Gas station without pumps

2016 August 3

Possible new lab order

Filed under: Circuits course — gasstationwithoutpumps @ 12:09
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I’ve been thinking about how to rearrange the labs (and the textbook) for a more sensible 2-quarter sequence. I need to have the basics done before October, since that is when I have to tell the lab staff what tools and parts to order for the winter quarter class.

Currently, the first half of the course is mainly voltage dividers and device characterization, and the second half is mainly amplifiers, but I’m thinking of changing the split so that all the audio stuff (microphone, loudspeaker, preamp, class-D amplifier) are in the second half, moving some of the other amplifiers (pressure sensor instrumentation amp and optical pulse monitor) to the first half.

There are 20 95-minute lab sessions each quarter, which is about the same total time as the 20 3-hour sessions of the old design (splitting a 3-hour session into two sessions adds some setup and teardown overhead, so two 95-minute session is no more than one 3-hour session, and may actually give students less time).

Here is the tentative new lab order:

1 T get parts, one person solders headers, other identifies and sorts parts
2 Th partners swap roles.
3 T Thermistor resistance measurement (ohmmeter) ice water
4 Th Thermistor resistance measurement (ohmmeter) hot water
5 T Thermistor voltage measurement (calibration check & recording)
REPORT (recording thermometer design)
6 Th function generator, oscilloscope, and PteroDAQ for time-varying signals. This is a tools lab, and I’m not sure exactly what form it will take.
7 T Sampling and aliasing (fixed sampling freq, downsample, record 0.1, 0.2, 0.4, 0.45, 0.5, 0.55, 0.6, 0.8, 0.9, 1.0, 1.1, 1.45, 1.6, 2.1 times sampling freq)
8 Th Sampling and aliasing continued (fixed input frequency, adjusting sampling frequency)
REPORT (sampling and aliasing)
9 T hysteresis threshold measurements using PteroDAQ & slow function generator, using 2 methods:

  • plotting Out-vs-in (with lines)and
  • Trigger on rising, trigger on falling to get thresholds.

Maybe add noise generator + power-supply → PteroDAQ digital inputs with and without hysteresis, but inputs on Teensy LC and Teensy 3.1/3.2 already have 0.06*Vdd = 200mV of hysteresis—maybe 74HC14N vs 74HC04, using PteroDAQ to look at digital output?

10 Th hysteresis oscillator on breadboard, view waveform on oscilloscope
11 T solder hysteresis oscillators & show PteroDAQ recording of freq vs. time for touch sensor
REPORT (hysteresis and relaxation oscillator)
12 Th Pressure sensor and instrumentation amp (low gain)
13 T Pressure sensor and inst amp + 2nd-stage op amp
14 Th Recording blood pressure measurements
15 T Drilling holes and recording breath pressure
REPORT (pressure sensor and instrumentation amp)
16 Th LED I-vs-V, phototransistor I-vs-V (dark), phototransistor I-vs-V (room light).
Question: how to make dark be dark enough?
Should we do phototransistor I-vs-V for room light through fingers?
17 T first-stage transimpedance, set gain to avoid saturation with DC.
Should I introduce log-transimpedance amplifier? Better design, but probably too much for first op-amp lab.
18 Th first-stage transimpedance, measure AC signal
19 T add high-pass & second-stage
20 Th low-pass in transimpedance to reduce 60Hz interference? 3-stage amplifier?
REPORT (optical pulse monitor)
quarter break
21 T get new parts + Microphone I-vs-V DC characterization
22 Th Microphone I-vs-V DC characterization
23 T Loudspeaker impedance
24 Th Loudspeaker impedance
REPORT (audio transducers)
25 T Mic preamp first stage
26 Th Mic preamp second stage
27 T Mic preamp soldering
28 Th Mic preamp soldering
REPORT (Mic preamp)
29 T nFET + pFET Id-vs-Vgs, Ron-vs-Vgs ??
Doing this right for power FETs is harder than I initially thought, so we’ll probably have to skip it, unless I come up with some clever way to make it easy.
30 Th Class D power amp
31 T Class D power amp
32 Th Class D power amp
REPORT (Class-D power amp)
33 T Electrode impedance (stainless steel)
34 Th Electrode impedance (stainless steel)
35 T Electroplating Ag/Agcl
36 Th Electrode impedance (silver)
REPORT (electrode impedance)
37 T EKG
38 Th EKG
39 T EKG
40 Th EKG

I’m thinking that reports will be due either Friday (for labs that end on a Tuesday) or Monday (for labs that end on a Thursday), with the intent of grading the labs on the next weekend and returning them on the following Monday.  There are still 10 lab reports due, but they are now spread over two quarters, so only biweekly, rather than weekly.

I’d like hearing from people (particularly students who’ve taken the course) about the order for the labs, the time allotted here for each lab, and ideas for things to add or remove. If no one has any better ideas, I’ll start rearranging the chapters of the book this week.


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