Shock from a camera flash is lethal!!

valich: Don't take my word for it. Ask your doctor. But, don't conduct an experiment on your own body.

 

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You have to hope that would-be users of this information are not very familiar with electronics. There is nothing special about triggering a camera flash and using it this way that hasn't been known for over 30 years to most real hobbyists and technicians. There isn't anything about it that can't be learned at most public libraries, either. The dumbing down of education might do it for us, though.

 

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Using scientific methodology, when you want to prove a hypothesis, you have to conduct experiments. Both My Nikon and Cannon SLRs have external camera flash outlets. I can push my finger on the two prongs, point-and-shoot, and I don't feel a thing. That's two experiments that support the null hypothesis.

 

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valich: The hypothesis is, as anyone with adequate reading skills would already know, is that a fractional ampere current passing through a human heart will stop it from beating. Stone cold dead. Sticking your fingers or other sufficiently small body members into your SLR flash ports proves/disproves absolutely nothing with respect to this thread.

My cannon (spelled with two ns ) was a Ruger 44 Magnum.

My Canon ( spelled with one n ) was my favorite camera, sharing history with my Olympus, my Mamiya, my Nikon, my Nikormat, my Polaroid my Kodaks, my Bell and Howells, my whatevers and a few mores. What do you want to play name-drop about next? Cars? Handguns? Ex-wives? Ex-girlfriends? Divorce lawyers? Favorite beer brands? What?

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IIRC, my old electronics textbook gave the figure of 0.1 amp-s (0.1 amp x 1 s or 1 amp x 0.1 s) as being capable of triggering fatal v fib. Of course the conditions would have to be perfect, so that the entire current passed through the heart muscle. In other words, intentionally taking any shock is a _really_ stupid idea.

Ever hear of the Darwin awards.

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Hi valich,
I don't know for sure, but I suspect you'll find that the external flash outlet has a built-in switch. It won't fire unless you actually have something plugged into it that's supposed to be there. That's pretty standard for any touchable contacts that give decent current on any electronic device.

The other possibility, of course, is if it's a hot-shoe that triggers a flash unit with it's own power.

But anyway, here's an interesting Darwin Award about a Navy guy who managed to kill himself with a multimeter powered by a 9 volt battery

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It's not confirmed, but the accompanying discussion is on the convincing side.

This bit is interesting:

One of the "rules of thumb" that the Navy teaches is the 1-10-100 rule of current. This rule states that 1mA of current through the human body can be felt, 10mA of current is sufficient to make muscles contract to the point where you cannot let go of a power source, and 100mA is sufficient to stop the heart.​

 

That sounds about right. My first etech book was a NAVPERS reprint. Although 9 volt seems a little low. Conditions would have to be nearly perfect. Duration has a lot to do will it. The total number of coulumbs conducted through tissue is the most accurate way determining the severity of shock. Trouble is that the path the current takes is critical, nerve and muscle tissue being vulnerable to depolarization. Nerve temporarily unable to fire and muscle contract. The best thing is to _never_ get shocked.

My favorite Darwin award is the guy who got ahold of a military rocket assist bottle and attached it to a VW beetle. Wanted his own rocket car. From the skidmarks they figured the brakes held out for about a half mile, at which point the bug became airborn, flew across a ravine, and impacted head on into a mountainside in excess of 150mph.

 

Mostly what kills you in an electric shock is lack of resistance, stand bare foot on a copper pipe while soaking wet and mess about with a TV picture tube or that camera and even low current could kill you.

When messing with electronics you have to know you can ground any current to the path of LEAST resistance, hence ground wires as electricity will choose to go in a ground wire instead of your body.

If you are completely dry, wearing rubber boots, keep one arm out of the way a shock might not be so bad.

I have to say though, that even if a shock does not kill you, its side effects can, could cause a spasm in an arm while holding a screwdriver, it might go in your leg, or you might fly across the room and smash your head on something.

 

For a current to be lethal, it has to hit the heart just right under the right conditions. Everyone's conductivity varies. So does their susceptibility and their physical condition. The path the voltage will take through the body is completely random, partly because the nerves are not great conductors of electricity either and they don't run that direction. There is no telling who will die from, in theory, receiving a jolt from a nine-volt battery or who will be relatively undamaged after bridging a 10,000 volt line with either hand. The current that can shut down a heart or start fibrillation is measurable in microamps at the site where it actually causes the damage. The fraction of the current applied that makes it in there is completely unpredictable.

It would take very careful estimates from actual incidents to get a handle on it. Taser deaths are coming up in the news because a lot of police officers think of them as toys and play nasty little games with them. They think that these devices are safe and they're not. It's not that safe to stress the body that way and tasers are already known to be lethal if abused enough.

The photoflash capacitor from any camera is around 300 microfarads, give or take, at about 300-400 volts. Someone can estimate for me if they want how many joules of energy that is. At 300-400 volts, the capacitor will dump all of its electricity through any skin it comes in contact with, if someone touches both terminals. Almost always the victim will survive with very minor injuries, but you don't know whose physiology is in the wrong place at the wrong time. It's not worth the risk just for a little bit of malicious mischief.

I would guess that a capacitor that weighed 150 pounds might hold enough power to, if dumped through a large enough strobe tube in one dump, flash-fry anyone standing next to it, let alone blind them. Even visible light can cause damage to skin and internal organs if it is bright enough, if for no other reason than because it is converted to heat. When you hold a piece of cardboard in front of a flashtube, you can feel the impact when the flash goes off. There's going to be some heating, oxidation, and actual physical impact when the pulse is strong enough.

An interesting experiment would be to see how powerful a flash it takes to blast light through a fresh sheet of aluminum foil.

 

dam.. i rember when me and my friends usued ot do that with disposable camras .. no idea how dangrus it was.. wow

 

By the way, a "hot shoe" is just a pair of contacts that go to a switch in the camera body. There isn't even a power source hooked up to it when the flash isn't attached. The power source is inside the camera. The switch, through the hotshoe, closes a low-voltage low-current circuit that triggers the circuitry that triggers the flash. It can directly trigger the SCR device that triggers the flash, or it can trigger a circuit that sends first a positive pulse then a negative pulse to the SCR to turn it on and then off again to control the duration of the flash. All sorts of variations are possible.

In short, neither the shoe on the camera nor the mating part on the flash carries dangerous voltage or current.

 

Thank you. Converting joules to kilogram-meters at the rate of .102 kg/m per joule, that's enough energy to raise a kilogram 1.88 meters into the air. That's at least the beginning of a pretty good hammer blow. A 2.2 pound weight falling from a height of just over 6 feet can shatter a fairly thick piece of terra cotta tile. It's enough to put a nice crater in the end of your finger.

 

I'm not sure if the energy to shatter a tile is representative of the energy to blow off a chunk of finger...

18.4 joules is just enough to heat up a gram of water by all of 4.4°C... doesn't sound like much any more, does it?

 

Try it with a screwdriver. The point of contact with this energy runs close to a millimeter in diameter. This is roughly a thousandth of a cc. Now we're talking about heat in the thousands of degrees C. I said a "crater." This is an excavation caused by a small explosion. You will get a burn with a little hole in it.

 

OK, that makes more sense. I had a different image in mind when you said "crater".

Yes, a few thousand degrees rise in a small volume seems convincingly enough to blow out a little hole and burn some surrounding flesh!

 

Hey do you have a physics explanation for this? Or some sort of illustration? I am really interested.

 

I flew out of my seat from a disposable camera shock in 6th grade. Basically my friend just took the cover off of it and jammed the whole thing on my arm

 

Slightly off-topic..

When I was a kid I once took a (big) capacitor from a fluorescent lamp set and stuck the wires into a power outlet. I waited for 15 minutes or so and then proceeded to put the wires to the contact points on a light bulb (by hand of course).
Just before I put the second wire on the contact point the capacitor generated a big spark that burned right through the copper bit of the lamp. It actually melted right through..
Naturally the lamp flashed very bright and broke.
I guess I was lucky...

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Unfortunately I'm pretty sure he was just spewing bullshit.