful EM fields surrounding >100kV transmission lines. Without them, there would be an effect on your skin simiar to the arcing that occurs when you put aluminum foil into the microwave. It would be very painful, but not fatal. These suits also ONLY work when they, you, and everything you are touching is at exactly the same potential. It's completely useles for amplifier work.
I just thought I would also mention that with the "one hand" rule, when working with high voltages, it would be a good idea to only use your right hand, as a current travelling from your left hand to your feet will go dangerously close to (or through) your heart. As other people have pointed out, voltage does not increase the lethality of an electric shock, but it can increase the likelihood of one.
As a general rule, never work on any live circuit, regardless of the voltage, unless you are trained to do so. Always assume a circuit is live even if the caps have bleeder resistors on them, and make sure you discharge the caps and verifiy that they are discharged. For extra safety, you can wait a week or two for them to discharge any remaining stored energy on their own, but still assume there is some stored juice until you verify otherwise.
Thick rubber gloves (not dish gloves) can provide protection against electric shock, but they are not 100% garanteed, and you should wear leather gloves over them to keep them from getting torn. You shouldn't work on live high voltages anyway, but gloves might be a good idea anyway if you "think" it's safe.
The best advice is to simply not touch it. If you don't know the dangers involved with high-voltage, high-current work and the appropriate safety measures, you should not rely on luck to keep you alive. There is not concrete number that is safe. Whether or not you will get shocked or sustain serious injury from a shock depends on a nearly infinite list of variables, so there can't be a rule. thousands of very highly-trained people who know every safety rule for working with electricity die every year because of miniscule mistakes, or sometimes just circumstances beyond their control. Playing with electricity if you don't know what you're doing is more dangerous that playing with a loaded gun.
smoking-amp said:
The woven metal suits that linemen wear are not meant to protect against electricution, but instead to shield them against the extremely powerful EM fields surrounding >100kV transmission lines. Without them, there would be an effect on your skin simiar to the arcing that occurs when you put aluminum foil into the microwave. It would be very painful, but not fatal. These suits also ONLY work when they, you, and everything you are touching is at exactly the same potential. It's completely useles for amplifier work.
I just thought I would also mention that with the "one hand" rule, when working with high voltages, it would be a good idea to only use your right hand, as a current travelling from your left hand to your feet will go dangerously close to (or through) your heart. As other people have pointed out, voltage does not increase the lethality of an electric shock, but it can increase the likelihood of one.
As a general rule, never work on any live circuit, regardless of the voltage, unless you are trained to do so. Always assume a circuit is live even if the caps have bleeder resistors on them, and make sure you discharge the caps and verifiy that they are discharged. For extra safety, you can wait a week or two for them to discharge any remaining stored energy on their own, but still assume there is some stored juice until you verify otherwise.
Thick rubber gloves (not dish gloves) can provide protection against electric shock, but they are not 100% garanteed, and you should wear leather gloves over them to keep them from getting torn. You shouldn't work on live high voltages anyway, but gloves might be a good idea anyway if you "think" it's safe.
The best advice is to simply not touch it. If you don't know the dangers involved with high-voltage, high-current work and the appropriate safety measures, you should not rely on luck to keep you alive. There is not concrete number that is safe. Whether or not you will get shocked or sustain serious injury from a shock depends on a nearly infinite list of variables, so there can't be a rule. thousands of very highly-trained people who know every safety rule for working with electricity die every year because of miniscule mistakes, or sometimes just circumstances beyond their control. Playing with electricity if you don't know what you're doing is more dangerous that playing with a loaded gun.
I have read through this thread with interest and some amazement. This is a very serious subject, there is no place for flippancy, and I don't think extreme statements like" "0.01 volts can kill you" are helpful in encouraging people to respect electricity.
IMHO, the wisest approach for a beginner is to avail him/herself of both good education and good training (they're not the same thing) in safe electrical practice, before embarking on any tube project. Electricity can kill you just as surely as a hand grenade exploding in your face.
IMHO, the wisest approach for a beginner is to avail him/herself of both good education and good training (they're not the same thing) in safe electrical practice, before embarking on any tube project. Electricity can kill you just as surely as a hand grenade exploding in your face.
I used to get a few questions like this in my e-mail. In response to those I put a safety section on my web site. Unfortunately these pages receive few hits. Anyone who has thoughts or questions regarding electric shock should read them. Anyone new to the hobby should read them. Read the section on how to set up your work area carefully and understand it BEFORE sticking your fingers into anything electrical!
http://www.tubelab.com/Safety.htm
http://www.tubelab.com/MeterUse.htm
http://www.tubelab.com/Safety.htm
http://www.tubelab.com/MeterUse.htm
Gambit995 said:Hey i was just curios like u said 20mA could kill u if thts the case than why doesn't a Rechargable Battery kill u cuz its 2100 mA !!!
Take a close look, they should be 2100mAh. It can deliver 2.1A@1V for one hour, 0.21A@1V for 10h,...
twenty mills kills...
If you manage to let the current of 20mA flow through your body, say from one hand to the other or from one hand through one of your legs (notice that the heart is on the current's path!), you're most probably dead.
Since U=R*I there are two thing that matter: The current's path and the voltage. The path determines R. From your tongue to you feet on wet lawn it shouldn't be too many Ohms. From hands wearing rubber gloves to feet in shoes with rubber soles it should be a couple Mega Ohms. The voltage depends on what you're working on.
Current always flows through something, basically it's moving electrons. Moving constantly from A to B you have DC, moving back and forth with a certain frequency, it's AC.
In your joints (knees, ellbows, fingers...) there's some liquid stuff, the synovial fluid. Having less resistance than bones or "flesh", a larger current will flow (I=U/R), causing it (the fluid) to heat up, maybe even evaporate. This causes a huge amount of pain that can be felt for hours after the shock, if it is survived. It can also cause permanent damage.
Your heart's muscle is stimulated by something called the "Nodus sinuatrialis", a bunch of special muscle cells that can build up a potential of 70mV (from 30mV to -40mV). If this potential is disturbed in some way, like a current flowing through the body or a surgeon touching the heart while he's on a different potential than the heart itself (by touching a lamp or not being properly grounded, way less than 20mA need!) the heart may stop to beat or start flickering.
Under normal circumstances (room temp, normal air) electrons need a potential of 1000V to travel through 1mm of air, so HV can get you without even having touched something physically.
To be blunt, I still can't believe this thread is growing (and yes i am aware I am contributing with this post). Maybe I can put this in some perspective by asking this question:
What height of fall won't kill me?
I mean, people have broken necks falling from a chair, others easily and routinely survive falls from several thousand feet - in fact, they do it deliberately. In the later case, it's called parachuting, and I would think using a parachute makes paramount difference regarding the result. Get my point?
What height of fall won't kill me?
I mean, people have broken necks falling from a chair, others easily and routinely survive falls from several thousand feet - in fact, they do it deliberately. In the later case, it's called parachuting, and I would think using a parachute makes paramount difference regarding the result. Get my point?
Hi John,
I have to agree with ilimzn here. Anything over 30V is considered a shock hazard in some circumstances. There are times when even lower voltages can be lethal if you get current flow to occur through your body.
Everything you have talked about is well above this. If you don't respect this, you are a potential Darwin award waiting to happen.
-Chris
I have to agree with ilimzn here. Anything over 30V is considered a shock hazard in some circumstances. There are times when even lower voltages can be lethal if you get current flow to occur through your body.
Everything you have talked about is well above this. If you don't respect this, you are a potential Darwin award waiting to happen.
-Chris
I have sat here in horror the last few minutes reading this thread so my reply probably won't be well received.
Quote:
How much voltage won´t kill me?
This is totally BS! Are you wanting to be careless up to a point where you have to start watching what the hell you are doing?
Do you have a death wish? This is totally crazy period.
First of all if you have to ask this question you have no business working on electronic equipment. Don't work on it! Don't touch it! Don't even be in the same room with it. Voltage coupled with enough amperage will fry your a**. View all voltage as that which can cause an immediate trip to the morgue.
Quote:
How much voltage won´t kill me?
This is totally BS! Are you wanting to be careless up to a point where you have to start watching what the hell you are doing?
Do you have a death wish? This is totally crazy period.
First of all if you have to ask this question you have no business working on electronic equipment. Don't work on it! Don't touch it! Don't even be in the same room with it. Voltage coupled with enough amperage will fry your a**. View all voltage as that which can cause an immediate trip to the morgue.
I feel obliged to add my thoughts on safe practice here. One very common mistake that I see is the belief that lots of good grounds make things more safe. In fact, the opposite is true. When working with high voltage - or even moderate voltage - one should also be very wary of any grounds thet are present. If one hand is grounded (or a big round stomach is touching a chassis) while the other hand contacts a HV source then you're going to get the crap scare out of you at best.
Every now and then I hear from a beginner wanting to set up the safest work area possible. They ask if it's worthwhile to use a work bench with a grounded metal surface. NO WAY! That's the most dangerous thing I can think of! Consider resting one hand on the bench and touching anything hot with the other hand.
My point is to worry about grounds just as much as sources of voltage. It's the current paths that include your body that are most dangerous.
On a different note: if anyone wants to know how little voltage is still safe they should try hooking jumper cables up to a 12V car battery and connecting the other and of the cable up to their nipples. It should be an interesting experiement. (Just kidding; don't do it.)
-- Dave
Every now and then I hear from a beginner wanting to set up the safest work area possible. They ask if it's worthwhile to use a work bench with a grounded metal surface. NO WAY! That's the most dangerous thing I can think of! Consider resting one hand on the bench and touching anything hot with the other hand.
My point is to worry about grounds just as much as sources of voltage. It's the current paths that include your body that are most dangerous.
On a different note: if anyone wants to know how little voltage is still safe they should try hooking jumper cables up to a 12V car battery and connecting the other and of the cable up to their nipples. It should be an interesting experiement. (Just kidding; don't do it.)
-- Dave
Dave Cigna makes a very good point about grounding. Ground your equipment... but don't go nuts grounding your world.
I once installed a string of 144 locomotive batteries for a total of about 2000 Volts. These batteries were 12 cells potted with tar in a thick metal case roughly 4 feet cubed.
A bunch of government, and university morons were way too involved. Rather than declaring the battery room to be "INHERENTLY DANGEROUS", we were forced, against our own knowledge, to ground ALL the metal cases for batteries... for the sake of safety. Also, we were not allowed to place breakers in the ground leg of the either the battery string OR the "safety" ground bus... the idea all "all those batteries" "floating" rubbed someone the wrong way.
The very same morons also insisted that we install an automatic system for replenishing the water in the cells... this was the equivalent of 1728 little floats and valves that work just like the refill valve in a toilet... are you with me here?
The batteries were put on automatic refill. Of course one of the valves didn't work and that battery overfilled and had acid all over the top. The idiots in the white coats insisted on standing in the way and discussing, inspecting, postulating, hypothesizing, and conjuring all sorts of useless theories as to how a $2 dollar float valve could have failed to close. The valve that failed just happened to be near the high voltage end of the string.
While all this was going on, none of the PHD's really seemed to notice (or care) that the spilled acid was steaming and spreading across the top of the battery. Eventually the acid made its way to a small nick in the powder coating that was on the metal battery case... the grounded metal case.
The acid, the steam, and the metal case made for great fun! A 2 foot long arc developed across the top of the battery. The arc looked kinda like a snake that had just been run over by a car.
At this point most of the ninnies were running out of the room... this was a good thing. One pinhead remained, being a brave sort, decided that a nearby push broom would be handy for sweeping away the acid. By this time, about 30 seconds, the tar on the suface had melted... so the broom... and the tar... caught fire. This pretty much cleared the room of all ninnies... one running away from the scene with a burning broom.
Eventually 2 engineers opened the breaker on the high end of string. Then worked together to use a hand-cuff-style cutter at the ground end of the battery string to break the current path.
A few minutes with fire extinguisher, curiously closer to the fire than the broom, made things right.
The investigations, by the VERY SAME MORONS, went on for weeks. Finally, 4 knotheads were reassigned, engineers were allowed to put disconnects where ever they damned well pleased, the automatic watering system went into the toilet, fiberglass safety rails were installed along the sides of the battery rows, the groundng system was removed, the batteries and their metal cases were allowed to float, and the room was declared as Inherently Dangerous / Authorized Personnel Only.
Grounds are not always good... thinking IS.
Your tax dollars at work...
I once installed a string of 144 locomotive batteries for a total of about 2000 Volts. These batteries were 12 cells potted with tar in a thick metal case roughly 4 feet cubed.
A bunch of government, and university morons were way too involved. Rather than declaring the battery room to be "INHERENTLY DANGEROUS", we were forced, against our own knowledge, to ground ALL the metal cases for batteries... for the sake of safety. Also, we were not allowed to place breakers in the ground leg of the either the battery string OR the "safety" ground bus... the idea all "all those batteries" "floating" rubbed someone the wrong way.
The very same morons also insisted that we install an automatic system for replenishing the water in the cells... this was the equivalent of 1728 little floats and valves that work just like the refill valve in a toilet... are you with me here?
The batteries were put on automatic refill. Of course one of the valves didn't work and that battery overfilled and had acid all over the top. The idiots in the white coats insisted on standing in the way and discussing, inspecting, postulating, hypothesizing, and conjuring all sorts of useless theories as to how a $2 dollar float valve could have failed to close. The valve that failed just happened to be near the high voltage end of the string.
While all this was going on, none of the PHD's really seemed to notice (or care) that the spilled acid was steaming and spreading across the top of the battery. Eventually the acid made its way to a small nick in the powder coating that was on the metal battery case... the grounded metal case.
The acid, the steam, and the metal case made for great fun! A 2 foot long arc developed across the top of the battery. The arc looked kinda like a snake that had just been run over by a car.
At this point most of the ninnies were running out of the room... this was a good thing. One pinhead remained, being a brave sort, decided that a nearby push broom would be handy for sweeping away the acid. By this time, about 30 seconds, the tar on the suface had melted... so the broom... and the tar... caught fire. This pretty much cleared the room of all ninnies... one running away from the scene with a burning broom.
Eventually 2 engineers opened the breaker on the high end of string. Then worked together to use a hand-cuff-style cutter at the ground end of the battery string to break the current path.
A few minutes with fire extinguisher, curiously closer to the fire than the broom, made things right.
The investigations, by the VERY SAME MORONS, went on for weeks. Finally, 4 knotheads were reassigned, engineers were allowed to put disconnects where ever they damned well pleased, the automatic watering system went into the toilet, fiberglass safety rails were installed along the sides of the battery rows, the groundng system was removed, the batteries and their metal cases were allowed to float, and the room was declared as Inherently Dangerous / Authorized Personnel Only.
Grounds are not always good... thinking IS.
Your tax dollars at work...
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