# Gas station without pumps

## 2013 September 22

### Projects for freshman design seminar

Filed under: freshman design seminar — gasstationwithoutpumps @ 12:15
Tags: , , ,

The Fall quarter is about to start, and I don’t have my web sites set up with all the homework assignments yet, but I’ve been thinking more about my Winter and Spring courses than my Fall ones.

This Winter I’ll be trying to run a new freshman design seminar for bioengineering majors.  This is intended to be a 2-unit course (that is, about 60 hours total work) and to have a lot of engineering design thinking.  The basic idea of the course is to have students design and build something relevant to their major, and to get them used to thinking of themselves as engineers, rather than as students who memorize stuff from books or as hands in a bio lab, who behave like low-cost robots to do whatever protocols they are told to implement.

The problem, of course, is that I can’t count on freshmen having learned anything useful yet, at least not universally.  Most of the students will have had little or no physics, many will have had little chemistry or biology, most will have had no computer programming, and essentially all will have had no electronics.  Collectively, there may be a fair amount of learning in the room, but individually, not so much.

This argues for doing a group project (the traditional way to get something done with large numbers of untrained people).  The danger, as with many group projects, is that one student might end up doing all the work, because that is more efficient than parceling out the work to less competent team members.  With only 60 hours per student (including class time, reading, lab safety training, and any other activities), I can’t have them picking large projects that are too big for one person to handle alone, which is the usual engineering school approach to ensuring that group projects are really group projects.

The course is not a required one, so I won’t have to deal with reluctant students who don’t want to be there, which removes one problem, but it also means that I have to come up with a course that excites the students, and makes them want to put in the effort to accomplish the project.  That means coming up with project ideas that are feasible for freshman at an only moderately selective school (we accept about 50% of applicants) with limited time, but that are exciting to do. A tough challenge!

In June, I mentioned 2 possible projects:

• A low-cost optical density meter for continuous monitoring of OD 600 (with an LED light source) or OD 650 (with a narrower-spectrum laser-diode light source) of cultures on a shaker table.
• A pulse oximeter for measuring blood oxygenation.

Over the summer, I played a bit with the pulse-oximeter idea, and I think it may be a bit too difficult for students with no analog electronics and no mechanical design skills—a pulse monitor using a bright IR or red LED shining through a finger seems feasible though.

I thought about some other projects students could work on, mostly on the theme of do-it-yourself lab equipment for home or cash-strapped high-school labs:

• 3-color colorimeter.  This consists of an RGB LED, a disposable cuvette, a phototransistor, and a microcontroller with analog-to-digital conversion.  The mechanical design is straightforward, the electronics trivial, and the programming not too difficult.  The resulting device would be useful in a number of AP chem labs.
• Conductivity meter.  I’ve posted about this idea already.  It also has trivial electronics and fairly simple programming.  There would need to be a bit more background on the idea of polarizable and non-polarizable electrodes, and most of the design difficulty is in mechanical design—designing a small probe that is consistently wet by the solution and can be handled by the user.
• Spectrophotometer.  Initially I thought that a spectrometer was a bit too ambitious for the freshman design seminar, but I’ve seen a couple of crude open-source designs (PublicLab design and Scheeline cellphone design) that could serve as starting points for a usable, low-quality spectrometer.  The biggest difficulty here is in getting the spectrum into digital form—the open-source designs use an external camera and a lot of existing software to finesse this problem.  I don’t particularly like the idea of using a DVD as a diffraction grating (the lines are spiral, rather than straight), especially since linear diffraction gratings cost under $1 each (down to 30¢ each in lots of 200). I looked up the track pitches of various optical disks:  CD 1.6±0.1 µm 3.95GB DVD-R 0.8 µm 4.7GB DVD-R 0.74 µm BluRay 0.32 µm and they are comparable with the 1µm pitch of the cheap linear diffraction gratings. The finer the pitch of the diffraction grating, the wider the resulting spectrum. Note that 4 of the 5 projects involve optoelectronics, and that all of them require programming (unless we take already written programs, like that available with the online spectrophotometer projects). Mechanical design for eliminating stray light paths and making sure that the optical path is consistent is important on all 4 projects, and the conductivity meter has similar mechanical design problems (for ensuring that the electrical paths between the electrodes remain consistent. ## 2013 September 3 ### Towards automatic measurement of conductivity of saline solution I’ve been thinking about a more automatic way to measure the conductivity of a saline solution than what I reported in Better measurement of conductivity of saline solution and Conductivity of saline solution. The original lab is suitable for the circuits class, because it measures with sine waves and models the impedance of the electrodes, but it requires a sine-wave oscillator and an AC voltmeter that can handle high frequencies—neither of which makes for a low-cost device. I was thinking that one could make a fairly simple device using the Freedom KL25Z board and a few extra components: Bias circuit and load resistor for making a conductivity meter. The idea is a simple one—instead of using a sine wave to drive the electrodes, use a square wave directly from the KL25Z. Connect the other electrode through a series resistor to a voltage centered between the two square-wave values, and use the 16-bit analog-to-digital converter to read the signal between the resistor and the electrodes just before changing the square-wave value. With a low frequency square-wave, the electrodes will act like a resistor, but much of the resistance will come from the insulating film on the electrode, rather than the solution. At high frequencies, the capacitance of the insulating file will not have time to charge and discharge, and the resistance of the electrodes will depend mainly on the conductivity of the solution. At high enough frequencies, the output waveform will look like a triangle wave, rather than a square wave, and the amplitude of the signal will be proportional to $\frac{R_{3}}{R_{S}+R_{3}}$, where R3 is the pull-down resistor in the diagram, and RS is the resistance of the solution. That means that $R_{S} \propto R_{3}(1/A - 1)$, and the conductance can be computed as the inverse of resistance. The measured value depends, of course, on the size and spacing of the electrodes, so one would have to calibrate with a known conductivity solution to get the proper scaling. I looked at the speed of the analog-to-digital converter on the KL25Z board, and they claim that they can get 16-bit conversion (though only with 12-bit accuracy, really) at 460k samples/sec—though I’ve not figured out the settings that really permit that. Higher accuracy is possible by averaging successive samples (which there is hardware support for), up to about 14.5 effective bits (averaging 32 differential samples, at a maximum rate of about 7.2kHz). By doing the averaging in software instead of hardware, we could run with a square-wave input up to about 90kHz (single-ended 16-bit samples at 180k samples/second seems to be fairly easy to set up). I think that is likely to be fast enough for all but the highest ionic concentrations, even using a very polarizable electrode like the 316L stainless steel ones we used for the Applied Circuits lab. One could check this by sweeping the frequency up, and seeing whether the estimate for RS converges. I’ve not tried building and testing this idea yet, because the Arduino boards have too slow and too low-resolution A-to-D converters, and my son is hogging the Freedom KL25Z board for his light glove prototype. (I guess I need to get another copy of the board). I don’t think I’ll be using this design in the Applied Circuits course (it is not suitable for teaching about modeling with linear components), but it might be a useful design for the freshman design seminar, or even for doing a titration lab in my son’s AP chem class. I understand that a standard lab is to titrate barium hydroxide with sulfuric acid, since the two reactants have conductive ions, but the barium sulfate precipitates out and the solution is essentially non-conductive when the two are perfectly balanced. The conductivity should form a nice “V” plot as sulfuric acid is added to a barium hydroxide solution—the units don’t even matter, since we just want to know what amount of sulfuric acid need to be added to attain the minimum, not what the conductivity is at the minimum. To make a useful conductivity meter for something like AP chem, I’d need a much smaller probe that the pair of electrodes I used in the Applied Circuits class. I think I could make a decent probe out of a piece of stainless steel tubing and a piece of the 316L welding rod, if I could come up with a good way to hold them together concentrically, make sure they were always immersed to the same depth, and keep any wires to the rod and tube out of the solution. This might be a good problem for the freshman design seminar. ## 2013 July 4 ### Blinky EKG fixed Filed under: Circuits course — gasstationwithoutpumps @ 18:26 Tags: , , , , , , In my earlier post today about the Blinky EKG, I wrote About the only thing I can think of is that there is too large a DC offset between the EKG electrodes, as the Blinky EKG uses a large gain on the first stage and a relatively small gain on the second stage. The DC-blocking high-pass filter is after the first stage. The EKG built on the protoboard used a smaller first-stage gain and larger second stage gain, so wouldn’t saturate the first stage as easily. (I’d learned more about EKG electrodes by the time I’d designed that circuit.) I could fix the gains by changing a few resistors on the EKG blinky board, which may be worth the pain of unsoldering and resoldering resistors. That may be worth trying today. I finally got a chance to test that this afternoon. I replaced the 470Ω Rgain resistor on the instrumentation amp with a 12kΩ resistor, reducing the first-stage gain from 175.2 to 11.667. With this change, I could see my heart beat with no problem, if I turned the second-stage gain all the way up to 111, as high as the trimpot would let me go. This gain was not enough to light the LED, though, so I replaced the 1kΩ resistor below the trimpot with a 100Ω resistor, which allows the second-stage gain to be adjusted from 10.9 to 1101. The combined gain is thus adjustable from 127.2 to 12845. UPDATE: 2013 July 5. I realized this afternoon that I would have been better off leaving the 1kΩ resistor alone, and changing the 100kΩ resistor above the trimpot from 100kΩ to 510kΩ, giving me a second-stage gain varying from 47.36 to 521, and a total gain of 552.6 to 6078. At high gain, the LED is always on, and at low gain the LED is always off, but when the gain is around 2300, the LED blinks nicely and the waveform recorded with the Arduino data logger is good. I believe that the problems I’ve been having with the Blinky EKG board have been the result of DC bias in the EKG electrodes saturating the first stage, so reducing the gain of the first stage and increasing the gain of the second stage was the right fix. I’ve been thinking of redesigning the blinky EKG board to be more decorative (so that it could be worn as a pin or a pendant)—if I do that, I’ll certainly change the gain. ### Blinky EKG hard to debug Filed under: Circuits course — gasstationwithoutpumps @ 11:46 Tags: , , , , , , , , I’ve been having a frustrating couple of days trying to debug the Blinky EKG. It worked when I first built it, but every time I’ve tried to demo it, the demo has failed, and I couldn’t get it working even at home on Tuesday. I have another, very similar EKG circuit that I built on my instrumentation amp protoboard, which has worked fine every time I’ve tried to use it. There are a few differences between the circuits (the blinky EKG is battery powered, for example, has an LED load on the final output, and has a trimpot for adjusting the gain of the second stage), but none that explain to me the difference in performance. On Tuesday my experiments were limited to hooking up one or the other of the EKG boards and using an oscilloscope or Arduino data logger to observe the outputs or various internal signals. Using the EKG board that worked convinced me that the EKG electrodes were providing a good 1mV signal (that had been a problem in the circuits course, as many students got EKG circuits that worked with electrodes on me, but no electrodes on themselves—we never figured out exactly why). But I could not get anything from the blinky EKG—even the output of the instrumentation amp seemed to be constant. I suspected that I had fried the amplifier chip, and was considering unsoldering it and putting in a new one. Yesterday, I tried a different test, making an artificial input source, using resistors and my Elenco FG-500 function generator. Test fixture for the EKG blinky board. Note that with a 10V peak-to-peak oscillator input, the output would be a differential signal of about 1.8mV peak-to-peak. The diagram was drawn with Digikey’s SchemeIt. With this test fixture, I convinced myself that the Blinky EKG board was amplifying the differential input signal correctly, over a range of about 1Hz to 40Hz, as long as the resistor for setting the DC bias was under about 300kΩ. Even with a 3.3MΩ resistor, I could see the output signal, but there was a fair amount of 60Hz noise added to it. The gain was adjustable with the trimpot, but was high enough at all settings that I should be able to see EKG signals at the output clearly with the Arduino data logger—the gain control is mainly to get the LED to blink appropriately. One effect I should have anticipated, but did not, was that the bias voltage showed a large change every time the LED turned on. If I redo the EKG Blinky design, I’ll probably use a voltage reference (like the TL431ILP) rather than just a voltage divider for the input to the Vbias op amp, and the LED will not be powered from the Vbias line. In any case, the Blinky EKG board seems to be working as intended as an amplifier, and I’m still a bit mystified why it is not working when connected to the EKG electrodes. About the only thing I can think of is that there is too large a DC offset between the EKG electrodes, as the Blinky EKG uses a large gain on the first stage and a relatively small gain on the second stage. The DC-blocking high-pass filter is after the first stage. The EKG built on the protoboard used a smaller first-stage gain and larger second stage gain, so wouldn’t saturate the first stage as easily. (I’d learned more about EKG electrodes by the time I’d designed that circuit.) I could fix the gains by changing a few resistors on the EKG blinky board, which may be worth the pain of unsoldering and resoldering resistors. That may be worth trying today. Note: I’m starting to use DigiKey’s SchemeIt for schematic capture, rather than Circuit Lab. There are a lot more symbols available in SchemeIt, and the user interface is fairly similar. SchemeIt does not have simulation capabilities, but CircuitLab’s never worked for me anyway. SchemeIt’s drawing is a bit cruder—they’ve not taken care to make sure that wires and components line up perfectly in the PNG output, but is better than Eagle‘s. Best of all, I know how DigiKey monetizes their schematic capture system: you can turn the Bill of Materials (BOM) into a DigiKey order with a couple of clicks, so I have no expectation that they will start charging for SchemeIt. I may even use the ordering capability in the way they intend, since I order from DigiKey fairly frequently already. ## 2013 April 10 ### 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 VIL, VIH, VOL, and VOH. 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.

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