Ohm's Law Problem
in [Design]
|
Prev: A novel way to measure magnetic fields, and DC current withouta shunt?
Next: 240V AC power switch - based on current drawn from outlet
From: Jim Thompson on 17 Feb 2010 11:30 On Wed, 17 Feb 2010 08:25:16 -0800, Charlie E. <edmondson(a)ieee.org> wrote: >On Wed, 17 Feb 2010 07:11:28 -0500, Bitrex ><bitrex(a)de.lete.earthlink.net> wrote: > >> >>> Bitrex, >>> Do you have a degree presently? Did you get another degree back in >>> the deeps of time? If so, then go for a masters in EE. Easier, and >>> more fun! >>> >>> Charlie >> >>No such luck I'm afraid, Charlie. I did several semesters of college as >>a Comp Sci major, back in the late 90s, but I made a poor choice of >>school and things didn't work out. I was searching for somewhere to >>transfer to when I fell ill the first time. After recovering from that >>I had to give up my educational aspirations in favor of making a living, >>at least until I fell seriously ill the second time...Go on like that >>for a while and suddenly a decade has passed. >> >>I do have a lot of "gen ed" prerequisite courses for transfer credit >>under my belt, I did them here and there at various community colleges >>(and Harvard's adult education program) over the years with the hope >>that someday I'd have the chance to enroll in a full degree program. >>Circumstances have granted me that opportunity now, and I feel this is >>probably my last chance. > >then, your greatest problem might be just getting accepted into a >program. Many EE programs are 'impacted', i.e. they have many more >applicants than they have slots for students, so they become very >selective. I know that twenty years ago, when I decided to go back >and get an EE degree, I ended up moving out of state to get accepted >to a program. Later, I found that I could get a masters in EE, even >with my bachelors in psychology, and so was able to move back... > >Charlie Just put on your application that you were tutored by Bill Ayers... you'll get admitted immediately... particularly if you apply to Berkeley ;-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
From: Joel Koltner on 17 Feb 2010 12:38 "Bitrex" <bitrex(a)de.lete.earthlink.net> wrote in message news:mqadnYzpo5LyQObWnZ2dnUVZ_t6dnZ2d(a)earthlink.com... > Circumstances have granted me that opportunity now, and I feel this is > probably my last chance. I say go for it. I don't think it's your last chance, but 30-ish is definitely a good time to return to school: You're still young enough you don't stick out like a sore thumb from the standpoint of getting job internships, going to recruiting events, etc.
From: Joel Koltner on 17 Feb 2010 12:42 "Charlie E." <edmondson(a)ieee.org> wrote in message news:nt5on5h3ssb5aqrckpof75947rfs055vn1(a)4ax.com... > Many EE programs are 'impacted', i.e. they have many more > applicants than they have slots for students, so they become very > selective. One way around this is to sign up initially as a "non-degree seeking student" -- you're just paying tuition but not impacting the school's "quality," so usually anyone can get in as such. Then you go around and find a few sympathetic professors who'll let you sign up for their EE classes (usually non-degree seeking student require instruction permissoin to take any so-called "professional" level courses), do well in them, and then the next year petition for acceptance into the department... now with several professors on your side.
From: Joerg on 17 Feb 2010 13:14 Jon Kirwan wrote: [...] > This moves now into a protracted discussion, which I'd better > not enter deeply here. But ad hoc rules, regardless of > apparent value, are rarely any more than the vague appearance > of a common "rule" from specific, repeated observation. Not > a very good foundation, as ideas go, to build upon. As such > things doesn't extrapolate very well to areas we haven't yet > trod. (More on this in a moment.) > > One can succeed with induction like this, almost as well with > Tarot cards, as necromancy, as pretty much any idea that > "seems to work" for some point in time and understanding. > Some are okay as far as they go, of course. But it is very > much like unearthing stones (fragments of utility) to make a > farm wall. Each bit of this kind of inductive knowledge > exists by itself and is barely connected to any other bit. > Works great so long as you don't go outside the experience > which created it. > > Still, a farm wall is useful and may keep the cows in. No > arguing with that. If you blow a hole in one part of it, the > rest stays, too. That is it's power, in a way. A rock over > on this part of the wall does NOT much depend upon a rock > over 'there' for its strength. But at the same time, that's > also its weakness. Structures formed like this cannot be > efficiently used to carry extremely heavy loads, since almost > none of it builds upon the strengths of other parts. They > must be in close proximity to cooperate. > However, you have picked a rather extreme example. And even with the farm wall people have managed early on by experimenting how to arrange them into arrays so they would cling to each other better. I could take an example of the other extreme: Winemakers and grape growers. They have induced pretty much everything, until recently there hasn't been a real science around any of this. Yet mighty fine wines have been produced even back in the days of the Romans. And whether the science around it really benefited the trade is highly disputed. > Science, of late, has focused upon deductive theory -- > preferring to test and falsify based up deduction of general > theory predicted into specific cases, given the particulars. > It yields knowledge structures that are quite different. > Induction still plays a role, but not nearly as important as > before. In science knowledge, the parts are highly unified. > > So in keeping with the above 'farm wall' concept, I'd now > introduce the archway concept. Stones in science are shaped > and fashioned so that they cooperate with each other, like > stones in a grand, curving archway; with each piece lending > strength to other pieces. The result is a structure that > _can_ carry a heavy load. Of course, if you blow a huge hole > in it, the whole thing falls down. ;) > > Same nuggets of stone, two different structures resulting. > But we don't know how ancient tribes found out. It might also have been something like "Oh, look, it holds up better that way". > In fact, what separates science from other forms of knowledge > isn't that science is "true" and the others less so. It's > the unifying nature of the resulting body. It's no more > "true" than anything else. But it is MUCH more unified. > > I like to think of science knowledge as being "Borg." You > can easily tell just how Borg some bit of knowledge is by how > well connected it happens to be with "the collective." If it > isn't connected into the collective, it's not Borg. And it's > not science. Doesn't mean it is wrong. Doesn't mean it is > useless. Just means it's not Borg/science. > I think both deduction and Borg have their place. But I bristle at the notion that we should refrain from attempting anything unless we have the science down pat. In my job it's 50:50. When I design a switcher there's lots of sheets of math and stuff, then I draw it up. Clearly the science path you prefer. When I do EMC it's more the opposite, seat of the pants. Without practical experience one typically gets nowhere. There were projects where engineers tried their darndest to calculate EMI effects, using software that cost as much as a nice family sedan. Didn't solve it. Now I don't want to sound arrogant here but 15-25h on my part and the root causes were found. Some initial disbelief at times but then they ran it through the EMC lab one more time and ended up with a nice report of conformity report in hand with the remark "Passed". Typically with very cushy margins. > Jon > > P.S. There is a great book on knowledge; IMHO very easily > grasped and extremely very well argued in six separate > lectures. The author is Jacob Bronowski and the book is > called, "The Origins of Knowledge and Imagination," 1979. > Copies are available for very little money (only a few > dollars) via abebooks or alibris. I consider it to be an > excellent primer, enjoyably told, and I gladly recommend it > to anyone. No matter how you come down on anything I write, > I think you'll enjoy his lectures -- they were given to very > young students and are very easy to follow, while > simultaneously engaging, too. I hope some day I'll have more time to devote to the more philosophical books. Right now I work in so many new fields that I have to constantly study (mostly ME stuff). -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Jon Kirwan on 17 Feb 2010 13:46
On Wed, 17 Feb 2010 10:14:41 -0800, Joerg <invalid(a)invalid.invalid> wrote: >Jon Kirwan wrote: > >[...] > >> This moves now into a protracted discussion, which I'd better >> not enter deeply here. But ad hoc rules, regardless of >> apparent value, are rarely any more than the vague appearance >> of a common "rule" from specific, repeated observation. Not >> a very good foundation, as ideas go, to build upon. As such >> things doesn't extrapolate very well to areas we haven't yet >> trod. (More on this in a moment.) >> >> One can succeed with induction like this, almost as well with >> Tarot cards, as necromancy, as pretty much any idea that >> "seems to work" for some point in time and understanding. >> Some are okay as far as they go, of course. But it is very >> much like unearthing stones (fragments of utility) to make a >> farm wall. Each bit of this kind of inductive knowledge >> exists by itself and is barely connected to any other bit. >> Works great so long as you don't go outside the experience >> which created it. >> >> Still, a farm wall is useful and may keep the cows in. No >> arguing with that. If you blow a hole in one part of it, the >> rest stays, too. That is it's power, in a way. A rock over >> on this part of the wall does NOT much depend upon a rock >> over 'there' for its strength. But at the same time, that's >> also its weakness. Structures formed like this cannot be >> efficiently used to carry extremely heavy loads, since almost >> none of it builds upon the strengths of other parts. They >> must be in close proximity to cooperate. > >However, you have picked a rather extreme example. And even with the >farm wall people have managed early on by experimenting how to arrange >them into arrays so they would cling to each other better. Perhaps I wasn't very clear. My example was _abstractly_ drawn. I was speaking with an allegory here. >I could take an example of the other extreme: Winemakers and grape >growers. They have induced pretty much everything, until recently there >hasn't been a real science around any of this. Yet mighty fine wines >have been produced even back in the days of the Romans. And whether the >science around it really benefited the trade is highly disputed. The point was allegorical. And missed, I see. My fault. And as I said, this is getting far afield. So I'll leave it for the book I recommended to paint better than I have. >> Science, of late, has focused upon deductive theory -- >> preferring to test and falsify based up deduction of general >> theory predicted into specific cases, given the particulars. >> It yields knowledge structures that are quite different. >> Induction still plays a role, but not nearly as important as >> before. In science knowledge, the parts are highly unified. >> >> So in keeping with the above 'farm wall' concept, I'd now >> introduce the archway concept. Stones in science are shaped >> and fashioned so that they cooperate with each other, like >> stones in a grand, curving archway; with each piece lending >> strength to other pieces. The result is a structure that >> _can_ carry a heavy load. Of course, if you blow a huge hole >> in it, the whole thing falls down. ;) >> >> Same nuggets of stone, two different structures resulting. > >But we don't know how ancient tribes found out. It might also have been >something like "Oh, look, it holds up better that way". You didn't get the allegory, it seems, so let's 'hold off' on a response from me on this. >> In fact, what separates science from other forms of knowledge >> isn't that science is "true" and the others less so. It's >> the unifying nature of the resulting body. It's no more >> "true" than anything else. But it is MUCH more unified. >> >> I like to think of science knowledge as being "Borg." You >> can easily tell just how Borg some bit of knowledge is by how >> well connected it happens to be with "the collective." If it >> isn't connected into the collective, it's not Borg. And it's >> not science. Doesn't mean it is wrong. Doesn't mean it is >> useless. Just means it's not Borg/science. > >I think both deduction and Borg have their place. But I bristle at the >notion that we should refrain from attempting anything unless we have >the science down pat. Of course!! Engineers must _design_ in the here-and-now with whatever is available for the task at hand. I certainly wasn't arguing there. >In my job it's 50:50. When I design a switcher >there's lots of sheets of math and stuff, then I draw it up. Clearly the >science path you prefer. When I do EMC it's more the opposite, seat of >the pants. Without practical experience one typically gets nowhere. >There were projects where engineers tried their darndest to calculate >EMI effects, using software that cost as much as a nice family sedan. >Didn't solve it. Now I don't want to sound arrogant here but 15-25h on >my part and the root causes were found. Some initial disbelief at times >but then they ran it through the EMC lab one more time and ended up with >a nice report of conformity report in hand with the remark "Passed". >Typically with very cushy margins. I think this is why there is art _and_ science in engineering. If I had to put a cap on what you are saying, I'd simply say that you should choose the best at hand. If there is very good, quantitatively predictive theory floating around for something, use it. If not, use what you have. Trial and error certainly has a place. So does an instinct that is developed through what you suggested, "experiment, experiment and experiment." >> P.S. There is a great book on knowledge; IMHO very easily >> grasped and extremely very well argued in six separate >> lectures. The author is Jacob Bronowski and the book is >> called, "The Origins of Knowledge and Imagination," 1979. >> Copies are available for very little money (only a few >> dollars) via abebooks or alibris. I consider it to be an >> excellent primer, enjoyably told, and I gladly recommend it >> to anyone. No matter how you come down on anything I write, >> I think you'll enjoy his lectures -- they were given to very >> young students and are very easy to follow, while >> simultaneously engaging, too. > >I hope some day I'll have more time to devote to the more philosophical >books. Right now I work in so many new fields that I have to constantly >study (mostly ME stuff). Hehe. Me, too. However, I think that book is extremely readable and enjoyable in each and every paragraph. You'll find it no trouble at all. And cheap, besides. Why not expose yourself to something merely on a lark once in a while. Might expand a horizon and find something fun you didn't realize was in you. ;) Jon |