ElectroBOOM sinking to new low in safety - what to do?

[bktemp]

Older capacitors often don't have a builtin discharge resistor. I made that experience some time ago.
I didn't touch the capacitor, only the wiring, but the insulation was old and brittle and the arc whent right through.
That was quite painful, but AC is often worse because capacitors typcially discharge quickly.

They can store much more than 5J: The typical value is 1uF, rated for around 2kVAC. Therefore they can be used at 5kVdc storing >10J. You can even go higher, but this risks damaging the capacitor.

[ZeTeX]

Yesterday my dad gave me a cheap chinese SMPS to repair. unfortunately, it didn't have a bleeder resistor across the main filter capacitors, and even though it was sitting unused for 12 hours, when I opened it up I got a nice little shock. a good way to start the morning, with the heart at 120BPM.

[firewalker]

I think there was a thread about the dead boy in the article.

http://www.seventeen.com/life/news/a39878/morgan-wojciechowski-was-attempting-an-experiment-called-jacobs-ladder-which-involves-a-high-voltage-arc-of-electricity/

Alexander.

[Berni]

I'm now working on a megawatt DC/DC converter, and the bus cap has max 5kJ stored in it. The cap bank itself is 3 2U chassis worth of GE oil filled paper caps.
I treat that 3 boxes as the lord of death himself. It has one slow discharger per box, to discharge it to less than 100V in a few hours.
It has a controllable normally close discharge relay that discharges it in minutes, and it also has a discharge stick that discharges it in a few seconds.
In case everything fails, we still have a discharge rod that is a dead short, aka Jesus stick.

That certainly sounds like something you really wouldn't wanna touch.

I was experimenting with a 1kJ electrolytic cap bank in making a coilgun for fun. First few tests went well but then the SCR triggering circuit lost a connection somewhere and didn't fire anymore. So i had the caps sitting there fully charged with nothing to empty them. My quick solution was a near by 100W incandescent bulb that i very carefully stuck across the bus bars, i found it a pretty nervous operation. Later on i wired in separate discharge circuit using the same 100W lamp as a load since it worked well and could discharge it reasonably low in about half a minute.

[aandrew]

I don't like the idea of a MOT for a Jacob's ladder to begin with.

When I did my stint in HV experiments I had built a two-transistor LC oscillator with a rewound HV transformer out of the biggest TV I could find.

There's a BIG difference between 60Hz few thousand volts out of a voltage-double/tripled MOT and the 40kHz 50-75kV I got out of my HV generator. Still hurts to get zapped but WAY, WAY safer.

... and made just as cool Jacob's ladders in addition to plasma globes and ion motors...

[jh15]

I and others started decades ago with Jacob's ladders and used neon sign or oil burner ignition xfmrs.

At my hackerspace someone asked if MOTs could be used. (Ihad a few around for various uses).

I said besides the high danger, there is no current limiting built-in like the former.

Be like trying it with a transmitter plate supply, no one will be happy.

A funny (because we survived), accident happened when a friend tried to connect his Van deGraph to a ladder. This was in 8th or 9th grade in 60's, but THAT memory never faded.

Is there a "my most embarrassing shop/lab/home experimenter" thread here?

I'm going to bed before watching the video.

[Zero999]

Yeah usually his videos are a great show, with very little actual risk to him if you beat away the safety nancys who are afraid to even look at an exposed mains wire (Inb4 euros smugging about outlets)  But a MOT packs a wallop, and I was uneasy with the long lighter between the  legs of the ladder. (ignition wire in lighter, metal spring, super questionable clearance on that, grounded core on MOT, a whole lot of trust on a little varnish and a bobbin)  But when the whole bit fell over on him, I went back, looked over the video, tried to see what he did, look for well done cut, something with the camera angle making it look closer than it actually, etc but was like "Nope, no, that was a full on dangerous accident, dude was inches from death" not his usual showmanship to make stuff look way more dangerous than it is.

I agree but I doubt he connected the core of the transformer to earth. In this case it probably would be safer to let the transformer and its secondary to float, so it's unlikely there would be a complete circuit when touching one side of the secondary.

[SeanB]

Well, this is how to make a DIY plasma ball. like the 1kW lamp used there as well, but would probably use one of the 400W MV reflector lamps i have instead.

[Zero999]

Well, this is how to make a DIY plasma ball. like the 1kW lamp used there as well, but would probably use one of the 400W MV reflector lamps i have instead.

Using an energy saving lightbulb driver for the flyback transformer is insane! The main problem is it makes it easier for clueless people to make.

The only idea of using a blocking oscillator was safer, not only because it's isolated from the mains but there's also slightly more skill required to make it, thus eliminating total nubies from the equation.

[ConKbot]

Yeah usually his videos are a great show, with very little actual risk to him if you beat away the safety nancys who are afraid to even look at an exposed mains wire (Inb4 euros smugging about outlets)  But a MOT packs a wallop, and I was uneasy with the long lighter between the  legs of the ladder. (ignition wire in lighter, metal spring, super questionable clearance on that, grounded core on MOT, a whole lot of trust on a little varnish and a bobbin)  But when the whole bit fell over on him, I went back, looked over the video, tried to see what he did, look for well done cut, something with the camera angle making it look closer than it actually, etc but was like "Nope, no, that was a full on dangerous accident, dude was inches from death" not his usual showmanship to make stuff look way more dangerous than it is.

I agree but I doubt he connected the core of the transformer to earth. In this case it probably would be safer to let the transformer and its secondary to float, so it's unlikely there would be a complete circuit when touching one side of the secondary.

Its been a while since I've read about exciting HV projects, but I could have sworn that one end of MOT was grounded to ease insulation requirements to the core (anything for cheaper manufacturing) and that lifting the ground was required for unipolar double stacks, or insane bipolar quad stacks.
 Hm, some achematics like below show the core as grounded too. Looks like the connection may be internal too.
http://kitchen.manualsonline.com/manuals/mfg/sanyo/ems2588w.html?p=2

Obviously it could vary from manufacturer to manufacturer, but if you're counting on the isolation, an insulation tester would be a very good idea.

[SKHILLBILLYSlures]

I tend to argue it taught me a lot about parasitic capacitance this something your electricronics technology teacher doesn't teach you (just that definitely shouldn't touch it not why just that you shouldn't )that touching ONE side of the live 2kv will shock you I never new this before that video and he even show cases it with MM probe watching him get shocked insures to me that I don't want to be shocked like that I only free for his safety and hope that he doesn't heart problems in the future from the excessive intentional misuse of ac electricity so that others may be inspired to not be shocked in much the way I was inspired to

[Zero999]

Yeah usually his videos are a great show, with very little actual risk to him if you beat away the safety nancys who are afraid to even look at an exposed mains wire (Inb4 euros smugging about outlets)  But a MOT packs a wallop, and I was uneasy with the long lighter between the  legs of the ladder. (ignition wire in lighter, metal spring, super questionable clearance on that, grounded core on MOT, a whole lot of trust on a little varnish and a bobbin)  But when the whole bit fell over on him, I went back, looked over the video, tried to see what he did, look for well done cut, something with the camera angle making it look closer than it actually, etc but was like "Nope, no, that was a full on dangerous accident, dude was inches from death" not his usual showmanship to make stuff look way more dangerous than it is.

I agree but I doubt he connected the core of the transformer to earth. In this case it probably would be safer to let the transformer and its secondary to float, so it's unlikely there would be a complete circuit when touching one side of the secondary.

Its been a while since I've read about exciting HV projects, but I could have sworn that one end of MOT was grounded to ease insulation requirements to the core (anything for cheaper manufacturing) and that lifting the ground was required for unipolar double stacks, or insane bipolar quad stacks.
 Hm, some achematics like below show the core as grounded too. Looks like the connection may be internal too.
http://kitchen.manualsonline.com/manuals/mfg/sanyo/ems2588w.html?p=2

Obviously it could vary from manufacturer to manufacturer, but if you're counting on the isolation, an insulation tester would be a very good idea.

Yes, one end of the MOT secondary is connected to the core but that could easily be left to float, if needs be. It may be dangerous to have a transformer with inadequate isolation between the core and mains primary unearthed but the safety of a HV floating secondary winding would outweigh the risk in this case.

[Berni]

Yep nobody forces you to connect the core to ground like it was done in the microwave.

I seen people use this to there advantage by connecting two microwave transformer outputs in series. Tho obviously you can't take this trick too far as eventually the insulation of the primary will arc over. My guess is that 3 in series is as far as you can get before it bursts in flame as soon as you turn it on.

To make things even crazyer you can mirror the series setup by flipping the primary connection to get an opposite phase output for a grand total of 8kV. I sure wouldn't want to stand anywhere near that thing thats for sure.

[timb]

Dumb never dies, err, wait...

http://www.nbcnews.com/news/us-news/teen-youtuber-shoots-kills-boyfriend-video-stunt-n777851

She claims it was his idea and he talked her into it.

That's got to be a Darwin Award winner.

Clearly he hadn't heard of the concept of a "dry run"

Apparently they did several dry runs, according to the article. Apparently she had been practicing on various books and showed him one that the bullet didn't penetrate.

The "trick" seems like it would work, in practice. However, so many things can wrong... You could two books with identical page counts and one would block the bullet and the other wouldn't, depending on the thickness, type, humidity and age of the paper and the thickness and material of the hardcover itself!

That's not even counting the ammunition! Depending on the age, storage humidity, brand and several other factors the speed of the  fired bullet can vary several hundred FPS.

There's also a matter of if she used JHP or FMJ rounds both times. A book might easily stop a hollow point, because it mushrooms and fragments on impact, dissipating much of the energy; whereas a FMJ, especially a .50 caliber(!), would punch right through a book like it was cheese cloth.

If a professional were to perform a stunt like this, they would load their own ammunition (or have it loaded), using only a tiny amount of powder (to limit the bullet's energy), use frangible ammunition and wear Kevlar (or replace the back panel of the book with Kevlar).

The fact she couldn't foresee how something would go wrong is mind boggling to me.

A god damned Desert Eagle. Seriously.

[grumpydoc]

Clearly he hadn't heard of the concept of a "dry run"

Apparently they did several dry runs, according to the article. Apparently she had been practicing on various books and showed him one that the bullet didn't penetrate.

The "trick" seems like it would work, in practice. However, so many things can wrong... You could two books with identical page counts and one would block the bullet and the other wouldn't, depending on the thickness, type, humidity and age of the paper and the thickness and material of the hardcover itself!

That's not even counting the ammunition! Depending on the age, storage humidity, brand and several other factors the speed of the  fired bullet can vary several hundred FPS.

There's also a matter of if she used JHP or FMJ rounds both times. A book might easily stop a hollow point, because it mushrooms and fragments on impact, dissipating much of the energy; whereas a FMJ, especially a .50 caliber(!), would punch right through a book like it was cheese cloth.

If a professional were to perform a stunt like this, they would load their own ammunition (or have it loaded), using only a tiny amount of powder (to limit the bullet's energy), use frangible ammunition and wear Kevlar (or replace the back panel of the book with Kevlar).

The fact she couldn't foresee how something would go wrong is mind boggling to me.

A god damned Desert Eagle. Seriously.

Ah, the reports that I saw were clearly edited down and didn't mention any preparation.

As you say, many variables which needed to be controlled, just weren't; very sad that this lesion in life was at the expense of someone's death.

[Yansi]

Yep nobody forces you to connect the core to ground like it was done in the microwave.

I seen people use this to there advantage by connecting two microwave transformer outputs in series. Tho obviously you can't take this trick too far as eventually the insulation of the primary will arc over. My guess is that 3 in series is as far as you can get before it bursts in flame as soon as you turn it on.

To make things even crazyer you can mirror the series setup by flipping the primary connection to get an opposite phase output for a grand total of 8kV. I sure wouldn't want to stand anywhere near that thing thats for sure.

Not sure if I understand you correct, but connecting two MOTs in series  is  always and should always be done with the cores grounded and primary connected out of phase to create a 2kV-0-2kV output, 4kV together. If not done that way, your MOT is not gonna last for long. (which is not gonna do anyway, if you want it just to draw some arcs with it, not even mentioning if someone pulls out the magnetic shunts to beef the output current further up).  Also all those new ones have a crap and cheap aluminium windings, so they overheat even quicker.

[Berni]

Yep nobody forces you to connect the core to ground like it was done in the microwave.

I seen people use this to there advantage by connecting two microwave transformer outputs in series. Tho obviously you can't take this trick too far as eventually the insulation of the primary will arc over. My guess is that 3 in series is as far as you can get before it bursts in flame as soon as you turn it on.

To make things even crazyer you can mirror the series setup by flipping the primary connection to get an opposite phase output for a grand total of 8kV. I sure wouldn't want to stand anywhere near that thing thats for sure.

Not sure if I understand you correct, but connecting two MOTs in series  is  always and should always be done with the cores grounded and primary connected out of phase to create a 2kV-0-2kV output, 4kV together. If not done that way, your MOT is not gonna last for long. (which is not gonna do anyway, if you want it just to draw some arcs with it, not even mentioning if someone pulls out the magnetic shunts to beef the output current further up).  Also all those new ones have a crap and cheap aluminium windings, so they overheat even quicker.

I never said it was a good idea to do, just something i seen people do, just to get massive amounts of power from the poor transformers.

I also seen someone put 3 of them together on to 3 phase to get even more power.

[Yansi]

Yep nobody forces you to connect the core to ground like it was done in the microwave.

I seen people use this to there advantage by connecting two microwave transformer outputs in series. Tho obviously you can't take this trick too far as eventually the insulation of the primary will arc over. My guess is that 3 in series is as far as you can get before it bursts in flame as soon as you turn it on.

To make things even crazyer you can mirror the series setup by flipping the primary connection to get an opposite phase output for a grand total of 8kV. I sure wouldn't want to stand anywhere near that thing thats for sure.

Not sure if I understand you correct, but connecting two MOTs in series  is  always and should always be done with the cores grounded and primary connected out of phase to create a 2kV-0-2kV output, 4kV together. If not done that way, your MOT is not gonna last for long. (which is not gonna do anyway, if you want it just to draw some arcs with it, not even mentioning if someone pulls out the magnetic shunts to beef the output current further up).  Also all those new ones have a crap and cheap aluminium windings, so they overheat even quicker.

I never said it was a good idea to do, just something i seen people do, just to get massive amounts of power from the poor transformers.

I also seen someone put 3 of them together on to 3 phase to get even more power.

If one cannot connect two in series the reasonable way, without having the core floating on 2kV against ground, he should not play with high voltage power to begin with!  **Grin** 

See this, especially the second one 

https://youtu.be/rYQP_p7WWmE

https://youtu.be/vfixjqWcOwg

[Yansi]

Or this one. That's really something   

[Berni]

Yep that's where i seen the 3 phase MOT. The result is rather impressive il give him that.

[Yansi]

That was this 

Awesome is his 3f socket in the bathroom. He has got three separate 1f sockets, each wired to a different phase. Clever!

[David Hess]

Dumb never dies, err, wait...

http://www.nbcnews.com/news/us-news/teen-youtuber-shoots-kills-boyfriend-video-stunt-n777851

She claims it was his idea and he talked her into it.

That's got to be a Darwin Award winner.

Darwin loses this one on a technicality; she is pregnant with her dead boyfriend's child.  It only counts as a Darwin award if they die before reproducing.

Apparently they did several dry runs, according to the article. Apparently she had been practicing on various books and showed him one that the bullet didn't penetrate.

My own informal experiments shooting books with various firearms leads me to believe that if she said this, then she made it up afterwards.  The only thing we found which would reliably *not* penetrate a book is a .22 CB cap and I used to use these indoors with a backstop made from a telephone book.

His neighbors must hate him.. all that EMI must wreak havoc with cellphones etc..

When we ran my Tesla coil for Halloween one year, I later got reports saying that it knocked out AM (expected), FM, TV (expected), *and* cable reception for a couple of blocks around my house.  We did not run it the following year but only because it was so scary, that the trick-or-treaters would drop their candy and run screaming and crying down the street.

[Yansi]

If it was a SGTC type of tesla coil, then yes, it will cause an EMC havoc. Otherwise not much likely.

[VulcanBB18]

Dumb never dies, err, wait...

http://www.nbcnews.com/news/us-news/teen-youtuber-shoots-kills-boyfriend-video-stunt-n777851

She claims it was his idea and he talked her into it.

That's got to be a Darwin Award winner.

Clearly he hadn't heard of the concept of a "dry run"

Apparently they did several dry runs, according to the article. Apparently she had been practicing on various books and showed him one that the bullet didn't penetrate.

The "trick" seems like it would work, in practice. However, so many things can wrong... You could two books with identical page counts and one would block the bullet and the other wouldn't, depending on the thickness, type, humidity and age of the paper and the thickness and material of the hardcover itself!

That's not even counting the ammunition! Depending on the age, storage humidity, brand and several other factors the speed of the  fired bullet can vary several hundred FPS.

There's also a matter of if she used JHP or FMJ rounds both times. A book might easily stop a hollow point, because it mushrooms and fragments on impact, dissipating much of the energy; whereas a FMJ, especially a .50 caliber(!), would punch right through a book like it was cheese cloth.

If a professional were to perform a stunt like this, they would load their own ammunition (or have it loaded), using only a tiny amount of powder (to limit the bullet's energy), use frangible ammunition and wear Kevlar (or replace the back panel of the book with Kevlar).

The fact she couldn't foresee how something would go wrong is mind boggling to me.

A god damned Desert Eagle. Seriously.

It really is such a shame.  While they aren't (& never were) overly scientific, if they'd just watched a little Mythbusters they might have had second thoughts, at least :



cheers,

[timb]

Dumb never dies, err, wait...

http://www.nbcnews.com/news/us-news/teen-youtuber-shoots-kills-boyfriend-video-stunt-n777851

Apparently they did several dry runs, according to the article. Apparently she had been practicing on various books and showed him one that the bullet didn't penetrate.

My own informal experiments shooting books with various firearms leads me to believe that if she said this, then she made it up afterwards.  The only thing we found which would reliably *not* penetrate a book is a .22 CB cap and I used to use these indoors with a backstop made from a telephone book.

I used to shoot a Ruger 10-22 in my backyard and used a cardboard box filled vertically with newspaper. I found that, on occasion, the bullets would punch right through. .22-LR rounds can be surprisingly powerful and can actually go faster than 9mm or .40 rounds! Eventually I started shooting sub-sonic ammo, which kept the neighbors happy and kept the bullets in my backstop.

But yes, in general I agree with you. I've seen a .357 Magnum shoot through three telephone books and a gallon milk jug filled with water like it was nothing. (And that was from a revolver with only a 2" barrel!)

To me, the bottom line is this: Guns are deadly serious business and you don't play with them, period. As tragic as this may be, she deserves to be in jail, if not to kept her sheer stupidity contained and away from the rest of us.

(It almost makes me wonder if maybe she *wanted* her boyfriend dead. Maybe she had insurance on him or something and thought she could get away with it by making it look like it was his idea and she just went along.)