High Voltage Danger? When?
Hi.
I am building a coilgun with some capacitors, and I would like to use a PIC handle the charging process. I read that gigh voltage capacitors are dangeroud, but what is it that makes electricity dangerous? If you were to pu 10 or 15 9-volt-batteries in series, and touch the contacts, would it shock you? Is it safe to build a capacitor bank (about 47000uf) at 25vdc?
What is the difference (speaking about dangers) betweeb DC and AC?
Thanks in advance!!!!
Manuel
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“hands on” electronics
Hi Manuel,Electricity thru people, is a strange acting phenomenon. It is difficult to predict what dangers or problems someone might run into making a coil-gun. It is a subject you should research in full before you start your project. There are better places to find out about general electric safety.Originally Posted by manumenzella
Capacitors have a “bad rap” because they can store a charge and catch unsuspecting victims days after the power has been removed. Proper circuit design and proper respect can keep them from surprising you. The coil can also give a nasty surprise as well.
10 to 15 9V batteries wired in series, would be slightly more than 90 to 135 Volts. Most professionals in “hands on” electronics, work around that amount of voltage on a regular basis. With nominal conventional precautions, this is considered a normal workday. Note that they do not touch the conductors barehanded (so I guess, “hands on”, may be just an expression). Wikipedia states “...death has occurred from supplies as low as 32 volts...”!
There is some beginning information and references to information you should learn. Wikipedia has a good start. http://en.wikipedia.org/wiki/Electric_shock There is some discussion on AC / DC comparisons too.
This should not be read as an all doom and gloom reply. It’s just your post sound like you may not have had much “hands on” experience. Do your homework and then you will be launching things on the coil-gun.
I am sure others will be adding to the discussion.
-Adam-
Ohm it's not just a good idea... it's the LAW !
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Here is something to think about.
Go to your local fire department and talk to the paramedics about the battery powered defibrillator's that they use.
Anything above 48 volts is considered dangerous. I can not say exactly how it effects the muscular system, but having had close calls with DC and AC it seems like DC is more dangerous at a lower voltage than AC. DC as the name implies is constant and would not allow me to let go at 90 volts. ( co worker had to throw a switch). AC swinging through Zero must be the reason I was able to break away from 240 volts.
I have heard some say it is the amps and others say voltage is what you should be concerned with. Personally I think it is watts.
Is there a DOCTOR in the house.
Dave
Always wear safety glasses while programming.
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History has never been a strong suit for me. But as I recall, back in the late 1800's there was a fierce battle between Edison and Westinghouse.
Edison had a DC electrical system wired up to an entire street full of electric lights. And his competition (Westinghouse) wanted to use an AC system because it could transmit the power over longer distances than DC could.
Well, Edison wanted no part of an AC system, so he set out to prove to everyone that AC voltages were too dangerous, and designed an "Electric Chair" using AC power, to show how easy it was to kill something if it wasn't DC.
Obviously, the ploy didn't work. The need for long distance transmission outweighed the potential for death. But the chair stuck around, and was used for both people and animals for many decades to come.
The standard rule for death by electrocution, is that 100 MA thru the heart, will stop the heart from beating. Actually causing death by asphyxia (lack of oxygen) rather than killing you outright with the voltage. It doesn't really matter if it's DC or AC. 100 MA will do it. But since alot of how voltage travels through the body depends on the capacitance of the body (among other things) AC gets through a lot easier.
If it doesn't go directly through the heart, you can withstand many AMPS and still survive. It'll hurt like hell, but it probably won't kill you.
Personally, I've been hit with 8,000V DC from the anode of a klystron amplifier.
Knocked me on my butt, and threw me backwards about 10-15 feet.
After regaining my senses and thinking I was lucky to be alive, everyone around me just laughed, and said ... That power supply may have 8,000V, but it only puts out 100ma, so you were never going to die, ya wimp.
I've also been locked in a "death grip" from a 90VAC telephone ringer voltage. Somebody dialed in while I was installing a phone jack. Fortunately, phones don't ring continuously. But that one rang too long for my comfort.
So I guess the moral here is, ... You must treat ALL electricity as if it's going to kill you. If you don't, some day you'll grab a wire you thought was low voltage, and it'll be the last thing you do. Cause it was really 220VAC.
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DT
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I'm going to underscore what Darrel has already stated--always treat electricity with respect!
My knowledge of history isn't all that great, either, but I believe the AC versus DC issue began with Edison versus Nikola Tesla; Westinghouse came in a little later.
On one hand, I routinely test 9-volt batteries by touching the terminals to the end of my tongue. In high school, I knew a TV repairman who could tell whether the AC line voltage was right by touching two bare wires with one hand, and he died of cancer at age 81. And a former co-worker of mine, about four years ago, survived 28,000 volts DC (television transmitter) but had some nasty burns and many skin grafts after. He's also suffered some subsequent neurological problems. (If you think I mean, "He's not as sharp as he used to be," you're right.)
When I was a kid, I learned the "one hand in your pocket" rule, and I still use it. (When you're working with a live circuit, keep one hand in your pocket.) All my close encounters with electricity have been with one hand--including about 1000 watts of RF across the palm of my right hand (and a burn). The scariest shock I ever got was from 90 volts of AC telephone ringer--again, just my right hand, but it wanted to grab and hold on.
And, of course, whenever possible, work on the circuit or equipment with the power off!
My understanding has always been that current kills, not voltage--otherwise we'd all keel over and croak when we get that static shock from a doorknob on a really dry day. The big difference, supposedly, is that low-frequency AC disrupts the electrical rhythm of the human heart, so it is much more dangerous at comparatively lower voltages; high-voltage DC just cooks you.
Don't be a resistor! (Very bad pun . . . )
Russ
N0EVC, xWB6ONT, xWN6ONT
"Easy to use" is easy to say.
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Hi,
FOR ALUMINUM ELECTROLYTIC CAPACITORS, CAUTION:
Personnel injury or property damage may result from a capacitor explosion or the expulsion
of electrolyte due to mechanical or electrical disruption of the capacitor. Contact with
liquid or vapor is to be avoided. In the event of contact with the skin or eyes, or accidental
oral ingestion, action may be taken as follows:
Emergency treatment is as follows:
Skin Contact: May result in irritation.
Flush and wash thoroughly with soap and water immediately.
Eye Contact: Contact lenses must be removed at once.
Immediately flush the open eye(s) with large amounts of water and seek immediate medical attention.
Oral Ingestion: As an interim emergency measure, administer warm water or milk, induce vomiting and
seek immediate medical attention.
Vapors: Avoid inhalation of vapors. Ventilate area thoroughly and go to fresh air.
* * * * *
Often risk takers are not aware of the danger they put themselves in:
Best regards,
Luciano
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Good old YouTube.
Blowing up capacitors.
Seems to be one of the favorite pass times there.
http://www.youtube.com/results?searc...plod+capacitor
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DT
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