Gas station without pumps

2013 January 11

Third day of circuits class

Filed under: Circuits course — gasstationwithoutpumps @ 21:08
Tags: , ,

Today’s lecture did not go well.  My co-instructor and I did not have time ahead of class to coordinate, and we had somewhat different purposes for the day.  We got a lot of good material out to the students, but in a rather disorganized way.  I’m afraid I interrupted his presentations too often with points that would have been relevant for what I had wanted to do, but were sidetracks for where he was going. We’ve taught together before, and I know we can do better than this, both individually and together.

I had planned to cover different temperature measuring devices (thermistors, thermocouples, RTDs, diode temperature sensors, bimetal strips with tilt switches, glass thermometers with cameras, …), so that students could talk about when thermistors were a good choice for bioinstrumentation in their lab reports.  We started out discussing symbols for schematic diagrams, then sidetracked into the definition of voltage, current, and resistance, sidetracked again into dynamic resistance, talked a bit about thermal resistance and thermal mass (though not in enough detail to be helpful), repeated material on voltage dividers, and were generally all over the map.

After class three of the students from the class (20% of the 15-student class) came to my office to give me feedback and suggestions.  They were feeling a bit overwhelmed and confused.  I don’t blame them—this first week has been too much, too fast.  I’ll try in the Monday and Wednesday lecture slots to give them everything they need for the next lab, and hope that it goes a bit smoother.

I’ve done a couple of things that might help a bit, like posting guidelines for the lab write-ups and reading lists with specific dates.  My son has also agreed to help students install Data Logger on Monday, which should help students do some stuff on their own that does not need all the lab equipment.  We’ll probably do the Data Logger installation in the same lab that is used for the Thursday sessions, since the EE101 course is not scheduled then.  Maybe I’ll move my Monday office hours to the lab and lengthen them, so that students can get more lab time with someone to help them.

I’ve also been thinking about how to make things work better next year, so students can have a somewhat gentler ramp up at the beginning of the quarter.  One obvious thing is to break the thermistor lab into two labs.  In the first lab, students would measure the resistance of the thermistor at about 10 temperatures and plot them with gnuplot.  This would just involve the thermistors, the thermometers, the multimeters, and gnuplot.  As a second lab, we could have them do the voltage divider calculations, the selection of the resistor, and the voltage measurements with the Arduino. The software seems to be a bigger problem that I had anticipated, so splitting the two programs (gnuplot and the Data Logger) into two different labs would reduce that load by a factor of 2.

I suspect that several of the labs could be profitably split into two labs in this way, but we’d end up with about 16–20 labs instead of 10 labs.  That’s an idea for next year: have 2 2-hour labs a week, where most of the learning takes place, and intersperse with the 3 70-minute lecture/discussions.  It would make the teaching be 75 contact hours (instead of the usual 35 for a lecture course or 55 for a lecture+lab course), which might make staffing a bit more of a problem.  I’d be willing to do such a course, but it would be hard to get other people to.  For this year, I’ll be pleased if the students can complete 8 of the 10 labs I’ve currently got planned (depending which 8, of course), but I’m going to try to include all 10.

One of the students suggested that we do “exit tickets” for the lectures (not the term she used, but that is the name for the technique in Lemov’s Teach Like a Champion).  While I like the idea, we’ve not ended any of the lectures or labs on time this week, and I don’t expect my time sense to improve over the quarter.  Exit tickets only work if you can free up a couple of minutes at the end of each lecture.  I’m more likely to be able to set up an entry routine, where everyone answers a question at the beginning of class.  I’ll try to come up with something for Monday.

This group of students is smart and adventurous enough to be guinea pigs for a new course, but they have a different background from students I have taught before, and so I have difficulty guessing which things they will find easy and which things hard.  I rely on them telling me, so that I can try to adapt the course,both this year and for future years.

3 Comments »

  1. One of the students e-mailed me asking for references for different thermosensor types. I sent the following

    http://en.wikipedia.org/wiki/Thermometer has some general coverage of thermometers (many non-electronic) and pointers to articles about specific types.

    http://en.wikipedia.org/wiki/Resistance_thermometer has a good discussion of RTDs, comparing them to thermocouples and thermistors (with pointers to articles about them)

    http://en.wikipedia.org/wiki/Infrared_thermometer covers infrared thermometers

    http://en.wikipedia.org/wiki/Silicon_bandgap_temperature_sensor is a rather poor stub of an article on the diode-drop thermometers

    I updated the list of links at the end of the http://en.wikipedia.org/wiki/Thermometer to include thermistors, infrared thermometers, and thermocouples, which are mentioned in the main body, but inexplicably omitted at the end.

    Comment by gasstationwithoutpumps — 2013 January 12 @ 18:08 | Reply

  2. Might be too little too late on this one, but have you considered using the DIRECT concept inventory? (Scroll about halfway down for the link, as well as other related assessments). Questions in that style might help you anticipate common difficulties in making sense of current, resistance, voltage, and power. It’s strictly a DC assessment, but I’ve found it quite helpful in getting my students to notice their thinking and articulate their questions.

    Comment by Mylène — 2013 January 13 @ 20:22 | Reply

    • I had not considered using the DIRECT inventory. I’ll look over it and see if it would help. I’m not sure that the information I would get from it is worth the class period it would take to administer. Of course, several of the students in the course read my blog now, so I certainly can’t use it as a graded test.

      Comment by gasstationwithoutpumps — 2013 January 14 @ 17:31 | Reply


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