4 step-down high-power resistors (no mains isolation)
Oh dear - you're obviously reluctant to try that again but perhaps you're not sure why, so let's do the math. Your average computer needs about 100 watts to run. Let's simplify things and assume for a second that they only need 12VDC as well. That's 8.5 amps. In order for a series voltage divider to work, your resistors must eat 90% of the voltage (120/(120-12)) - 108 volts. 108 volts at 8.5 amps is 918 watts, roughly the same as a large element on a kitchen stove. Divide this by 4 and you get 229 watts per resistor. I don't believe you can buy those kinds of resistors at Radio Shack.
Also, if you fried the motherboard, then your resistors were probably of too low a value. You need 12.7 ohms total, so for a bridge rectifier where only two of the diodes would be conducting at any given time and the resistors would effectively be in series, you'd want 6.4 ohm resistors. Mouser sells a 6.8 ohm 300 watt resistor that would work. Make sure to bolt it to a heatsink of the proper size.
So now you know what you need to fix before you try it again, and this time, please, get the solder rain on videotape.
Switched-mode power supplies instead chop up the input AC signal, rectify it and smooth it. However, this also means that if a component in the PSU fails, your component is effectively directly connected to the mains and it's quite likely that your devices willget the full 110V / 220V put across them.
No. Old-school power supplies worked by transforming 120VAC at 60hz into the desired output voltage at 60hz, then rectifying and filtering it. Thing is, an inductor must be very large and heavy to work at 60hz (you need an iron core roughly the size of a small fist). New style power supplies first rectify and filter the 120VAC into 120VDC. It is then inverted into AC at a much higher frequency (usually 20khz to 500khz). Then it is transformed to the output voltage and rectified/filtered into DC. The higher frequencies are what allows for much smaller/lighter transformers and capacitors. Your mains potential is still separated from your load by the transformer, though.
Actually, no. Most sites have terms of service that you accept by using their site.
And if I choose to breach those terms, what law have I broken? It's no more a valid contract than me saying "By reading this you agree to send me $100", even ignoring the quid pro quo facet of that analogy.
Re:Yeah, we think highly of foreigners here.
on
Greenbacks No More
·
· Score: 5, Funny
Or is the next 'new math' going to be based on adding colors, instead of numbers? Yeah, you gave me two blues ($5) and a yellow ($10), so thats a blue-green ($20.)
That would lead to the most valuable denominations having the most subtle color variations. The new colors will be based on a proven scheme most Americans are familiar with:
$1 white
5 pink
10 yellow
20 green
50 blue
100 gold
500 bronze
No. It will penetrate a sheet of paper but probably be stopped by something such as your hand. I would be impressed if this setup will go 15 miles through a thunderstorm.
Will it be fixed-point (ie. you must be aimed directly at the antenna, making use of this with laptops/pdas/phones impossible.)
Not necessarily however the line-of-sight requirements would make roaming with omnidirectional antennas very disappointing.
75-90GHz means wavelengths between 4mm and 3.33mm. A quarter-wave antenna would be only 1mm long. You'd probably manufacture antennas for this by using phased dipole arrays on a printed circuit board [Warning: powerpoint link] (probably the same circuit board as the transceiver) aimed at a parabolic dish reflector.
some countries, including Japan, try to spice up their product manuals in order to entice the users to read them.
Proof that this works:
<Overfiend> hey, check out http://master.debian.org/~branden/xsf.html for a
content-free beginning.
<Overfiend> what, nobody likes my template?
<dark> Overfiend: I'm looking at it with lynx:)
<Overfiend> dark: well, look at it with GRAPHICAL browser!
* Overfiend grins
<dark> Overfiend: Well I didn't know yet if it would be worth the 20-second startup time:)
<dark> Overfiend: If there aren't any naked girls on it then I'm not bothering!
<Overfiend> dark: probably not. But do it anyway:)
<Overfiend> dark: I could change that, but it might not be a popular decision:)
<Overfiend> Not with the market-conscious developers, anyway:)
<dark> Overfiend: Then they're not very market-conscious:-)
<dark> Ah, I have a window!
<Overfiend> dark: all right, smartass, reload the page. Like that better?:):):)
<dark> Whee 115 bytes per second.
<Overfiend> be grateful the jpg's are only about 30k apiece
<Overfiend> and the.png's are tiny.
* Overfiend is wondering if anyone ELSE is loading/reloading that page:)
<dark> They'd better not be, there are laws in this country you know.
* netgod falls over laughing
<Overfiend> netgod: like it? 8-D
* dark wonders if this girl can walk.
Ok, I just checked out Sony's site - they claim to be doing 2822400 samples/sec and 1 bit/sample. They claim a frequency response of 0-100khz with this which means their effective max sample rate is slightly above 200khz (they claim 20khz for 44100 sample/sec cd audio, a ratio of 2.205, which is reasonable), perhaps 220khz. This is 7.8% of the aforementioned 2822400 samples/sec - if there's one thing you can say about this encoding format, it is massively redundant.
More interestingly, they are not using a blue laser to get 4.7GB per disc - 650nm is reddish-orange - they're doing it using multiple layers.
Samples happen 1 bit at a time, but they are made much more frequently to achieve near-analog accuracy
That just described how a 1-bit DAC on a CD player works. For the data itself to be encoded like that would be silly - for exactly the same quality, you'd need a 2^16*44100=2890137600 bits/sec data rate (without counting the parity/recovery bits).
Go watch some R/C glider pilots sometime. It is absolutely amazing to watch a pilot single-handedly bring his bird in from fifty feet away five feet off the ground, fly it directly towards himself, and get the timing on the flare so perfect that it stalls in his other hand.
If a bunch of hobbyists can do that even with wind gusts (gusts + hills seem to attract R/C glider pilots), there's no reason someone couldn't cleanly land something remotely on a carrier that usually carries aircraft seven times as heavy.
An FM tranmission is at an effective quality of 22kHz
Not necessarily - the FM broadcast band layout gives each channel 200kHz of bandwidth (which is why all FM broadcast stations have center frequencies ending in an odd digit). Nyquist's theorem says you only need 2x bandwidth to represent a given frequency.
If you're operating under Part 15, then how much AF spectrum you represent with this is up to you. The more you use, the better the signal/noise ratio you need (Shannon's law), however representing 1kHz of AF with 4.5kHz of RF is already overkill.
Isn't that only if the computer is off with the power supply switch still on?
It would appear that the ATX power supply predates the ATX power supply switch by about a year, depending on manufacturer.
A lot of those first-gen ATX power supplies had severe reliability problems as well (I've seen batches with %20+ failure rates after six months), so they're increasingly rare.
Death, n. At least 12db signal loss. See also: cinder block, forests, high chain link fences, 2.4ghz wireless phones, and malfunctioning microwave ovens.
anybody have any experience running a wireless network between two adjacent buildings?
1. Don't get two Linksys WAP11's and put one of them in Access Point Client mode. You will have to reboot that access point nearly every day because of firmware bugs (even with the latest firmware). Not bitter.
2. Get as close to a line-of-sight path as possible. You need at least an -83dBm signal to do 11mbps, so shoot for -75dBm during install if you want to maintain -83 when people walk in front of it, it rains, etc. Shooting through glass or drywall doesn't hurt very much (I've gotten -75dBm between an Orinoco Silver and a Dlink DWL-1000AP with 10 sheets of drywall in the way and stock antennas) but thicker things like concrete really hurt. So do more than a couple trees (the drops of water that tend to hang on their leaves some of the time are opaque at 2.4ghz).
3. If the only way to get a usable line-of-sight is to mount something on the roof, then do it, but keep cable runs to an absolute minimum and use LMR400 coax. Install properly-grounded lightning arrestors where the coax enters the roof. As for the antenna itself, you can weatherproof just about anything by putting it in PVC pipe or you could get a dish, panel antenna, or yagi from any of these people.
4. Security - since WEP sucks, you'll want to do a VPN of some sort between networks. You'll probably want to spend a few weeks learning how IPSec works on the systems you'll be using as your routers to accomplish this. I would recommend against any of the VPN appliances as a lot of them are too stupid to do things like put the default route across the tunnel.
I hate to break it to you but "ground" here and "ground" a few hundred feet away may NOT be the same and that difference can cause current to flow.... through your computer if necessary.
Even dry sand has a conductivity of 0.5 millisemens per meter, if your homes are 100 meters apart (max ethernet distance) that's about 200 kiloohms (for reference, most of the pull-down resistors in CMOS logic circuitry to keep the control inputs from floating are at least one megaohm). Which means that at more than a few volts, enough current will pass to keep static between the homes down to the dull roar that the isolation circuits in ethernet cards can handle (I remember hearing that 802.3 required 600V of isolation somewhere but I can't back that up with a URL which is why I didn't include it in my original post).
I'm not saying this stuff is recommended, it's just that the fear mongering here is unreasonable IMHO.
you cannot strng cat-5 to your neighbor's because of ground problems.
Twisted-pair ethernet uses differential signaling (a transmitted "one" bit is sent out as a positive pulse on the TX+ line and a negative pulse on the TX- line). There is no requirement for a common ground.
It is entierely possibal for your comptuer to be at 100 volts realtive to your neighbors.
No, because the ground on both computers is plugged into, well, the ground.
Flourescents, high-pressure sodium, metal-hallide, etc top out at about 12-15%. For that matter, most cheapo incandescents are more like 3%. The best yellow/orange LED's hit 18%.
60% is positively huge, although I wonder how cheaply they'll be able to put microscopic tungsten lattices in flashlight bulbs and relatia.
I realize that their are probably some Alpha and Sparc owners on this board and in the community but how many of those people are actually running Debian?
Meaningless misleading statistics on how many packages of each architecture are downloaded every day from gluck.debian.org (a main http.us.debian.org rotation server) are available here. Someday I'll get the rrdtool feed working.
If you walk out of a store and set off the alarms, you have to show a receipt for your merchandise to prove that you paid for it.
Alternatively, you could tell them to call the cops, stand there until they arrive, and make your case to the officer (or if he also disagrees, to a judge, in which case you would have the right to an attorney and so forth).
Chances are this is too much of a pain in the ass for both parties so you voluntarily forfeit some rights to get on with your life.
Slashdot Mirror
Hey, it really happens:
<bfinn> THE QUACK IS GAME TO PLAY TO KILL OF PEOPLE TO GUN
Oh dear - you're obviously reluctant to try that again but perhaps you're not sure why, so let's do the math. Your average computer needs about 100 watts to run. Let's simplify things and assume for a second that they only need 12VDC as well. That's 8.5 amps. In order for a series voltage divider to work, your resistors must eat 90% of the voltage (120/(120-12)) - 108 volts. 108 volts at 8.5 amps is 918 watts, roughly the same as a large element on a kitchen stove. Divide this by 4 and you get 229 watts per resistor. I don't believe you can buy those kinds of resistors at Radio Shack.
Also, if you fried the motherboard, then your resistors were probably of too low a value. You need 12.7 ohms total, so for a bridge rectifier where only two of the diodes would be conducting at any given time and the resistors would effectively be in series, you'd want 6.4 ohm resistors. Mouser sells a 6.8 ohm 300 watt resistor that would work. Make sure to bolt it to a heatsink of the proper size.
So now you know what you need to fix before you try it again, and this time, please, get the solder rain on videotape.
No. Old-school power supplies worked by transforming 120VAC at 60hz into the desired output voltage at 60hz, then rectifying and filtering it. Thing is, an inductor must be very large and heavy to work at 60hz (you need an iron core roughly the size of a small fist). New style power supplies first rectify and filter the 120VAC into 120VDC. It is then inverted into AC at a much higher frequency (usually 20khz to 500khz). Then it is transformed to the output voltage and rectified/filtered into DC. The higher frequencies are what allows for much smaller/lighter transformers and capacitors. Your mains potential is still separated from your load by the transformer, though.
And if I choose to breach those terms, what law have I broken? It's no more a valid contract than me saying "By reading this you agree to send me $100", even ignoring the quid pro quo facet of that analogy.
That would lead to the most valuable denominations having the most subtle color variations. The new colors will be based on a proven scheme most Americans are familiar with:
$1 white
5 pink
10 yellow
20 green
50 blue
100 gold
500 bronze
No. It will penetrate a sheet of paper but probably be stopped by something such as your hand. I would be impressed if this setup will go 15 miles through a thunderstorm.
Will it be fixed-point (ie. you must be aimed directly at the antenna, making use of this with laptops/pdas/phones impossible.)
Not necessarily however the line-of-sight requirements would make roaming with omnidirectional antennas very disappointing.
75-90GHz means wavelengths between 4mm and 3.33mm. A quarter-wave antenna would be only 1mm long. You'd probably manufacture antennas for this by using phased dipole arrays on a printed circuit board [Warning: powerpoint link] (probably the same circuit board as the transceiver) aimed at a parabolic dish reflector.
Proof that this works:
<Overfiend> hey, check out http://master.debian.org/~branden/xsf.html for a content-free beginning. :) :) :) :) :) :-) :) :) :) .png's are tiny. :)
<Overfiend> what, nobody likes my template?
<dark> Overfiend: I'm looking at it with lynx
<Overfiend> dark: well, look at it with GRAPHICAL browser!
* Overfiend grins
<dark> Overfiend: Well I didn't know yet if it would be worth the 20-second startup time
<dark> Overfiend: If there aren't any naked girls on it then I'm not bothering!
<Overfiend> dark: probably not. But do it anyway
<Overfiend> dark: I could change that, but it might not be a popular decision
<Overfiend> Not with the market-conscious developers, anyway
<dark> Overfiend: Then they're not very market-conscious
<dark> Ah, I have a window!
<Overfiend> dark: all right, smartass, reload the page. Like that better?
<dark> Whee 115 bytes per second.
<Overfiend> be grateful the jpg's are only about 30k apiece
<Overfiend> and the
* Overfiend is wondering if anyone ELSE is loading/reloading that page
<dark> They'd better not be, there are laws in this country you know.
* netgod falls over laughing
<Overfiend> netgod: like it? 8-D
* dark wonders if this girl can walk.
More interestingly, they are not using a blue laser to get 4.7GB per disc - 650nm is reddish-orange - they're doing it using multiple layers.
That just described how a 1-bit DAC on a CD player works. For the data itself to be encoded like that would be silly - for exactly the same quality, you'd need a 2^16*44100=2890137600 bits/sec data rate (without counting the parity/recovery bits).
Did I say silly? Oops, I meant nigh-impossible.
Go watch some R/C glider pilots sometime. It is absolutely amazing to watch a pilot single-handedly bring his bird in from fifty feet away five feet off the ground, fly it directly towards himself, and get the timing on the flare so perfect that it stalls in his other hand.
If a bunch of hobbyists can do that even with wind gusts (gusts + hills seem to attract R/C glider pilots), there's no reason someone couldn't cleanly land something remotely on a carrier that usually carries aircraft seven times as heavy.
Not necessarily - the FM broadcast band layout gives each channel 200kHz of bandwidth (which is why all FM broadcast stations have center frequencies ending in an odd digit). Nyquist's theorem says you only need 2x bandwidth to represent a given frequency.
If you're operating under Part 15, then how much AF spectrum you represent with this is up to you. The more you use, the better the signal/noise ratio you need (Shannon's law), however representing 1kHz of AF with 4.5kHz of RF is already overkill.
It would appear that the ATX power supply predates the ATX power supply switch by about a year, depending on manufacturer.
A lot of those first-gen ATX power supplies had severe reliability problems as well (I've seen batches with %20+ failure rates after six months), so they're increasingly rare.
Death, n. At least 12db signal loss. See also: cinder block, forests, high chain link fences, 2.4ghz wireless phones, and malfunctioning microwave ovens.
1. Don't get two Linksys WAP11's and put one of them in Access Point Client mode. You will have to reboot that access point nearly every day because of firmware bugs (even with the latest firmware). Not bitter.
2. Get as close to a line-of-sight path as possible. You need at least an -83dBm signal to do 11mbps, so shoot for -75dBm during install if you want to maintain -83 when people walk in front of it, it rains, etc. Shooting through glass or drywall doesn't hurt very much (I've gotten -75dBm between an Orinoco Silver and a Dlink DWL-1000AP with 10 sheets of drywall in the way and stock antennas) but thicker things like concrete really hurt. So do more than a couple trees (the drops of water that tend to hang on their leaves some of the time are opaque at 2.4ghz).
3. If the only way to get a usable line-of-sight is to mount something on the roof, then do it, but keep cable runs to an absolute minimum and use LMR400 coax. Install properly-grounded lightning arrestors where the coax enters the roof. As for the antenna itself, you can weatherproof just about anything by putting it in PVC pipe or you could get a dish, panel antenna, or yagi from any of these people.
4. Security - since WEP sucks, you'll want to do a VPN of some sort between networks. You'll probably want to spend a few weeks learning how IPSec works on the systems you'll be using as your routers to accomplish this. I would recommend against any of the VPN appliances as a lot of them are too stupid to do things like put the default route across the tunnel.
Maybe you could try the patches here?
Even dry sand has a conductivity of 0.5 millisemens per meter, if your homes are 100 meters apart (max ethernet distance) that's about 200 kiloohms (for reference, most of the pull-down resistors in CMOS logic circuitry to keep the control inputs from floating are at least one megaohm). Which means that at more than a few volts, enough current will pass to keep static between the homes down to the dull roar that the isolation circuits in ethernet cards can handle (I remember hearing that 802.3 required 600V of isolation somewhere but I can't back that up with a URL which is why I didn't include it in my original post).
I'm not saying this stuff is recommended, it's just that the fear mongering here is unreasonable IMHO.
Twisted-pair ethernet uses differential signaling (a transmitted "one" bit is sent out as a positive pulse on the TX+ line and a negative pulse on the TX- line). There is no requirement for a common ground.
It is entierely possibal for your comptuer to be at 100 volts realtive to your neighbors.
No, because the ground on both computers is plugged into, well, the ground.
it will destroy your computers.
But what won't these days?
Mine, too.
*ducks and runs*
If that were true, a 40-watt flourescent tube would output ~20000 lumens, not ~3000.
100% efficiency would be about 680 lumens per watt. Flourescents do about 80, incandescents do about 18.
Oh, and misspelling words like "flourescent" and "ballast" hurts your credibility.
60% is positively huge, although I wonder how cheaply they'll be able to put microscopic tungsten lattices in flashlight bulbs and relatia.
I was asked to research this at work a few weeks ago - here's a few links:
News.com, December 11, 2001: "Businesses should limit these commitments to product lines that Gartner has already identified as strategically sound [...]: Compaq Proliant servers"
News.com, March 8, 2002: "At a minimum, HP will adopt the Proliant line, according to every source interviewed"
Steven Vaughan-Nichols, September 5, 2001: "the Proliant (always a troublesome line, in my experience), will gradually be phased away in favor of Netserver. I'll be surprised if there's a new 2002 line of Proliants." (...I tend to believe the opposite of whatever this man predicts.)
Meaningless misleading statistics on how many packages of each architecture are downloaded every day from gluck.debian.org (a main http.us.debian.org rotation server) are available here. Someday I'll get the rrdtool feed working.
Look at the bright side, you got a karma point out of it.
</cynic>
Alternatively, you could tell them to call the cops, stand there until they arrive, and make your case to the officer (or if he also disagrees, to a judge, in which case you would have the right to an attorney and so forth). Chances are this is too much of a pain in the ass for both parties so you voluntarily forfeit some rights to get on with your life.
The burden of proof is always on the accuser.
Try this, it works beautifully:
Cashier: ...And can I have your last name please?
You: No.
See how easy that is? Even if you need to pay with a check or card, if you don't want them to put your name in their database, they'll respect that.