Unfortunately, our body has enough capacitance that it does not matter working on CRT's. Your dead.
When I layed the palm of my hand on the exposed pin matrix of the CRT socket for a Tek 2200-something scope that was on and had active input, my hand forgot to jump off. But my brain realized, after a few moments, that something felt different. I'm glad the voltages weren't quite as high as those in some of the older scopes. But really it wasn't too bad.
As far as actually being killed is concerned, the really-dangerous current level is roughly 0.1 to 0.2 amps. Above that, your heart muscle tends to be clamped, such that if you somehow get removed from the current, your heart will start to beat again, BY ITSELF. BUT, within the 0.l to 0.2 amp range, or thereabouts, your heart will FIBRILLATE, instead of being clamped, and EVEN IF the current is disconnected, your heart will probably NOT start beating again, by itself. THAT'S a bad situation to be in. And then, usually, you're dead.
I did once forget to turn off and disconnect the power of an antique tube radio that I was refurbishing, while I removed a 400-Volt capacitor by clipping its leads to half their length. And I did then absent-mindedly hold the cap by one lead. And I did then grasp the other lead with my other hand, sending the current straight through my heart. I actually noticed a short glitch in my consciousness and a few more seconds of it decaying back to normal. Got lucky, I guess. (But I was much younger, back then.)
My Dad grabbed a live utility line that had been knocked down by a storm, in 1945, in the Phillipines. The only person within a mile knocked it out of his hand with a wooden broomstick after they heard his whistling stop abruptly and came to investigate, after what I estimate was at least 30 seconds. His army boot was on fire, and the sole was largely melted, and he had a burn-path down his arm and leg, but he was back on duty within a couple of days (as far as he knows), with a new pair of boots.
As far as actually being killed is concerned, the really-dangerous current level is roughly 0.1 to 0.2 amps. Above that, your heart muscle tends to be clamped, such that if you somehow get removed from the current, your heart will start to beat again, BY ITSELF. BUT, within the 0.l to 0.2 amp range, or thereabouts, your heart will FIBRILLATE, instead of being clamped, and EVEN IF the current is disconnected, your heart will probably NOT start beating again, by itself. THAT'S a bad situation to be in. And then, usually, you're dead.
I did once forget to turn off and disconnect the power of an antique tube radio that I was refurbishing, while I removed a 400-Volt capacitor by clipping its leads to half their length. And I did then absent-mindedly hold the cap by one lead. And I did then grasp the other lead with my other hand, sending the current straight through my heart. I actually noticed a short glitch in my consciousness and a few more seconds of it decaying back to normal. Got lucky, I guess. (But I was much younger, back then.)
My Dad grabbed a live utility line that had been knocked down by a storm, in 1945, in the Phillipines. The only person within a mile knocked it out of his hand with a wooden broomstick after they heard his whistling stop abruptly and came to investigate, after what I estimate was at least 30 seconds. His army boot was on fire, and the sole was largely melted, and he had a burn-path down his arm and leg, but he was back on duty within a couple of days (as far as he knows), with a new pair of boots.
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Another way to get killed, without actually touching anything: Some electricians were wiring a new high-capacity 440-volt (or somesuch) service panel in a room in a commercial building, near here, a few years ago. There were some aluminum (I think) conduit pipes propped against a wall. One of the pipes rolled and fell and struck the exposed electrical connections in the new box. The resulting arc-flash fire killed everyone in the room.
Close enough. I have heard that number, too. Better to err on the side of extra caution.
And it's easier than a lot of people think, to get there. Skin resistance might be fairly high, usually. But if you make a slight puncture, or contact a mucous membrane, it's a totally-different circuit.
I remember reading a newspaper story about a prison inmate who died after biting into the DC wire powering his walkman-type device, while sitting on a metal toilet. Just lucky, I guess.
I still love remembering the time when a non-technical Scottich bagpipe-maker said to me in an email, once: "Electricity is nice. But don't get any on you.".
And it's easier than a lot of people think, to get there. Skin resistance might be fairly high, usually. But if you make a slight puncture, or contact a mucous membrane, it's a totally-different circuit.
I remember reading a newspaper story about a prison inmate who died after biting into the DC wire powering his walkman-type device, while sitting on a metal toilet. Just lucky, I guess.
I still love remembering the time when a non-technical Scottich bagpipe-maker said to me in an email, once: "Electricity is nice. But don't get any on you.".
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Actualy the number is 50mA. It's more like an average. Don't know what soviets averaged there... state secret.
Fun note: I got shocked at 230V/50Hz, 277V/60Hz. I prefer the 60Hz. DC is the nastiest. Always touch an electrical part first with BACK of my hand. Contraction will breake the contact. Nothing scarry.
Flash-arc is not a joke thou. I saw the front of an electrical panel flying across the hallway followed by melted copper in a big bowl of fire. There is no escape from that...
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And then there's the "TENS" (sp?) diy website about electrical muscle stimulators that says that (presumably in order to save money) your stereo speaker outputs are perfect to use for that!
I actually tried it once, briefly, but using bare wires it felt like being burned and stuck with needles at the same time.
That's as far as I went but apparently they have specially-made attachments that are supposed to be used, especially for "certain body regions". What an embarrassing way to be found dead THAT would be! (assuming you can still be embarrassed after you're dead)
Then again, it might also be a great way to hear AND feel an orchestra! Maybe even DISCO would become tolerable?! <grin>
However, I must admit that the part with the data about the effects of hooking the leads to the inner sides of the ankles or calves of females did catch my interest. (OK. Sorry. I'll say no more. It probably depends on what music you play, anyway.)
I wonder if anyone has died, yet, doing any of the things they discuss on that website.
Cheers,
Tom (but drunk)
I actually tried it once, briefly, but using bare wires it felt like being burned and stuck with needles at the same time.
That's as far as I went but apparently they have specially-made attachments that are supposed to be used, especially for "certain body regions". What an embarrassing way to be found dead THAT would be! (assuming you can still be embarrassed after you're dead)
Then again, it might also be a great way to hear AND feel an orchestra! Maybe even DISCO would become tolerable?! <grin>
However, I must admit that the part with the data about the effects of hooking the leads to the inner sides of the ankles or calves of females did catch my interest. (OK. Sorry. I'll say no more. It probably depends on what music you play, anyway.)
I wonder if anyone has died, yet, doing any of the things they discuss on that website.
Cheers,
Tom (but drunk)
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More about the 'skid marks'. They led to a master cut-off button that we had in prime locations for just such an event, that cut off the power of the whole building. Apparently, one of my fellow technicians got caught on a 440V AC line, and one of the engineers literally skidded to the cut-off button, saving his life.
My, my, you guys are really feeling jolly today, what with all the fun'n'games stories.
@Wavebourn
The hand thing, I think it's called here-comes-mamma-and-my-hand's-in-the-cookie-jar-again syndrome.
@Thorsten
My hat off to you, sir, it appears you can type and wench at the same time, no small feat. Otherwise, I don't know where you'd get the time.
@John Curl
John, I don't know if you have ever been in any potentially lethal situation, but if you have, you will probably remember than an odd thing happens. Your brain goes into warp speed and real time seems to slow down, the world starts working in slow motion. And it's so fast that even you don't realize what's going on, you understand this only afterwards, it comes back to you, so to speak.
That notwithstanding, the tech you mentioned was very lucky to have the engineer who saved him nearby, because not many will react rationally to an irrational situation. Not when it's not themselves in actual peril. It's different when somebody else needs saving.
I've been in both sides, believe me, not of my choosing. In 1975, I was waiting for a tram, and this cop steps straight on the rails, with his head turned away, so he doesn't see or hear a tram arriving. The net weight of the tram is 18 metric tons empty (around 40,000 lbs), so you can't exactly stop it on a dime. I see this and my brain goes into overdrive - I step out a single step, grab the cop with both my hands and pull him like a lunatic. He ended about 3 feet begind me, on the ground - I'm 6'3'' and weigh in at around 240 lbs, so my body mass was quite enough to do that, it was mostly my legs which did the job.
Anayway, nothing happened in the end, he quickly understood what happened, and I couldn't resist mentioning the fact he was a traffic cop behaving badly. He was about my age then (I was 22 at the time) and he was really embarassed.
The point is, it all happened so fast that I was even aware of what I had done only several minutes after it was all over. What amazed me was the mental calculation it seems I did while in overdrive - the tram stopped inches away from me, but the positioning and the all out power command were impeccable. I honestly don't think I could consciously (in real time) do it anywhere near that well. Because that's so, I cannot in all honesty take any credit for anything, it was in effect either a subconscious, or more appropriately, a superconscious act. I mean, what are you going to do, you can't just stand by and let a man be run over by a tram.
The only thing that amazes me to this day is how could that cop not see a damn big, red painted tram coming his way.
So, there I am, the big super hero who saved a man, and a couple of days later, I swap polarities on a capacitor, pop goes the weasel, and I get a wonderful scar on my left hand to remind me for life that you don't work with your mind out in the pastures.
@Wavebourn
The hand thing, I think it's called here-comes-mamma-and-my-hand's-in-the-cookie-jar-again syndrome.
@Thorsten
My hat off to you, sir, it appears you can type and wench at the same time, no small feat. Otherwise, I don't know where you'd get the time.
@John Curl
John, I don't know if you have ever been in any potentially lethal situation, but if you have, you will probably remember than an odd thing happens. Your brain goes into warp speed and real time seems to slow down, the world starts working in slow motion. And it's so fast that even you don't realize what's going on, you understand this only afterwards, it comes back to you, so to speak.
That notwithstanding, the tech you mentioned was very lucky to have the engineer who saved him nearby, because not many will react rationally to an irrational situation. Not when it's not themselves in actual peril. It's different when somebody else needs saving.
I've been in both sides, believe me, not of my choosing. In 1975, I was waiting for a tram, and this cop steps straight on the rails, with his head turned away, so he doesn't see or hear a tram arriving. The net weight of the tram is 18 metric tons empty (around 40,000 lbs), so you can't exactly stop it on a dime. I see this and my brain goes into overdrive - I step out a single step, grab the cop with both my hands and pull him like a lunatic. He ended about 3 feet begind me, on the ground - I'm 6'3'' and weigh in at around 240 lbs, so my body mass was quite enough to do that, it was mostly my legs which did the job.
Anayway, nothing happened in the end, he quickly understood what happened, and I couldn't resist mentioning the fact he was a traffic cop behaving badly. He was about my age then (I was 22 at the time) and he was really embarassed.
The point is, it all happened so fast that I was even aware of what I had done only several minutes after it was all over. What amazed me was the mental calculation it seems I did while in overdrive - the tram stopped inches away from me, but the positioning and the all out power command were impeccable. I honestly don't think I could consciously (in real time) do it anywhere near that well. Because that's so, I cannot in all honesty take any credit for anything, it was in effect either a subconscious, or more appropriately, a superconscious act. I mean, what are you going to do, you can't just stand by and let a man be run over by a tram.
The only thing that amazes me to this day is how could that cop not see a damn big, red painted tram coming his way.
So, there I am, the big super hero who saved a man, and a couple of days later, I swap polarities on a capacitor, pop goes the weasel, and I get a wonderful scar on my left hand to remind me for life that you don't work with your mind out in the pastures.
All these stories remind me of my own vary scary experience: Back in 2000 I was testing big CRT's at Philips, actually I was designing a reference PCB for CRT amplifiers. One of the tests that have to be performed are the flassover tests to see if the amps survive such an event. Now these big screen CRT's run at 45KVDC!! With on of the flashover tests the Aquadag lead touched the metal cart the setup was placed upon, which in turn touched my knee. I wasn't even part of the (main) circuit here but surge blow me of my chair and left me unable to walk for about 15 minutes...
I also remember that these big tubes seemed to charge themselves without being in a circuit. Discharge such a tube, leave it over night, pick it up the next morning and get a nasty shock...
I also remember that these big tubes seemed to charge themselves without being in a circuit. Discharge such a tube, leave it over night, pick it up the next morning and get a nasty shock...
Well according to my teacher at the time (I was an intern there) the "stray electrical and magnetic fields here are strong enough to charge the tube to a certain extent"
I never really give any second tought to this, for me the practical experience of picking up a tube in the morning before discharging was enough.. Mind you this charge was only a fraction of the charge during normal use, but still plenty to drop a 20Kg tube, bad thing to do... I did find these tubes are quite sturdy
just don't drop them on the cathodes and you usually will be fine.
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Time warp. OOOOh yea. I was free climbing in Colorado many years ago. I was crossing a snow slide when it all gave way. I was on the playground slide going down the with the perverable 200 foot drop to rocks bellow. Somehow I got over to the edge and caught a rock with my boot ending sideways with one cheek over the edge. Funny, the time warp was in slow motion but only had enough time for the "Oh Sh@#" and did not quite get to full life passing. My climbing partner was in the "what am I going to tell his wife?" Time sure is relevant. So, I consider my remaining days here as free. I don't begrudge when my time is up. I don't try to hasten it either. I can say the adrenalin rush did get us off that face faster than we had planned.
They don't charge "from stray fields"...
It's called dielectric polarization. When capacitor plates are charged, the dielectric gets polarized too. Dis-charging with a short time connection will deplete only the charges on the plates, but the dielectric molecules will still be polarized - are slow to "rotate" back. In a few seconds, minutes, the dielectirc will de-polarize and all that energy will re-charge the plates (via the high value internal loss resistences, that's why takes so long). At lower voltage, but if the original voltage was 1000V, 800V is "lower" but still high for some people.
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Er, are you implying that 800V is just fine for some people, and high for others?
Or was that just unfortunate phrasing?
I mean, I haven't tried, but I think 800V would send me on to kingdom come. And I ain't exactly small and flimsy.
I think you're quite right, I also seem to remember something along those lines.
It appears that AC in the range of our heartbeat +/- 30% is the most dangerous zone to be in, which is to say the range 40 ... 80 Hz.
This makes me think - Wayne, if you are a fan of the bass section, make real sure you don't get your flingers across those speaker posts while running your amp at higher power levels. With your double down principle, assuming you are clean and have not had any pot lately, your body impedance might be as low as 2 Ohms, so those 50W your speakers are taking would work out to 200W your body might need to take. At that rate, you wouldn't need any blue LEDs to signal to your wife that your are in high gear.
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