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#71
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"Bob Eager" wrote in message ... On Sat, 10 Jul 2004 21:43:19 UTC, "half_pint" wrote: But electronic devices are not connected directly to the mains they are connected to a power supply which is *designed* to copy with large cueernts. But not *that* large...and they too contain semiconductor devices. I dount there are many 100mw components in a PS and even if there were and they did blow they would protect your computer. However before it did blow it would probably required a several fold increase in current for a substained period which would obviously blow the fuse first. For semiconductor devices, the sustained period is a lot shorter than for a fuse. No it isn't otherwise fuses would be made from semiconductors. And if you are saying that semi conductor devices are inherently sensitive to current then obviously we would make fuses out of them. However semiconductors are make out of silicone which has No, silicon. Not the same. How many semiconductor-packed breasts do you know of? I don't wear breast implants, but good luck with the 'op' anyway ;O) Semiconductors materials are probably never damaged by heat, at least not untill long after the metalic contacts have vapourised. Perhaps not the base material, but semiconductor materials are a bit more complex than that (hint: look up 'doping'). Maybe I should look up 'dope' :OP we are basically talking about very stable elements, similar to silicon which are 'woven' into the silicon lattice they will form a very stable structure. -- Bob Eager |
#72
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half_pint wrote:
But electronic devices are not connected directly to the mains they are connected to a power supply which is *designed* to copy with large cueernts. I suppose you think that means something but it's irrelevant to the point that electronic devices react to electrical faults hundreds of times faster than any fuse can. More to the point, any current that could possibly blow a fuse is the RESULT of a failure which, by definition, means the fuse cannot 'protect' from it as it's already happened. No we are talking about a surge in current from outside the house No, we're talking about a voltage surge. so to speak. That surge must go through the fuse first, strictly speaking, well, at leaaast at the same time anyway. There will be no current unless something conducts. I.E. If there were no devices plugged in (or wired in) the only effect would be a voltage spike on the interior power lines, but no current flow per see (besides leakage). If, however, a susceptible device is connected to the power line and the voltage spike is sufficient to cause electrical breakdown then the device fails and may pull excessive current as a result of the failure, which, if severe enough, will blow the fuse. But the failure has already occurred by the time the fuse sees anything, much less blows. OK if you connect one leg of your 3GHz pentuim to the mains live connection and the other leg to earth you will probably damage it but I am not recommending that. And it's inherent to the nature of electronics. By the time an electronic device is pulling excessive current whatever is at fault inside has long since gone to the happy hunting grounds, or else it would not be pulling excessive current. And there's nothing you can do about it by 'sizing' the external fuse as the failed device could be a 100mw component inside a 200 watt computer where the normal operating power fluctuations are hundreds of times larger. I dount there are many 100mw components in a PS and even if there were and they did blow they would protect your computer. For that to even begin to make sense you'd first have to consider a blown power supply as the device still 'working', but I doubt most people do. Further, I have no idea what makes you think a 'blown' component in the PSU will 'protect' the computer. All one need imagine is the reference voltage zener blowing, resulting in lord knows what voltage being thrown into the system and destroying massive numbers of components. A zener diode is already 'blown' so to speak, thats how they work. No, it isn't. The voltage across them is basically the same whatever the input voltage. An obvious contradiction, as stated. A zener conducts when the voltage across it reaches a certain level, otherwise is does not conduct, and the source better be current limited, most commonly by a series resistor, or else the zener will self destruct. In that case, by over heating. Essentially it is a grain of sand, Not hardly. its not going to melt, 'Melting' has nothing to do with it. at least not before other metal components vapourise. And the first component to vapourise will be the fuse in the plug, you can be sure of that. No offense but you really don't understand semi-conductors at all. That is, of course, why all decent PSUs include over voltage protection on the power rails. Ah hah!! And while you may gleefully scream "ah hah!," as if that means something to your case, it isn't done with fuses because fuses are too slow to protect electronic components. I think you will find 99% of surge protectors contain a fuse, which is a bit odd really if they are surplus to requirements? No one ever said they were 'surplus'. The problem is you don't understand the nature of electronics and the purpose of various protection devices. A fuse blows on a sustained current fault and breaks the connection: a preferable situation to continuing to draw fault current because, for one, it prevents fires. That has nothing to do with 'protecting' what is already a damaged device causing the current fault. The issue isn't 'where' the fault occurs in the device but that a fuse simply cannot 'protect' from it (voltage induced failure). However before it did blow it would probably required a several fold increase in current for a substained period which would obviously blow the fuse first. This is where you are sorely mistaken as you seem to think that the only way any device, of any kind, fails is by current induced heating but that is simply not the case with electronic devices. Too much voltage, as perhaps induced by a surge, will instantly destroy semi-conductor components; after which they may simply do nothing or, more common, draw excessive current. At which point, anything a 'fuse' detects is long since after the fact. No that current has to come in via the fuse which is designed to fail as quickly as possible, as opposed to other components which are designed *not* to fail. You're never going to understand it till you get it out of your head that 'excessive current' is the only thing that damages semi-conductors. (Heat can destroy them too but that isn't the mode we're talking about with surge protection) And if you are saying that semi conductor devices are inherently sensitive to current then obviously we would make fuses out of them. It is your mistaken notion that only 'current' causes failure that leads you to invalid assumptions. But I am right of course, *only* current *ever* causes electrical failures. A semiconductor device, or any electrical device will work quite happilly a 1 billion volts. Surely you jest. Why in the word do you think power supplies, much less multi-voltage units, even exist if electronics works 'quite happily' at just any old voltage? However semiconductors are make out of silicone which has an extremly high melting point. Which is irrelevant because that is not what causes device failure. Heat is the only cause of device failure. Ever. Period. Just plain wrong. Really now, even your own decryption, as misguided as it is, contradicts THAT absurdity because, if it were true, there would never ever be an electronic failure, unless someone shoved it inside a 900F oven. And that is clearly not the case. (we are basically talking about sand) indeed silicone has replaced asbestos as a safer heat resistant material. http://www.candochefs.com/silbakmat1.html " Use in up to 900 degrees F! " Obvioulsy fuses are *designed* to melt quickly at low temperatures. Semiconductors materials are probably never damaged by heat, at least not untill long after the metalic contacts have vapourised. 'Melting' is not the failure mechanism of semi-conductor devices. Yes it is. No, it isn't. And I'd advise you to go learn something about semi-conductors before you make such statements because they make it rather obvious you have no idea how they work. And even if you did have a 'constant power consumption' electronic device, for which you could 'tightly' size a fuse, electronic components can, and do, go into catastrophic failure hundreds of times faster than a fuse can blow. Surge -- component failure -- excessive current -- fuse blows They blow before the device draws enough current to be damaged, that is how they are designed. That is certainly the myth. It is not, however, reality. You don't have a huge backlog of expensive surge protectors to shift by any chance? I don't 'sell' anything nor is it any skin off my nose if your computer is damaged because you think a fuse will 'protect' it. Nice try buddy, uk.comp.vendors, pull the other one, I wasn't born yesterday. I'm posting from alt.comp.hardware.pc-homebuilt. There of dozen of devices in my home which contain IC's none has ever failed due to a power surge, zilcho. And you think that 'proves' what? There are also many IC's in my car which regularly gives me a big zap of static electricity, I can assure you that the shock has effected me far more than my car stereo etc.... Oh, really? And what were you doing with the case to these devices open so that you were getting a 'static discharge' from the 'ICs'? But since you bring it up you could expand your horizons by doing a web search on ICs and static electricity and, in particular, ESD protection. Here's one to get you started: http://www.informit.com/articles/art...21704&seqNum=3 "In general, MOS devices are sensitive to voltage spikes and static-electricity discharges. This can cause many problems when you have to replace MOS devices, especially complementary-symmetry metal-oxide semiconductor (CMOS) devices. The level of static electricity on your body is high enough to destroy the inputs of a CMOS device if you touch its pins with your fingers." I have also worked in enviroments where there are dozen's upon dozens of computers, no surge protection and no failed computers. Which you think 'proves' what? I get the feeling that someone here is trying to shift a job lot of surge protectors on ebay, either that or having a larf. Think I will go and take a look Have fun. |
#73
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half_pint wrote:
"Bob Eager" wrote in message ... On Sat, 10 Jul 2004 21:43:19 UTC, "half_pint" wrote: But electronic devices are not connected directly to the mains they are connected to a power supply which is *designed* to copy with large cueernts. But not *that* large...and they too contain semiconductor devices. I dount there are many 100mw components in a PS and even if there were and they did blow they would protect your computer. However before it did blow it would probably required a several fold increase in current for a substained period which would obviously blow the fuse first. For semiconductor devices, the sustained period is a lot shorter than for a fuse. No it isn't otherwise fuses would be made from semiconductors. And if you are saying that semi conductor devices are inherently sensitive to current then obviously we would make fuses out of them. However semiconductors are make out of silicone which has No, silicon. Not the same. How many semiconductor-packed breasts do you know of? I don't wear breast implants, but good luck with the 'op' anyway ;O) Semiconductors materials are probably never damaged by heat, at least not untill long after the metalic contacts have vapourised. Perhaps not the base material, but semiconductor materials are a bit more complex than that (hint: look up 'doping'). Maybe I should look up 'dope' :OP we are basically talking about very stable elements, similar to silicon which are 'woven' into the silicon lattice they will form a very stable structure. And they're still nice 'stable elements' after the device has failed too, it just isn't a working device anymore. |
#74
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In article , David Maynard
writes [snip pointless attempt to reason with half_pint] David, you're wasting your time arguing with half_wit. He's a regular poster on uk.legal, where the quality of his "advice" is on a par with his knowledge of electronics. I have him killfiled everywhere he pops up. -- A. Top posters. Q. What's the most annoying thing on Usenet? |
#75
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In article , David Maynard
writes http://www.crra.com/ewaste/ttrash2/ttrash2/ That article is so filled with hysterical hyperbole that I can't tell how much, if any, of it deserves serious consideration. It was amongst the first hits I got when I googled for "third world computer recycling" or similar. The original article I was thinking of was printed in the Guardian, a liberal UK newspaper. These reports are more even-handed: http://www.guardian.co.uk/weekend/st...849530,00.html http://www.guardian.co.uk/internatio...725756,00.html -- A. Top posters. Q. What's the most annoying thing on Usenet? |
#76
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On Sun, 11 Jul 2004 02:31:23 UTC, "half_pint"
wrote: For semiconductor devices, the sustained period is a lot shorter than for a fuse. No it isn't otherwise fuses would be made from semiconductors. Of course it is...fuses have to cope with switch on surges WITHIUT blowing. And if you are saying that semi conductor devices are inherently sensitive to current then obviously we would make fuses out of them. However semiconductors are make out of silicone which has No, silicon. Not the same. How many semiconductor-packed breasts do you know of? I don't wear breast implants, but good luck with the 'op' anyway ;O) Missed the point (sigh) -- Bob Eager begin a new life...dump Windows! |
#77
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half_pint wrote: [...] As said before, voltages also kills semiconductor devices. Why do you think there are such things as electrostatic bags? To protect semiconductors from static electricity as opposed to mains electricity. LOL! How much do you know about electricity? |
#78
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"Johannes H Andersen" wrote in message news:40F11D7F.CCB37EDF@sizefitterlikneasfuongtuint gsjadfasejk.com... half_pint wrote: [...] As said before, voltages also kills semiconductor devices. Why do you think there are such things as electrostatic bags? To protect semiconductors from static electricity as opposed to mains electricity. LOL! How much do you know about electricity? I have forgotten far more than you will ever know. |
#79
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"David Maynard" wrote in message ... half_pint wrote: "Bob Eager" wrote in message ... On Sat, 10 Jul 2004 21:43:19 UTC, "half_pint" wrote: But electronic devices are not connected directly to the mains they are connected to a power supply which is *designed* to copy with large cueernts. But not *that* large...and they too contain semiconductor devices. I dount there are many 100mw components in a PS and even if there were and they did blow they would protect your computer. However before it did blow it would probably required a several fold increase in current for a substained period which would obviously blow the fuse first. For semiconductor devices, the sustained period is a lot shorter than for a fuse. No it isn't otherwise fuses would be made from semiconductors. And if you are saying that semi conductor devices are inherently sensitive to current then obviously we would make fuses out of them. However semiconductors are make out of silicone which has No, silicon. Not the same. How many semiconductor-packed breasts do you know of? I don't wear breast implants, but good luck with the 'op' anyway ;O) Semiconductors materials are probably never damaged by heat, at least not untill long after the metalic contacts have vapourised. Perhaps not the base material, but semiconductor materials are a bit more complex than that (hint: look up 'doping'). Maybe I should look up 'dope' :OP we are basically talking about very stable elements, similar to silicon which are 'woven' into the silicon lattice they will form a very stable structure. And they're still nice 'stable elements' after the device has failed too, it just isn't a working device anymore. No because the metalic contacts have evapourated. Replace the contacts and it would be fine. |
#80
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"Bob Eager" wrote in message ... On Sun, 11 Jul 2004 02:31:23 UTC, "half_pint" wrote: For semiconductor devices, the sustained period is a lot shorter than for a fuse. No it isn't otherwise fuses would be made from semiconductors. Of course it is...fuses have to cope with switch on surges WITHIUT blowing. As do semiconductors. And if you are saying that semi conductor devices are inherently sensitive to current then obviously we would make fuses out of them. However semiconductors are make out of silicone which has No, silicon. Not the same. How many semiconductor-packed breasts do you know of? I don't wear breast implants, but good luck with the 'op' anyway ;O) Missed the point (sigh) -- Bob Eager |
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