Gas station without pumps

2014 March 17

Revised plan for circuits labs

Filed under: Circuits course — gasstationwithoutpumps @ 14:39
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In Plan for rearranged circuits labs I provided a tentative schedule for the applied circuits course and lab,  which starts on 2014 March 31.But after my experimenting with optical pulse detection this weekend, I need to rearrange the labs to move the phototransistor lab later and allow more time for it.  This post is my attempt to do that rearrangement.

Monday 2014 Mar 31 Administrivia: structure of course, rotating partners, labs not cookbook—need to read carefully before coming to lab. Pre-lab homework. Demo pressure sensor or EKG?
Ohms law, voltage dividers.
Homework: install gnuplot on own computers, read Wikipedia on thermistors and the Steinhart-Hart equation, draw voltage divider with schematic capture tool (probably Digi-key’s SchemeIt)
Tuesday 2014 Apr 1 Unpacking parts, labeling capacitor bags, using wire strippers, making clip leads, measuring input resistance of multimeter, measuring thermistor resistance at many temperatures.
Wednesday 2014 Apr 2 Do-now resistance-to-voltage converter. Gnuplot: fitting thermistor theory to measured data. Derivatives of voltage w.r.t. temperature to maximize sensitivity (and linearize output). Homework: install data logger on own computer and KL25Z, record accelerometer?
Thursday 2014 Apr 3 Soldering headers onto KL25Z boards, downloading data logger to KL25Z, if not already done. Measuring voltage of thermistor voltage divider, recording voltage vs. time.
See soldering instructions at Soldering headers on a Freedom board and Jameco soldering tips
Friday 2014 Apr 4 Voltage-divider do-now exercise. Other temperature measuring devices (RTDs, thermocouples, silicon bandgap temp sensors).
Monday 2014 Apr 7 Three-resistor do-now question. Feedback on design reports, i-vs-v plots, how electret mic works.  AC voltage (sine wave: amplitude, peak-to-peak, RMS voltage). DC blocking capacitors, RC filters (without complex impedance).
Tuesday 2014 Apr 8 Measure I-vs-V DC characteristic of resistor and of electret mic, both with multimeter and with KL25Z board.
Wednesday 2014 Apr 9 Gnuplot: plotting transformed data, fitting various models to i-vs-v (resistor, current source, blending of resistor and current source, more complex model).
Thursday 2014 Apr 10 Look at mic with resistor load on oscilloscope (AC & DC coupling).  Capacitor for own AC coupling. Loudspeaker on function generator?
Friday 2014 Apr 11 Another 3-resistor do-now question. Voltage sources, current sources, load lines, Thévenin and Norton equivalents.
Monday 2014 April 14 Hysteresis. Applications: cleaning up noisy signals to on/off signals, feedback control. Differential equation for capacitor, derived from Q=CV, RC time constant. Basic idea of hysteresis oscillator (demo of touch tensor?)
Tuesday 2014 Apr 15 Characterize hysteresis in Schmitt trigger chip using data logger. Breadboard hysteresis oscillator with various R and C values, measuring frequency or period (oscilloscope or frequency meter?).
Make and test touch sensor with breadboard oscillator. Solder hysteresis oscillator. Estimate capacitance of touch from change in period of hysteresis oscillator.
Note:I’ll have to write touch sensor code for KL25Z.
Wednesday 2014 Apr 16 Theory of sampling and aliasing
Thursday 2014 Apr 17 Sampling and aliasing lab. Awkward that this gets split from sampling and aliasing theory, but I want to analyze loudspeaker data this week.
Friday 2014 Apr 18 High-pass and low-pass RC filters as voltage dividers. Gnuplot plots and Bode plots for amplitude. Make sure they see ω=0 and ω=∞ simplifications, and straight-line approximations (f, 1/f, constant) away from corner frequency.  Introduce dB and dB/decade rolloff.
Monday 2014 Apr 21 RC filter/voltage divider quiz/midterm
Tuesday 2014 Apr 22 Impedance of stainless steel (polarizing) electrodes in different NaCl concentrations (at several frequencies).
Wednesday 2014 Apr 23 Gnuplot: Functions for impedance: Z_C, Z_L, Z_parallel. Fitting R1+(R2‖C) models to data, maybe fitting other models?
Polarizing and nonpolarizing electrodes.
Properties of stainless steel (corrosion resistance in oxidizing environments, biocompatibility, poor choice for electrodes)
Thursday 2014 Apr 24 Impedance of Ag/AgCl (non-polarizing) electrodes in different NaCl concentrations (at several frequencies)
Friday 2014 Apr 25 Intro to op amps, unity gain buffer, transimpedance amplifier.
Monday 2014 Apr 28 Inverting and non-inverting amplifier.
Tuesday 2014 Apr 29 Characterizing impedance of loudspeaker vs. frequency
Wednesday 2014 Apr 30 Gnuplot: fitting models for loudspeaker impedance.
Thursday 2014 May 1 Measuring nFET current with constant VDS and varying VGS, also with constant VGS and varying VDS. (pFET also?)
Friday 2014 May 2 Gnuplot: fitting nMOS transistor models to measured data. nFET and pFET as switches.
Monday 2014 May 5 System thinking and block diagrams: developing for audio amplifier
Tuesday 2014 May 6 Low-power single-stage audio amplifier with op amp
Wednesday 2014 May 7 Op-amp quiz/midterm
Thursday 2014 May 8 catchup day? characterizing pFET? characterizing LED?
Friday 2014 May 9 Op amps with RC voltage dividers (active filters)
Monday 2014 May 12 Do now: transimpedance amplifier.  Models for photodiodes and phototransistors.  (other photosensors?)
Tuesday 2014 May 13 Photodiode and phototransistor with single-stage simple transimpedance amplifier.
Freeform soldering to attach leads for fingertip transmission sensor. I need to drill a dozen blocks of wood for the fingertip alignment blocks.
Cut-and-try design for transimpedance gain needed to see reasonable signal without saturating amplifier. (Determine AC and DC components of current)
Wednesday 2014 May 14 Gnuplot: model gain of 1-stage and 2-stage amplifiers with RC filters.  Develop block diagram for 2-stage pulse detector with approximately 0.3Hz–30Hz bandpass.
Thursday 2014 May 15 Fingertip pulse sensor with 2-stage amplifier and bandpass filtering.
Friday 2014 May 16 class D amplifier  concept.
Monday 2014 May19 Developing class D block diagram
Tuesday 2014 May 20 class D audio amplifier day 1(preamp and comparators)
Wednesday 2014 May 21 Gnuplot: analyzing loudspeaker load, adding LC filter in front of loudspeaker to make sharp cutoff without ringing.
Thursday 2014 May 22 class D audio amplifier day 2 (output stage)
Friday 2014 May 23 Do-now: Wheatstone bridge. Strain gauges and Wheatstone bridges. Instrumentation amps.
Homework: block diagram and design for pressure sensor.
Monday 2014 May 26 Memorial Day, no class
Tuesday 2014 May 27 Pressure sensor day 1: design and soldering instrumentation amp prototype board
Wednesday 2014 May 28 catch up day?
Thursday 2014 May 29 Pressure sensor day 2: further debugging.
Recording pressure pulses from aquarium air pump?  Would need to buy some more air pumps.
Friday 2014 May 30 Action potentials in nerve and muscle cells?
Monday 2014 Jun 2 Why EKG signals differ based on placement of electrodes.  (Vector model)
Tuesday 2014 Jun 3 EKG day 1:  breadboard and debugging (confident students could go directly to soldering)
Wednesday 2014 Jun 4 Catch up?
Thursday 2014 Jun 5 EKG day 2: soldering, debugging, and demo.  Last day for any catchup labs.
Friday 2014 Jun 6 Catch up?
Monday 2014 Jun 9 4–7 p.m. Final exam? (probably not needed, except as a lab catch-up day)

I’m not 100% satisfied with this schedule, and things will probably slip as I discover unexpected difficulties in student preparation, but I think it is likely to run more smoothly than last year, and last year was not bad.

If any of my readers have suggestions on improvements that could be made in the labs or the order of topics, please let me know. I have to buckle down and (re)write the lab handouts soon!


  1. […] written and released the syllabus, a schedule of labs and lectures, guidelines for design reports, a study sheet (which they don’t need yet) with everything […]

    Pingback by Panicking about circuits class | Gas station without pumps — 2014 March 30 @ 22:08 | Reply

  2. […] my notes on last year’s hysteresis lab, I realized that my schedule for this week in the Revised plan for circuits labs, with both the hysteresis lab and the sampling lab in the same week was too ambitious. There was a […]

    Pingback by Hysteresis lab too long | Gas station without pumps — 2014 April 15 @ 22:35 | Reply

  3. […] Revised plan for circuits labs I provided a tentative schedule for the applied circuits course and lab, which I ended up not […]

    Pingback by Starting on book for circuits lab—scheduling labs | Gas station without pumps — 2014 June 12 @ 23:59 | Reply

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