A minimum current rating for a residential service drop would be 100 amps here in the USA. Most new construction is 200A, or even 400A for the "McMansions". The human body, like all conductors, obeys Ohm's law, and 120/240V simply isn't going to push anywhere near 100A (much less 200-400) through the resistance of a human body. The victim would sit there cooking away, and the breaker wouldn't even get warm. To go back to your electric chair example, typical current levels through the condemned are in the neighborhood of 8 amperes. Plenty to kill you, but nowhere near the trip level of even a 15A branch circuit breaker, much less something that would be protecting a service entrance.
, but it would reduce the severity of an arc-flash accident.
It only takes ~1/10 of an ampere through your body to kill you, which is practically nothing compared to the current rating of a breaker that would be used to protect a service drop. Circuit breaker or not, if you become a current path to ground, you are going to get a shock at the very least.
[quote]If there were just some sparks with the protection on the electrical circuits preventing a fire as designed then there's no reason to change the ordinances.[/quote]
If this was actually the building's "electric main" (properly called the service conductors), there isn't really any overcurrent protection on them. The service drop and wiring between the meter and the main breaker/disconnect are UNFUSED, with the only protection being a fuse on the primary side of the transformer out on the utility pole, which generally serves 5-6 homes, if not the entire block.
In the event of a short circuit on these wires, fault currents of thousands of amperes are potentially available. The end of the drill bit used by that Verizon tech most likely turned into a ball of plasma when it hit those wires. The guy is lucky that the accident happened inside a wall cavity, or he likely would have gotten a faceful of metal vapor and some nasty burns.
Accidents involving arc-flash burns like this actually kill more electricians than outright electrocution does.
There simply AREN'T any US manufactured TV sets, VCR's, DVD players, PC motherboards, etc. currently available AT ANY PRICE.
About the only consumer electronics that you might find that are still manufactured in the US would be a few brands of high-end audio equipment (Krell, Mark Levinson, etc.), and even then, I sincerely doubt that 100% of the component parts are of US origin. The semiconductors might be branded TI, Motorola, Intel, etc. but they sure as hell aren't made in the USA anymore....
My point is that potentially eye-damaging lasers are already freely available to anyone who wants them--in the form of a DVD burner. The level of technical skill needed to pull off the "conversion" described in the article is so low that it presents little practical barrier to anyone who wants such a laser for nefarious purposes.
MANY common consumer items contain parts that could be used to construct potentially hazardous devices. Given the wide availability of such components (and no practical hope of ever changing this), it would seem that there are only 2 courses of action:
1:) Create new laws in an attempt to suppress the INFORMATION needed to build such devices.
2:) Enforce existing laws prohibiting the use of dangerous weapons against people and property.
Given the moral and practical arguments against option "A", I'll go with "B".
Laser diodes generally require some type of current limiting to prevent damage. In the DVD burner circuit, that is the function of the third pin on the diode package (that the article simply blows off as "not used"). This pin connects to an internal photodiode, which is used to measure output power, and provide feedback through an external driver circuit to continuously control the current applied to the laser diode junction.
The article simply places the laser diode directly across the 3V battery supply, with not even a ballast resistor to limit the current. You might get away with this with AA batteries, but if someone were to try this trick with a D-cell maglite, they would most likely let the magic smoke out of the laser very quickly.
Greenstone appears to be a tube DISTRIBUTOR, not a manufacturer. But yes, tubes are still being manufactured for certain niche applications, and will be for a long, long time. Manufacturers include CPI/Eimac, Econco, MU, National Electronics/Richardson, Svetlana, Thompson, Litton, and Thales.
More on topic, the overwhelming majority of Apollo electronics was solid state. The guidance computer was the first large scale application of integrated circuits, and nearly everything else used discrete semiconductors. The only tubes I can think of in the Apollo systems are pickup tubes (vidicons) in the TV cameras, RF power amplifiers in the communications/radar systems, and a CRT for one of the cockpit displays (radar?).
There is a difference between neurotically smothering your kids, and recognizing that there can be hazards involved in certain activities, and taking precautions where warranted. You will notice that NOWHERE in my post did I say that crazy blender experiments shouldn't be done (too much potential for fun), but common sense would dictate not snorting the resulting powdered remains, and using a blender that you don't intend to use for preparing food.
I did a lot of crazy shit when I was a kid or teenager, including activities that today would draw the immediate attention of the BATF, DEA, DHS, and FCC. Because my parents didn't share my curiosity about science/engineering, I did a lot of stuff on my own or with friends of a similar age. It is only by dumb luck that we didn't get seriously hurt with some of our "projects".
Now that I have a kid of my own (whose favorite TV show is "Mythbusters", BTW), one of my favorite activities is to show him various science experiments and demonstrations, some of which would horrify those of the "soccer mom" stereotype (like the time we fired off a bunch of old automotive airbags and the noise brought out the cops, or set an old microwave on fire by nuking various non-food items). But I ALWAYS make a point of demonstrating proper safety precautions, including drawing the line at demonstrations that cannot be done safely in a suburban backyard. Those are either not done, or they wait until we can find a suitable place to do them.
Sure, most of the kids of past generations survived their own experimentation unscathed. But how many didn't? How many kids would have gone on to a great career, but poisoned/maimed/electrocuted/blew themselves up simply because they were ignorant of the hazards involved with whatever they were playing around with?
Not to mention the fact that the blender jar and blades are now contaminated with the remnants of the iPhone, rendering the blender unfit for food preparation. I know I wouldn't be too happy if my kid ruined an expensive blender, even if they were doing something cool in the process.
And at a high volume filling ststion (where fuel is delivered at least once daily), those insulated tanks will do a good job of keeping the fuel at the temperature THAT IT WAS DELIVERED AT, rather than the more or less constant 60 degree underground temperature.
That fuel was most likely stored in an ABOVE GROUND tank at the depot, then driven to the station in an uninsulated tanker truck. It could be quite a bit warmer than 60F by the time it gets into the storage tank at the filling station.
Exactly why would they require insulated underground storage tanks for gasoline, anyway? Unless the "insulation" is just a byproduct of double-wall construction to prevent leaks, it would seem that the stations are TRYING to keep the fuel warm for some reason, no?
None of those cards are FCC certified for broadcast use, and wouldn't be usable by a licensed LPFM station. They might be a good start toward a pirate station for someone without RF knowledge/experience.
they are assuming that linux users might be more likely than most buyers to open up the box, swap cards, add drives/RAM, etc. In the process potentially exposing the machines to "user induced failures" from ESD, dropped screws, damaged parts, etc.
If that Moeller unit is like the other locking Estops I have used, the key doesn't prevent it being PUSHED, but the button won't pop back OUT without the key. I believe that requiring a key in order to activate an E-stop is an OSHA violation. Requiring a key to reset a tripped button is OK, and sometimes helpful in knowing which button was pressed when there are many installed.
http://www.automationdirect.com/ is one good supplier. This kind of industrial grade hardware is expensive, so eBay might be the best choice. What you want is commonly called a "mushroom head emergency stop pushbutton". If using it for a PC reset switch, you want normally open contacts, whereas most E-stop systems would use normally closed.
Not sure how that could cause the shock problem, as the grounded side of all 3 ports are connected together to the case of the splitter, at least on every CATV splitter I have ever seen. Poor signal strength, yes, but not the electrical shock problem. A bad ground out at the pole (and no ground at the house) certainly could, though...
An outdoor antenna cable (or CATV coax) is supposed to be tied to the main electrical grounding system, at or near the point that the cable enters the building. This is primarily for lightning protection. Even if separate ground rods are driven (like for one of those old style large satellite dishes), the new rod STILL gets tied back to the main building ground.
If you are getting shocks or seeing sparks when connecting an antenna to a TV set, call a qualified electrician.
2.45GHz is NOT the resonant frequency of water...
on
How Bad Can Wi-fi Be?
·
· Score: 3, Informative
The operating frequency of microwave ovens was chosen to be in an unlicensed (ISM) frequency band, that would provide good penetration into foods, and lent itself to the mass production of inexpensive magnetron tubes.
The lowest resonant frequency for a water molecule is 22.235 GHz, or nearly 10X the operating frequency of a microwave oven.
Curious about everything around them, and how everything works.
Until they hit 5 or 6, at which time pop culture, peer pressure, and the public school system start working together to stomp the spark of interest wight out of most of them....
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A minimum current rating for a residential service drop would be 100 amps here in the USA. Most new construction is 200A, or even 400A for the "McMansions". The human body, like all conductors, obeys Ohm's law, and 120/240V simply isn't going to push anywhere near 100A (much less 200-400) through the resistance of a human body. The victim would sit there cooking away, and the breaker wouldn't even get warm. To go back to your electric chair example, typical current levels through the condemned are in the neighborhood of 8 amperes. Plenty to kill you, but nowhere near the trip level of even a 15A branch circuit breaker, much less something that would be protecting a service entrance.
, but it would reduce the severity of an arc-flash accident.
It only takes ~1/10 of an ampere through your body to kill you, which is practically nothing compared to the current rating of a breaker that would be used to protect a service drop. Circuit breaker or not, if you become a current path to ground, you are going to get a shock at the very least.
[quote]If there were just some sparks with the protection on the electrical circuits preventing a fire as designed then there's no reason to change the ordinances.[/quote]
If this was actually the building's "electric main" (properly called the service conductors), there isn't really any overcurrent protection on them. The service drop and wiring between the meter and the main breaker/disconnect are UNFUSED, with the only protection being a fuse on the primary side of the transformer out on the utility pole, which generally serves 5-6 homes, if not the entire block.
In the event of a short circuit on these wires, fault currents of thousands of amperes are potentially available. The end of the drill bit used by that Verizon tech most likely turned into a ball of plasma when it hit those wires. The guy is lucky that the accident happened inside a wall cavity, or he likely would have gotten a faceful of metal vapor and some nasty burns.
Accidents involving arc-flash burns like this actually kill more electricians than outright electrocution does.
There simply AREN'T any US manufactured TV sets, VCR's, DVD players, PC motherboards, etc. currently available AT ANY PRICE.
About the only consumer electronics that you might find that are still manufactured in the US would be a few brands of high-end audio equipment (Krell, Mark Levinson, etc.), and even then, I sincerely doubt that 100% of the component parts are of US origin. The semiconductors might be branded TI, Motorola, Intel, etc. but they sure as hell aren't made in the USA anymore....
My point is that potentially eye-damaging lasers are already freely available to anyone who wants them--in the form of a DVD burner. The level of technical skill needed to pull off the "conversion" described in the article is so low that it presents little practical barrier to anyone who wants such a laser for nefarious purposes.
MANY common consumer items contain parts that could be used to construct potentially hazardous devices. Given the wide availability of such components (and no practical hope of ever changing this), it would seem that there are only 2 courses of action:
1:) Create new laws in an attempt to suppress the INFORMATION needed to build such devices.
2:) Enforce existing laws prohibiting the use of dangerous weapons against people and property.
Given the moral and practical arguments against option "A", I'll go with "B".
or just require a permit and registration before purchase?
Should we ban CRT displays because you can use the flyback transformer to build a stun gun?
Laser diodes generally require some type of current limiting to prevent damage. In the DVD burner circuit, that is the function of the third pin on the diode package (that the article simply blows off as "not used"). This pin connects to an internal photodiode, which is used to measure output power, and provide feedback through an external driver circuit to continuously control the current applied to the laser diode junction.
The article simply places the laser diode directly across the 3V battery supply, with not even a ballast resistor to limit the current. You might get away with this with AA batteries, but if someone were to try this trick with a D-cell maglite, they would most likely let the magic smoke out of the laser very quickly.
That looks more like the results of LSD, not coke. If you wanna see what the results of coke end up looking like, click here:
http://www.bushspeaks.com/img/noellebush.jpg
Greenstone appears to be a tube DISTRIBUTOR, not a manufacturer. But yes, tubes are still being manufactured for certain niche applications, and will be for a long, long time. Manufacturers include CPI/Eimac, Econco, MU, National Electronics/Richardson, Svetlana, Thompson, Litton, and Thales.
More on topic, the overwhelming majority of Apollo electronics was solid state. The guidance computer was the first large scale application of integrated circuits, and nearly everything else used discrete semiconductors. The only tubes I can think of in the Apollo systems are pickup tubes (vidicons) in the TV cameras, RF power amplifiers in the communications/radar systems, and a CRT for one of the cockpit displays (radar?).
>This is why you don't give a mouse a cookie...
Or in this case, why you don't give a pig a camera...
There is a difference between neurotically smothering your kids, and recognizing that there can be hazards involved in certain activities, and taking precautions where warranted. You will notice that NOWHERE in my post did I say that crazy blender experiments shouldn't be done (too much potential for fun), but common sense would dictate not snorting the resulting powdered remains, and using a blender that you don't intend to use for preparing food.
I did a lot of crazy shit when I was a kid or teenager, including activities that today would draw the immediate attention of the BATF, DEA, DHS, and FCC. Because my parents didn't share my curiosity about science/engineering, I did a lot of stuff on my own or with friends of a similar age. It is only by dumb luck that we didn't get seriously hurt with some of our "projects".
Now that I have a kid of my own (whose favorite TV show is "Mythbusters", BTW), one of my favorite activities is to show him various science experiments and demonstrations, some of which would horrify those of the "soccer mom" stereotype (like the time we fired off a bunch of old automotive airbags and the noise brought out the cops, or set an old microwave on fire by nuking various non-food items). But I ALWAYS make a point of demonstrating proper safety precautions, including drawing the line at demonstrations that cannot be done safely in a suburban backyard. Those are either not done, or they wait until we can find a suitable place to do them.
Sure, most of the kids of past generations survived their own experimentation unscathed. But how many didn't? How many kids would have gone on to a great career, but poisoned/maimed/electrocuted/blew themselves up simply because they were ignorant of the hazards involved with whatever they were playing around with?
finely divided glass dust is NOT something that you want to inhale.
http://en.wikipedia.org/wiki/Silicosis
Not to mention the fact that the blender jar and blades are now contaminated with the remnants of the iPhone, rendering the blender unfit for food preparation. I know I wouldn't be too happy if my kid ruined an expensive blender, even if they were doing something cool in the process.
And at a high volume filling ststion (where fuel is delivered at least once daily), those insulated tanks will do a good job of keeping the fuel at the temperature THAT IT WAS DELIVERED AT, rather than the more or less constant 60 degree underground temperature.
That fuel was most likely stored in an ABOVE GROUND tank at the depot, then driven to the station in an uninsulated tanker truck. It could be quite a bit warmer than 60F by the time it gets into the storage tank at the filling station.
Exactly why would they require insulated underground storage tanks for gasoline, anyway? Unless the "insulation" is just a byproduct of double-wall construction to prevent leaks, it would seem that the stations are TRYING to keep the fuel warm for some reason, no?
weed GROWING robot, or even the weed SMOKING robot..
the logical next step is to attack the PRINTER side of the equation. Mod chips, third-party firmware, solder a wire between point X and point Y, etc.
None of those cards are FCC certified for broadcast use, and wouldn't be usable by a licensed LPFM station. They might be a good start toward a pirate station for someone without RF knowledge/experience.
that a lake disappeared into a hole in the ground:
http://en.wikipedia.org/wiki/Lake_Peigneur
Columbia had Laurel Clark and Kalpana Chawla, and Challenger had Judy Resnik and Christa McAuliffe.
they are assuming that linux users might be more likely than most buyers to open up the box, swap cards, add drives/RAM, etc. In the process potentially exposing the machines to "user induced failures" from ESD, dropped screws, damaged parts, etc.
If that Moeller unit is like the other locking Estops I have used, the key doesn't prevent it being PUSHED, but the button won't pop back OUT without the key. I believe that requiring a key in order to activate an E-stop is an OSHA violation. Requiring a key to reset a tripped button is OK, and sometimes helpful in knowing which button was pressed when there are many installed.
http://www.automationdirect.com/ is one good supplier. This kind of industrial grade hardware is expensive, so eBay might be the best choice. What you want is commonly called a "mushroom head emergency stop pushbutton". If using it for a PC reset switch, you want normally open contacts, whereas most E-stop systems would use normally closed.
Not sure how that could cause the shock problem, as the grounded side of all 3 ports are connected together to the case of the splitter, at least on every CATV splitter I have ever seen. Poor signal strength, yes, but not the electrical shock problem. A bad ground out at the pole (and no ground at the house) certainly could, though...
An outdoor antenna cable (or CATV coax) is supposed to be tied to the main electrical grounding system, at or near the point that the cable enters the building. This is primarily for lightning protection. Even if separate ground rods are driven (like for one of those old style large satellite dishes), the new rod STILL gets tied back to the main building ground.
If you are getting shocks or seeing sparks when connecting an antenna to a TV set, call a qualified electrician.
The operating frequency of microwave ovens was chosen to be in an unlicensed (ISM) frequency band, that would provide good penetration into foods, and lent itself to the mass production of inexpensive magnetron tubes.
The lowest resonant frequency for a water molecule is 22.235 GHz, or nearly 10X the operating frequency of a microwave oven.
Curious about everything around them, and how everything works.
Until they hit 5 or 6, at which time pop culture, peer pressure, and the public school system start working together to stomp the spark of interest wight out of most of them....