Circuits I & II suggestions.
- Thread starter WBahn
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I realize that, but I'd still be willing to bet you would get the overwhelming majority of them correct.
10,12,15,18,22,27,33,39,47,56,68,82, (100)
Split the difference, rounding down.
10,[11],12,[13],15,[16],18,[20],22,[24],27,[30],33,[36],39,[43],47,[51],56,[62],68,[75]82,[91] (100)
As we can see, this rule produces the correct value for all twelve of the new additions. I don't know if I have ever noticed this before or not -- if I have I didn't remember it.
I wonder if it works from the E6 to the E12
10,[12],15,[18],22,[27],33,[*40*=>39],47,[*57*=>56],68,[*84*=>82], (100)
Nope. But there is an understandable pattern. The bias toward lower values gets stronger the wider the gap, so in the first third you round down, in the second third you round down and reduce by one, and in the last third you round down and reduce by two.
Let's see if there is an easy way to construct the E6.
10,15,22,33,47,68, (100)
Here you are increasing by 50% (roughly), which would make it
10,15,22,33,*49*=>47,*70*=>68
Here once you get past the first third, you round down and reduce by two.
Like you, I seldom use anything from the E24 series. The three exceptions are 20, 51 (basically 50), and 75 because they work well with back of the envelope and mental computations.
10,12,15,18,22,27,33,39,47,56,68,82, (100)
Split the difference, rounding down.
10,[11],12,[13],15,[16],18,[20],22,[24],27,[30],33,[36],39,[43],47,[51],56,[62],68,[75]82,[91] (100)
As we can see, this rule produces the correct value for all twelve of the new additions. I don't know if I have ever noticed this before or not -- if I have I didn't remember it.
I wonder if it works from the E6 to the E12
10,[12],15,[18],22,[27],33,[*40*=>39],47,[*57*=>56],68,[*84*=>82], (100)
Nope. But there is an understandable pattern. The bias toward lower values gets stronger the wider the gap, so in the first third you round down, in the second third you round down and reduce by one, and in the last third you round down and reduce by two.
Let's see if there is an easy way to construct the E6.
10,15,22,33,47,68, (100)
Here you are increasing by 50% (roughly), which would make it
10,15,22,33,*49*=>47,*70*=>68
Here once you get past the first third, you round down and reduce by two.
Like you, I seldom use anything from the E24 series. The three exceptions are 20, 51 (basically 50), and 75 because they work well with back of the envelope and mental computations.
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Look here for a product that appears to do a lot of what you want:
http://www.digilentinc.com/Products/Detail.cfm?Prod=ANALOG-DISCOVERY
More expensive ($99 for students, $159 for faculty and $199 for the unwashed masses) than the audio port of a PC but the cost versus value is incredible.
There is a big brother that is more expensive ($199, $299 and $599) but has a power supply and solderless breadboard as well as other improved functions:
http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,842,883&Prod=EEBOARD
That's a good suggestion and I'll check them out.
I haven't bought anything from Digilent in quite some time. I was one of their earliest customers and, in general, was quite happy with their stuff even though their documentation seemed to have more errors in it than seemed reasonable.
I haven't bought anything from Digilent in quite some time. I was one of their earliest customers and, in general, was quite happy with their stuff even though their documentation seemed to have more errors in it than seemed reasonable.
I went and checked out the Digilent stuff and think it will work well.
I ordered the Discovery module and also the parts kit that could be bundled with it. For $50, it actually looks like a pretty decent collection. I also bought the TINA student license (for just $7) and a couple other things.
I ordered the Discovery module and also the parts kit that could be bundled with it. For $50, it actually looks like a pretty decent collection. I also bought the TINA student license (for just $7) and a couple other things.
Wow - what an honor to teach Circuits I and II at Mines! Congrats!
One of the things that has helped me through the years that my circuits I and II professors pressed on me is that a voltage is not on a single node - voltages are only across two nodes, and we had to label every voltage on our schematics with a + and -. Of course, it's common in industry to just label a node with a voltage name assuming the reference to ground, but you need to learn to walk before you run.
Can the students still use the school labs to learn the concepts anyway? Maybe offer extra credit for students that spend some time in the lab even though it's not part of the ciriculum. This seems the way with everything these days - simulate everything - test nothing until you receive the product. My boss wants me to design a complex mixed signal card with minimal bread boarding and no respin between development and production. *slap forehead*.
Honestly, I wouldn't recommend a school to a budding engineer if the first critical classes aren't at least partially lab based. You absolutely have to know how to use a oscilloscope, waveform generator, breadboard, dmm, isolation transformer, variac, etc to get a job from me. I would be going to the dean and doing everything in my power to get this new policy changed. Mines has always been on my top 10 list of engineering schools - this comes as sad news to me.
If you're using PSPICE then I'd maybe try to figure out how to put a spice question on exams that will give a illogical solution - just to drive home the point that simulations are only as good as you make them. Maybe the small 'm' versus 'Meg' would be a good one?
One of the things that has helped me through the years that my circuits I and II professors pressed on me is that a voltage is not on a single node - voltages are only across two nodes, and we had to label every voltage on our schematics with a + and -. Of course, it's common in industry to just label a node with a voltage name assuming the reference to ground, but you need to learn to walk before you run.
Can the students still use the school labs to learn the concepts anyway? Maybe offer extra credit for students that spend some time in the lab even though it's not part of the ciriculum. This seems the way with everything these days - simulate everything - test nothing until you receive the product. My boss wants me to design a complex mixed signal card with minimal bread boarding and no respin between development and production. *slap forehead*.
Honestly, I wouldn't recommend a school to a budding engineer if the first critical classes aren't at least partially lab based. You absolutely have to know how to use a oscilloscope, waveform generator, breadboard, dmm, isolation transformer, variac, etc to get a job from me. I would be going to the dean and doing everything in my power to get this new policy changed. Mines has always been on my top 10 list of engineering schools - this comes as sad news to me.
If you're using PSPICE then I'd maybe try to figure out how to put a spice question on exams that will give a illogical solution - just to drive home the point that simulations are only as good as you make them. Maybe the small 'm' versus 'Meg' would be a good one?
Thanks. I'm curious, how'd you know it was Mines?
I got my undergrad and masters at Mines and, as a grad student, taught the controls lab and microcontroller lab back in the early '90s. I also taught Circuit I and coordinated senior design my last year there before going to work as an IC designer for a small company. For many years I taught part-time at UCCS and got to teach for a year at the Air Force Academy (now THAT was an honor and a dream come true). Last year I taught as a visiting prof at Mines teaching Comp Sci courses and this next year I will be teaching a mix of EE and comp sci. I'm hoping to get a permanent gig there and finish out my professional career there, but the competition for faculty positions is pretty fierce. I almost had one the year before last by lost out to someone that has degrees from both MIT and Stanford. Hell, I would have hired her over me, too!
The move to deemphasize labs isn't so much a "policy" and it isn't at all new. Rather, it is a creeping trend that is driven by budget and resources. My understanding that even MIT and other top-tier private schools ar enot immune to it.
Realistically, I think the only way to stem the progression is to figure out ways to get the students required hands-on experiences that do not require equipment or faculty resources. I think that means requiring that students purchase their own equipment and supplies, such as the digilent setup. If you are required to use it for several courses, then the cost of ownership per course goes down significantly.
I make a pretty big deal about labelling voltages and currents properly, which means that polarities must be indicated, and emphasizing the distinction between generic voltages and refered voltages. A big part fo that emphasis is understanding that voltage, by definition, only makes sense as a measrement between two points.
Hello,
The wiki has two interesting pages about resistors and their values:
http://en.wikipedia.org/wiki/Resistors
http://en.wikipedia.org/wiki/Preferred_number#E_series
With the E-series the steps are 10^(1/x) , where x is the number of the E-series.
Bertus
The wiki has two interesting pages about resistors and their values:
http://en.wikipedia.org/wiki/Resistors
http://en.wikipedia.org/wiki/Preferred_number#E_series
With the E-series the steps are 10^(1/x) , where x is the number of the E-series.
Bertus
Well, it really depends on how motivated the student is towards a career in Electrical Engineering (since few now consider electronics a hobby).
I've been around enough to know some of you guy's stories from other posts. I remember you saying once you worked at Mines and I figure I might actually run into you someday, especially if I ever get the chance to go to one of the IEEE power meetings. I'm in Littleton working for one of the big employers down here - don't want to name it by name though.
This is a total cop-out by the schools. How the hell are you suppose to learn to be an engineer if you don't get the chance to build something using real engineer tools!??!? All the while tuition has increased at least 2x from when I graduated in '07, and the football teams always have all the equipment they need - why don't the EE's get a lab to learn circuit basics? (I don't think mines has a football team, but you get my point) and the president's drive nicer cars.
A school that doesn't encourage hands-on learning is not a school I'd want to go to. I learned so much in the labs at school. It is very helpful to have a TA there to see where you may have made a mistake, or correct you where your theory went askew. Not to mention learning how to use an oscilloscope, waveform generator, etc. My school even had a old Tek curve tracer! It really is a priceless experience.
I implore you to push-back and make sure new prospective EE's get the experience they need and deserve from such a good school.
Truth.
My school tried to take away the lab requirement from Physics. At that point physics is just a word-problem math course.
Along the same line, and I apologize if I'm critiquing your teaching style, emphasize the mechanics and forces before you teach the math. Teachers that have been in the field for a long time tend to teach that such and such occurs BECAUSE of the numbers, which is like saying the news happened because someone wrote a story. Principles explained in english, then math.
Yes and no. It's a rational shift in strategy in response to the distorted market forces placed upon them.
Only about 1/3rd of revenues to a university come directly from the students and their taxpayer-funded loans. In other words, the "customers" are not so much the students themselves as it is government bureaucrats and, distantly, taxpayers. The later success or failure of the students has some bearing on later revenue (from highly successful alumni and their employers, for example) but not nearly as much influence as, well, politics.
Just like publicly held companies, the incentives are biased towards short term gain at the expense of long term success. So cut the lab budget and hope nobody notices.
It's actualy somewhat more interesting that the wiki reveals because if you were to start with a clean piece of paper and come up with a set of preferred values you wouldn't end up with quite the same sequence. As near as I can tell (me and some others got interested and did some digging many years ago, so maybe information has since be put online) the reasons for why a few of the values were chosen has been lost to history.
On of the exercises I have students do is to start from scratch with the following problem (or some variant):
You are going to manufacture a component with a tolerance of 5%. Since the values you will need to make (and vendors will need to stock) will span several orders of magnitude, say ten, you want to choose a set of preferred values that span one decade such that the number of distinct values is a minimum and that any desired value is within the tolerance range of one of a preferred value.
It's interesting to see the number of students that struggle with turning the basic concept into a mathematical construct, even after walking through the theory in class. Then even the students that don't have any problem with that tend to be blind toward the practical aspect and want to have the preferred values be ideal, irrational values. But that gives an ideal opportunity to talk about these issues.
Once they have done that, I add the constraint that the preferref values must be integers in the 10 to 100 decade. I then add the goal of having the preferred values in the 10% and 20% ranges be subsets of the 5% range.
I do this before mentioning the E6, E12, or E24 series so that very few students are aware of it. With this background, they then seem to grasp the preferred values pretty easily (much more easily than when I used to just present them in lecture) and even the higher series and the slight disconnects between the E24 and E48 series.
At the institutional level, I definitely agree. Not so much as the departmental level, which have real budget constraints.
The problem is that the money coming into the school just doesn't make it to the departments (the same way that money in public K12 just doesn't make it to the classroom).
When I was teaching at UCCS as an adjunct (called "honoraria" there), the pay was $2000 per course. That didn't change the entire decade (roughly 1998 to 2008) I was teaching there and I did some searching and ran across a 1994 CCHE (Colorado Commission on Higher Education) report that specifically stated that UCCS needed to double its $2000 honoraria rate, which hadn't changed in many years at that time, in order to be competitive with other institutions. In 1995 I was an adjunct at Mines getting $5000/course, so that recommendation definitely wasn't out-of-line. So, despite tuition going up at well over twice the rate of inflation every year, the school paid its adjunct instructors the same rate for twenty years. It finally raised that a few years back from $2000 to $2300 and used the 15% increase as part of the justification for a huge tuition hike the following year.
The adjunct rate at Mines has been similarly stalled. It has been nearly 20 years since I was an adjunct in '95 and the rate has only increased by 20% over that time period. Since there are no benefits for adjuncts, I couldn't afford to even consider such a position these days, no matter how much I love teaching there.
Now, part of that is our own damn fault. Like flight instructors, there are lots of people willing to teach as an adjunct for low pay and so low pay (and no benefits) dominates the adjunct world. I don't have a big problem with that in and of itself because it is a relfection of market forces and, as a strong believer in the free market, I have to accept the bad with the good. What I have the problem with is that the students are not benefiting from it in lower tuition rates.
People keep demanding that we spend more to improve education (both K12 and higher), but don't demand that there actually be any improvement. So we spend more, get no improvement, and then demand that we spend more to improve education.
Oh, Mines has a football team and the last couple years it's actually done fairly well. But you certainly don't have students being recruited to the athletic programs and getting admitted with lower standards just because they are good athletes. It's odd, in a way. Other schools justify their athletic programs, in part, on the claim that physical fitness is an important part of life and should be a part of the college experience, yet they don't require the average student to take any kind of physical education at all. Mines, on the other hand, requires four semesters of it. I guess other schools see physical education as a spectator activity while Mines knows that no on is going to get any physical fitness benefit from watching ITS teams play!
I don't have too much of a problem with schools that have lavish sports programs as long as those sports programs are paying for themselves -- and many do and also are a significant source of revenue for the school as a whole. I think it is a sad commentary on society, but the market allows for sad commentaries. At the K12 level I have a much bigger problem because I think many schools have taxpayer-funded athletic budgets that are completely out of proportion with the notion of doing the most good for the greatest number of students. But that's another discussion entirely.
I'd love to and I'm doing what I can, but as visiting faculty my imfluence is pretty much non-existent. For one thing, at the level I'm at it is a case of preaching to the choir.
I try to balance the two. The math models the behavior of what we see, allowing us to describe and predict that behavior. But, as you will notice in lots of my posts, I like to describe what is happening in terms of a qualitative chain of events -- an increase in temperature causes and expansion in the bar the strain gage is mounted on, which causes the resistor elements to lengthen and and narrow, which causes an increase in resistance because you have to have a higher voltage to get the same current through a narrower and longer pipe, which causes ....
This makes it fairly easy to keep coming back to the point that the mathematical models are just that, models that capture the important traits, but not all of the traits and not to perfection.
I think you mean imperfection. The math describes a precise model, it's nature that instills the imperfection to the traits.
No, that's correct. He is stating that the models are only good at capturing the important traits of the real world. It is the incomplete model that does not capture the traits of the real world to perfection.I think you mean imperfection. The math describes a precise model, it's nature that instills the imperfection to the traits.
You misunderstood what I was saying because you assumed too much.
For example, you can model the resistance of a resistor using Ohm's law and also add in the thermal variations to the resistor. This model gives a precise description of a idealistic resistor. Nature also add noise to the real world, which makes the model imperfect. I never said that the models accurately reflect the real world. I said the math describes a precise model and that nature adds imperfections.
He meant the models do not capture real life. I assume you are trying to respond to what you quoted...I think you mean imperfection. The math describes a precise model, it's nature that instills the imperfection to the traits.
