Well, I won't argue about semantics, but reputable manufacturers like Panasonic make it quite clear how they measure noise. For example, here's what Panasonic has to say (source): "the noise data is measured at 1 meter from the intake side of the fan suspended in a semi-anechoic chamber (background noise 13 dBA maximum)".
Zalman, Thermaltake and others neglect to specify this, which is no surprise since their claims always clash with each other and with their suppliers'.
And there's also the subjective side of things, but that's a whole other issue. Two fans with the same noise emission levels aren't necessarily as pleasant, since their spectra may be completely different. Reducing RPMs will give you less overall noise, but crappier fans will always give you irritating bearing noise, for instance, even though they may be quiet on average.
Unfortunately most (all?) manufacturers of silent computer products lie about noise levels.
For example, the Silent Boost heatsink/fan from Thermaltake is advertised as being as loud as 21 dBA. However, closer inspection will tell you that it uses an 80cm Panaflo 2450 RPM fan, and Panasonic says the fan alone (without the heatsink, which will add to the noise due to additional turbulence) is 28 dBA loud.
The same goes for all sorts of fans and PSUs advertised as being silent. Manufacturers exaggerate their claims, and the one with the lowest number typically sells the loudest product.
Jennifer Trosper said that Spirit should be up in a couple of weeks, and it's quite probable that it will be fully functional.
Steve Squyres mentioned a few times that during planning NASA estimated that 1 in every 3 days would be lost due to technical issues. Therefore, the time wasted isn't that big a deal, specially since no days were lost beforehand with Spirit (and none so far with Opportunity).
Also, 90 days is the design's minimal requirement (or as Squyres said, "when the warranty expires"). Due to the many safety margins used to design all subsystems, the actual lifespan is estimated to exceed that considerably.
Using an HP 49G, TI-89 or any high end calculator in those tests is probably going to slow you down with menus and multi-line displays.
I used an HP32SII when taking the SATs. It's a very practical programmable single line RPN. It obviously doesn't have any graphing, matrix or symbolic calculus capabilities, but it still satisfies most of my needs (I'm now a 4th year EE student). It's also a mean dice roller for D&D sessions:)
For all the rest I use either an HP 49G, Matlab, Octave or Maple.
Regular switching power supplies also operate in the ultrasonic range.
Well designed supplies are reasonably quiet (as one can verify by making them operate in lower frequencies), so pets tolerate them.
Likewise, badly designed supplies really pollute the airwaves. It's usually impossible to tune an AM radio within 20 meters of a cheap desktop computer PSU.
I actually like System Shock I better, but the sequel twisted my mind in a way I didn't think possible.
People familiar with the game will recall that Shodan controls security all over the levels, and one way to make things safer is to shoot security cameras. So you tend to have a completely paranoid attitude and gain a reflex to aim and shoot whenever you spot them.
A days after finishing the game I find myself at the mall. I casually go around a corner, and in a split second I twitch my head with the reflex. Turns out a camera appeared in the corner of my eye and I was pulling the imaginary trigger.
Fortunately I was discreet enough and no one noticed, but weird things were going on in my head:)
For starters, you analogy is flawed. Fixing a laptop involves replacing defective parts with new/refurbished ones. It's also easy to detect what's defective and what's not. Physicians don't work this way.
And what sort of "extra information" would you like to know? There's nothing else to say about how the laptop got damaged, only *why*. And knowing why it was put in the oven won't help you fix the problem.
And by the way, I don't have a problem with sharing stories, but I _do_ have a problem with people not minding their own business.
Re:I'm more amazed....
on
Baked Apple
·
· Score: 2, Insightful
He's being paid to fix it, not to ask questions.
As long as she's willing to pay money for the job, it's none of his business.
And that's one of the advantages diploid organisms have, allowing heterozygous organisms for even a deleterious mutation to be able to live normally.
So in a way this guy's right about nature's built in error tolerance methods. But he still throws around words like "chaos" and "unpredictability" without really saying anything remarkable.
This is only part 1 of what will supposedly be a series, but this looks nothing more to me than an artist's view of a computational problem. From a pragmatic perspective, it makes obvious observations, weak statements that only cite impressive concepts (out of dynamical systems theory, computer science and biology) and proposes no answers.
To wrap it up, he suggests the reader should question where Turing, Shannon and von Neumann were wrong. Well, guess what: these were all mathematicians and even though one may question why they studied particular topics, their mathematics isn't and never will be wrong because it's logically sound.
It's pretty obvious whenever the authors add tons of mostly irrelevant references which are mostly irrelevant to the topic in an attempt to make their research look thorough and important. I don't see how this is news to anyone who's gone through college...
I'm just saying that CmdrTaco and friends shouldn't think that their success as the creators of Slashdot gives them any license to be arrogant, especially while giving regular displays of gross ignorance.
Slashdot "editors" seem to take pride in their shitty spelling and grammar, and someone who actually takes their time to produce readable, correct text is a target for their contempt.
It all goes back to what we've all been saying for several years (and CmdrTaco has admitted it himself): if not for Slashdot, these guys would be flipping burgers.
Note that I'm not pressing anyone to act like a square -- I just want them to have a little more class.
As an EE student, I know how a switching power supply works, thanks. And actually, they first rectify and then make a pulsed signal at x kHz (where x is NOT a constant value), transform and rectify again, so this is not what I'm saying.
I meant that we'd have to transmit at 60 Hz, somehow transform to 20 kHz to use inside our households and then supply our appliances at this frequency. The appliances themselves would decide on what to do, and this would in general involve yet another transformation step. So we'd have 2 transformation steps instead of 1, which is down right idiotic.
The idea is that even thought switching power supplies use high frequency transformers, (1) the frequency changes drastically depending on the load, so providing a fixed 20 kHz feed is absolutely *useless*; (2) even if the frequency didn't change, different supplies need different frequencies; (3) not every device/machine needs a switching power supply (the higher consuming ones DON'T), so we'd be wasting a lot of energy in this transformation step.
God, it's amazing how much bullshit Slashdot can generate from such any subject. You guys should either go to school (and pay attention) or stop making uninformed "corrections".
I actually read your post and my criticism was targeted at "20kHz may not be ideal, but transformer efficiency is definitely not one".
One can't "just substitute ferrite cores instead of iron laminate" as you claim, because costs would be prohibitive. Our problem isn't a theoretical limitation. Consider large (MVA scale) transformers and the size of their cores. The efficiency gain you'd get from ferrites isn't all that great because the magnetic coupling that iron gives you is quite larger than what is achievable with ferrites (and this is why we have efficiencies on order of 99% on existing transformers). So despite the smaller hysteresis and foucault losses, the transformer wouldn't be so tiny as to compensate for the ferrite's price.
The "inherent size limitation" I talked about is based on the manufacturing costs. Ferrites are too expensive to be used on anything but small transformers due to their cores' small volume, and iron cores are actually quite excellent for us to consider an alternative. (Notice that I'm referring to large transformers and not to the ones found in consumer devices).
There are also manufacturing problems. For example, you'd have to build your large ferrite core from a bunch of relatively small ferrite blocks, which could be inconvenient as they're extremely fragile. And their fragility will grow with size, rendering construction trickier (or maybe impossible in practice, considering the need to transport the transformer? I don't know.)
Please go have a course on power conversion at the school of engineering if you're still in college. Here are some reasons against using 20 kHz:
1. Ferrite cores have obvious size limitations and are extremely expensive when compared to iron cores, so you can only build domestic appliances with your idea. Even so, most domestic appliances use DC anyway so why even supply them with high-frequency AC?
2. How do you suggest we transmit power over long distances? Using ferrite transformers at substations? *snicker*
So we'd end up transmitting at 60 Hz and then transforming to 20 kHz and then rectifying? This seems amazingly stupid to me.
Faraday's law states that the induced voltage on the ends of a coil is equal (in magnitude) to the derivative of the magnetic flux through the coil times its number of turns.
If you multiply the frequency by k, you multiply the derivative by k as well (we're dealing with sinusoidal signals here). Therefore, the voltage induced also ends up being multiplied by k.
For sinusoidal signals you have that: E = 4.44fNF, where:
E: voltage
f: frequency
N: number of turns in your winding
F: magnetic flux (the right symbol would be a phi)
So consider the transformer's primary winding. Suppose you connect it to a 127 V outlet, so E = 127 V (RMS). N is a fixed value, so let's ignore it in our analysis. We have that the larger the frequency, the smaller our flux will have to be. The flux is proportional to the current through the winding, so there you have it.
Disregarding losses, a transformer operating at 400 Hz will only draw 15% of the current of one operating at 60 Hz in order to magnetize its core. Therefore, if you design a transformer for 400 Hz you'll use a thinner wire gauge (among other things). But this will limit its use at 60 Hz as you've witnessed.
Regardless, this doesn't have much to do with my previous point. 400 Hz transformers are much less efficient if you use a ferromagnetic core. You can go around hysteresis losses by using ferrite cores, but your transformer will be larger. And ferrite cores can only be used for small transformers, so there's no way you'd be using them for power transmission. Your claim of higher frequencies being "better for devices" doesn't make sense. What does that even mean? As far as domestic devices are concerned, most of them are DC anyway so we'd end up rectifying the signal, thus rendering frequency irrelevant.
The skin effect is irrelevant at such low frequencies. As a matter of fact, your argument is used by audio equipment salesmen for tricking people into buying new cables and connectors and whatnot.
There is NO WAY a sinusoidal waveform at a few kHz will have a significant impact in signal power. There are plenty of usenet posts on this subject as well if you'd like to confirm my claims.
It might be easier if we switched from 60Hz to something around 20kHz.
This would be a very bad idea. As you may know, ferromagnetic materials present what is called the hysteresis cycle. If you don't know what this is, Google for it.
In short, what it means is that magnetic domains inside the material retain their orientation even after an external magnetic field has been switched off. This happens because disaligning the domains would require energy.
Transformers use ferromagnetic cores, so essentially the domains inside the core change orientation 60 times per second in 60 Hz systems. Doing so dissipates heat due to the fact that the domains "resist" being realigned in an opposite direction.
If you increase the frequency by a factor f, you end up increasing hysteresis losses by f as well, and this is a *very* big deal. In short, transformers would be much less efficient.
The band is back together. They have a new live album called RePlugged.
My favorite Tesla album is Five Man Acoustical Jam.
Back on topic, the engineer Tesla filed hundreds of patents (I've read differing reports about the exact number, but it usually lies between 600 and 1000). Many of them were classified and have stayed so ever since.
I believe Tesla was technically superior to Edison. Edison was only interested in conventional ideas which could eventually bring revenue. Tesla was interested in the innovation, no matter the expense.
Slashdot Mirror
It's revolting that something as pointless and ghetto as this made it to the front page.
True, but the Silent Boost is a processor cooler without any thermal control. The Panaflo runs on 12 V continuously.
Zalman, Thermaltake and others neglect to specify this, which is no surprise since their claims always clash with each other and with their suppliers'.
And there's also the subjective side of things, but that's a whole other issue. Two fans with the same noise emission levels aren't necessarily as pleasant, since their spectra may be completely different. Reducing RPMs will give you less overall noise, but crappier fans will always give you irritating bearing noise, for instance, even though they may be quiet on average.
For example, the Silent Boost heatsink/fan from Thermaltake is advertised as being as loud as 21 dBA. However, closer inspection will tell you that it uses an 80cm Panaflo 2450 RPM fan, and Panasonic says the fan alone (without the heatsink, which will add to the noise due to additional turbulence) is 28 dBA loud.
The same goes for all sorts of fans and PSUs advertised as being silent. Manufacturers exaggerate their claims, and the one with the lowest number typically sells the loudest product.
Jennifer Trosper said that Spirit should be up in a couple of weeks, and it's quite probable that it will be fully functional.
Steve Squyres mentioned a few times that during planning NASA estimated that 1 in every 3 days would be lost due to technical issues. Therefore, the time wasted isn't that big a deal, specially since no days were lost beforehand with Spirit (and none so far with Opportunity).
Also, 90 days is the design's minimal requirement (or as Squyres said, "when the warranty expires"). Due to the many safety margins used to design all subsystems, the actual lifespan is estimated to exceed that considerably.
It's Meg Ryan's orgasm clip from "When Harry met Sally".
Using an HP 49G, TI-89 or any high end calculator in those tests is probably going to slow you down with menus and multi-line displays.
:)
I used an HP32SII when taking the SATs. It's a very practical programmable single line RPN. It obviously doesn't have any graphing, matrix or symbolic calculus capabilities, but it still satisfies most of my needs (I'm now a 4th year EE student). It's also a mean dice roller for D&D sessions
For all the rest I use either an HP 49G, Matlab, Octave or Maple.
Regular switching power supplies also operate in the ultrasonic range.
Well designed supplies are reasonably quiet (as one can verify by making them operate in lower frequencies), so pets tolerate them.
Likewise, badly designed supplies really pollute the airwaves. It's usually impossible to tune an AM radio within 20 meters of a cheap desktop computer PSU.
I actually like System Shock I better, but the sequel twisted my mind in a way I didn't think possible.
:)
People familiar with the game will recall that Shodan controls security all over the levels, and one way to make things safer is to shoot security cameras. So you tend to have a completely paranoid attitude and gain a reflex to aim and shoot whenever you spot them.
A days after finishing the game I find myself at the mall. I casually go around a corner, and in a split second I twitch my head with the reflex. Turns out a camera appeared in the corner of my eye and I was pulling the imaginary trigger.
Fortunately I was discreet enough and no one noticed, but weird things were going on in my head
For starters, you analogy is flawed. Fixing a laptop involves replacing defective parts with new/refurbished ones. It's also easy to detect what's defective and what's not. Physicians don't work this way.
And what sort of "extra information" would you like to know? There's nothing else to say about how the laptop got damaged, only *why*. And knowing why it was put in the oven won't help you fix the problem.
And by the way, I don't have a problem with sharing stories, but I _do_ have a problem with people not minding their own business.
He's being paid to fix it, not to ask questions.
As long as she's willing to pay money for the job, it's none of his business.
And that's one of the advantages diploid organisms have, allowing heterozygous organisms for even a deleterious mutation to be able to live normally.
So in a way this guy's right about nature's built in error tolerance methods. But he still throws around words like "chaos" and "unpredictability" without really saying anything remarkable.
This is only part 1 of what will supposedly be a series, but this looks nothing more to me than an artist's view of a computational problem. From a pragmatic perspective, it makes obvious observations, weak statements that only cite impressive concepts (out of dynamical systems theory, computer science and biology) and proposes no answers.
To wrap it up, he suggests the reader should question where Turing, Shannon and von Neumann were wrong. Well, guess what: these were all mathematicians and even though one may question why they studied particular topics, their mathematics isn't and never will be wrong because it's logically sound.
I'm not impressed.
Anyway, this comic seems appropriate.
True.
I'm just saying that CmdrTaco and friends shouldn't think that their success as the creators of Slashdot gives them any license to be arrogant, especially while giving regular displays of gross ignorance.
If anything, it makes them look like fools.
Well said.
Slashdot "editors" seem to take pride in their shitty spelling and grammar, and someone who actually takes their time to produce readable, correct text is a target for their contempt.
It all goes back to what we've all been saying for several years (and CmdrTaco has admitted it himself): if not for Slashdot, these guys would be flipping burgers.
Note that I'm not pressing anyone to act like a square -- I just want them to have a little more class.
Try changing the encoding (in View -> Character Encoding).
As an EE student, I know how a switching power supply works, thanks. And actually, they first rectify and then make a pulsed signal at x kHz (where x is NOT a constant value), transform and rectify again, so this is not what I'm saying.
I meant that we'd have to transmit at 60 Hz, somehow transform to 20 kHz to use inside our households and then supply our appliances at this frequency. The appliances themselves would decide on what to do, and this would in general involve yet another transformation step. So we'd have 2 transformation steps instead of 1, which is down right idiotic.
The idea is that even thought switching power supplies use high frequency transformers, (1) the frequency changes drastically depending on the load, so providing a fixed 20 kHz feed is absolutely *useless*; (2) even if the frequency didn't change, different supplies need different frequencies; (3) not every device/machine needs a switching power supply (the higher consuming ones DON'T), so we'd be wasting a lot of energy in this transformation step.
God, it's amazing how much bullshit Slashdot can generate from such any subject. You guys should either go to school (and pay attention) or stop making uninformed "corrections".
One can't "just substitute ferrite cores instead of iron laminate" as you claim, because costs would be prohibitive. Our problem isn't a theoretical limitation. Consider large (MVA scale) transformers and the size of their cores. The efficiency gain you'd get from ferrites isn't all that great because the magnetic coupling that iron gives you is quite larger than what is achievable with ferrites (and this is why we have efficiencies on order of 99% on existing transformers). So despite the smaller hysteresis and foucault losses, the transformer wouldn't be so tiny as to compensate for the ferrite's price.
The "inherent size limitation" I talked about is based on the manufacturing costs. Ferrites are too expensive to be used on anything but small transformers due to their cores' small volume, and iron cores are actually quite excellent for us to consider an alternative. (Notice that I'm referring to large transformers and not to the ones found in consumer devices).
There are also manufacturing problems. For example, you'd have to build your large ferrite core from a bunch of relatively small ferrite blocks, which could be inconvenient as they're extremely fragile. And their fragility will grow with size, rendering construction trickier (or maybe impossible in practice, considering the need to transport the transformer? I don't know.)
1. Ferrite cores have obvious size limitations and are extremely expensive when compared to iron cores, so you can only build domestic appliances with your idea. Even so, most domestic appliances use DC anyway so why even supply them with high-frequency AC?
2. How do you suggest we transmit power over long distances? Using ferrite transformers at substations? *snicker*
So we'd end up transmitting at 60 Hz and then transforming to 20 kHz and then rectifying? This seems amazingly stupid to me.
If you multiply the frequency by k, you multiply the derivative by k as well (we're dealing with sinusoidal signals here). Therefore, the voltage induced also ends up being multiplied by k.
For sinusoidal signals you have that: E = 4.44fNF, where:
E: voltage
f: frequency
N: number of turns in your winding
F: magnetic flux (the right symbol would be a phi)
So consider the transformer's primary winding. Suppose you connect it to a 127 V outlet, so E = 127 V (RMS). N is a fixed value, so let's ignore it in our analysis. We have that the larger the frequency, the smaller our flux will have to be. The flux is proportional to the current through the winding, so there you have it.
Disregarding losses, a transformer operating at 400 Hz will only draw 15% of the current of one operating at 60 Hz in order to magnetize its core. Therefore, if you design a transformer for 400 Hz you'll use a thinner wire gauge (among other things). But this will limit its use at 60 Hz as you've witnessed.
Regardless, this doesn't have much to do with my previous point. 400 Hz transformers are much less efficient if you use a ferromagnetic core. You can go around hysteresis losses by using ferrite cores, but your transformer will be larger. And ferrite cores can only be used for small transformers, so there's no way you'd be using them for power transmission. Your claim of higher frequencies being "better for devices" doesn't make sense. What does that even mean? As far as domestic devices are concerned, most of them are DC anyway so we'd end up rectifying the signal, thus rendering frequency irrelevant.
If you insist on this, prove it.
The skin effect is irrelevant at such low frequencies. As a matter of fact, your argument is used by audio equipment salesmen for tricking people into buying new cables and connectors and whatnot.
There is NO WAY a sinusoidal waveform at a few kHz will have a significant impact in signal power. There are plenty of usenet posts on this subject as well if you'd like to confirm my claims.
Anyway, stop trolling.
This would be a very bad idea. As you may know, ferromagnetic materials present what is called the hysteresis cycle. If you don't know what this is, Google for it.
In short, what it means is that magnetic domains inside the material retain their orientation even after an external magnetic field has been switched off. This happens because disaligning the domains would require energy.
Transformers use ferromagnetic cores, so essentially the domains inside the core change orientation 60 times per second in 60 Hz systems. Doing so dissipates heat due to the fact that the domains "resist" being realigned in an opposite direction.
If you increase the frequency by a factor f, you end up increasing hysteresis losses by f as well, and this is a *very* big deal. In short, transformers would be much less efficient.
The skin effect is only relevant with frequencies of the order of MHz (or higher).
Way to go on retelling the story of one of the worst movies ever made, 2 years late.
Am I supposed to agree with the reviewer and cheer?
The band is back together. They have a new live album called RePlugged.
My favorite Tesla album is Five Man Acoustical Jam.
Back on topic, the engineer Tesla filed hundreds of patents (I've read differing reports about the exact number, but it usually lies between 600 and 1000). Many of them were classified and have stayed so ever since.
I believe Tesla was technically superior to Edison. Edison was only interested in conventional ideas which could eventually bring revenue. Tesla was interested in the innovation, no matter the expense.