Showing is better than telling, but not by much

Robert Talbert, in Examples and the light bulb – Casting Out Nines – The Chronicle of Higher Education, wrote

I have a confession to make: At this point in the semester (week 11), there’s a question I get that nearly drives me to despair. That question is:

Can we see more examples in class?

Why does this question bug me so much? It’s not because examples are bad. On the contrary, the research shows (and this is surely backed up by experience) that studying worked examples can be a highly effective strategy for learning a concept. So I ought to be happy to hear it, right?

The difficulty, of course, is that the students are asking to see examples, rather than working on the examples themselves—they are asking to be spoonfed mush rather than chewing for themselves.

I have found in my own learning that I can get a certain amount by reading, but that really understanding material requires me to work out problems for myself.  Sometimes this just means doing exercises from the textbook (a boring task which I have trouble forcing myself to do without the structure of a course), and sometimes it means struggling with making something work to solve a real problem. Real problems are both motivating and frustrating—just doing carefully drafted exercises that are designed to work out easily doesn’t always help much in applying ideas to the real world.

Talbert gets the point across well:

Of course at the beginning of a semester, students aren’t experts, and showing them examples is important. But what I also have to do is (1) teach students how to study examples and (2) set and adhere to an exit strategy for giving examples. My job is not to give more and more examples. Instead it’s to say: Rather than give you more examples, let me instead give you the tools to create and verify your own examples.  And then, at some point in the semester, formally withdraw from the role of chief example-giver and turn that responsibility over to the students.

This is the same idea as in my post Descaffolding, which was prompted by a post by Grant Wiggins, Autonomy and the need to back off by design as teachers.  It also fits in with Dan Meyer’s theme to “be less helpful”.

Given how frequently teachers and teacher leaders discuss it, I think that over-scaffolding is a common problem for many teachers.  We all want to help the struggling student succeed, but too often we make them incapable of succeeding without us.  If they always outsource their thinking, they’ll never develop their own skills.

To use analogies from other fields: overscaffolding is like showing the students only great literature and telling them about writing process, but never having them struggle through 5 to 10 drafts of a piece of writing, or teaching art by showing only cast bronzes and mosaics, but never having them do a sketch or sculpt in clay.  Showing or telling students how to do something is often necessary (students can’t be expected to guess non-obvious methods), but it needs to be followed by students doing things for themselves.

A lot of us put a lot of time into polishing our presentations so that the students see the cleanest, most elegant way of doing a proof or solving a problem, but never see the debugging and refinement process that creates such elegant results.  I’ve never been guilty of the over-polished lecture: I give my lectures as extemporaneous performances that are never the same twice.  For one course, I did not even prepare any lectures, but had the students give me problems from the homework that they wanted to see how to do, a process I called live-action math.  That approach required a thorough understanding of the material and a confidence that I could do any of the problems in front of an audience without prior prep.

Not all my classes are so extreme, but when I give examples I always try to make them examples of problem solving (as opposed to examples of solved problems).  In the circuits course last quarter I probably did about the right number of examples in class and got the students involved in solving them, but I did not give the students enough simple problems to practice on.  I was withdrawing the supports too quickly and trying to have them jump from the material in the reading (which they weren’t doing) directly to design problems. Next year I’ll assign some more routine exercises (though I’ve always hated the drill work) to help them build their skills.

So too many examples is not a big problem in my teaching style. The bigger teaching difficulty I have is in not doing debugging for the students.  In labs and programming courses I can find student problems much more quickly than they can, and I have to restrain myself from just pointing out the (to me) obvious problem. I can think of several times in the circuits lab last quarter when I glanced at a breadboard that students had asked for help with and just asked them “where’s the connection to ground for this component?” or “why are all these nodes shorted together?”  That was not quite the right approach—it got them unstuck and left them some of the debugging still to do (that is, it was better than just moving the wires around for them), but did not help them develop the skills needed to see the problem at a glance themselves.

Some other approaches, like “Show me your schematic—I can’t debug without a clear schematic of what you are trying to build,” were probably more effective—there were a couple of students who kept trying to build without a clear schematic and being unable to debug the resulting mess.  I probably walked away from them 3 or 4 times during the quarter, telling them I’d help once they had proper schematics to debug from.

It might be better for me to go through a checklist with the students—for example, having them check that each component has the right number of connections and check the breadboard against the schematic to see if the wiring is the same.  Occasionally I’d still have to step in to correct a misunderstanding (particularly at the beginning when some students don’t understand how the holes of the breadboard are connected together underneath and put components in sideways), but by stepping them through a process I think I could eventually get more of them debugging on their own.

After all, the point of the programming assignments and labs to teach students how to debug, not just to get them to produce working programs or circuits.  It is much harder to teach a student how to debug than to demonstrate debugging—I’m still working on better ways to do that.  I think that what I did in the circuits course worked for some students (they were debugging pretty independently by the end of the quarter), but others were still relying too much on help even at the end of the quarter.

A big chunk of learning how to teach is figuring out how to withdraw the initial support without students failing.  Suddenly yanking it out from under them will make many collapse, but being too slow to remove support will leave them still leaning on the crutch when they should be running on their own.

Supplemental sheets, draft 3

This post updates and replaces the Supplemental sheets, draft 2. It reflects the redesign of the course based on running a prototype version of the course in as a group tutorial in Winter 2013.

Lecture Course

Undergraduate Supplemental Sheet
Information to accompany Request for Course Approval
Sponsoring Agency: Biomolecular Engineering
Course #: 101
Catalog Title: Applied Circuits for Bioengineers

Please answer all of the following questions using a separate sheet for your response.
1. Are you proposing a revision to an existing course? If so give the name, number, and GE designations (if applicable) currently held.

This is not a revision to any existing course.A prototype version of the course was run as BME 194 Group Tutorial in Winter 2013. Notes on the design and daily running of that prototype can be found at https://gasstationwithoutpumps.wordpress.com/circuits-course-table-of-contents

2. In concrete, substantive terms explain how the course will proceed. List the major topics to be covered, preferably by week.

The Applied Circuits course is centered around the labs in the accompanying lab course.  Concepts are taught as needed for the labs, with design and analysis exercises in the lecture course cementing the understanding. The recurring theme throughout the course is voltage dividers: for change of voltage, for current-to-voltage conversion, for high-pass and low-pass RC filters, in Wheatstone bridges, and as feedback circuits in op amp circuits.  The intent of this course is to provide substantial design experience for bioengineering students early in their studies, and to serve both as as bridge course to entice students into the bioelectronics concentration and as a terminal electronics course for those students focussing on other areas.

1. Basic DC circuit concept review: voltage current, resistance, Kirchhoff’s Laws, Ohm’s Law, voltage divider, notion of a transducer.
   The first week should cover all the concepts needed to do the thermistor lab successfully.
2. Models of thermistor resistance as a function of temperature. Voltage and current sources, AC vs DC, DC blocking by capacitors, RC time constant, complex numbers, sine waves, RMS voltage, phasors. The second week should cover all the concepts needed to do the electret microphone lab successfully.
3. Low-pass and high-pass RC filters as voltage dividers, Bode plots. Concepts necessary for properly understanding digitized signals: quantized time, quantized voltage, sampling frequency, Nyquist frequency, aliasing.
4. Amplifier basics: op amps, AC coupling, gain computation, DC bias for single-power-supply offsets, bias source with unity-gain amplifier.  In the lab, students will design, build, and test a low-gain amplifier (around 5–10 V/V) for audio signals from an electret microphone. We’ll also include a simple current-amplifier model of a bipolar transistor, so that they can increase the current capability of their amplfier.
5. Op amps with feedback that has complex impedance (frequency-dependent feedback), RC time constants, parallel capacitors, hysteresis, square-wave oscillator using Schmitt triggers, capacitance-output sensors, capacitance-to-frequency conversion.   Topics are selected to support students designing a capacitive touch sensor in the accompanying lab.
6. Phototransistors and FETs for the tinkering lab and for the class-D amplifier lab. In preparation for the lab in which students model a pair of electrodes as R+(C||R), we will need a variety of both electronics and electrochemistry concepts: variation of parameters with frequency, impedance of capacitors, magnitude of impedance, series and parallel circuits, limitations of R+(C||R) model, and at least a vague understanding of half-cell potentials for the electrode reactions: Ag → Ag⁺ + e^-, Ag⁺ + Cl^- → AgCl, Fe + 2 Cl^-→ FeCl₂ + 2 e^-.
7. Differential signals, twisted-pair wiring to reduce noise, strain gauge bridges, instrumentation amplifier, DC coupling, multi-stage amplifiers.
   Topics are selected to support the design of a 2-stage amplifier for a piezoresistive pressure sensor in the lab.
8. System design, comparators, more on FETs. Students will design a class-D power amplifier to implement in the lab.
9. A little electrophysiology: action potentials, electromyograms, electrocardiograms. Topics are chosen so that students can design a simple 3-wire electrocardiogram (EKG) in the lab.There will also be a bit more development of simple (single-pole) filters.
10. The last week will be review and special topics requested by the students.

3. Systemwide Senate Regulation 760 specifies that 1 academic credit corresponds to 3 hours of work per week for the student in a 10-week quarter. Please briefly explain how the course will lead to sufficient work with reference to e.g., lectures, sections, amount of homework, field trips, etc. [Please note that if significant changes are proposed to the format of the course after its initial approval, you will need to submit new course approval paperwork to answer this question in light of the new course format.]

The combination of BME101 and BME101L is 7 units (21 hours per week).  The time will be spent approximately as follows:

• 3.5 hours lecture/discussion
• 3.5 hours reading background and circuits text
• 3 hours read lab handouts and doing pre-lab design activities
• 6 hours lab
• 5 hours writing design reports for lab

4. Include a complete reading list or its equivalent in other media.

No existing book covers all the material.  For the prototype run of the course, we relied heavily on Wikipedia articles, which turned out to be too dense for many of the students.  Other alternatives (such as Op amps for everyone by Ron Mancini http://www.e-booksdirectory.com/details.php?ebook=1469 Chapters 1–6 and Op Amp Applications Handbook by Analog Devices http://www.analog.com/library/analogDialogue/archives/39-05/op_amp_applications_handbook.html Sections 1-1 and 1-4) were also much too advanced.

In future we will most likely use the free on-line text All about Circuits as the primary text, with material not covered there (such as the various sensors) coming mainly from Wikipedia and the datasheets for the components.

5. State the basis on which evaluation of individual students’ achievements in this course will be made by the instructor (e.g., class participation, examinations, papers, projects).

Students will be evaluated primarily on design reports with some in-class or take-home quizzes to ensure that they do the needed reading on theoretical concepts.

6. List other UCSC courses covering similar material, if known.

EE 101 covers some of the same circuit material, but without the focus on sensors and without instrumentation amps.  It covers linear circuit theory in much more depth and focuses on mathematical analysis of complicated linear circuits, rather than on design with simple circuits.  The expectation for bioengineering students is that those in the bioelectronics track would take BME 101 before taking EE101, and that those in other tracks would take BME 101 as a terminal electronics course providing substantial engineering design.  The extra material in BME 101 would prepare the bioengineering students better for EE 101.

Physics 160 offers a similar level of practical electronics, but focuses on physics applications, rather than on bioengineering applications, and is only offered in alternate years.

7. List expected resource requirements including course support and specialized facilities or equipment for divisional review. (This information must also be reported to the scheduling office each quarter the course is offered.)

The lecture part of the course needs no special equipment—a standard media-equipped classroom with a whiteboard, screen, and data projector should suffice. Having a portable laptop-connected oscilloscope would make demos much easier to do, but is not essential.

The lecture course is not really separable from the associated lab course,whose equipment needs are described on the supplemental sheet for that course.

The course requires a faculty member (simultaneously teaching the co-requisite Applied Circuits lab course) and a teaching assistant or undergraduate group tutor for discussion sections and assistance in grading.  The same TA/group tutor should be used for both the lecture and the lab courses.

8. If applicable, justify any pre-requisites or enrollment restrictions proposed for this course. For pre-requisites sponsored by other departments/programs, please provide evidence of consultation.

Students will be required to have single-variable calculus and a physics electricity and magnetism course. Both are standard prerequisites for any circuits course. Although DC circuits can be analyzed without calculus, differentiation and integration are fundamental to AC analysis. Students should have already been introduced to the ideas of capacitors and inductors and to serial and parallel circuits.

The prerequisite courses are already required courses for biology majors and bioengineering majors, so no additional impact on the courses is expected.

9. Proposals for new or revised Disciplinary Communication courses will be considered within the context of the approved DC plan for the relevant major(s). If applicable, please complete and submit the new proposal form (http://reg.ucsc.edu/forms/DC_statement_form.doc or http://reg.ucsc.edu/forms/DC_statement_form.pdf) or the revisions to approved plans form (http://reg.ucsc.edu/forms/DC_approval_revision.doc or http://reg.ucsc.edu/forms/DC_approval_revision.pdf).

This course is not expected to contribute to any major’s disciplinary communication requirement, though students will get extensive writing practice in the design reports (writing between 50 and 100 pages during the quarter).

10. If you are requesting a GE designation for the proposed course, please justify your request making reference to the attached guidelines.

No General Education code is proposed for this course, as all relevant codes will have already been satisfied by the prerequisites.

11. If this is a new course and you requesting a new GE, do you think an old GE designation(s) is also appropriate? (CEP would like to maintain as many old GE offerings as is possible for the time being.)

No General Education code is proposed for this course, as all relevant codes (old or new) will have already been satisfied by the prerequisites.

Lab course

Undergraduate Supplemental Sheet
Information to accompany Request for Course Approval
Sponsoring Agency Biomolecular Engineering
Course # 101L
Catalog Title Applied Circuits Lab

Please answer all of the following questions using a separate sheet for your response.
1. Are you proposing a revision to an existing course? If so give the name, number, and GE designations (if applicable) currently held.

This is not a revision to any existing course. A prototype version of the course was run as BME 194F Group Tutorial in Winter 2013. Notes on the design and daily running of that prototype can be found at https://gasstationwithoutpumps.wordpress.com/circuits-course-table-of-contents

2. In concrete, substantive terms explain how the course will proceed. List the major topics to be covered, preferably by week.

The course is a lab course paired with BME 101, Applied Circuits for Bioengineers.  The labs have been designed to be relevant to bioengineers and to have as much design as is feasible in a first circuits course.  The labs are the core of the course, with lecture/discussion classes to support them. There will be six hours of lab a week, split into 2 3-hour sessions. Lab assignments will generally take two lab sessions, with data collection in the first lab session, and data analysis and design between lab sessions.   Some of the more straightforward labs will need only a single session.  Except for the first intro lab, these labs have been used in the prototype run of the class as 3-hour labs.  Most did not fit in one 3-hour lab session and would benefit from being split into two separate lab sessions with data analysis and design between the sessions.

1. Intro to parts, tools, and lab equipment (single session)
2. Thermistor
3. Microphone
4. Sampling and aliasing (single session)
5. Audio amp
6. Hysteresis oscillator and soldering lab
7. FET and phototransistor
8. Electrode modeling
9. Pressure sensor and instrumentation amp (soldered)
10. Class-D power amplifier
11. EKG (instrumentation amp with filters, soldered)

1. Intro to parts, tools, and lab equipment
   Students will learn about the test equipment by having them use the multimeters to measure other multimeters. What is the resistance of a multimeter that is measuring voltage? of one that is measuring current? what current or voltage is used for the resistance measurement? Students will be  issued their parts and tool kits, learn to use the wire strippers and make twisted-wire cables for the power supplies to use all quarter.  They will learn to set the current limits on the power supplies and  measure voltages and currents for resistor loads around 500Ω.  This lab will not require a written lab report.
   Lab skills developed: wire strippers, multimeter for measuring voltage and current, setting bench power supply
   Equipment needed: multimeter, power supply
2. Thermistor lab
   The thermistor lab will have two lab sessions involving the use of a Vishay BC Components NTCLE413E2103F520L thermistor or equivalent.
For the first lab session, the students will use a bench multimeter to measure the resistance of the thermistor, dunking it in various water baths (with thermometers in them to measure the temperature). They should fit a simple curve to this data based on standard thermistor models. A class period will be spent on learning both the model and how to do model fitting with gnuplot, and there will be a between-lab exercise where they derive the formula for maximizing | dV/dT | in a voltage divider that converts the resistance to a voltage.
   For the scond lab session, they will add a series resistor to make a voltage divider. They have to choose a value to get as large and linear a voltage response as possible at some specified “most-interesting” temperature (perhaps body temperature, perhaps room temperature, perhaps DNA melting temperature).  They will then measure and plot the voltage output for another set of water baths. If they do it right, they should get a much more linear response than for their resistance measurements. 
Finally, they will hook up the voltage divider to an Arduino analog input and record a time series of a water bath cooling off (perhaps adding an ice cube to warm water to get a fast temperature change), and plot temperature as a function of time.
   Lab skills developed: use of multimeter for measuring resistance and voltage, use of Arduino with data-acquisition program to record a time series, fitting a model to data points, simple breadboarding.Equipment needed: multimeter, power supply, thermistor, selection of various resistors, breadboard, clip leads, thermoses for water baths, secondary containment tubs to avoid water spills in the electronics lab. Arduino boards will be part of the student-purchased lab kit. All uses of the Arduino board assume connection via USB cable to a desktop or laptop computer that has the data logger software that we will provide.
3. Electret microphone
   First, we will have the students measure and plot the DC current vs. voltage for the microphone. The microphone is normally operated with a 3V drop across it, but can stand up to 10V, so they should be able to set the Agilent E3631A  bench power supply to various values from 0V to 10V and get the voltage and current readings directly from the bench supply, which has 4-place accuracy for both voltage and current. Ideally, they should see that the current is nearly constant as voltage is varied—nothing like a resistor.  They will follow up the hand measurements with automated measurements using the Arduino to measure the voltage across the mic and current through it for voltages up to about 4v.  The FET in the microphone shows a typical exponential I vs. V characteristic below threshold, and a gradually increasing current as voltage increases in the saturation region.  We’ll do plotting and model fitting in the data analysis class between the two labs.
   Second, we will have them do current-to-voltage conversion with a 5v power supply and a resistor to get a 1.5v DC output from the microphone and hook up the output of the microphone to the input of the oscilloscope. Input can be whistling, talking, iPod earpiece, … . They should learn the difference between AC-coupled and DC-coupled inputs to the scope, and how to set the horizontal and vertical scales of the scope. They will also design and wire their own DC blocking RC filter (going down to about 1Hz), and confirm that it has a similar effect to the AC coupling on the scope. Fourth, they will play sine waves from the function generator through a loudspeaker next to the mic, observe the voltage output with the scope, and measure the AC voltage with a multimeter, perhaps plotting output voltage as a function of frequency. Note: the specs for the electret mic show a fairly flat response from 50Hz to 3kHz, so most of what the students will see here is the poor response of a cheap speaker at low frequencies.
   EE concepts: current sources, AC vs DC, DC blocking by capacitors, RC time constant, sine waves, RMS voltage, properties varying with frequency.Lab skills: power supply, oscilloscope, function generator, RMS AC voltage measurement.Equipment needed: multimeter, oscilloscope, function generator, power supply, electret microphone, small loudspeaker, selection of various resistors, breadboard, clip leads.
4. Sampling and Aliasing
   Students will use the data logger software on the Arduino to sample sine waves from a function generator at different sampling rates.  They will need to design a high-pass RC filter to shift the DC voltage from centered at 0 to centered at 2.5v in the middle of the Arduino A-to-D converter range.  They will also design a low-pass filter (with corner frequency below the Nyquist frequency) to see the effect of filtering on the aliasing.
   EE concepts: quantized time, quantized voltage, sampling frequency, Nyquist frequency, aliasing, RC filters.
   Equipment needed:  function generator, Arduino board, computer.
5. Audio amplifier
   Students will use an op amp to build a simple non-inverting audio amplifier for an electret microphone, setting the gain to around 6 or 7. The amplifier will need a a high-pass filter to provide DC level shifting at the input to the amplifier. Note that we are using single-power-supply op amps, so they will have to design a bias voltage supply as well. The output of the amplifier will be recorded on the Arduino (providing another example of signal aliasing).
   The second half of the lab will add a single bipolar transistor to increase the current and make a class A output stage for the amplifier, as the op amp does not provide enough current to drive the 8Ω loudspeaker loudly.
   EE concepts: op amp, DC bias, bias source with unity-gain amplifier, AC coupling, gain computation.
   Lab skills: complicated breadboarding (enough wires to have problems with messy wiring). If we add the Arduino recording, we could get into interesting problems with buffer overrun if their sampling rate is higher than the Arduino’s USB link can handle.
   Equipment needed: breadboard, op amp chip, assorted resistors and capacitors, electret microphone, Arduino board, optional loudspeaker.
6. Hysteresis and capacitive touch sensor
   For the first half of the lab, students will characterize a Schmitt trigger chip, determining V_IL, V_IH, V_OL, and V_OH. Using these properties, they will design an RC oscillator circuit with a specified period or pulse width (say 10μs), and measure the frequency and pulse width of the oscillator.
   For the second half of the lab, the students will build a relaxation oscillator whose frequency is dependent on the parasitic capacitance of a touch plate, which the students can make from Al foil and plastic food wrap. In addition to breadboarding, students will wire this circuit by soldering wires and components on a PC board designed for the oscillator circuit. Students will have to measure the frequency of the oscillator with and without the plate being touched. We will provide a simple Arduino program that is sensitive to changes in the pulse width of the oscillator and that turns an LED on or off, to turn the frequency change into an on/off switch.  Students will treat the oscillator board as a 4-terminal component, and examine the effect of adding resistors or capacitors between different terminals.
   EE concepts: frequency-dependent feedback, oscillator, RC time constants, parallel capacitors.
   Lab skills: soldering, frequency measurement with digital scope.
   Equipment needed: Power supply, multimeter, Arduino, clip leads, amplifier prototyping board, oscilloscope.
7. Phototransistor and FET
   First half: characterize phototransistor in ambient light and shaded.  Characterize nFET and pFET.
   Second half: students will “tinker” with the components they have to produce a light-sensitive, noise-making toy.
   EE concepts: phototransistors, FETs.
   Equipment needed: breadboard, phototransistor, power FETs, loudspeaker, hysteresis oscillator from previous lab, oscilloscope.
8. Electrode measurements
   First, we will have the students attempt to measure the resistance of a saline solution using a pair of stainless steel electrodes and a multimeter. This should fail, as the multimeter gradually charges the capacitance of the electrode/electrolyte interface.Second, the students will use a function generator driving a voltage divider with a load resistor in the range 10–100Ω. The students will measure the RMS voltage across the resistor and across the electrodes for different frequencies from 3Hz to 300kHz (the range of the AC measurements for the Agilent 34401A Multimeter). They will plot the magnitude of the impedance of the electrodes as a function of frequency and fit an R2+(R1||C1) model to the data, most likely using gnuplot. There will be a prelab exercise to set up plotting of the model and do a little hand tweaking of parameters to help them understand what each parameter changes about the curve.Third, the students will repeat the measurements and fits for different concentrations of NaCl, from 0.01M to 1M. Seeing what parameters change a lot and what parameters change only slightly should help them understand the physical basis for the electrical model.Fourth, students will make Ag/AgCl electrodes from fine silver wire. The two standard methods for this involve either soaking in chlorine bleach or electroplating. To reduce chemical hazards, we will use the electroplating method. As a prelab exercise, students will calculate the area of their electrodes and the recommended electroplating current.  In the lab, they will adjust the voltage on the bench supplies until they get the desired plating current.Fifth, the students will measure and plot the resistance of a pair of Ag/AgCl electrodes as a function of frequency (as with the stainless steel electrodes).Sixth, if there is time, students will measure the potential between a stainless steel electrode and an Ag/AgCl electrode.EE concepts: magnitude of impedance, series and parallel circuits, variation of parameters with frequency, limitations of R+(C||R) model.Electrochemistry concepts: At least a vague understanding of half-cell potentials, current density, Ag → Ag⁺ + e^-, Ag⁺ + Cl^- → AgCl, Fe + 2 Cl^-→ FeCl₂ + 2 e^-.Lab skills: bench power supply, function generator, multimeter, fitting functions of complex numbers, handling liquids in proximity of electronic equipment.Equipment needed: multimeter, function generator, power supply, stainless steel electrode pairs, silver wires, frame for mounting silver wire, resistors, breadboard, clip leads, NaCl solutions in different concentrations, beakers for salt water, secondary containment tubs to avoid salt water spills in the electronics lab.
9. Pressure sensor and instrumentation amplifier
   Students will design an instrumentation amplifier with a gain of 300 or 500 to amplify the differential strain-gauge signal from a medical-grade pressure sensor (the Freescale MPX2300DT1), to make a signal large enough to be read with the Arduino A/D converter. The circuit will be soldered on the instrumentation amp/op amp protoboard. The sensor calibration will be checked with water depth in a small reservoir. Note: the pressure sensor comes in a package that exposes the wire bonds and is too delicate for student assembly by novice solderers. We will make a sensor module that protects the sensor and mounts the sensor side to a 3/4″ PVC male-threaded plug, so that it can be easily incorporated into a reservoir, and mounts the electronic side on a PC board with screw terminals for connecting to student circuits.  This sensor is currently being prototyped, and if it turns out to be too fragile, we will use a Freescale MPX2050GP, which has a sturdier package, but is slightly less sensitive and more expensive. (It also isn’t made of medical-grade plastics, but that is not important for this lab.) Note that we are deliberately notusing pressure sensors with integrated amplifiers, as the pedagogical point of this lab is to learn about instrumentation amplifiers.EE concepts: differential signals, twisted-pair wiring, strain gauge bridges, instrumentation amplifier, DC coupling, gain.Equipment needed: Power supply, amplifier prototyping board, oscilloscope, pressure sensor mounted in PVC plug with breakout board for easy connection, water reservoir made of PVC pipe, secondary containment tub to avoid water spills in electronics lab.
10. Class-D power amplifier
11. Electrocardiogram (EKG)
    Students will design and solder an instrumentation amplifier with a gain of 2000 and bandpass of about 0.1Hz to 100Hz. The amplifier will be used with 3 disposable EKG electrodes to display EKG signals on the oscilloscope and record them on the Arduino.Equipment needed: Instrumentation amplifier protoboard, EKG electrodes, alligator clips, Arduino, oscilloscope.

3. Systemwide Senate Regulation 760 specifies that 1 academic credit corresponds to 3 hours of work per week for the student in a 10-week quarter. Please briefly explain how the course will lead to sufficient work with reference to e.g., lectures, sections, amount of homework, field trips, etc. [Please note that if significant changes are proposed to the format of the course after its initial approval, you will need to submit new course approval paperwork to answer this question in light of the new course format.]

The combination of BME101 and BME101L is 7 units (21 hours per week).  The time will be spent approximately as follows:

• 3.5 hours lecture/discussion
• 3.5 hours reading background and circuits text
• 3 hours read lab handouts and doing pre-lab design activities
• 6 hours lab
• 5 hours writing design reports for lab

4. Include a complete reading list or its equivalent in other media.

Lab handouts: there is a 5- to 10-page handout for each week’s labs, giving background material and design goals for the lab, usually with a pre-lab design exercise.  The handouts from the prototype run of the course can be found at http://users.soe.ucsc.edu/~karplus/bme194/w13/#labs
Data sheets: Students will be required to find and read data sheets for each of the components that they use in the lab.  All components are current commodity components, and so have data sheets easily found on the web.  Other readings are associated with the lecture course.

5. State the basis on which evaluation of individual students’ achievements in this course will be made by the instructor (e.g., class participation, examinations, papers, projects).

Students will be evaluated on in-lab demonstrations of skills (including functional designs) and on the weekly lab write-ups.

6. List other UCSC courses covering similar material, if known.

CMPE 167/L (sensors and sensing technologies) covers some of the same sensors and design methods, but at a more advanced level.  BME 101L would be excellent preparation for the CMPE 167/L course.

Physics 160 offers a similar level of practical electronics, but focuses on physics applications, rather than on bioengineering applications, and is only offered in alternate years.

7. List expected resource requirements including course support and specialized facilities or equipment for divisional review. (This information must also be reported to the scheduling office each quarter the course is offered.)

The course will need the equipment of a standard analog electronics teaching lab: power supply, multimeter, function generator,  oscilloscope,  computer, and soldering irons. The equipment in Baskin Engineering 150 (commonly used for EE 101L) is ideally suited for this lab. There are 12 stations in the lab, providing a capacity of 24 students since they work in pairs rather than as individuals.  The only things missing from the lab stations are soldering irons and circuit board holders (such as the Panavise Jr.), a cost of about $45 per station.  Given that a cohort of bioengineering students is currently about 35–40 students, two lab sections would have to be offered each year.

In addition, a few special-purpose setups will be needed for some of the labs, but all this equipment has already been constructed for the prototype run of the course.

There are a number of consumable parts used for the labs (integrated circuits, resistors, capacitors, PC boards, wire, and so forth), but these are easily covered by standard School of Engineering lab fees.  The currently approved lab fee is about $131, but may need some adjustment to change exactly what tools and parts are included, particularly if the students are required to buy their own soldering irons (a $20 increase).

The course requires a faculty member (simultaneously teaching the co-requisite Applied Circuits course) and a teaching assistant (for providing help in the labs and for evaluating student lab demonstrations). Because the lab is such a core part of the combined course, it requires faculty presence in the lab, not just coverage by TAs or group tutors.

8. If applicable, justify any pre-requisites or enrollment restrictions proposed for this course. For pre-requisites sponsored by other departments/programs, please provide evidence of consultation.

Students will be required to have single-variable calculus and a physics electricity and magnetism course. Both are standard prerequisites for any circuits course. Most of the labs can be done without calculus, but it is essential for the accompanying lecture course.

9. Proposals for new or revised Disciplinary Communication courses will be considered within the context of the approved DC plan for the relevant major(s). If applicable, please complete and submit the new proposal form (http://reg.ucsc.edu/forms/DC_statement_form.doc or http://reg.ucsc.edu/forms/DC_statement_form.pdf) or the revisions to approved plans form (http://reg.ucsc.edu/forms/DC_approval_revision.doc or http://reg.ucsc.edu/forms/DC_approval_revision.pdf).

This course is not expected to contribute to any major’s disciplinary communication requirement, though students will get extensive writing practice in the design reports (writing between 50 and 100 pages during the quarter).

10. If you are requesting a GE designation for the proposed course, please justify your request making reference to the attached guidelines.

No General Education code is proposed for this course, as all relevant codes will have already been satisfied by the prerequisites.

11. If this is a new course and you requesting a new GE, do you think an old GE designation(s) is also appropriate? (CEP would like to maintain as many old GE offerings as is possible for the time being.)

No General Education code is proposed for this course, as all relevant codes (old or new) will have already been satisfied by the prerequisites.

Self-taught teacher

I recently got some praise on the AP Bio teachers’ forum for answering some statistical questions, which embarrassed me a little.  I always feel like an imposter when I help anyone with statistics.  Despite having a B.S. and M.S. in math, and a Ph.D. in computer science, I learned statistics rather late in life—my first course in it was a graduate stochastic processes course in 1999, when I was 44, and my second was a Bayesian statistics course in 2001.  Other than those two courses, I’m pretty much self-taught in statistics and have to rely heavily on Wikipedia and other on-line sources.

I occasionally answer biology questions on the forum also, though my biology has an even shakier foundation: one freshman bio course, one junior-level biochem class (without the prerequisite general and o. chem), one graduate protein structure class—again, I have to rely heavily on things I’ve heard from colleagues or seen on the internet.  I feel like a real imposter answering bio questions on the AP Bio teachers’ forum, since everyone else on the forum has had far more courses in biology than I ever will. I doubt that I have the knowledge to teach even an 8th-grade life science course, much less an AP bio course.

While I’m always willing to share what I know, I frequently have gaps in my understanding that I’m not even aware of.

Of course, I’ve gotten used to teaching things I’ve had to teach myself—several of the courses I’ve created have been in subjects where I had had no formal instruction:

• applied circuits for bioengineers (2013)
• technical writing (1987–1999)
• digital typography course (1996–1998). Just this month I met an alumnus of that course, who got into graphical design, then web design and programming as a result of that course—he regrets that he did not take any other computer courses in college.
• bicycle transportation engineering (1997)
• bioinformatics: models and algorithms (our core grad bioinformatics course, 1998–present)
• protein structure prediction (1996–2011)
• banana slug genomics (2010, 2011)
• how to be a grad student (1990–present)
• resource-efficient programming (2004)

Other courses I’ve created after only one prior course:

• VLSI design (1982–2000)
• digital synthesis of music (1989 and 1991)

For that matter, my first faculty position was a joint appointment between an EE and a CS department, teaching mainly EE courses, based on having a CS PhD and having taken 3 EE courses (digital logic, microprocessors, and VLSI design).

Of course, I’ve also taught several courses designed by others, often with little prior training in the field.  I find that more difficult than teaching a course that I’ve designed myself, even if it takes me six months or more to teach myself the material before designing a course (as with the circuits course).

Because so much of what I’ve taught is material that I’ve had to teach myself, I tend to take a different approach to teaching than many other faculty.  I see my role as trying to provide guidance for students to learn the material faster than I did, with less time chasing down blind alleys, not to just dump some pre-digested knowledge into their heads for them to memorize and regurgitate. I don’t teach them as I’ve been taught, but as how I wish I had been taught.  I tend to pose them problems to guide their learning, rather than giving them information, then expecting them to repeat it back to me. (I’m self-taught in pedagogy also, but that is normal for university faculty.)

I want them to learn skills (not facts) that can serve them as a basis for further learning—for example, in the circuits course, I wanted the students to be able to design and build simple amplifier circuits and to be able to write design reports.  I didn’t care so much whether they could work book problems as that they acquired the mental attitudes of engineers—that they could design and build things, that data sheets are worth consulting, that precise and accurate recording of what was designed and measured is essential, that often you have to check things for yourself (not blindly trusting the data sheets or simple models), that consistency and sanity checks are an important part of any problem solving, that breaking a problem into subproblems is an essential element of design in any engineering field, and so forth.  (I think they got some of that, but it takes more than 10 weeks for the attitudes to really become part of their worldview.)

I think that the flattery on the AP Bio teachers’ forum was to soften me up to mentor a bright high school student that the teacher knew.  I’m willing to serve as a mentor for smart and motivated kids interested in bioinformatics, but not in other branches of biology—I just don’t know enough in those fields to guide anyone.  Even in bioinformatics, I don’t find it easy to guide students below a certain level of training—I have a few programming projects I could use student help on, but I don’t have many ideas for students who aren’t already expert programmers.

I have one pending request from a high school student wanting to do computational protein work in my lab this summer—something I don’t really do any more.  I have no idea what to tell her—10 years ago, I had an active lab that I could have worked her into, but with the repeated failure of grant requests and my subsequent disillusionment with the whole grant rat race, I no longer have a lab. I’m now working more as a consultant on other people’s research (helping out with statistics, signal processing, genome assembly, and other things I’m self-taught in) and putting most of my time into teaching and creating new courses.

Triangle-wave oscillator

One of the student suggestions from the “bar exam” was to design a protoboard for the class D amplifier, so that they could keep it as a permanent object (a more useful one than the pressure-sensor amplifier, since they don’t have any strain gauges).

I’ve been thinking about that and see a few problems:

• The block diagram the students came up with this fall (with my guidance) calls for 3 power supplies, which makes the amplifier a bit impractical to power from a battery or wall-wart power supply.
• The students used an external triangle-wave generator.
• The protoboard would have to be fairly large to accommodate the FETs and inductor and enough wiring space, which would probably result in a larger board than 5cm × 5cm, and so $2/board rather than $1/board.

I’ve not given much thought yet to the power-supply problem, but I did think a little about the triangle-wave generator.  Since they only need to generate triangle waves at a single frequency (in the 60kHZ–100kHz range), it should be possible to use a hysteresis oscillator with an integrator rather than a simple RC timing circuit.  Something like the following might work:

The slew rate of the MCP6004 op amps is only 0.6 V/µs, but the triangle wave only swings from V_IL to V_IH, or about 1V, so the minimum period is about 3.3µs, for a maximum frequency of 300kHz. If we use another op amp to amplify the signal to make it swing almost 5v, instead of 1V, the maximum frequency would be only 60kHz.

I might want to try this circuit out this week, to see if it is worth having the students play with next year.

Student writing

In How does blogging about science benefit students?, Sandra Porter recommends that students (specifically biotech students at Portland COmmunity College) keep a blog :

My hypothesis is that a science blog for a science student can serve the same purpose that a portfolio serves for an artist or a set of articles serves for a writer.  Your blog can be your record of accomplishments.

Not only can your blog document your work, your blog can show that you can write, that you can spell (not a skill to take for granted), and can give you a chance to describe what you’ve done.

She describes her first job interview and what she is doing to avoid similar embarrassment for her students.  She has students in one class keep a professional lab notebook and bring it to interviews—showing that they can keep a proper lab notebook and providing documentation to support their assertion of knowing various protocols.

Student blogging is another approach she is experimenting with.  She encourages the students to use blogs as an on-line notebook (much like I’ve been doing on this blog for the circuits course), and to include the URL for the blog in resumes and cover letters for jobs.  If interviewers are interested, they can check out a few posts on the blog to see if the student can write coherently (a very important skill that can not be automatically assumed of college graduates) and, if there are search boxes and appropriate tags on the posts, whether the students know the protocols and equipment that the job requires.

In a subsequent post, The ten commandments of student science blogging, she talks about the guidelines she gives students for their blogs, to keep them from accidentally doing unprofessional things that would hurt, rather than, help their chances of getting a job.

The biggest problem I see with her recommendations is that the only audience she has identified for the student is a mysterious “job interviewer” whom the students have never met.  Writing for an unknown, difficult-to-imagine audience is hard. Writing for an imagined expert (an interviewer or professor) almost always brings out the worst writing, with inflated diction, misused jargon, and awkward ungrammatical sentences.  When writing to show that they know something to someone who knows it better, students stumble over nearly every sentence—leaving out important concepts and tossing in irrelevant minor points in a vain attempt to impress.

I think it might benefit the students to be given a more specific audience—one that they can picture writing to directly and actually informing of something new.  For an online lab notebook, it could be students at other schools (“look at the cool stuff we get to do here!”) or future students in the same lab (“never use the pink labels in the freezer—the glue on them cracks in the cold and the labels fall off”), both of whom are imaginable audiences.

The advice I gave in my circuits course is the standard advice I give to students: Write to students taking the course next year.  Assume they know what you knew coming into the course, but explain to them anything that you didn’t already know.  Make the report detailed enough that a student reading it could duplicate your work without having access to the original assignment—though they might have to looks a few things up on the web or in text books. (Provide pointers to appropriate readings, when possible.)  Explain not just what you did, but why, and provide warnings to help your reader avoid mistakes that you made.

Most of the students in the circuits course got this idea, and the reports were mostly coherent and directed at the right audience, though they were a little light on pointers to appropriate reading.

One thing that Sandra Porter doesn’t mention in her “ten commandments”, but which I had to really rant about in my course: “Get the details right!”  Sandra mentions spelling and punctuation, which are markers for attention to details, but the accuracy of the content is far more important. I can forgive an occasional typo (though failure to run text through a spell checker indicates a level of sloppiness that would disturb me as a job interviewer), but the main engineering content needs to be checked and double-checked, both for consistency with the lab notebook notes and for general sanity (recompute the corner frequency from the RC values in the schematic—is that what was intended?).

If you are giving a circuit schematic, every wire must be correctly connected, every component must have the correct value, and pin numbers should be correct.  The students  in the circuits course had incredible difficulty with checking their own and each other’s work for accuracy, and obvious errors (like power-ground shorts) occurred on most of the assignment first drafts.  For a biotech student, the equivalent would be getting the wrong reagent in a protocol, putting ice in autoclave, or replacing µg with mg.

The rate of errors in schematics did not drop much over the quarter, though I felt it should have.  Other writing problems (like poor audience assessment, overuse of passive, or misuse of “would”) were generally fixed after being pointed out, but the sloppiness in the circuit diagrams continued to be a problem all quarter.  By “sloppiness” I don’t mean poor drawing skills, as most of the students used CircuitLab to draw neat schematics, but semantic errors that changed the meaning of the circuits.

If anyone has ideas for improving student attention to details in schematics, I’d appreciate hearing them.