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I was working on a project converting 220V AC to 5V DC and I accidentally touched the underside of the transformer which gave me a big shock and I was wondering if it's a good idea to ground my self like with a wrist band or something like that to the ground too if this happens again, I protect my heart, etc.

Is this something I should do or what precautions should I take to protect my self?

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    \$\begingroup\$ you really need to review your knowledge of electricity .... would you stand in a tub filled with water and stick a fork into an energized toaster? \$\endgroup\$
    – jsotola
    Jul 18 '20 at 20:24
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    \$\begingroup\$ You don't know enough to be messing with unshielded high voltage. Quit doing it until you have learned enough that you have no need of asking questions like this. \$\endgroup\$ Jul 19 '20 at 3:29
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    \$\begingroup\$ In the good old days before flat-screen LED televisions, technicians working on CRTs that needed thousands of volts on the yoke were trained to keep one hand behind their back when working on a live system or, better yet, to not work on a live system. I had no idea this basic rule of common sense was no longer taught in schools. \$\endgroup\$ Jul 19 '20 at 8:09
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    \$\begingroup\$ @jsotola is being snarky. Just to make this clear: If you do what they describe, your death will be counted as a suicide. \$\endgroup\$
    – Nobody
    Jul 19 '20 at 11:47
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    \$\begingroup\$ You probably heard of the wristband thing in connection with e.g. working on electronics. There the idea is to have the (tiny amount of) static electricity go through you instead of the sensitive device. That's not what you want to happen here. \$\endgroup\$ Jul 19 '20 at 17:53

11 Answers 11

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Grounding won't protect you against shocks when touching live wires! Quite the opposite, the better you are grounded, the higher the resulting current through your body will be.

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    \$\begingroup\$ What if you have a good and strong connection from both wrists to ground? Shouldn’t that prevent current from going through your heart? I don’t know what it would do to your hands though … \$\endgroup\$
    – Michael
    Jul 19 '20 at 6:15
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    \$\begingroup\$ @Michael No. The more grounded you are the more liable you are to receive a shock. TRying to direct current paths "safely" through your body is not a known way of shock minimisation. \$\endgroup\$
    – Russell McMahon
    Jul 19 '20 at 7:40
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    \$\begingroup\$ Trying to go "through" the body is definitely a bad idea. Around the body, however, is a thing: youtube.com/watch?v=Snibt3CNqBA. No idea if that works with AC mains or just Tesla coils though. \$\endgroup\$
    – aroth
    Jul 19 '20 at 11:42
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    \$\begingroup\$ @aroth It works with mains too. youtu.be/FGoaXZwFlJ4 \$\endgroup\$
    – Phil Frost
    Jul 19 '20 at 20:20
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    \$\begingroup\$ The Faraday suits that the helicopter guys wear are for protection from the electric field. The AC field surrounding those transmission lines is so intense that, without the suit, it would cause harmful current to circulate within their bodies. No physical connection to ground or to the line is needed. With the suit, the current circulates in the metal mesh and (I'm not a physicist, so I can't confidently say how) that excludes the field from the space inside the suit. \$\endgroup\$ Jul 20 '20 at 12:54
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Grounding oneself, while working on live electrical equipment, would be an open invitation to disaster.

Insulating oneself from ground would be the only way to ensure total safety.

That's why rubber mats are provided on the door side of control panels. Electrical maintenance personnel are also provided with rubber shoes and rubber gloves and tools like pliers are also well insulated.

In spite of such protection the bigger danger is touching a live point with one hand and ground with the other. The best precaution against such an eventuality would be to always keep one hand in ones pocket while dealing with live equipment.

Such basic precautions should not be ignored even when use of GFCIs is mandatory.

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    \$\begingroup\$ And protective eyewear when sparks or tools fly. \$\endgroup\$
    – P2000
    Jul 18 '20 at 19:36
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    \$\begingroup\$ we were taught to put the mains plug of the appliance we're working on in our pocket as well. OP: if you get a shock from touching a transformer case or chassis, something is seriously wrong. both primary and secondary are insulated against the transformer core, and metal parts should be grounded unless doubly-insulated, and shorts to chassis should trip the GCFI. measure transformer insulation (resistances, powered off!) and replace if found faulty. \$\endgroup\$
    – dlatikay
    Jul 19 '20 at 10:05
  • \$\begingroup\$ I can’t find a reference, but is it worth mentioning that insulation won’t save you as your insulated body acts like a capacitor when touching AC? \$\endgroup\$
    – rrauenza
    Jul 19 '20 at 16:05
  • \$\begingroup\$ @rrauenza I don't think that's true. I did a quick Google search which shows that the self-capacitance of the human body is about 100 pF. If my calculations are correct, then that, combined with 220 volts at 60 Hz, should produce about 10 µA, too little to cause injury. (Don't take my word for it; I could be wrong!) \$\endgroup\$ Jul 19 '20 at 19:11
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    \$\begingroup\$ @TannerSwett self-capacitance is just a lower bound, for pretty much the bird-on-a-wire situation. If you're working right next to a grounded metal closet, your capacitance will be a lot higher. \$\endgroup\$ Jul 20 '20 at 15:13
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You need to review basic electrical safety with your professor assuming you are in college. If in the workplace someone didn’t do a good job interviewing you and you need to ask for training. Electricity can kill you by causing your heart to stop and afib and it can literally cook you and cause your muscles to lock up as it is shocking you. You also need to know what to do if your buddy is getting shocked otherwise both of your could die vs only one. This is serious stuff. Anyone who works on electrical items even on their house must learn electrical safety

Edit: getting shocked at 220v is an incident that you must report in writing and is not your fault. Leadership needs to be aware so they can take the appropriate corrective action. This could be a problem with how you were instructed and the professor needs training on how to teach safety. You should have been tested and passed on safety before anyone let you on that project near high voltage. Your question confirms you were not tested on safety. If you are trying something out you saw on YouTube, please report it to YouTube so it can be removed. None of us here want you or anyone else hurt.

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  • \$\begingroup\$ Not from YouTube etc. I was working on personal projects and I touched a live wire by accident. It was my first time working with high voltage that wy I asked. Mainly because of those wrist bands I saw for working with electronics. But after reading all posts I now have a better understanding of precautions for this type of work \$\endgroup\$
    – DeadSec
    Jul 19 '20 at 19:28
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    \$\begingroup\$ Talking of YouTube: I found On The Safe SIDE on YouTube. Switch off, Isolate, Dump, Earth. \$\endgroup\$
    – JdeBP
    Jul 19 '20 at 22:08
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    \$\begingroup\$ @DeadSec To be clear, if you value your life, then you should take a class on working with high-voltage electrical equipment before doing any more such work. There are a lot of dangers that you don't know about, and the only way you can protect yourself about those dangers is by taking a class that teaches you about all of them. \$\endgroup\$ Jul 20 '20 at 17:56
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    \$\begingroup\$ "Ask your professor", "ask your boss", or "write yourself up", does not convey any actual information about how to work safely. \$\endgroup\$
    – Drew
    Jul 25 '20 at 4:26
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220VAC can often cause severe permanent injury or death. Stop working with those voltage levels until you have professional training.

In an official communication, OSHA has stated that they consider all voltages above 50V to be hazardous. Just like with car accidents, not every electric shock above 50V will severely maim or kill you, but as explained in the OSHA link, the likelihood of injury increases drastically as you go above 50V.

Stack exchange is the wrong place to learn about safety in life-or-death scenarios. Take a course from a trained professional.

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  • \$\begingroup\$ Will do. Thanks for answering! \$\endgroup\$
    – DeadSec
    Jul 19 '20 at 19:31
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    \$\begingroup\$ @DeadSec no problem. Very glad that you weren't hurt more badly \$\endgroup\$
    – John M
    Jul 19 '20 at 21:33
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    \$\begingroup\$ Just note that telephone wires carries 50 volts, and can jump to 90 volts when the phone rings. Don't play around with plugged in phone cords just because they look "thin". It'll shock and/or kill you just the same. \$\endgroup\$
    – Nelson
    Jul 20 '20 at 2:15
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    \$\begingroup\$ The IEC you referenced references another wiki page. That wiki page then referenced another wiki page. It doesn't reference an actual IEC. But 50 volts AC is still potentially dangerous under the right conditions. Although DC is different varying on many different things. \$\endgroup\$ Jul 21 '20 at 0:43
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    \$\begingroup\$ I checked it and it's all good. Thanks for fixing that :) \$\endgroup\$ Jul 21 '20 at 5:05
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Wrist Bands are to protect equipment from you(ESD) not you from from equipment. Best you can do is to not work on live equipment and use RCD if you really have to (Also, isolation transformers are a good thing, but you have some learning to do as they have some subtle issues of their own).

The wrist bands (if they are good ones and not some random ebay junk) have a large series resistor in the connection to ground (typically 1 Mega ohm) precisely to minimise the dangers inherent in contacting a power line while earthed. This resistor allows the static to dissipate quickly (The human body is figured to be a 100pF cap for ESD purposes) while limiting the current in the case of contact with a high voltage supply to a level unlikely to kill.

You really do NOT want to be firmly earthed if you contact a high voltage source.

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    \$\begingroup\$ One can do better than hope that an RCD will save you by using an isolating transformer, gloves and rubber mat. \$\endgroup\$
    – Transistor
    Jul 18 '20 at 18:40
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    \$\begingroup\$ RCD (or GFI in N.Amer.) protects in the event of double handed touching. Isolation transformer and rubber mat won't. (Gloves will) \$\endgroup\$
    – P2000
    Jul 18 '20 at 19:34
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    \$\begingroup\$ It would be nice to expand RCD. You can always say "if you don't know it you shouldn't be touching electricity", nevertheless this is a public site, and it isalso read all across the world, where English abbrevs don't mean anything. \$\endgroup\$
    – Gnudiff
    Jul 19 '20 at 13:37
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    \$\begingroup\$ Please edit your answer to include the extra info, not just a comment. Expect some future readers to just skim answers, not dig through comments, so edit accordingly. \$\endgroup\$ Jul 20 '20 at 0:38
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    \$\begingroup\$ @P2000 RCD won't protect you if you touch live and neutral simlutaneously \$\endgroup\$
    – Erbureth
    Jul 20 '20 at 11:56
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Mains electrical person here.

There is no reason to work on a 230V -> 5V converter.

They are common as dirt, and you can buy one literally more places than you can buy eggs. Every gas station, liquor store, smoke shop, five-and-dime aka dollar store, apothecary, grocery.

Their common-ness does NOT make them a good choice for hobbyist hacking. You found out why.

Hobbyists should never be opening up an AC mains power supply. The items are commodities. Simply obtain a UL-Listed AC mains supply that gives the low voltage output you want to work with, and don’t open it up or tamper with it.

If you want to work with high voltage but low current AC, such as a Jacob’s Ladder, then obtain a UL-listed, isolating, 24 volt AC power supply, preferably one with intrinsic current limiting, and an appropriate step-up transformer to kick it up to your high voltage. That makes it an isolated “service” which means if you touch one leg of it and building earthing, nothing happens. Even if you touch leg-leg, as long as your high voltage is limited to 5 milliamps (due to current limiting on the low voltage side), it is rather unlikely to harm you.

EVERY AC mains shock is death brushing against your shoulder

Every single time you experience an AC shock, it is because the conductances (1/resistance) of the various current paths just happened to be too little to kill you that day.

However, these ad-hoc current paths are highly variable. If they didn’t kill you today, they can’t count on doing the same tomorrow. The humidity in the air might change. Your skin might be sweaty.

A stun is as good as a kill, if you’re unlucky. The picture postcard example is electrical drownings. But you can also be killed falling off a ladder, or collapsing (face-planting) into the mains AC equipment you are working on.

Stay on your side of the wall wart

For hobbyists, there is so much rich and fertile ground to be worked in the low voltage DC space, that there really isn’t any reason to fool around in AC mains. And if you look at the countless electronic projects in kit form, or made in low volume (many things on Kickstarter for instance), it’s the same refrain: a complicated ingenious low voltage DC product, coupled with a commodity wall-wart that is UL-Listed. Even though the project/kit makes not attempt to UL-List.

(And BSI, TUV, ETL etc. are valid NRTL substitutes for UL; however CE is not, unless it’s built and sold at bricks-n-mortar retail inside the EU proper. Everywhere else, CE means Chinese Excrement, because there are no consequences for faking it).

Needless to say you void the UL listing when you open one up.

Some people deride that ubiquitous wall wart and wish every product had an AC line cord or socket on the device. OK, that makes the UL listing vastly more complicated. Now the device’s internal power supply must grind through the much tougher White Book rules applicable to AC mains. If you notice, the first Mac Mini shipped with a power block. That’s because Apple was able to push the power block through the lengthy and complex UL listing process without revealing to UL what the product was. The Mac Mini itself could breeze through quite late, since it was entirely low voltage. *So, do you want your kit manufacturer or Kickstarter small-volume builder to really have to grind through that expense and delay? No.

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  • \$\begingroup\$ Quality wall warts aren't quite as easy to find as you suggest. Some of the ones that are found at convenience stores may be shockingly bad. \$\endgroup\$
    – supercat
    Jul 20 '20 at 22:33
  • \$\begingroup\$ That is a pretty narrow definition of hobbyist there, some of us build valve based EME transmitters and last I checked I could not get the 3kV anode supply (Good for about half an amp) down the local gas station! Now one should not generally play too far outside ones competence, and yea, for flea power low voltage stuff just buy the supply already. However even building a hifi amp can hit 100V DC between the rails at a good few amps, and radio gear is sometimes much worse, we do not hear of many hams dying from power supply accidents. \$\endgroup\$
    – Dan Mills
    Jul 20 '20 at 23:50
  • \$\begingroup\$ @DanMills My general view is that people who specialize like that must by necessity bone up on the essentials. I play with 600VDC myself. However you wouldn't hear about it... for the same reason you don't hear of people dying from NEMA 10 dryer/range accidents either (a simple loose neutral energizes the machine chassis). The reporters are simply not technical enough to make any sense of what happened, and they simply report it as defective wiring. \$\endgroup\$ Jul 21 '20 at 0:45
  • \$\begingroup\$ @Harper-ReinstateMonica Tapping 120V to ground on NEMA 10 is just plain wrong, and something only the US could think was acceptable behaviour. If it happened to hobbyists of the high energy sort much you may not hear about it in the press, but you would hear about it in the community. Deaths due to misadventure working on QRO amplifiers would be talked about. In my experience it is not the obviously dangerous that you need to sweat, it is the more subtle things that cause injury, muppets with scope ground clips and switched mode supply hot sides spring to mind. \$\endgroup\$
    – Dan Mills
    Jul 21 '20 at 12:40
  • \$\begingroup\$ Thanks for your feedback. I stopped that project and used a better, more safe transformer and asked an electrician to help me out and explain to me in the meanwhile how it all works. I like developing PCBs and programming, and that project needed to be plugged into mains because there weren't any plugs where I wanted to install the PCB. \$\endgroup\$
    – DeadSec
    Feb 11 at 23:23
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No you shouldn't. The current will probably pass through your heart and kill you. See this link for the origin of this picture and some useful facts. https://www.mikeholt.com/mojonewsarchive/ET-HTML/HTML/EletricalShockHazard~20020326.htm

enter image description here

https://www.mikeholt.com/mojonewsarchive/ET-HTML/HTML/EletricalShockHazard~20020326.htm

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  • \$\begingroup\$ Note that the OP asked about a wrist strap. If they grounded themselves at the wrist of the one hand they were using to touch live parts, that might restrict current to going through fingers/hand, but not body. Still probably better to insulate, though; that works even better if you restrict yourself to working with one hand. \$\endgroup\$ Jul 20 '20 at 0:41
  • \$\begingroup\$ @PeterCordes he did not say that he was working with the (single) grounded hand so the picture is pretty accurate \$\endgroup\$
    – Fritz
    Jul 20 '20 at 14:15
  • \$\begingroup\$ @Fritz: I know that, I'm talking about the hypothetical case where you know what you're doing but can't be sure you've avoided grounding your feet. Grounding the wrist of the one hand and only work with that hand, it might be worth mentioning that possibility. But probably not; you want better precautions against something that hazardous. I just thought it was an interesting thought experiment that was different from the diagram being discussed. \$\endgroup\$ Jul 20 '20 at 14:30
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You ask about additional precautions regarding shocks:

  • wear no metallic jewelry, including rings, bangles.
  • if you have a wristwatch, use a leather band, not metal.

Metal-backed wristwatch is somewhat hazardous. Your skin is damp underneath, making skin resistance lower. A cheap plastic-shelled watch is an improvement.

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To sum it up:

  • Definitely do NOT ground yourself, as this is likely to increase current (The wrist bands many people working with pcbs wear are used to protect the circuits from esd)
  • Review your basic knowledge about working with electric components
  • Whenever possible do NOT work with live wires, setup your measurements before turn on measure, turn off, change measurement setup, repeat (In most cases you don't need to mess with your system while it's connected)
  • If you insist on working with a live wire:
    • make sure you have a RCD in you system to at least protect you to some degree
    • Try using only one hand
    • Try to isolate yourself (e.g. using a mat)
    • Have a second person close by, in case you mess up badly and need help (Person should actually first aid and how to turn your stuff of before touching you)
  • If you do this for your work (college or industry) there is most likely someone responsible workers safety, speak to them

Generally I always recommend to not work with live wires

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As all others already mentioned, don't ground yourself, isolate yourself or the circuit ... or even both

  • never work on life systems > 50VAC (especially untrained)
  • You could isolate the circuit by using an transformer, so the only risk is touching 2 different live parts (Phase & ground for example). If you just touch one nothing should happen
  • use proper protection like a RCD (german FI)

the mentioned wristbands usually have 10MOhm so the current would be 0.02 for 220V and combined with your internal resistance low enough to not die.

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Do not ground yourself to anything. The only safe way you can work like this is to be flying or hanging by a rope which is very unlikely.

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