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2014 November 17

Faculty writing community

Filed under: Circuits course — gasstationwithoutpumps @ 20:35
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Eric L. Muller wrote in Developing the Faculty as a Writing Community | AAUP,

I have also come to see how many other pleasures and labors of life are enhanced by companionship and accountability. Lots of people exercise more in groups, read more books with groups, lose more weight in groups. Wouldn’t it stand to reason that many faculty members might write more in groups, too?

That was a question that the Center for Faculty Excellence (CFE) at UNC at Chapel Hill set out to explore in the summer of 2013. The CFE is the university’s pan-campus faculty development center. Together with the Institute for the Arts and Humanities in the College of Arts and Sciences, the CFE piloted the Summer Writing Group program for faculty members across the university. The response was enthusiastic.

He went on to describe what sounds like a fairly successful experiment in faculty development.  I note that it did not appear to include any engineering or science faculty, though perhaps there were one or two in the “completely interdisciplinary” groups.

It sounds like an interesting idea, and it probably would have helped me last summer while I was trying to work on my textbook for the bioengineering electronics class.  I ended up practicing all sorts of “creative procrastination” instead of writing.  I got some stuff done on the book over the summer, but not nearly as much as I had hoped at the beginning of the summer. A writing group may have helped me keep my nose to the grindstone (a metaphor I’ve always found rather gross if taken literally).  I don’t know how much I’ll get done before I have to use the book in the Spring, since I’m teaching two classes each quarter, as well as all the work of being undergrad director and program chair for the bioengineering program.

I’ve not been part of writing group since grad school, when I was in a poetry-writing group with a bunch of people twice my age or older. Having a monthly meeting did help me then, and it was important that we read each others’ work and took it seriously (not just providing rah-rah comments). I’m not sure that the UNC approach would help much, unless the other faculty were close enough in their expertise to be willing and able to read and comment on the draft chapters.

Have any of the faculty who read this blog ever participated in anything like the UNC summer writing group? Did it help you keep to a schedule? Was it important to share drafts with each other?

 

2014 May 30

Class-D amplifier lab done, EKG block diagrams begun

Filed under: Circuits course — gasstationwithoutpumps @ 21:08
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Yesterday’s lab ran long (as expected), because students had not gotten enough done in Tuesday’s lab.  But everyone in the lab did get a working class-D power amplifier.  Several also managed to measure the turn on and turn off times for the comparators driving the FETs, though that required some hands-on guidance in using the digital scopes (setting the trigger level to the FET threshold voltage, then looking to see how long the rise or fall was before reaching the trigger level.  As expected, everyone had chosen values that made the pFETs turn on and off quickly, but it was difficult to get the nFETs to turn off quickly.  I don’t know whether anyone managed to equal turn on and turn off times for the nFET (they turned on fairly fast), but several groups managed to keep their FETs cool.  Even those with warm FETs did not dissipate so much in them that they got dangerously hot.

I’ll be reading the design reports over the weekend, and I’ll see whether the students really understood PWM or not.  I suspect that about half the groups understood what they were doing well enough, and the other half got part of the ideas.  There should be time on Monday to review the idea of PWM and to explain again why it is a good choice for efficient power delivery, particularly for inductive loads.

Today, I returned the quiz 2s redone as homework.  Students did fairly well on them as homework (range 18.5 to 31.5 out of 36, up from 7 to 17 on the timed quiz).  The biggest difficulty was with the last problem, which asked them to design a simple amplifier, giving both a block diagram and a schematic.  A lot of students did not understand the question as I phrased it, perhaps because I had not been clear enough earlier in the quarter about what a block diagram means and how to use it.

Students have not yet internalized the idea of something having inputs and outputs, and a block diagram being a refinement of an I/O spec into I/O specs for subunits.  I may need to use that language more explicitly earlier next year. I’m thinking also that I need to add more text to the lab handouts next year and refer to them as a draft textbook rather than as lab handouts.  How many pages do I have so far?

handout pages
01-thermistor  11
02-microphone  9
03-hysteresis  11
04-electrodes  7
05a-loudspeaker  8
03b-sampling  7
06-audio-amp  6
07-pulse-monitor  11
08-pressure-sensor  8
09-power-amp  13
09-power-amp-addendum  6
10-EKG  5
total  100

One hundred pages is a bit short for a textbook, but there is a lot of explanatory material still missing (most of which I provided in class or in lab). If I worked on it diligently over the summer, I could probably create a book with most of what the students need that would be around 200 pages. Do I have the energy to turn this into a textbook? Is it worth the effort?

After going over the block diagram of the quiz problem, I helped the students develop an EKG block diagram.They did get to the realization that the unknown but potentially large DC offset from the EKG electrode half cells limits the gain that they can ask from the first stage of the EKG, and that they’ll have to high-pass filter and add more gain.  The design is similar to their pressure sensor instrumentation amp, but the gain needs to be higher (1000 to 1500, rather than 100 to 250), and the pressure sensor amplifier had to go down to DC, so did not include a high-pass filter.

I was a little worried that I may have suggested too high a lower end for the passband (0.1Hz to 40Hz).  They’ll get less baseline drift with a 0.5Hz cutoff instead of 0.1Hz.  My EKG designs have used 0.05Hz—88.4Hz and 1.0Hz–7.2Hz for the blinky EKG.  Both worked ok, but I now think that the 7.2Hz cutoff is too low (it was adequate for blinking an LED, but not for recording the waveform).  Since I did not have much problem with a 0.05Hz corner frequency, I think they’ll be ok with a 0.1Hz one.  The blinky EKG circuit has an adjustable gain (needed to make the R spike large enough to light the LED), but it is probably better to have a fixed gain.

It would be really nice if they could finish the EKG on Tuesday, since the annual undergraduate poster symposium is scheduled for the same time as the Thursday lab, and I always like to spend an hour or so looking at the posters.

2013 July 6

Disseminating the applied circuits labs

Filed under: Circuits course — gasstationwithoutpumps @ 11:41
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The post I just published about academic conferences lead me to thinking (again) about how I should disseminate my course design (or individual lab designs) for the Applied Circuits course.  I suppose I should write up a paper and submit it to a conference or some journal like the Journal of Engineering Education.

One problem is that my course designs are not education research—they are attempts to solve particular curricular problems by taking advantage of my strengths as a teacher.  Some of the course design generalizes to other teachers and other institutions with somewhat different curricular needs, but there is no controlled experiment to say that my course design is “better” than another is some predefined, measurable way.

I’m not sure where this sort of here-are-some-good-ideas-you-may-be-able-to-use course design work fits in academic publishing.  If I were teaching physics, I would probably submit to The Physics Teacher, but I don’t know what the closest equivalent is in engineering—particularly interdisciplinary stuff like teaching circuits to bioengineers.  There don’t seem to be good journals intended for disseminating instructional labs and curricular design. Maybe Advances in Engineering Education would be a better fit than Journal of Engineering Education, even if I don’t feel that my course design contains “significant, proven innovations in engineering education practice, especially those that are best presented through the creative use of multimedia.”

Of course, distilling down the 200–400 pages of notes on my circuits course that I’ve collected on this blog to a conference presentation or a journal article is a daunting task—one that I’ll probably keep putting off until it is so stale that even I’m not interested in it any more.  It might even be easier to turn the notes into a book than into an article, since I would not have to do 100-to-1 compression.

I’m not sure who the right audience for such a book would be—instructors trying to create a new course, students taking my course, hobbyists wanting to learn the material at home, … ? That is, should I be writing about a case study in course design, should I be trying to create a textbook for the course, or should I be trying to put together a self-study book that could accompany a kit of parts for people to learn electronics at home?

Again, the book project is big enough that I’d probably keep putting off indefinitely.  If I was sure there was an audience, I’d be more inclined to put in the effort to disseminate the material beyond this blog, though.

Another approach for disseminating the course materials would be to put together stand-alone kits for each lab (with detailed tutorials) that could be sold independently.  Releasing one lab at a time would be a more incremental effort than doing all 10 labs in one package, but would require some redesign, both for reduced expectations of lab equipment and to make the kits more modular.

I suspect that one could do most of the experiments of the circuits course for about $360 in lab equipment and tools, using something like the Velleman Lab2U unit (which PartsExpress sells for $210), a $40 multimeter,  a $17 soldering station, an Arduino, and the $66 bag of tools and parts I put together for the course.  The Lab2U is only a single power supply, so some of the projects that used a multiple supply would need to be redesigned—most notably the class-D power amp.  Unfortunately, $360 is too big a chunk of money for anyone but a dedicated hobbyist, who quite likely already has most of the needed equipment.

Making the kits more modular might be difficult. For example, many of the labs require students to choose resistors and capacitors from a large set of possibilities, since their lab kit contained 10 each of 112 different resistors and 10 each of 25 different ceramic capacitors.  It is easy to justify the cost of those parts spread over 10 labs, but harder to provide that much selection for a single lab.  Perhaps one would have to sell a core kit (with breadboard, resistors, capacitors, …) to use with the Arduino and add-on kits for each lab.  The core kit would need to have some fundamental experiments (like RC time constants), so that it would be instructional even without add-ons.

I wonder if there is a market for such lab kits, and how I would find out if there were a market (without sinking months of my time and thousands of dollars). I wouldn’t want to assemble or market the resulting lab kits either, but would want to distribute them through a company like Sparkfun electronics, Adafruit Industries, or Seeedstudio, who have already set up the necessary business infrastructure.

I also wonder whether I’m capable of writing the tutorials at an introductory enough level to work for hobbyists, while still covering enough of the theory.  I’ve never cared for kits that have great assembly instructions, but treat the way the things works as too difficult for the purchaser of the kit.

Writing instructions that included the use of an oscilloscope or multimeter, when there are many different ones that the person may be trying to use, would be a very challenging task.  Oscilloscopes in particular have evolved to have many radically different user interfaces, some of which are very complicated.

Also, all my writing has been for well-educated people: college professors, university students chosen from the top 10% of high school students, my loyal blog readers, … .  Can I make my writing intelligible for an average, or slightly above average, high school student, without sounding condescending or patronizing?  From the rather unsuccessful attempts I’ve seen in kit instructions in the past, that is not an easy task.

2012 September 2

Wikipedia books, another approach for a free/cheap textbook

Filed under: Circuits course — gasstationwithoutpumps @ 14:06
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I’ve been thinking about another approach to providing a low-cost textbook for the circuits class: bundling a number of Wikipedia articles into a Wikipedia book, like the Introduction to Electronics one.  The idea is an appealing one, as many of the Wikipedia articles are excellent (better written than many textbooks), we can customize what topics to include, small errors in the text can be corrected, and students can either access the “book” online, download it in in PDF, ZIM, or OpenDocument format, or even pay for a printed copy.  The downloaded or printed copies will be frozen, while the live Wikipedia book gets updated every time one of the contained articles is edited.  We could provide frozen copies on the course web site, as a precaution against major rewrites removing information we expect students to read.

The Introduction to Electronics Wikipedia book does not have exactly the subjects we would need for our course, but several of the articles there are appropriate.  One attraction of this approach is that we can tailor our book to have exactly the content we need (assuming the articles we need exist) in the order we want. We can design our course by listing the topics we need in the order we need, and automatically have a text that matches. Given the somewhat idiosyncratic nature of our course (from basic circuits to EKG design, with side trips into electrodes and possibly fluidics modeling), we’re going to have to cobble together multiple sources anyway, so a Wikipedia book may be a good way to create the main text.  No matter what text we use, we’ll have to supplement with manufacturers’ data sheets, which can’t be included in a Wikipedia book because of copyright restrictions.

One disadvantage of Wikipedia books is that the articles in Wikipedia are by different authors and have no implicit ordering, so concepts cannot be developed in a gradual manner.  Individual articles are written at very different levels of sophistication, and some articles will have only a few sections that are relevant to the course.  The book would not be as smooth as a well-written textbook, but better than many of the poorly written ones on the market. I believe that we can add some manually created text (part of the book, but not part of Wikipedia) to introduce chapters, but I’m not exactly sure how (probably it involves including pages that are part of Wikipedia user space rather than public space).

Note: Wikipedia books are different from WikiBooks, which are from a project to create crowd-sourced free textbooks.  The electronics books currently available from WikiBooks are very incomplete and not as well written as Wikipedia articles, so I don’t think that they will be useful this year.

I started playing a bit with Wikipedia’s “Book Creator” and found it to be a very awkward interface.  Clicking on pages to add them to the book being created worked ok, but dragging the pages around to reorder them did not and the claimed button for adding chapters never appeared.  Furthermore, once you save a draft book, the book creator assumes you want to start a new one, so clicking on pages can’t add to an existing draft.  It seems that the book creator is damn near useless after the first 5 minutes, and after that you just have to edit the book like any other Wikipedia page.

2012 August 31

All about circuits, a possible supplemental text

Filed under: Circuits course — gasstationwithoutpumps @ 22:54
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I’ve been dipping into All about circuits, a free electronic textbook written (mostly) by Tony R. Kuphaldt, as a possible textbook for the circuits class.  I like that it is free, as that makes it much more likely that students will have ready access to it (many decide not to buy expensive texts, and end up trying to borrow them from friends).

The format, as 100s of HTML files, is a bit awkward to read, but fairly easy to search with Google (by adding “site:allaboutcircuits.com” to the keywords ins the search box), so indexing is not really an issue.  The book starts at about a middle-school level, but gets up to the beginnings of circuit theory (Thevenin’s TheoremRC and L/R time constants, Reactance and impedance—R, L, and C, …).  The Operational amplifier chapter looks usable, though it does not have a design focus—circuits are presented as almost magical rather than carefully analyzed from first principles (as is done in more theoretical circuits books) or from design rules of thumb (as is done in books like Horowitz and Hill).

I think that All about Circuits can be a good supplemental text for students who need something at a lower reading and math level than Horowitz and Hill, for review of physics electricity and magnetism concepts, and to fill in gaps in prior education (such as complex numbers).

I don’t know that I want to use Horowitz and Hill as the main text, though, as it is pretty expensive for such an old electronics book. I wonder if there is another free book that is somewhat higher level than All about Circuits that can be combined with it to make a textbook at the right level for the range of students expected in the class.

I think we may need a more mathematical presentation of some of the material, if the students are to be able to continue into later electronics classes. This may not matter, because the chair of the EE department has made it pretty clear that no subsequent electronics course would use this course as a prerequisite, and that students would have to take the “real” circuits course in order to take any further electronics courses.  Of course, if he holds to that for the bioelectronics class, then he’ll have almost no students in that class, since few if any of the bioengineers will subject themselves to the dry, repetitive linear algebra manipulations of the standard circuits class in order to take a bioelectronics class that doesn’t even include a lab component.  If we get to teach our applied circuits course, we should be able to convince the professor creating the bioelectronics course to accept it as a prereq in place of the standard circuits course.

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