But I did say: ''Im not disputing that its possible I have been shocked myself in this way I simply dont understand how it works.''
Again I do not deny it can happen I want to understand how it can happen.
It's a very important safety issue.
I didn't say earth is an insulator I said the floor is. And that can be proven by laying bare mains wiring on the floor.
The question is how I can be shocked from only one point.
Again I do not deny it can happen I want to understand how it can happen.
It's a very important safety issue.
I didn't say earth is an insulator I said the floor is. And that can be proven by laying bare mains wiring on the floor.
The question is how I can be shocked from only one point.
Professor smith said:
Hello Professor,
Two things:
First to answer your question, even though there may be a very high resistance between you and earth ground, and thus not much current will flow, the voltage is still present and will provide a nasty shock.
The safety standards assume that a person may (will?) be at earth potential and thus a large (lethal) current will flow through the person if they were to contact a chassis that was at mains voltage.
Dave
David Davenport said:
The trouble is I still dont understand how such a low voltage as 110v or 240v could shock someone. There's two things:
One is that a very high voltage such as say 10kv can cause a shock but not kill if the current is very low.
Conversely a low voltage such as 240v can kill if the current is high enough.
But I did not think that it would be a high enough voltage to cause a tingling sensation. Is it the current which is to blame here for the tingling?
I'm talking about if you make contact with one of the AC wires.
By the way is it just as shokcing to touch live or neutral via earth?
Please, seriously, do not handle any mains connections without revising at least a high-school grade textbook on basic electricity.
A 9 or 12 V battery is enough to cause a tingling sensation. If you lick it.... (Yes I've done this way too many times, it was prime-time entertainment when we were kids. It does not mean you should encourage yours to lick any electricity source, however)
A 48V DC can cause your fingers to tingle. If you've a minor cut on one of them. While your co-workers won't feel a thing.
12 V dc can send you in cardiac fibrillation. Sure, you'll need to stab yourself in the chest with the electrodes, but it can.
Look into how safety earth wiring is done in a building as well and most importantly - why. Check Rod Elliot's pages for a pretty well-defined article on that. Click here: http://sound.westhost.com/earthing.htm .
Finally, voltage, or potential difference, does not cause anything in you. Unless you're for some reason made up from a bunch of capacitors and your body functions depended on them. It's the current that does the job, given that your resistance is low enough. And it will be quite a lot lower if you manage to penetrate your skin. If you really want to try the difference, get a low voltage DC source, grab it with the fingers of 1 hand, feel nothing. Then make a cut in your finger and check the buzz you'll get. Fun times.
Disclaimer: Do not take any of the above ideas as something serious and please, kids, do not try any of this at home. Read up what you need to read up and do things right. Electricity is not scary. It's just that it can be very scary, that is the problem.
A 9 or 12 V battery is enough to cause a tingling sensation. If you lick it.... (Yes I've done this way too many times, it was prime-time entertainment when we were kids. It does not mean you should encourage yours to lick any electricity source, however)
A 48V DC can cause your fingers to tingle. If you've a minor cut on one of them. While your co-workers won't feel a thing.
12 V dc can send you in cardiac fibrillation. Sure, you'll need to stab yourself in the chest with the electrodes, but it can.
Look into how safety earth wiring is done in a building as well and most importantly - why. Check Rod Elliot's pages for a pretty well-defined article on that. Click here: http://sound.westhost.com/earthing.htm .
Finally, voltage, or potential difference, does not cause anything in you. Unless you're for some reason made up from a bunch of capacitors and your body functions depended on them. It's the current that does the job, given that your resistance is low enough. And it will be quite a lot lower if you manage to penetrate your skin. If you really want to try the difference, get a low voltage DC source, grab it with the fingers of 1 hand, feel nothing. Then make a cut in your finger and check the buzz you'll get. Fun times.
Disclaimer: Do not take any of the above ideas as something serious and please, kids, do not try any of this at home. Read up what you need to read up and do things right. Electricity is not scary. It's just that it can be very scary, that is the problem.
If the current can travel through the carpet, through the bricks of my house, and through my skin, all of these resistances add up to a very high value. Much higher than the plastic plug used to insulate a mains plug, and of course you do not suffer a shock from handling these, so why is that?
Hello Professor,
Think about where the resistance is and where the voltage is.
In one case, you are in direct contact with the voltage and there is a very large resistance between you and earth.
In the other case, in the worst case, you are in direct contact with earth and there is a very large resistance between you and the voltage.
In both cases there is are two resistances in series, the very large resistance and the relatively small you. When the small you is in contact with the voltage and the very large resistance is in contact with earth, the voltage divider is such that there is a large voltage on you. When the small you is in contact with the earth, and the very large resistance is in contact with the voltage, there is a small voltage on you.
Dave
Think about where the resistance is and where the voltage is.
In one case, you are in direct contact with the voltage and there is a very large resistance between you and earth.
In the other case, in the worst case, you are in direct contact with earth and there is a very large resistance between you and the voltage.
In both cases there is are two resistances in series, the very large resistance and the relatively small you. When the small you is in contact with the voltage and the very large resistance is in contact with earth, the voltage divider is such that there is a large voltage on you. When the small you is in contact with the earth, and the very large resistance is in contact with the voltage, there is a small voltage on you.
Dave
Yes, because it is similar to the control signals your brain sends. Sometimes people, who touch a live wire, cannot let go of it again, because the current flowing through their body is giving the command to contrapt the muscles.Professor smith said:
Normally not. Live is at mains voltage of 115 or 230 V, while Neutral is near zero, so Neutral is less dangerous. Depending on the current that flows through Neutral and the wire length (=resistance) from the connection point between Neutral and Earth however, a voltage can develop at the point, where you touch, which can be dangerous, if your skin is wet or injured or if the current path through your body is short or passes directly through heart or brain or any combination of those conditions. Therefore it is only safe to touch Neutral, when no current flows through it. The best thing is not to touch either wire.Professor smith said:
If the resistance values are the same in both examples, the voltage drop across the human body is the same. As Atilla wrote, its the current that matters, and that depends on the voltage and the body resistance. Body resistance can be high, when the skin is dry or low, when the skin is wet.David Davenport said:
Now that you mention it, I am not sure about the M8 connectors. There are versions of the M12 connectors that come with a dedicated PE contact. They are called valve connectors then. A manufacturer here in Germany is Turck. There should be others, because it is a standardized connector type.454Casull said:
The previous question was for the rectifier used to convert the transformer secondary AC to DC.
I'd like to know now if I can solder the legs of the disconnecting network's resistor and cap, or if they too need to be crimped/screwed for safety. Don't like doing that to solid wire, though...
I'd like to know now if I can solder the legs of the disconnecting network's resistor and cap, or if they too need to be crimped/screwed for safety. Don't like doing that to solid wire, though...
It takes a very high current, e. g. short-circuit, for a significant amount of time to melt the solder on the rectifier tabs. With adequate fuses a short-circuit current should be interrupted long before that.
Crimping solid wire is okay with the adequate crimping tool. If you want to screw solid wires, the trick is to bend them into shape, so that the wires resemble cable lugs.
Crimping solid wire is okay with the adequate crimping tool. If you want to screw solid wires, the trick is to bend them into shape, so that the wires resemble cable lugs.
I thought I had already addressed that.454Casull said:
@ mini amperes the diode brige drops ~600 to 700mV
@ maxi amperes it drops ~1V
@ Fault current it probably drops 2V to 5V
Now apply those sort of maximum voltages during fault current period and see what dissipations you get in the resistor and cap.
Hi,
separate low voltage dual secondary transformer feeding a rectifier and smoothing caps.
This feeds a pair of voltage regulators.
Even better, a pair of rectifiers and caps for each channel from the dual secondaries.
Best of all: separate chassis with a complete PSU and regulators feeding a single channel in pure monoblock mode with separate regulators for each stage of the crossover.
separate low voltage dual secondary transformer feeding a rectifier and smoothing caps.
This feeds a pair of voltage regulators.
Even better, a pair of rectifiers and caps for each channel from the dual secondaries.
Best of all: separate chassis with a complete PSU and regulators feeding a single channel in pure monoblock mode with separate regulators for each stage of the crossover.