Young Players & The Dangers of Mains Electricity

[AG6QR]

One of the nastiest shocks I ever got was from 4 AA batteries. 

But their current had been through a charge pump, and charged a photographic flash unit.  The main capacitor could store around 60 Joules.  Before I opened the flash, I took the batteries out and popped the flash to discharge the capacitor, but I didn't realize how much charge would be left over after the flash fired.  I just got a tiny fraction of the jolt that flash could potentially deliver, but it was enough to remind me never to make that mistake again.

[dexters_lab]

for educational purposes i would be tempted to demonstrate why you have to be safe, discharge a few capacitors of various sizes... the loud cracks, flashes and bangs should be enough to see the potential hazards first hand

[Ian.M]

... or to start him down the PhotonicInduction road! 

[Simon]

To be honest that will happen either way if it is to be. Have a look at his videos...... very little, in fact no electronics he just plays with high voltage or current. If our young learner is into electronics he won't be interested in that sort of play.

At the end of the day all photonic induction does is destroy stuff not design anything.

[rolycat]

pfffffft. The mains has never hurt me.  When I was a kid i had a few shocks from the mains. I just sat there because it felt funny.

Yea but in the USA you don't have real mains - only 110V!
Stick your finger in 240 of Her Majesty's Volts & you'll know all about it for sure 

I thought yankee volts and her majesty's volts where the same (unless there's a bloody imperial volt too now!) it's just that he majesty packs twice as many.

Good gracious no, dear boy. Her Majesty's volts are far more refined than those brash colonial upstarts.

The AC waveforms are classier - they glide along at an elegant 50Hz instead of the pushy 60Hz favoured by our transatlantic cousins. They also typically come to us via modestly buried underground cables, rather than the vulgar transformers brazenly flaunted on poles all over the USA. <Shudder>.

[Ian.M]

@Simon: My point is that any demos should be interesting and non-frightening.  To start him down the road towards sound safety habits one should engage his intellect and avoid boredom, not raise his adrenalin levels.

[Simon]

pfffffft. The mains has never hurt me.  When I was a kid i had a few shocks from the mains. I just sat there because it felt funny.

Yea but in the USA you don't have real mains - only 110V!
Stick your finger in 240 of Her Majesty's Volts & you'll know all about it for sure 

I thought yankee volts and her majesty's volts where the same (unless there's a bloody imperial volt too now!) it's just that he majesty packs twice as many.

Good gracious no, dear boy. Her Majesty's volts are far more refined than those brash colonial upstarts.

The AC waveforms are classier - they glide along at an elegant 50Hz instead of the pushy 60Hz favoured by our transatlantic cousins. They also typically come to us via modestly buried underground cables, rather than the vulgar transformers brazenly flaunted on poles all over the USA. <Shudder>.

indeeeeed, indeed old chap 

[IanB]

Also, yankee's voltage can kill. It is actually 240V with center tap, so if you poke your fingers into 2 different sockets, you might die, and GFCI won't help you.

If you can poke your fingers into two different sockets you have very long arms and very slender fingers... 

[jlmoon]

They also typically come to us via modestly buried underground cables, rather than the vulgar transformers brazenly flaunted on poles all over the USA. <Shudder>.

My pole pig is a "pad pig" over here.

Yes, but we in America can see when things release the magic smoke and usually recover faster ... sometimes.

[dexters_lab]

To be honest that will happen either way if it is to be. Have a look at his videos...... very little, in fact no electronics he just plays with high voltage or current. If our young learner is into electronics he won't be interested in that sort of play.

At the end of the day all photonic induction does is destroy stuff not design anything.

he does make a good job putting his power supplies together though!

[tautech]

Get him a 10nF cap charged up to 2kV, and he will behave quite nice for a loooong time.

I was once zapped by a 33nF 20kV cap when I was 15, then I never touched anything above 1kV, for safety reasons.

This reminds me of another favourite trick mechanics used to do back in the days of points ignitions.

Charge up the cap from the ignition circuit and gently throw it to the apprentice for them to catch. ZAP.

Or leave a charged one on their bench.....

Most quickly got wise to these tricks. 

[jlmoon]

UG cables are actually more reliable then OH lines, because many incidents are actually caused by squirrels and trees.

Not to mention better transient absorption from ESD and such. 
 

[smjcuk]

Or the fastest way to suicide is to steal power cables. Many dies on doing this every year. 12.47kV distribution cables == instant death.

That isn't pretty to deal with. A guy I used to work with was a power engineer in South Africa (now a software guy ironically as well). He had to play "poke the dead guy stuck to the interruptor with a fiberglass pole" once. Apparently humans smell of bacon.

[jobog]

Get him a 10nF cap charged up to 2kV, and he will behave quite nice for a loooong time.

I was once zapped by a 33nF 20kV cap when I was 15, then I never touched anything above 1kV, for safety reasons.

This reminds me of another favourite trick mechanics used to do back in the days of points ignitions.

Charge up the cap from the ignition circuit and gently throw it to the apprentice for them to catch. ZAP.

Or leave a charged one on their bench.....

Most quickly got wise to these tricks. 

Had a physics instructor in high school that used to pull the same trick.  Didn't take long to learn never to catch anything he threw to you.  We kind of got even one afternoon.  The desks were lab tables with a little tower with outlets on each one.  Several of us got together and brought a small piece of wire to class.  A few turns around a wood pencil and when his back was turned we all plugged in.  Popped a couple breakers and put the lights out in a couple classrooms.  Detention hall was pretty crowded that afternoon but worth it.

[tautech]

Get him a 10nF cap charged up to 2kV, and he will behave quite nice for a loooong time.

I was once zapped by a 33nF 20kV cap when I was 15, then I never touched anything above 1kV, for safety reasons.

This reminds me of another favourite trick mechanics used to do back in the days of points ignitions.

Charge up the cap from the ignition circuit and gently throw it to the apprentice for them to catch. ZAP.

Or leave a charged one on their bench.....

Most quickly got wise to these tricks. 

Had a physics instructor in high school that used to pull the same trick.  Didn't take long to learn never to catch anything he threw to you.  We kind of got even one afternoon.  The desks were lab tables with a little tower with outlets on each one.  Several of us got together and brought a small piece of wire to class.  A few turns around a wood pencil and when his back was turned we all plugged in.  Popped a couple breakers and put the lights out in a couple classrooms.  Detention hall was pretty crowded that afternoon but worth it.

   

[Ian.M]

Heh.
The most famous lab prank at my old school was the time that a certain joker waited till the whole physics class was using Bunsen burners, and took the gas hose off one and connected it to a mains pressure cold water tap.  Result: a  classroom full of pretty fountains and a very full detention.   I don't think the school handyman who had to drain the gas pipes was too happy either.

[tggzzz]

Heh.
The most famous lab prank at my old school was the time that a certain joker waited till the whole physics class was using Bunsen burners, and took the gas hose off one and connected it to a mains pressure cold water tap.  Result: a  classroom full of pretty fountains and a very full detention.   I don't think the school handyman who had to drain the gas pipes was too happy either.

Pah. We just took the rubber tube in our mouth and blew. It extinguished all the bunsens all along the bench.

But then were were given small lumps of sodium to put in water, concentrated sulphuric acid to add to sugar, liquid mercury, and potassium cyanide (plus a warning to only use it in the fume cupboard and not to put acid down the sink until it had been cleaned).

The school's radioactive sources were locked away, but that didn't matter... One of my friends had a fob-watch that was several times more radioactive than the school's most powerful source. Had to be sent away to Harwell (Aldermaston?) to be destroyed.

[smjcuk]

Heh.
The most famous lab prank at my old school was the time that a certain joker waited till the whole physics class was using Bunsen burners, and took the gas hose off one and connected it to a mains pressure cold water tap.  Result: a  classroom full of pretty fountains and a very full detention.   I don't think the school handyman who had to drain the gas pipes was too happy either.

Pah. We just took the rubber tube in our mouth and blew. It extinguished all the bunsens all along the bench.

But then were were given small lumps of sodium to put in water, concentrated sulphuric acid to add to sugar, liquid mercury, and potassium cyanide (plus a warning to only use it in the fume cupboard and not to put acid down the sink until it had been cleaned).

The school's radioactive sources were locked away, but that didn't matter... One of my friends had a fob-watch that was several times more radioactive than the school's most powerful source. Had to be sent away to Harwell (Aldermaston?) to be destroyed.

Ha. Sounds like your school was more responsible than mine. Our physics teacher: "yeah help yourself to anything you want from the store, but please stay away from the sodium and uranium until you've done the first year". The same let us add some creosote to a wood burner to make giant smoke rings and light the gas taps without the burners.

Edit: actually my first electronics lesson there I was working my way through a 100 pack of 5mm red LEDs and the bench 24V AC supply. Worked out if you connect enough of them in series they don't explode. Well not immediately. Also red LEDs go orange for a bit when overvolted.

Edit 2: now my kids are at school they deemed soldering too dangerous

[Ed.Kloonk]

A car battery, jumper leads and my nipples all put together makes my eyes light up. Even more exciting than wearing my wife's knickers.

[Ed.Kloonk]

 

[zerorisers]

pfffffft. The mains has never hurt me.  When I was a kid i had a few shocks from the mains. I just sat there because it felt funny.

That is just childish, I left another forum because it has such statements of stupidity from so called knowledgeable people. 

Don't forget this is the begginers section. And everything stated there is the truth of what goes on in my mind and my past experience (and lack of experience) I have never stated I was knowledgeable either. I apolagize for making just one more post you didn't want/or need to read.

[mrkev]

pfffffft. The mains has never hurt me.  When I was a kid i had a few shocks from the mains. I just sat there because it felt funny.

That is just childish, I left another forum because it has such statements of stupidity from so called knowledgeable people. 

Yes, it's childish. However perfectly healthy human almost can't die from a "simple" 230V shock. Thing is, nobody knows how healthy they are and what is it really gonna do. I remember almost every time I've touched mains, even discharging cap from a voltage converter, or touching its heatsink.

// beginning of rant
But the biggest respect came from methods of possibly the worst teacher (and technically the best ) I've had at high school. He showed us all the "great" stuff.
 
From blowing paper and electrolytic caps, how to extinct arc (he made V shape with wires and connected whole thing on the output of old CRT HV transformer, he touched it by mistake when trying to ignite the arc with match), he showed us 3f asynchr. motor running on two and one phase (and didn't noticed that one string of the live wire was touching stator chassis, many ugly words were flying that day as he tried to give it a start-kick). He blew up old Russian transistors - I never forget that bright orb and metal cap flying just near my head drilling 1cm hole in the brick wall (and his question  - phase to base or to emitter?), we even build 1,5 m height tesla-coil and there were few people who discharged those caps in a painful way...

That lab had screws in place of main fuses... And the best thing was, that when someone screwed up and connected something wrong, he let him switch it on and see the magic smoke... F.e. we did motor reverse with two contactors. One group connected the safety aux contacts (that shouldn't allow direct switching of the direction) to the same contactor, effectively making astable multivibrator, 3f 480V motor jumping madly followed...

[tggzzz]

pfffffft. The mains has never hurt me.  When I was a kid i had a few shocks from the mains. I just sat there because it felt funny.

That is just childish, I left another forum because it has such statements of stupidity from so called knowledgeable people. 

Yes, it's childish. However perfectly healthy human almost can't die from a "simple" 230V shock. Thing is, nobody knows how healthy they are and what is it really gonna do. I remember almost every time I've touched mains, even discharging cap from a voltage converter, or touching its heatsink.

Ah, the "I haven't died so there isn't a problem" chain of reasoning (and I use that word very loosely). Not impressive. You are a good example of the Dunning-Krueger effect in action.

"Health" is a secondary issue. What matters is where the electricity goes. In particular milliamps through the heart is very bad news, even for the healthiest person.

[Shock]

Get 10-20mA and your body won't move (unless you collapse), you can just sit there sizzling away while thinking about how healthy you are.

[Simon]

Get 10-20mA and your body won't move (unless you collapse), you can just sit there sizzling away while thinking about how healthy you are.

or about how funny it feels