Young Players & The Dangers of Mains Electricity - Page 1
Forum section: electronics / beginners

author: German_EE
author_rank: Super Contributor
timestamp: April 08, 2015, 08:47:42 am
content: Board members may remember that I have a regular visitor to my workshop, the son of a neighbor who is rather eager to learn as much as he can about electricity and electronics. At seven years old he is at a very impressionable age and here is where I have a small problem.What do I do about mains powered devices?I know that everything in my workshop is safe, if it wasn't then I would not be using it, but there is nothing to stop my curious young friend from pulling the back off the nearest TV set (with the mains connected) and having a look around. I need some way to teach him about the dangers of mains electricity but without turning him into a younger version of Photonic Induction where, having experienced something dangerous, he wants to try it again and make a bigger bang.So far all I have is a promise from him that all his experiments will be battery powered. What else can I do?

author: Simon
author_rank: Unknown
timestamp: April 08, 2015, 09:18:31 am
content: Explain that anything with a wire going to the wall that is plugged in is dangerous which I guess you have. Show him an insect killer (don't mention that it's 6KV in reality) and what it does to insects. Do sparks demonstrate dangers ? show how the mains will destroy even a power resistor whereas the batteries won't.Teach him to use a power supply brick and to treat it as a black box not to be opened.

author: tautech
author_rank: Super Contributor
timestamp: April 08, 2015, 09:19:18 am
content: It's not JUST mains.Youngsters must get in their heads, there are tools to see this invisible stuff that BITES.We already have the benefit of experience, your and me, but how do we effectively pass it on?Some thoughts. No particular order.Get or make a battery powered electric fence, a very simple one will look very innocent until you touch the wrong end. Old lawn mower ignition is a good experience, just a gentle rotation while holding the lead will do the trick.Boys especially can be tactile learners, a harmless shock will make them think twice about where their fingers investigate.My first shock was from a small engine ignition lead at ~10 yrs old.....45 yrs later and I still haven't forgotten.Visual aids can be good too, set the electric fence to jump a tiny gap(after he's been shocked) then take him to an engineers to observe welding.Warn him, if you ever find out he's been doing stupid stuff, don't come back.Get him a DMM, even an old AVO, turn the process into a project, get manuals, demonstrate safe use, get Croc clips for the leads(safer for nervous hands).Glass fuses are impressive when they blow, remember safety glasses.End of rant.Never had any problems with my 2 boys, their mother wacked their fingers if they went near power sockets. Every kid is different, you'll have work out what suits him.Good luck.

author: tggzzz
author_rank: Super Contributor
timestamp: April 08, 2015, 09:26:25 am
content: Quote from: German_EE on April 08, 2015, 08:47:42 amIs a soldering iron safe?Life is about understanding, predicting and avoidingunacceptablerisks, but I'm sure you know that!Ultimately, if he "wants" to hurt himself, he will. If that is his personality then you should keep him out of your workshop. I have come across children (ofanyage) like that. If, on the other hand, he is curious and inexperienced but listens and understands and acts appropriately, then you'll have great fun.I used these techniques with my daughter, so they might be relevant:get him to describe a situation in which he was in pain, then say that the equipment in the workshop could cause more pain for longertell him stories about how you had lucky escapes, and why youreallydon't want them happen againtell him that everything can hurt him if he misuses ittell him that if he uses things properly, he will be OK - and that you will show him how to do things properlymake sure he knows to ask before touching/using new things, and then do aninformal"risk assessment" with himmake sure that he doesn't try to cover up his mistakes - he should learn from themdeliberately stage a small accident, and show him how you work outwhyit happened and how to avoid it in the futurelet him realise that fear/panic are unhelpful. (When somebody at school had the chemicals in a test tube catch fire, he calmly put an asbestos mat over the flame and extinguished it. The teacher looked up, saw what happened, and said "Well done, carry on")vaccinate him, e.g. give him a 20kV static shock (e.g. a Milty Zerostat) and make him realise mains is much worseand most importantly, sit near him while he is doing things, so you can let him getneartrouble - before you deliberately go "cough cough" to warn him that he's treading on thin ice.That last technique also works when they are on the internet/web, and when they are learning to fly a glider. (Since you in Germany you will have plenty of opportunity to let them start learning to fly at 12 before going solo at 14! Such youngsters are mature beyond their age)

author: Ian.M
author_rank: Super Contributor
timestamp: April 08, 2015, 09:41:57 am
content: Batteries only is no guarantee of safety. By age 13 I had a 1.5KV stack of date expired but still good 90V dry batteries!At that age there is rarely enough common sense for self-preservation against invisible hazards without continuous reinforcement. Discuss the issues with the parents so they know he's promised NOT to mess with mains powered stuff and what to watch for. Spare mains plugs or detatchable mains leads must not be kept in an accessible location. Explain to the parents which types of appliances are likely to have dangerous high voltage capacitors or readily accessible dangerous, toxic or corrosive substances inside (e.g CRTs, large lithium batteries or Asbestos insulation) Any other electrical/electronic junk is fair game for dismantling, but any mains leads must be cut off and mains plugs MUST be destroyed by cutting the pins off before he's allowed to open them. Suggest he asks you first before dismantling anything complete in case its a candidate for an easy/cheap repair. Assist in salvaging components he can use and by soldering long enough leads for breadboarding onto them.Consider finding/building him a safe current limited low voltage PSU. If you build it, use tamperproof case screws.

author: Simon
author_rank: Unknown
timestamp: April 08, 2015, 09:48:20 am
content: hm is he into taking stuff apart or making stuff from scratch ? making stuff from scratch is more controllable as he only has what he is given to mess with, I'd tell him that existing appliances don't have anything useful in them.

author: opty
author_rank: Regular Contributor
timestamp: April 08, 2015, 09:53:39 am
content: Quote from: tggzzz on April 08, 2015, 09:26:25 amWhen I was around 10yo (and stubbornly didn't believe electricity could be dangerous) my father allowed me to get controlled 220v shock (through a Christmas lights chain though). I still remember this 'funny' event, my shock (and my mother screaming at my father- what probably even strengthtened my perception of seriousness of the situation ) But point is, it did teach me a sound lesson about voltate/current.Perhaps you could give the kid a lighter to tear down with piezo-electric element to play with later?

author: tggzzz
author_rank: Super Contributor
timestamp: April 08, 2015, 10:31:40 am
content: Quote from: opty on April 08, 2015, 09:53:39 amAlternative: find an old electromagnetic relay and wire it up in such a way that when power is applied the contacts open, which remove power, which.... Connected to a battery this makes a nice spark-gap transmitter (ahem), and provides a suitably shockign experience.

author: Ian.M
author_rank: Super Contributor
timestamp: April 08, 2015, 10:37:04 am
content: @Simon: If you lie to a child and they catch you out, you loose their respect and they are far less likely to keep any promises they have made to you. IMHO its not worth risking that when the internet is full of instructions and videos of salvaging cool stuff from gadgets and appliances that the child is highly likely to encounter. Better to have clear policies on dismantling stuff in that house agreed with and enforced by the parents.The bug-zapper demonstration may be worthwhile but for %DEITY%'s sake get the parents fully involved before planning ANY safety demos or similar education.If you introduce him to relay circuits, he's likely to find for himself the buzzer configuration and find out that back EMF bites! That would be a good point to introduce the bug zapper and a newspaper article of a local death by electrocution (as a local newspaper article wont be too graphic but should 'hit home').

author: smjcuk
author_rank: Frequent Contributor
timestamp: April 08, 2015, 10:42:54 am
content: Quote from: tggzzz on April 08, 2015, 10:31:40 amThis was my first zap experience on a radio shack 100-in-1 kit. I built it by accident and gave myself a zap. Then I did it again. Then I found a relay inside something else and made a bigger more painful one. Then I zapped my sister. Then I got told off. Then I learned (I'm a slow learner)

author: Simon
author_rank: Unknown
timestamp: April 08, 2015, 11:03:55 am
content: Quote from: Ian.M on April 08, 2015, 10:37:04 amIf e is learning to design with new parts then salvaged parts are of no use at the moment. Moving on to how to salvage higher value and harder to find parts like transformers etc can come later.

author: opty
author_rank: Regular Contributor
timestamp: April 08, 2015, 11:30:08 am
content: We are talking about 7 year old boy here. In all seriousness a battery and a few basic components to do a flashing diode and beeping thing should be just enough. Anything above 9V is out of question, imo.You will probably achieve more by showing him a proper methodological approach, following/exaggerating safety rules and maintaining a tidy desk...

author: zerorisers
author_rank: Regular Contributor
timestamp: April 08, 2015, 01:38:35 pm
content: 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. I have not yet been shocked by a capacitor and am scared to sh*t to get shocked by one. I have been induced to high voltage but never anything like that. Always when working on something if I get shocked by a transformer I'm fine, but if I get near big caps I turn it off and hit them with a prybar.

author: KerryW
author_rank: Regular Contributor
timestamp: April 08, 2015, 01:39:09 pm
content: Teaching electrical safety by giving him a shock is like teaching fire safety by setting his hair on fire.Tell him about Galvani and dead frogs. Luigi Galvani discovered that electricity causes muscles to contract. He was 43 at the time. I discovered the same thing at age 3. We lived in a trailer park, and one of the neighbor kids dared me to grab their awning pole. Due to a miswiring, it was hot and I could not let go. Fortunately, the kid's father heard my screams and rushed out and pulled me off.Between that and my Navy training, there are 3 lessons:1 Never intentionally take a shock2 Don't wear rings or watches when working with electricity3 Never work with electricity aloneYou should also equip your shop with groung fault devices.

author: Simon
author_rank: Unknown
timestamp: April 08, 2015, 01:43:16 pm
content: Quote from: zerorisers on April 08, 2015, 01:38:35 pmThat is just childish, I left another forum because it has such statements of stupidity from so called knowledgeable people.

author: rolycat
author_rank: Super Contributor
timestamp: April 08, 2015, 02:00:51 pm
content: Quote from: Simon on April 08, 2015, 01:43:16 pmWell technically zerorisers is a child - he is 17 according to his profile. And he does not describe himself as knowledgeable, but as a 'young noobie'.Having said that, 'noobies' should be aware that if you treat mains electricity casually and have not been seriously hurt, it is because so far you have been lucky, not because it is remotely safe. Part of the danger is that the shock you get can differ wildly according to where you are, what else you are touching, the humidity and many other things over which you have little or no control. A mild shock today could be fatal tomorrow.

author: BradC
author_rank: Super Contributor
timestamp: April 08, 2015, 02:10:34 pm
content: Quote from: KerryW on April 08, 2015, 01:39:09 pmIt took me quite a while to explain to my (now) wife why I don't wear any jewelery, and therefore why I'll never actually wear a wedding ring. Once she understood the concept of the surface area significantly reducing the resistance to shock she's never even mentioned it.Now *this* is a wedding ring. Symbolic, and never to be worn in anger.

author: Zero999
author_rank: Super Contributor
timestamp: April 08, 2015, 02:38:40 pm
content: Quote from: Simon on April 08, 2015, 01:43:16 pmDon't forget he's in the US with only wimpy 120VAC for mains. He should come over to Europe and connect himself up to the real mains.Quote from: tautech on April 08, 2015, 09:19:18 amYou could show him some scary photos of people who have been seriously injured by electric shock.It's common sense really. The fact it's used as a method of execution should be enough to deter anyone with any sense from sticking their fingers in the sockets.

author: Simon
author_rank: Unknown
timestamp: April 08, 2015, 02:43:25 pm
content: On a European system to get a "funny" electric shock you just need to take the house main earth wire from the earthing point of the house in one hand and touch the wall with the other hand........

author: Lightages
author_rank: Unknown
timestamp: April 08, 2015, 02:48:52 pm
content: Scaring the shit of a 7 year old with horrible pictures, dying bugs, and shocks, are all likely to make him too afraid of the subject to continue. He is 7, and at that age he will only remember the fear and drama, not the lesson.As said before, children learn by observation. Always demonstrating proper procedure and being consistent is what will work the best in the end. Explain calmly that anything that plugs into the wall can be dangerous and demonstrate proper procedures with some examples. Give him some things that are safe to work on himself, and have a collection of things put aside that you insist that he only touches when you are together.

author: jlmoon
author_rank: Unknown
timestamp: April 08, 2015, 02:51:49 pm
content: I have had a service lab for over 30 years now. Back during my sons formative days, they grew up in this environment, I demonstrated to them (hoping they would learn 'common sense') the effects of what I consider high power and the various attributes and derivations of. In various ways I demonstrated how you can derive energy transfer in the form of Heat, Light, Sound and the by products of these. Such as how electricity can act like a hammer, you just can not see the hammer hiding within the wires. Sparks & Fire were pretty impressive to them when charging up large high voltage caps and making them pop or when you can take a high power audio amplifier (they were thinking those speaker wires were harmless!) and dump the raw power into some nichrome wire loads turning them into glowing red hot curly things and catching paper towel on fire, not to mention the lethal voltages present on those wires. To this day, I truly believe these common sense lessons instilled into them a bit of respect for power in general. When working with mains based equipment they continue to call dad over to do their dirty or risky business. Basically it is all about COMMON SENSE and how people perceive that. My teachings must have worked!

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: April 08, 2015, 03:26:49 pm
content: Quote from: zerorisers on April 08, 2015, 01:38:35 pmYea 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

author: jlmoon
author_rank: Unknown
timestamp: April 08, 2015, 03:41:06 pm
content: Quote from: mikeselectricstuff on April 08, 2015, 03:26:49 pmLOL. Mike, I hope I never run into a chic named that. No here in the USA we have 120 and 120 you just have to work hard a using one leg as the common or return.people have tried though!

author: tggzzz
author_rank: Super Contributor
timestamp: April 08, 2015, 03:42:16 pm
content: Quote from: mikeselectricstuff on April 08, 2015, 03:26:49 pmWhen I was holding a neutral in one hand and lightly touched a live thyristor can with a finger on the other hand, both biceps contracted very rapidly and caused me to drop the circuit (fortunately).Personally I'm at least as concerned by the EHT on a CRT's capacitor, and am aware of the stories regarding dielectric absorbtion.

author: Simon
author_rank: Unknown
timestamp: April 08, 2015, 05:01:36 pm
content: Quote from: mikeselectricstuff on April 08, 2015, 03:26:49 pmI 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.

author: AG6QR
author_rank: Frequent Contributor
timestamp: April 08, 2015, 05:02:13 pm
content: 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.

author: dexters_lab
author_rank: Unknown
timestamp: April 08, 2015, 05:19:07 pm
content: 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

author: Ian.M
author_rank: Super Contributor
timestamp: April 08, 2015, 05:27:22 pm
content: ... or to start him down thePhotonicInductionroad!

author: Simon
author_rank: Unknown
timestamp: April 08, 2015, 05:37:17 pm
content: 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.

author: rolycat
author_rank: Super Contributor
timestamp: April 08, 2015, 05:42:39 pm
content: Quote from: Simon on April 08, 2015, 05:01:36 pmGood 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>.

author: Ian.M
author_rank: Super Contributor
timestamp: April 08, 2015, 05:50:16 pm
content: @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.

author: Simon
author_rank: Unknown
timestamp: April 08, 2015, 05:54:16 pm
content: Quote from: rolycat on April 08, 2015, 05:42:39 pmindeeeeed, indeed old chap

author: IanB
author_rank: Super Contributor
timestamp: April 08, 2015, 07:05:16 pm
content: Quote from: blueskull on April 08, 2015, 06:29:10 pmIf you can poke your fingers into two different sockets you have very long arms and very slender fingers...

author: jlmoon
author_rank: Unknown
timestamp: April 08, 2015, 07:40:57 pm
content: Quote from: rolycat on April 08, 2015, 05:42:39 pmMy 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.

author: dexters_lab
author_rank: Unknown
timestamp: April 08, 2015, 08:11:49 pm
content: Quote from: Simon on April 08, 2015, 05:37:17 pmhe does make a good job putting his power supplies together though!

author: tautech
author_rank: Super Contributor
timestamp: April 08, 2015, 08:28:43 pm
content: Quote from: blueskull on April 08, 2015, 06:29:10 pmThis 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.

author: jlmoon
author_rank: Unknown
timestamp: April 08, 2015, 08:56:49 pm
content: Quote from: blueskull on April 08, 2015, 07:58:14 pmNot to mention better transient absorption from ESD and such.

author: smjcuk
author_rank: Frequent Contributor
timestamp: April 08, 2015, 09:21:02 pm
content: Quote from: blueskull on April 08, 2015, 07:10:33 pmThat 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.

author: jobog
author_rank: Regular Contributor
timestamp: April 08, 2015, 09:43:03 pm
content: Quote from: tautech on April 08, 2015, 08:28:43 pmHad 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.

author: tautech
author_rank: Super Contributor
timestamp: April 08, 2015, 09:45:13 pm
content: Quote from: jobog on April 08, 2015, 09:43:03 pm

author: Ian.M
author_rank: Super Contributor
timestamp: April 08, 2015, 09:51:27 pm
content: 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.

author: tggzzz
author_rank: Super Contributor
timestamp: April 08, 2015, 10:36:15 pm
content: Quote from: Ian.M on April 08, 2015, 09:51:27 pmPah. 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 sourceswerelocked 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.

author: smjcuk
author_rank: Frequent Contributor
timestamp: April 08, 2015, 11:33:29 pm
content: Quote from: tggzzz on April 08, 2015, 10:36:15 pmHa. 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

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: April 09, 2015, 12:17:59 am
content: 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.

author: zerorisers
author_rank: Regular Contributor
timestamp: April 09, 2015, 02:14:25 am
content: Quote from: Simon on April 08, 2015, 01:43:16 pmDon'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.

author: mrkev
author_rank: Regular Contributor
timestamp: April 09, 2015, 02:57:12 am
content: Quote from: Simon on April 08, 2015, 01:43:16 pmYes, 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 rantBut 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...

author: tggzzz
author_rank: Super Contributor
timestamp: April 09, 2015, 07:23:33 am
content: Quote from: mrkev on April 09, 2015, 02:57:12 amAh, 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.

author: Shock
author_rank: Super Contributor
timestamp: April 09, 2015, 07:42:03 am
content: 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.

author: Simon
author_rank: Unknown
timestamp: April 09, 2015, 07:53:37 am
content: Quote from: Shock on April 09, 2015, 07:42:03 amor about how funny it feels

author: tautech
author_rank: Super Contributor
timestamp: April 09, 2015, 08:04:08 am
content: The really sad part of this discussion is the people that have lost life or limb either from carelessness or simple error. You CAN"T see electricity, thats why it's dangerous. Knowledge of it's behaviour and use of equipment is paramount for ones safety.Be careful out there.

author: mrkev
author_rank: Regular Contributor
timestamp: April 09, 2015, 10:04:00 am
content: Quote from: tggzzz on April 09, 2015, 07:23:33 amOh, am I now. I think you misunderstood me completely, almost like if you didn't even read that post...No one should be careless and ignore safety. You SHOULD take EVERY precaution to avoid ANY potentially hazardous situations, every time, especially when you're near mains.I was just pointing out, that healthy human will survive shock from mains in <99% cases. Since the resistance of human body is well above the resistance that would allow deadly current. Most of the cases of deaths by voltage are at bathroom and usually involve naked people (at least partially) covered in water, other common thing is a lot of sweat, precondition (f.e. weak heart) or pierced or burned outer layer of skin (which drops overall resistance significantly). Most dangerous is when one is well grounded at feet (f.e. by wet floor) and touches something sharp or with a lot of surface by left hand.Quote from: tggzzz on April 09, 2015, 07:23:33 amNot at all. Health is usually huge factor, since on it depends things like body resistance (amount of sweat), probability of fast recovery, mental state (caution, vulnerability to shock) and reaction time, i.e. it affects current and time thus the amount of energy (which is the reall killer).

author: tggzzz
author_rank: Super Contributor
timestamp: April 09, 2015, 10:16:43 am
content: Quote from: mrkev on April 09, 2015, 10:04:00 amNo, I didn't misunderstand what was written in that post. Maybe you (especially as a non-native English speaker?) didn't understand what was and wasn't written.Your last paragraph merely re-inforces my statement.(Oh, BTW, silly animated emoticons don't enhance your argument.)

author: mrkev
author_rank: Regular Contributor
timestamp: April 09, 2015, 10:26:42 am
content: My argument is that healthy calm and cautious person have better chance surviving (and even preventing) the HV shock (not that health alone can guarantee surviving) and I don't see anything silly about that.Also, I wrote the most important thing that you shouldn't play with chance, so "I haven't died so there isn't a problem" is the definition of misunderstanding of my post...

author: tggzzz
author_rank: Super Contributor
timestamp: April 09, 2015, 12:43:06 pm
content: Quote from: mrkev on April 09, 2015, 10:26:42 amThat islessstupid, but thatis not what you wrote! You wrote '... perfectly healthyhuman almost can't diefrom a "simple" 230V shock' and that you had "touched mains" multiple times; I presume you have survived.QuoteNo, youdidn'twrite that. You wrote something obscure about "nobody knows how healthy they are and what is it really gonna do".You may have known what you meant, but the people reading your post are not mind readers. There are some young and/or inexperienced people reading this forum, and we must take care not to mislead them about safety.

author: amyk
author_rank: Super Contributor
timestamp: April 09, 2015, 01:20:24 pm
content: You should make sure he is not a masochist first, if you're thinking of non-lethal "test shocks". Otherwise it could have the opposite effect.

author: Zero999
author_rank: Super Contributor
timestamp: April 09, 2015, 01:26:30 pm
content: I think what he meant was 230VAC is unlikely to kill, not that it can't kill you or you shouldn't respect it, just that in most cases, just touching the mains is unlikely to cause death.Quote from: Shock on April 09, 2015, 07:42:03 amIt depends on where the current flows and the frequency. That statement applies to mains frequencies which will cause muscle spasms, possibly stopping one from letting go of the conductor. If it's 100kHz, it'll just feel warm. DC will hurt more when the current starts/stops.See table #2 on the page linked below:http://www.highvoltageconnection.com/articles/ElectricShockQuestions.htm

author: mrkev
author_rank: Regular Contributor
timestamp: April 09, 2015, 01:35:21 pm
content: Quote from: tggzzz on April 09, 2015, 12:43:06 pmOK, I deleted few lines because my post was already too long and I wrote it well after midnight. Looking back, they were making MO on safety much more clear.I wrotealmostand"simple"(meaning short timed), which is still true from medical point of view (taking that resistance of human body - before any damage to the skin occurs - is >1Mohm), or do you disagree?Part about how I remember each time I've touched mains meant that it was never a pleasant experience and those were the mistakes (as a curious kid) that I have learned from and never wanna repeat. (wasn't that obvious?)Same goes for whole story that followed in my post, those labs were dangerous and I'm glad that nobody got ever seriously hurt. That teacher was kicked of the school later (not only for letting pupils in real danger), which was the punch line that I was "clever" to delete...Quote from: tggzzz on April 09, 2015, 12:43:06 pmWhich is basically the same thing. If you have medical condition that you don't even know about, much less than 230V can kill you. And even if you don't, it's never good idea to test what it does... It's like playing russian roulette with gun that has slightly bigger magazine, but the bullet is still there...

author: SoundTech-LG
author_rank: Frequent Contributor
timestamp: April 09, 2015, 03:18:34 pm
content: and maybe the main/s lesson here is never make any assumptions at all, until you prove to yourself something is safe, and is exactly what you think it is.I did not have to stretch my arms at all to find both 120V phase legs in a duplex outlet. Depending on who did the wiring, they are not necessarily all wired with just one phase, although they should be. Fortunately it was just sparks, and no contact.Try a 9 volt battery on the tip of your tongue... how long can you hold it there?it teaches quite a lot very quickly.

author: tggzzz
author_rank: Super Contributor
timestamp: April 09, 2015, 03:36:04 pm
content: Quote from: SoundTech-LG on April 09, 2015, 03:18:34 pmQuite.I've had a mains switch clearly in the "off" position, yet it was still conducting. Yes, the switch had become faulty.Trust, but verify.

author: mrkev
author_rank: Regular Contributor
timestamp: April 09, 2015, 05:18:03 pm
content: Quote from: tggzzz on April 09, 2015, 03:36:04 pmVoltage tester comes in really handy.I remember working on outlets at my friends house, the right circuit-breaker was switched off, I checked every single outlet before I started working on it (just changing the old for new ones). And found out that the last one was still live...As we later realized, old owner added it by himself. And as he didn't want to cut into walls, he drilled connection from the next room that was on separated circuit with its own circuit-breaker...

author: XynxNet
author_rank: Regular Contributor
timestamp: April 10, 2015, 10:19:10 am
content: Applying an electric schock to anyone, especially a child is an absolute no-go in my opinion.In my classes I demonstrate the energies involved with 240V 16A mains by evaporating a roughly 2cm to 8cm aluminium foil strip (behind an acrylic security screen).Although this doesn't demonstrate in any way the consequences of electric shooks, the students reliable get the point, that with mains the energy involved is not to be underestimated.I'll link a video next week. It is quite spectacular.

author: Zero999
author_rank: Super Contributor
timestamp: April 10, 2015, 11:28:14 am
content: Quote from: tggzzz on April 09, 2015, 03:36:04 pmMost mains switches are only functional and should never be relied upon for electrical safety or isolation. Only isolators and circuit breakers provide proper protection but you should still check.Quote from: XynxNet on April 10, 2015, 10:19:10 amThe problem with that demonstration is it's misleading. You could perform exactly the same demonstration with a car battery but there would be no risk of lethal shock.

author: acarpenter
author_rank: Contributor
timestamp: April 10, 2015, 11:53:44 am
content: Quote from: tautech on April 08, 2015, 09:19:18 amThe best way i learned not to play with knifes was when i cut my finger open and had 6 stitches.Its harsh but true, that we learn through bad experiences...(or try to) we just hope that the younger learners have a small shock and not a fatal one.Andy.

author: XynxNet
author_rank: Regular Contributor
timestamp: April 10, 2015, 11:57:39 am
content: Quote from: Hero999 on April 10, 2015, 11:28:14 amYou are right. I doesn't demonstrate the dangers of electric schock but focuses on the energy involved.The car battery is another good example. In fact in my basic engineering classes I use it to demonstrate the danger of inadvertent welding in seemingly harmless situations.

author: rolycat
author_rank: Super Contributor
timestamp: April 10, 2015, 12:31:18 pm
content: Quote from: blueskull on April 10, 2015, 12:03:37 pmI agree with XynxNet. You should not subject young children to electric shocks, even shocks youbelieveto be harmless and with the best intentions. Doing it to the child of somebody trusting you to keep them safe would not only be reprehensible but might lead to serious legal consequences.

author: Shock
author_rank: Super Contributor
timestamp: April 10, 2015, 01:04:12 pm
content: Geezus nice to know all the people who are willing to electrocute the kid for a lesson.Talk to the mother first about it, and then just ask the kid:Has mommy ever told you about how to be careful with electricity? Yes/No.Well we have to practice our lab safety rules here and be careful as we don't want to get hurt.We will practice together then you can tell me what you have learned as we go.Have a container of lollies outside his reach and say each time he can recite the lab rules he gets one, and when he is tall enough to reach the container, he can help himself. Make a simple list of rules on a piece of paper and stick it by the wall. If he is a frequent visitor you can guarantee he will memorize it in no time.Positive reinforcement it's called.

author: mtdoc
author_rank: Super Contributor
timestamp: April 10, 2015, 03:07:03 pm
content: Quote from: Shock on April 10, 2015, 01:04:12 pmOh, man , he's not a lab rat or circus poodle... That's a sure way to drive away any kid with an ounce of spark(!!) in him IMO.

author: German_EE
author_rank: Super Contributor
timestamp: April 10, 2015, 03:28:54 pm
content: Thank you for all of the suggestions and comments. The idea of giving my young pupil a mild electric shock is really a non-starter as whilst we attend to technical matters mother is sitting on the workshop couch reading her copy of Blick. Anyway, a swift jolt would no doubt result in tears and a departure for home. However, I have demonstrated some of the dangers of mains power by carefully searching for videos on YouTube and then extracting a solemn promise that he will never take the covers off a mains powered device. Failure to heed this warning will result in the ending of his workshop visits.Just in case I spent an hour this afternoon fitting security screws to the TV, the DVD player and the microwave in their apartment whilst he was at school. I believe this is called a 'belt and braces' approach.

author: Sigmoid
author_rank: Frequent Contributor
timestamp: April 10, 2015, 05:49:12 pm
content: I kind of still remember being 7 years old and totally into electronics, so I'm sure most of you also do. Try to remember what would have worked for you as a kid, and don't ever underestimate children.Demonstrations of high power are fun, but they do not really do much to convey dangers. Also, arbitrary limits, like "you cannot do anything above 9V" only mystifies high voltage. When I was 7, I already knew how to use a mains socket tester, and the basics of mains wiring (my dad taught me, along with the safety mindset that comes with it - he's an electric safety inspector, so I had a good teacher). I also had some successes, I remember fixing a broken table lamp by replacing the damaged switch on the cable.What really drove the importance of safety for me is for one, the good example of my father, and a few educational videos I've seen on TV. I remember one had examples of fatal accidents from electric shocks. It was shocking, but it made the dangers of electricity obvious.Back then we were limited to what was on TV, but now you can just go on Youtube and select any safety training material you want. Find one that has real life examples.Also, practice good safety, explain the risks of high voltage in televisions (pulling arcs at a dista ce, capacitors remaining charged, etc.), teach him how to remain safe.

author: Shock
author_rank: Super Contributor
timestamp: April 10, 2015, 06:09:06 pm
content: Quote from: mtdoc on April 10, 2015, 03:07:03 pmWow you sure did take that the wrong way. But seriously read more into it and come up with more fanciful ideas, try to portray what I said in as much negative light as possible, in your own mind, then express it here, with your credentials and a little bit about your personal upbringing, and why the mere mention of positive reinforcement got you so up in arms. Then update your playlist to something more recent, Muse - "Uprising" should do it, food for oppressed souls.

author: gilbenl
author_rank: Regular Contributor
timestamp: April 10, 2015, 06:18:41 pm
content: Sorry to interrupt, but...Has anyone else noticed that this is largely a 6 page thread on how to electrocute young children?

author: mtdoc
author_rank: Super Contributor
timestamp: April 10, 2015, 06:39:04 pm
content: Quote from: Shock on April 10, 2015, 06:09:06 pmNot at all. I have 6 yr and 9 yr old boys. I use positive reinforcement all the time. I reward them when they do the right thing, not for reciting a list of rules, while holding a jar of candy out of their reach.Maybe you didn't mean it that way but that's how I read it.Reward good judgement and behaviour, not recitation of a list of rules posted on the lab wall ( which they're then sure to want to violate as soon as you're not around!).

author: Shock
author_rank: Super Contributor
timestamp: April 10, 2015, 07:20:52 pm
content: Yeah you're reading too much into it. You already got my kid violating rules in your own mind, listening to Pink Floyd and dropping acid. You underestimate how far a bit of creativity and the power of the lollies goes, they can be used for good.

author: mrkev
author_rank: Regular Contributor
timestamp: April 10, 2015, 07:24:42 pm
content: Quote from: Shock on April 10, 2015, 07:20:52 pmI'd rather listen to Pink Floyd...

author: Zero999
author_rank: Super Contributor
timestamp: April 10, 2015, 08:04:02 pm
content: Electrocution means to be killed by an electric shock, which I don't think anyone here has seriously suggested.It's important to note that children are more easily electrocuted than adults so a shock which may make you swear and shout, could be lethal to a 6 year old.

author: Ian.M
author_rank: Super Contributor
timestamp: April 10, 2015, 08:47:51 pm
content: ... and what if the kid has an undiagnosed heart condition? Risking deliberate or negligent electric shock is *TOTALLY* unacceptable.

author: TimFox
author_rank: Super Contributor
timestamp: April 10, 2015, 10:40:50 pm
content: Does anyone remember the TV program "Dinosaurs" (done by the Henson people)?The characters watched a prehistoric TV program "Watch Mr Lizard", where the catch-phrase was "Time to get another Timmy!" after each experiment.

author: KDC
author_rank: Contributor
timestamp: April 10, 2015, 11:11:15 pm
content: Could always do an electric pickle. Looks cool, but then you realize that that breaker doesn't trip and the pickle is cooked, just like you could be.