# Gas station without pumps

## 2014 April 13

### Designing courses to teach design—draft 3

The talk I was scheduled to give last quarter (2014 Feb 24) was rescheduled, because two of the four speakers were unable to make that date.  It is now scheduled for Wed 2014 Apr 23  at 3:30 in the Merrill Cultural Center, which used to be the Merrill Dining Hall, before they consolidated dining halls in the east colleges. There are now 6 speakers in 90 minutes, which means 15 minutes each (maybe 10 minutes speaking, 5 minutes for questions).  I’ll have to run over from my class which ends at 3:10 on the opposite side of campus (0.6 miles, 13 minutes according to Google Maps), though running may be difficult along the crowded sidewalks between classes.

The talk needs to be updated from last quarter, as I have now taught prototype runs for both the applied circuits class and the freshman design class, and am in the second run of the applied circuits class.

Here is my current draft of the text—please give me some suggestions in the comments for improvement.  The ending seems particularly awkward to me, but I’m having trouble fixing it.

Designing Courses to Teach Design

I believe that the main value of a University education does not come from MOOCable mega-lecture courses, but from students working in their field and getting detailed feedback on that work. I’ll talk today about some courses I’ve created ths year and last to teach students to do engineering design. These courses are high-contact, hands-on courses—the antithesis of MOOC courses.

Design starts from goals and constraints: “what problem are you trying to solve?” and “what resources are available?” So what were my goals and constraints?

The two problems I was trying to solve were in the bioengineering curriculum:

1. students weren’t getting enough engineering design practice (and what they were getting was mostly in the senior year, which is much too late) and
2. too many students were selecting the biomolecular concentration, where we were exceeding our capacity for senior capstone and senior thesis projects.  The other concentrations were under-enrolled.

The main constraints were that

1. there was no room in the curriculum for adding required courses,
2. there were no resources for new lab space or equipment, and
3. all relevant engineering courses had huge prerequisite chains.

Furthermore, I would have to teach any new course myself, so the content had to be something I already knew or could learn quickly. Those constraints meant the new course would not have wet labs (though I have encouraged wet-lab faculty to add design exercises to their existing courses).

My first partial solution was to replace the required EE circuits course with a new Applied Circuits course. The existing EE101 course is a theory class (mostly applied math) that prepares students to do design in later courses—but most bioengineering students never take those later courses, so were getting prepared for something they didn’t do. Due to “creeping prerequistism” in the 8 or 9 departments providing courses for the major, the bioengineering students were already taking far too many preparatory courses and far too few courses where they actually did things.

The goal of the new course is to have students design and build simple amplifiers to interface biosensors to computers. I chose a range of sensors from easy ones like thermistors, microphones, and phototransistors to ones more difficult to interface like EKG electrodes and strain-gauge pressure sensors. I’m not interested in cookbook, fill-in-the-blank labs—I want students to experience doing design in every lab, even the first one where they knew almost no electronics—and I want them to write detailed design reports on each lab, not fill-in-the-blank worksheets, like they get in chem and physics labs, and even intro EE labs.

The course was designed around the weekly design projects, not around preset topics that must be covered. Themes emerged only after the design projects were selected—the class comes back again and again to variations on voltage dividers, complex impedance, and op amps with negative feedback.

Students used a free online textbook rather than buying one, but bought about \$90 of tools and parts. I tried out every potential design exercise at home—rejecting some as too hard, some as too easy, and tweaking others until they seemed feasible. I designed and had fabricated three different printed circuit boards for the course (not counting two boards which I redesigned after testing the lab at home).  One of the PC boards is a prototyping board for students to solder their own amplifier designs for the pressure-sensor and EKG labs. (Pass boards around.)

Developing a hands-on course like this is not a trivial exercise. I spent about 6 months almost full time working on the course design (without course relief). I made over 100 blog posts about the design of the course before class even started, and I now have over 230 posts (the URL is on the quarter-page handout, along with the URL for the course syllabus and lab assignments).  Since the posts average a couple of pages, this is more writing than a textbook (though not nearly as organized).

The course was prototyped last year as BME 194+194F “Group Tutorial” before being submitted to CEP for approval, and I wrote up notes after each class or lab (another 60 or so blog posts). Last year’s prototyping lead me to increase the lab time from 3 hours to 6 hours a week, which means I’m spending a lot of time this quarter rewriting all the lab handouts—splitting the material between the lab times and adding at-home or in-class design exercises between the two parts. Some of the fixes have worked well (students got comfortable plotting their data with gnuplot weeks earlier this year), but we’ve still run over time in some labs, even with 6 hours a week of lab, so more tweaking is needed.

This course is expensive in terms of professor time: I’m spending over 10 hours a week of direct classroom and lab time (not counting office hours, grading, prep time, or rewriting the lab handouts). Just providing feedback on the 5–10-page weekly design reports takes about 15 minutes per student per week (half an hour per report).

The students taking Applied Circuits last year were mostly seniors who had been avoiding EE 101, rather than the sophomores I’d intended the class for. This year, I have juniors and seniors, but still no sophomores. So the course still does not provide early exposure to engineering design, nor does it direct more students to the bioelectronics concentration rather than the biomolecular one (those there’s still hope for the latter).

My second partial solution was to create a new freshman design seminar in conjunction with the student Biomedical Engineering Society. This course has no prereqs, is only 2 units, and does not count towards any major or campus requirements.

Unlike the Applied Circuits course, I didn’t choose the design projects for this course ahead of time, because I had no idea what skills and interests the students would bring to the class—I’d not taught a freshman class in over a decade, having taught mainly seniors and grad students. I did try out 3 or 4 design projects on my own to gauge the skills needed to do them, but those projects all assumed some computer programming skills.

I prototyped the freshman design course last quarter as BME 94F and have submitted course forms to CEP for approval. Once again, I blogged notes after each class meeting (only about 39 posts, though—this was a less intensive effort on my part).

With no prereqs, I couldn’t assume that students had any relevant skills, though it turned out that all this year’s students had had biology, chemistry, and at least conceptual physics in high school. Only one student had ever done any computer programming, though—a big hole in California high school education—and only a few had any experience building anything. (AP physics classes were the most common exposure to building something.) On the first-day survey the students indicated an interest in learning some programming and electronics, so we did a little programming with an Arduino microcontroller board—I’ll try to up that content next year.

I started out teaching generic design concepts using a photospectrometer as an example. The concepts include specifying design goals and constraints, dividing a problem into subproblems, interface specification, and iterative design.The photospectrometer turned out to be too complex, and I’ll probably start with a simpler colorimeter next year, and have the students design, build, and program it before they start on their own projects.

My third partial solution has been a complete overhaul of the bioengineering curriculum, which is currently before CEP for approval. No new courses were created for this overhaul, but all the concentrations were changed. For example, half the chemistry courses were removed from concentrations other than biomolecular, to make room for more courses in electronics, robotics, psychology, or computer science. And some the orphan math courses were removed from the biomolecular concentration to make room for more advanced biology. Long-term, I’m hoping to convince some of the other departments to remove excessive prerequisites, so that students can take more interesting and useful courses before their senior year.

I could go on all afternoon about these courses and curriculum design, but I’m running out of  time, so I’ll leave you with these take-away messages:

1. The value of University education is in detailed feedback from professors in labs and on written reports, not in the lectures.
2. Students should be solving real problems with multiple solutions, not fill-in-the-blank or multiple-choice toy exercises.
3. These courses require a lot of time from the professors, and so they are expensive to offer.
4. Failure to teach such courses, though, makes the University education no longer worthy of the name.

For those of you not present—the quarter-page handout will have the URLs for this blog’s table of contents pages for the circuits course and the freshman design course, in addition to the two class web pages:

In addition to the quarter-page handout, I also plan to have copies of the prototyping board (both bare boards and ones that I used for testing out EKG or instrumentation amp circuits), one of the pressure sensors (on another PC board I designed), and the hysteresis oscillator boards.  If I can get it working again, I may also wear the blinky EKG while I’m talking.

Preparing this talk has been weird for me—I can’t remember ever having scripted out a talk to this level of detail.  For research talks, I usually spend many hours designing slides, and relying on the slides to trigger the appropriate talk. For classes, I usually think obsessively about the material for a day or two ahead of time, sometimes writing down a few key words to trigger my memory, but mainly giving an extemporaneous performance that relies heavily on audience participation. I had one memorable experience where a student asked me for a copy of my lecture notes after a class—I handed her the 1″ PostIt that had my notes, but warned her that I’d only covered the first word that day, and that it would take the rest of the week to cover the rest.

Doing this short a talk without slides and without time to rehearse will probably require me to read the talk—something else I’ve never done. (I know, I should have rehearsed during our one-week spring break, but I had a 2-day RNA research symposium, a faculty meeting about who we would offer our faculty slot to, meetings with grad students, and feverish rewriting of the first few lab handouts for the circuits course.)

## 2014 April 12

Filed under: Uncategorized — gasstationwithoutpumps @ 16:40
Tags: ,

Katrin Becker in her post Six things that will demoralise staff, which is a response to Six things that will demoralise staff @ smh.com.au, commented on the difficulty of getting adjunct professor appointments at one Canadian university:

Curiously, I actually tried to become an adjunct at my Alma mater—twice. The first time was just after I’d graduated, and won a research award. That time my paperwork mysteriously disappeared—twice. The other time it took months of cajoling to even elicit a response from the Dean, and then they said they weren’t really interested. An adjunct appointment in Canada is a completely resource neutral appointment. It costs the University NOTHING, yet allows them to claim my achievements as part of their “output”. I can’t imagine why anyone would turn that down, but they did.

This phenomenon is not limited to Canada, nor to people whose only connection to the university is as an alumnus or alumna.  On our campus, adjunct professor with 0% salary appointments are up to the deans, and they don’t always make rational decisions.

For example, a few years ago our department had an extremely active researcher and teacher who had created courses for the department, taught them and trained others to teach them, taught one of our core grad courses, written grant proposals (he was on soft money), and basically done all the things that a good assistant professor would do. Our department voted unanimously to give him adjunct assistant professor status with a 0% appointment, which would have no fiscal effect, except that when he taught a course he would be paid like a visiting professor, rather than like a lecturer—the difference is not huge, but it meant that he would not have to take a pay cut from his research position in order to teach.

The dean refused to make the appointment, with the lame excuse that the person had not been a postdoc long enough (despite the fact that most of the tenure-track faculty in the School of Engineering are hired directly from PhD programs without postdoctoral training, and the person had 20 years of industrial experience in a related field).

Who can understand the minds of university administrators?

## 2014 April 11

### Impedance, finally

Filed under: Circuits course — gasstationwithoutpumps @ 21:32
Tags: , , , ,

I finally got a chance to cover impedance in class today.

I started with complex numbers and Euler’s formula ($e^{j\theta} = \cos(\theta) + j \sin(\theta)$), showed them how the amplitude and phase terms could easily be factored out to make a phasor, then had them develop the formulas for impedance of resistors and capacitors.  For capacitors, I had to guide them a bit, but they came up with $Q=CV$, $i = dQ/dt$, and taking the derivative of the voltage.  That actually went a bit smoother than I expected, and almost everyone in the class was participating.

I then had them come up with the circuit for an RC filter (they only know one circuit, the voltage divider, so this was pretty easy). They used the voltage divider formula to get the gain of the filter, and I showed them how to plot it by hand (a Bode plot).  The filter we started with was a low-pass filter, so I challenged them to design a high-pass filter.  This is an easy task, and they almost instantly suggested swapping the resistor and capacitor.  They derived the formula for the gain of that filter, and I showed them the how to draw the Bode plot for it also.

Note: we only do amplitude Bode plots in this class, not phase.  For what they are doing, the phase response is not very important.  I did let them know that there were more advanced classes where the phase response was carefully determined, and that filter design got a lot more complicated than simple RC filters.

I covered in class almost exactly what I set out to do, and the students came up with most of what I wrote on the board, so I felt that the Socratic questioning I used to guide them worked fairly well.  I’ll probably have to give them some design exercises soon, to see if they actually understand the material or were just nodding along with their classmates.

This weekend I’ll grade their second design reports (for the microphone lab), and try to rewrite the week-4 labs, which will be characterizing polarizing and non-polarizing electrodes.  I have a bunch of other stuff to do this weekend also (mow lawn, do state taxes, read a thesis proposal, read a chapter of a thesis, replace the rear wheel on my bike, rewrite the designing courses to tech design talk, write a letter of recommendation for a former student trying to get a green card, feed the cats and the fish, … ). I may have a bit less time than usual this weekend, because I’m cooking for myself—my wife and my son have gone to an admitted-students weekend at UCSB.

### Arthur Benjamin: Teach statistics before calculus!

I rarely have the patience to sit through a video of a TED talk—like advertisements, I rarely find them worth the time they consume. I can read a transcript of the talk in 1/4 the time, and not be distracted by the facial tics and awkward gestures of the speaker. I was pointed to one TED talk (with about 1.3 million views since Feb 2009) recently that has a message I agree with: Arthur Benjamin: Teach statistics before calculus!

The message is a simple one, though it takes him 3 minutes to make:calculus is the wrong summit for k–12 math to be aiming at.

Calculus is a great subject for scientists, engineers, and economists—one of the most fundamental branches of mathematics—but most people never use it. It would be far more valuable to have universal literacy in probability and statistics, and leave calculus to the 20% of the population who might actually use it someday.  I agree with Arthur Benjamin completely—and this is spoken as someone who was a math major and who learned calculus about 30 years before learning statistics.

Of course, to do probability and statistics well at an advanced level, one does need integral calculus, even measure theory, but the basics of probability and statistics can be taught with counting and summing in discrete spaces, and that is the level at which statistics should be taught in high schools.  (Arthur Benjamin alludes to this continuous vs. discrete math distinction in his talk, but he misleadingly implies that probability and statistics is a branch of discrete math, rather than that it can be learned in either discrete or continuous contexts.)

If I could overhaul math education at the high school level, I would make it go something like

1. algebra
2. logic, proofs, and combinatorics (as in applied discrete math)
3. statistics
4. geometry, trigonometry, and complex numbers
5. calculus

The STEM students would get all 5 subjects, at least by the freshman year of college, and the non-STEM students would top with statistics or trigonometry, depending on their level of interest in math.  I could even see an argument for putting statistics before logic and proof, though I think it is easier to reason about uncertainty after you have a firm foundation in reasoning without uncertainty.

I made a comment along these lines in response to the blog post by Jason Dyer that pointed me to the TED talk. In response, Robert Hansen suggested a different, more conventional order:

1. algebra
2. combinatorics and statistics
3. logic, proofs and geometry
5. calculus

It is common to put combinatorics and statistics together, but that results in confusion on students’ part, because too many of the probability examples are then uniform distribution counting problems. It is useful to have some combinatorics before statistics (so that counting problems are possible examples), but mixing the two makes it less likely that non-uniform probability (which is what the real world mainly has) will be properly developed. We don’t need more people thinking that if there are only two possibilities that they must be equally likely!

I’ve also always felt that putting proofs together with geometry does damage to both. Analytic geometry is much more useful nowadays than Euclidean-style proofs, so I’d rather put geometry with trigonometry and complex numbers, and leave proof techniques and logic to an algebraic domain.

## 2014 April 10

### Second mic lab went well

Filed under: Circuits course — gasstationwithoutpumps @ 21:23
Tags: , , ,

The second half of the mic lab went fairly well, but there were a couple of overly ambitious requests in the handout that I’ll have to trim out for next year.  Because we have not gotten to complex impedance yet (tomorrow, I swear!), the students were unable to choose a reasonable size for the DC-blocking capacitor, and guessing was not good enough.  The 10MΩ input impedance of an oscilloscope with a 10× probe makes for too long a time constant with the 0.1µF capacitor I  initially suggested, at least with the digital scopes—they did not manage to get the DC offset removed even after a minute, which surprised me.  Students got decent results with a 0.022µF capacitor, though.  I even got some of the students to be able to make measurements with the Tektronix digital scopes (always a feat, since they have mind-bogglingly complex menu systems).

I did tell the students not to bother with the last question on the handout and just to write up what they actually did.

It took the students longer than I had expected to come up with a reasonable value for the pullup resistor for the mic. But I was careful not to be too helpful, so that I’m reasonably sure that at least one in each pair of students knew how they got their answer. I did have them add load lines to their i-vs-v plots of the electret microphones, corresponding to rounding their desired pullup up or down to the nearest value they had in their kits.  That probably added a little time over a simple rounding, especially since I suggested to a couple of the students that they think about which resistor would give higher sensitivity.

I did have one student ask what a “pullup” resistor was—I had used that term in the handout without ever explaining it!  I gave a one-minute lecture explaining that a pullup was a resistor to the positive power supply and a pulldown a resistor to ground (we had examples of each already on the whiteboard). Speaking of things on the board, I’ll have to remember to bring markers to the lab on Tuesday, as the ones in there are all dead. A spray bottle of alcohol and some rags for cleaning the year-old buildup off the boards would also be good.

Even the pair of students who had run over on Tuesday finished on time today, despite collecting all the data that the other students collected on Tuesday, so I’m feeling a bit better about the size of the labs.

Next week may get a bit hectic, though, with two unrelated labs: hysteresis and relaxation oscillators on Tuesday and sampling and aliasing on Thursday.  I’ll have to remember on Tuesday to upload the hysteresis oscillator code to all the machines in the lab.

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