40 ms·

Even if you're a "computer person" who is comfortable messing with the internals of a PC, be very careful with the power supply. Opening it up should really be

Even if you're a "computer person" who is comfortable messing with the internals of a PC, be very careful with the power supply. Opening it up should really be left to professionals. Capacitors can remain charged for a long time after disconnecting the power cord. If despite all the warnings, you open it up to fiddle with internals because you think you understand the components and can pay attention not to touch things, at the very least, use only one hand at a time to avoid creating a circuit through your heart. In most other parts of the computer the worst that can happen in most cases is that you damage the computer, the power supply is different, there you also have a good chance of getting shocked.

parsecs 5y ago
Also a good tip to touch things with the back of your hand first, as the current can't force you to grip harder. This is more for line connected stuff though.
- LambdaComplex 5y ago
  An even better tip would be to use an insulated screwdriver instead of your hand. Or even a capacitor discharge tool, since those apparently exist.
  - Scoundreller 5y ago
    When I had to do an air conditioning capacitor, I used a piece of wood with a nail. I couldn’t tell if adding steel wool to the mix would be a good idea or not.
    - baud147258 5y ago
      Wouldn't steel wool catch fire when exposed to an electric current? It might be useful to indicate there was still some charge in the capacitors, though
      - Scoundreller 5y ago
        That was my worry. The resistance might be too high and get too heated. The nail avoids that issue. In a power supply, you'd also have to worry about shorting and shocking other ICs with steel wool, but not with a big capacitor.
aequitas 5y ago
Or just short out the capacitor terminals with a metal object like the screwdriver and you're fine. But still, if you don't do that and you get chocked it will just be a little painful jolt.
- exmadscientist 5y ago
  You know, you'd think that would work, wouldn't you? But dielectric soakage runs in reverse, too. So even if you short out the capacitor once, it can recover some voltage after days to months left open again. (The energy comes from the molecules in the dielectric relaxing, very slowly.) This isn't a problem if the designer has put in a bleeder resistor across the capacitor. But some designers are cheap, and don't want to pay the extra few cents to make their products non-lethal to technicians. Some are just stupid (yes, dumbfuck "senior engineer" coworker, I am thinking of you here, you colossal waste of oxygen). What you want to do is short it out, with a screwdriver or otherwise, then keep it shorted with a gator cable or even resistor. Then you'll be safe even if you set the project aside for a week. Or three months.
  - h2odragon 5y ago
    Had a pallet of military surplus capacitors, packaged as 3 big (soda can sized) caps on a blade frame and wrapped in conductive foil, plastic, then heavy paper. From the 70s and they were fine when i got them in 1997. I wired up an unwisely huge bank out of them for some fun HV experiments. They were in a shed outside and could self charge to useful levels in the course of a windy day. Dont recall the actual numbers but it could vaporize dimes handily.
    - LargoLasskhyfv 5y ago
      Reading that, I wonder how much solar power you'd need to charge them to that level? And if that could be applied to complement solar/wind power?
      - h2odragon 5y ago
eurekin 5y ago
I noticed some of them include a simple light, which slowly gets dimmer after disconnecting the power. Is it to discharge that capacitors?
- exmadscientist 5y ago
  That's discharge + indication all in one. It's a great solution, elegant, effective, and one of my favorites. But you have to find the cents for the neon (usually) bulb.
- jlgaddis 5y ago
  Be careful, that's (probably) just on the DC side...
  - Scoundreller 5y ago
    Isn’t the AC side connected to the wall prongs? I touch/step on those all the time after unplugging things. Or is there something isolated from both the DC side and prongs where charge could be stored up?
    - garaetjjte 5y ago
      Yes, there's bridge rectifier.
    - bonzini 5y ago
      Those big-ass black capacitors (470 uF each) are on the AC side. They are the bit that converts 230AC to 320DC, and they might keep their charge for some time.
      - SAI_Peregrinus 5y ago
        Those are after the bridge rectifier, so there's no path for current to flow back out the plug from them. That also means you can't discharge them via the plug, of course.
pvitz 5y ago
This happened to me as a young teenager. I tried to figure out which part of the power supply was broken. The case was opened, I measured some parts, connected it, turned it on and tested if it was working again and disconnected it before continuing to work. After the fourth time, I forgot to disconnect it before touching something with both hands. Fortunately, the GFCI was working as intended, but the cramp in my arms and a very strange feeling around my heart is something I will never forget. So, to add another advice, be sure that you have a ground fault circuit interrupter or residual-current device and test it regularly.
- Cederfjard 5y ago
  Question for any medical professionals around: If you experience a substantial electrical shock, but it didn’t cause you to go into cardiac arrest and you don’t have any severe burns, is it likely that the danger is over? Or should you still seek medical attention as soon as possible?
  - deleted 5y ago
    [deleted]
  - jaidan 5y ago
    I’m not a medical person but I am an electrician. If you receive a shock, if can affect the rhythm of your heart and cause problems later. We’re taught to go and get an ECG after receiving a shock. Like jump in the car and go to the doctor or hospital and have someone else drive you. If you’ve received a shock - go get checked out.
    - gugagore 5y ago
      Are you part of a union, and is this recommendation feasible because of "worker's compensation"? I imagine I might not go get checked out if I felt like the risk was low enough and I was worried enough about being able to pay the bill.
      - adrianN 5y ago
dghughes 5y ago
A CRT enters the room... Seriously thought electrolytic capacitors need to be respected but not feared.
- agumonkey 5y ago
  I opened quite a few, and I wonder if they have bleeder resistors around the tube.. it's also interesting to witness a bit glass thing acting like a capacitor ps: for long I wanted to make a discharge rod but never finished it
  - deleted 5y ago
    [deleted]
  - userbinator 5y ago
    it's also interesting to witness a bit glass thing acting like a capacitor The very first capacitors were glass jars: https://en.wikipedia.org/wiki/Leyden_jar https://en.wikipedia.org/wiki/Leyden_jar
- deleted 5y ago
  [deleted]
- gugagore 5y ago
  How about the electrolytic capacitor of a camera flash circuit? Knowing that they could deliver a nasty shock, I discharged one once by shorting the terminals with a screw driver. The sound of the spark, and the scorch mark left on the PCB and screw driver left me fearful of them. Or was that caused by the knowledge that I had a friend who said he put one of those capacitors in a highlighter, thereby making a makeshift, single-use, "shelf-unstable" taser?
- rytis 5y ago
  Many moons ago I worked at a computer service shop that also repaired CRTs. Once, as a practical joke, someone asked me to hold a lead... Which was live with around 4kV. Wasn't pleasant experience.
agumonkey 5y ago
seconded, not to be alarmist but anything mains voltage is dangerous (caps are rated 400V~), shit happens fast. it can be a tough jolt or it can burn your skin, or pierce it or burn nerves or maybe shock you into worse cases i repeat danger
- LASR 5y ago
  It’s not even the mains voltage. There are components in there that can exceed mains voltage when probed the wrong way. When you start getting into the higher voltages, the body’s resistance is much lower. It only takes a few milliamps to stop the heart.
  - Dylan16807 5y ago
    > There are components in there that can exceed mains voltage when probed the wrong way. Not in a normal power supply.
    - kens 5y ago
      In the described power supply, you'll find voltages of about 340 volts DC, for two reasons. First, AC is measured in RMS, which is considerably lower than the peak voltage. I.e., 120 volts from the wall swings between -170 volts and +170 volts. Second, this power supply uses a voltage doubler, so you end up with 340 volts DC inside.
      - Dylan16807 5y ago
        Doubling 120 to 240 is still mains voltage in my book, if a supply these days even does double. Sure it's peak rather than RMS, but a warning that something "exceeds mains voltage" to me sounds like a description of a significantly bigger danger than that.
toast0 5y ago
> at the very least, use only one hand at a time to avoid creating a circuit through your heart. The Alanis Morissette method; I've got one hand in my pocket, and the other's probing a live circuit.
- geoduck14 5y ago
  This is the best thing I've read in a long time.
- coryrc 5y ago
  Keep your left hand back (unless you are one of those rare people with your heart on the wrong side).
  - meierjo 5y ago
    Especially if you wear a wedding band!
  - fabioyy 5y ago
    dude, the heart is in the middle of your chest.
    - mauvehaus 5y ago
      Anybody care to explain the downvotes on this one? I mean the poster isn't technically correct, but a constructive and informative response might include why that actually matters in the scenario under discussion. I mean, we're talking about an organ that runs off of millivolts. Surely the heart is close enough to the middle when we're talking about running 120 or 240 volts of AC through it?
slicktux 5y ago
When I was a teenager I opened a disposable camera to explore its contents; the flash was charged when I touched the circuit and I got the SHOCK of my life. I learned about capacitors the stupid way.
- martinmunk 5y ago
  When I was ~14 I used to take out the caps of disposable cameras, bend the legs down its sides, and convert the rest to be just a charger. It was a big hit in school! You could leave the caps at friends desks and they would curiously pick it up. Toss them at somebody at yell “catch” ect. IIRC they were rated at 600v, and would leave black indents in the skin. Kids are effing stupid…
- homero 5y ago
  I did that too, disposable camera shocked me when I took it apart as a kid. There's a lot of us that always took things apart to see how they worked.
- maddyboo 5y ago
  I did this exact same thing!! I was probably 10. It scared the hell out of me and I’ve respected capacitors ever since.
- brunoTbear 5y ago
  I’m glad I’m not the only one! Looks like there’s at least a half dozen of us!
  - mellavora 5y ago
    half dozen who survived :)
- chaosite 5y ago
  The stupid but relatively safe way - it's rather difficult to discharge that capacitor with BOTH hands, and the one in disposable cameras is not that big compared to power supply caps. You'll get a nice, painful reminder to respect electricity that'll last a few days, and not be in any actual danger. (I also did the exact same thing as a teenager)
Kirby64 5y ago
Simplest solution is to discharge the power supply: i.e., flip the switch on the power supply and then try to turn on the PC/electronic/whatever. You'll discharge the vast majority of the energy while it attempts to power on, leaving a relatively safe working environment. No tools needed.
- AussieWog93 5y ago
  Unless it doesn't, because the power supply is faulty.
  - nikau 5y ago
    This. Additionally there are typically bleed resistors to drain capacitors to safe levels, but they can also go open.
- gugagore 5y ago
  Or better yet, just unplug the computer while it's on /s.
- aforwardslash 5y ago
  Dont use this as general rule. Its quite easy to find electronics that uses a master/slave approach. If master is down, slave won't connect, but you may still have the capacitor bank charged. Usually there should be a shunt resistor to discharge capacitors, but you'd be surprise how often is missing.
bluedino 5y ago
Got a nice zap from an iMac power supply
zelon88 5y ago
My father was an expert class HAM radio operator. I remember him teaching me this as a child and illustrating it with one of his amplifiers to cement it in my head at a young age. He took the cover off his amp which was unplugged from the wall, took a screwdriver, touched ground and then touched one of the massive capacitors. The arc created a loud bang and scarred the surface of the screwdriver. But that didn't stop him from encouraging me to experiment while taking precautions. As a teenager I destroyed two ATX PSUs trying to add 110vac compatibility to an 12vdc RC battery charger. Third time was the charm.
01100011 5y ago
Around '93 I tried to fix a friend's power supply. I don't remember why, but I was trying to remove a short jumper(solid copper wire about 1cm long) by wiggling it back and forth. The wire touched something hot, vaporized in my hand, and left me with a copper coated thumbnail. Even after that, I continued to do dumb things around electricity. I'm not all that smart.
- isodude 5y ago
  At least you are being honest about it.
NoPicklez 5y ago
As someone who has been in the computer building game for quite some time like many others, I have no appetite to touching the inside of my PSU's. Absolutely none. They're inexpensive for desktop/gaming machines and if there's a fault its either in warranty or its time to purchase a new one.
hutzlibu 5y ago
Ok, so this thread, with all the replies of people unaware of this in teenage years - seems to imply we should teach this stuff in schools early on. As teenagers are in general low on money and the most likely to try to repair something that get them back to gaming, while ignoring warning stickers ...
Mauricebranagh 5y ago
Mr Carlson covers this in https://www.youtube.com/watch?v=CyKHVl3xF70 https://www.youtube.com/watch?v=CyKHVl3xF70 Personally I would probably not want to mess around inside a AXT supply.
kodah 5y ago
I worked on electronics for the military, one of which was a giant 2000 Watt HF amplifier that was stock to a MRC-148. When we got new Marines one of the first things we'd show them was when you remove the cover, turn the lights off, and have a florescent light bulb nearby it will activate. The purpose was to demonstrate the distance which electricity, unabated can travel. That was followed by explaining: - Always ground yourself to an actual building rod or a rod planted at least six feet deep. - Lock out, tag out everything. Our tools were metal, go work on ONE truck with a battery array without an extension and you will almost certainly arc something. - Voltage isn't what kills. It takes an insanely low amount of amperage to stop a heart. - Always have another person nearby with a wood or rubberized object to disconnect the circuit. Being stuck being electrocuted is a surprisingly slow death that you will be entirely conscious for.

parsecs 5y ago

Also a good tip to touch things with the back of your hand first, as the current can't force you to grip harder. This is more for line connected stuff though.

LambdaComplex 5y ago
An even better tip would be to use an insulated screwdriver instead of your hand. Or even a capacitor discharge tool, since those apparently exist.
- Scoundreller 5y ago
  When I had to do an air conditioning capacitor, I used a piece of wood with a nail. I couldn’t tell if adding steel wool to the mix would be a good idea or not.
  - baud147258 5y ago
    Wouldn't steel wool catch fire when exposed to an electric current? It might be useful to indicate there was still some charge in the capacitors, though
    - Scoundreller 5y ago
      That was my worry. The resistance might be too high and get too heated. The nail avoids that issue. In a power supply, you'd also have to worry about shorting and shocking other ICs with steel wool, but not with a big capacitor.

aequitas 5y ago

Or just short out the capacitor terminals with a metal object like the screwdriver and you're fine. But still, if you don't do that and you get chocked it will just be a little painful jolt.

exmadscientist 5y ago
You know, you'd think that would work, wouldn't you? But dielectric soakage runs in reverse, too. So even if you short out the capacitor once, it can recover some voltage after days to months left open again. (The energy comes from the molecules in the dielectric relaxing, very slowly.) This isn't a problem if the designer has put in a bleeder resistor across the capacitor. But some designers are cheap, and don't want to pay the extra few cents to make their products non-lethal to technicians. Some are just stupid (yes, dumbfuck "senior engineer" coworker, I am thinking of you here, you colossal waste of oxygen). What you want to do is short it out, with a screwdriver or otherwise, then keep it shorted with a gator cable or even resistor. Then you'll be safe even if you set the project aside for a week. Or three months.
- h2odragon 5y ago
  Had a pallet of military surplus capacitors, packaged as 3 big (soda can sized) caps on a blade frame and wrapped in conductive foil, plastic, then heavy paper. From the 70s and they were fine when i got them in 1997. I wired up an unwisely huge bank out of them for some fun HV experiments. They were in a shed outside and could self charge to useful levels in the course of a windy day. Dont recall the actual numbers but it could vaporize dimes handily.
  - LargoLasskhyfv 5y ago
    Reading that, I wonder how much solar power you'd need to charge them to that level? And if that could be applied to complement solar/wind power?
    - h2odragon 5y ago

eurekin 5y ago

I noticed some of them include a simple light, which slowly gets dimmer after disconnecting the power. Is it to discharge that capacitors?

exmadscientist 5y ago
That's discharge + indication all in one. It's a great solution, elegant, effective, and one of my favorites. But you have to find the cents for the neon (usually) bulb.
jlgaddis 5y ago
Be careful, that's (probably) just on the DC side...
- Scoundreller 5y ago
  Isn’t the AC side connected to the wall prongs? I touch/step on those all the time after unplugging things. Or is there something isolated from both the DC side and prongs where charge could be stored up?
  - garaetjjte 5y ago
    Yes, there's bridge rectifier.
  - bonzini 5y ago
    Those big-ass black capacitors (470 uF each) are on the AC side. They are the bit that converts 230AC to 320DC, and they might keep their charge for some time.
    - SAI_Peregrinus 5y ago
      Those are after the bridge rectifier, so there's no path for current to flow back out the plug from them. That also means you can't discharge them via the plug, of course.

pvitz 5y ago

This happened to me as a young teenager. I tried to figure out which part of the power supply was broken. The case was opened, I measured some parts, connected it, turned it on and tested if it was working again and disconnected it before continuing to work. After the fourth time, I forgot to disconnect it before touching something with both hands. Fortunately, the GFCI was working as intended, but the cramp in my arms and a very strange feeling around my heart is something I will never forget. So, to add another advice, be sure that you have a ground fault circuit interrupter or residual-current device and test it regularly.

Cederfjard 5y ago
Question for any medical professionals around: If you experience a substantial electrical shock, but it didn’t cause you to go into cardiac arrest and you don’t have any severe burns, is it likely that the danger is over? Or should you still seek medical attention as soon as possible?
- deleted 5y ago
  [deleted]
- jaidan 5y ago
  I’m not a medical person but I am an electrician. If you receive a shock, if can affect the rhythm of your heart and cause problems later. We’re taught to go and get an ECG after receiving a shock. Like jump in the car and go to the doctor or hospital and have someone else drive you. If you’ve received a shock - go get checked out.
  - gugagore 5y ago
    Are you part of a union, and is this recommendation feasible because of "worker's compensation"? I imagine I might not go get checked out if I felt like the risk was low enough and I was worried enough about being able to pay the bill.
    - adrianN 5y ago

dghughes 5y ago

A CRT enters the room... Seriously thought electrolytic capacitors need to be respected but not feared.

agumonkey 5y ago
I opened quite a few, and I wonder if they have bleeder resistors around the tube.. it's also interesting to witness a bit glass thing acting like a capacitor ps: for long I wanted to make a discharge rod but never finished it
- deleted 5y ago
  [deleted]
- userbinator 5y ago
  it's also interesting to witness a bit glass thing acting like a capacitor The very first capacitors were glass jars: https://en.wikipedia.org/wiki/Leyden_jar https://en.wikipedia.org/wiki/Leyden_jar
deleted 5y ago
[deleted]
gugagore 5y ago
How about the electrolytic capacitor of a camera flash circuit? Knowing that they could deliver a nasty shock, I discharged one once by shorting the terminals with a screw driver. The sound of the spark, and the scorch mark left on the PCB and screw driver left me fearful of them. Or was that caused by the knowledge that I had a friend who said he put one of those capacitors in a highlighter, thereby making a makeshift, single-use, "shelf-unstable" taser?
rytis 5y ago
Many moons ago I worked at a computer service shop that also repaired CRTs. Once, as a practical joke, someone asked me to hold a lead... Which was live with around 4kV. Wasn't pleasant experience.

agumonkey 5y ago

seconded, not to be alarmist but anything mains voltage is dangerous (caps are rated 400V~), shit happens fast. it can be a tough jolt or it can burn your skin, or pierce it or burn nerves or maybe shock you into worse cases i repeat danger

LASR 5y ago
It’s not even the mains voltage. There are components in there that can exceed mains voltage when probed the wrong way. When you start getting into the higher voltages, the body’s resistance is much lower. It only takes a few milliamps to stop the heart.
- Dylan16807 5y ago
  > There are components in there that can exceed mains voltage when probed the wrong way. Not in a normal power supply.
  - kens 5y ago
    In the described power supply, you'll find voltages of about 340 volts DC, for two reasons. First, AC is measured in RMS, which is considerably lower than the peak voltage. I.e., 120 volts from the wall swings between -170 volts and +170 volts. Second, this power supply uses a voltage doubler, so you end up with 340 volts DC inside.
    - Dylan16807 5y ago
      Doubling 120 to 240 is still mains voltage in my book, if a supply these days even does double. Sure it's peak rather than RMS, but a warning that something "exceeds mains voltage" to me sounds like a description of a significantly bigger danger than that.

toast0 5y ago

> at the very least, use only one hand at a time to avoid creating a circuit through your heart. The Alanis Morissette method; I've got one hand in my pocket, and the other's probing a live circuit.

geoduck14 5y ago
This is the best thing I've read in a long time.
coryrc 5y ago
Keep your left hand back (unless you are one of those rare people with your heart on the wrong side).
- meierjo 5y ago
  Especially if you wear a wedding band!
- fabioyy 5y ago
  dude, the heart is in the middle of your chest.
  - mauvehaus 5y ago
    Anybody care to explain the downvotes on this one? I mean the poster isn't technically correct, but a constructive and informative response might include why that actually matters in the scenario under discussion. I mean, we're talking about an organ that runs off of millivolts. Surely the heart is close enough to the middle when we're talking about running 120 or 240 volts of AC through it?

slicktux 5y ago

When I was a teenager I opened a disposable camera to explore its contents; the flash was charged when I touched the circuit and I got the SHOCK of my life. I learned about capacitors the stupid way.

martinmunk 5y ago
When I was ~14 I used to take out the caps of disposable cameras, bend the legs down its sides, and convert the rest to be just a charger. It was a big hit in school! You could leave the caps at friends desks and they would curiously pick it up. Toss them at somebody at yell “catch” ect. IIRC they were rated at 600v, and would leave black indents in the skin. Kids are effing stupid…
homero 5y ago
I did that too, disposable camera shocked me when I took it apart as a kid. There's a lot of us that always took things apart to see how they worked.
maddyboo 5y ago
I did this exact same thing!! I was probably 10. It scared the hell out of me and I’ve respected capacitors ever since.
brunoTbear 5y ago
I’m glad I’m not the only one! Looks like there’s at least a half dozen of us!
- mellavora 5y ago
  half dozen who survived :)
chaosite 5y ago
The stupid but relatively safe way - it's rather difficult to discharge that capacitor with BOTH hands, and the one in disposable cameras is not that big compared to power supply caps. You'll get a nice, painful reminder to respect electricity that'll last a few days, and not be in any actual danger. (I also did the exact same thing as a teenager)

Kirby64 5y ago

Simplest solution is to discharge the power supply: i.e., flip the switch on the power supply and then try to turn on the PC/electronic/whatever. You'll discharge the vast majority of the energy while it attempts to power on, leaving a relatively safe working environment. No tools needed.

AussieWog93 5y ago
Unless it doesn't, because the power supply is faulty.
- nikau 5y ago
  This. Additionally there are typically bleed resistors to drain capacitors to safe levels, but they can also go open.
gugagore 5y ago
Or better yet, just unplug the computer while it's on /s.
aforwardslash 5y ago
Dont use this as general rule. Its quite easy to find electronics that uses a master/slave approach. If master is down, slave won't connect, but you may still have the capacitor bank charged. Usually there should be a shunt resistor to discharge capacitors, but you'd be surprise how often is missing.

bluedino 5y ago

Got a nice zap from an iMac power supply

zelon88 5y ago

My father was an expert class HAM radio operator. I remember him teaching me this as a child and illustrating it with one of his amplifiers to cement it in my head at a young age. He took the cover off his amp which was unplugged from the wall, took a screwdriver, touched ground and then touched one of the massive capacitors. The arc created a loud bang and scarred the surface of the screwdriver. But that didn't stop him from encouraging me to experiment while taking precautions. As a teenager I destroyed two ATX PSUs trying to add 110vac compatibility to an 12vdc RC battery charger. Third time was the charm.

01100011 5y ago

Around '93 I tried to fix a friend's power supply. I don't remember why, but I was trying to remove a short jumper(solid copper wire about 1cm long) by wiggling it back and forth. The wire touched something hot, vaporized in my hand, and left me with a copper coated thumbnail. Even after that, I continued to do dumb things around electricity. I'm not all that smart.

isodude 5y ago
At least you are being honest about it.

NoPicklez 5y ago

As someone who has been in the computer building game for quite some time like many others, I have no appetite to touching the inside of my PSU's. Absolutely none. They're inexpensive for desktop/gaming machines and if there's a fault its either in warranty or its time to purchase a new one.

hutzlibu 5y ago

Ok, so this thread, with all the replies of people unaware of this in teenage years - seems to imply we should teach this stuff in schools early on. As teenagers are in general low on money and the most likely to try to repair something that get them back to gaming, while ignoring warning stickers ...

Mauricebranagh 5y ago

Mr Carlson covers this in https://www.youtube.com/watch?v=CyKHVl3xF70 https://www.youtube.com/watch?v=CyKHVl3xF70 Personally I would probably not want to mess around inside a AXT supply.

kodah 5y ago

I worked on electronics for the military, one of which was a giant 2000 Watt HF amplifier that was stock to a MRC-148. When we got new Marines one of the first things we'd show them was when you remove the cover, turn the lights off, and have a florescent light bulb nearby it will activate. The purpose was to demonstrate the distance which electricity, unabated can travel. That was followed by explaining: - Always ground yourself to an actual building rod or a rod planted at least six feet deep. - Lock out, tag out everything. Our tools were metal, go work on ONE truck with a battery array without an extension and you will almost certainly arc something. - Voltage isn't what kills. It takes an insanely low amount of amperage to stop a heart. - Always have another person nearby with a wood or rubberized object to disconnect the circuit. Being stuck being electrocuted is a surprisingly slow death that you will be entirely conscious for.