Gas station without pumps

2013 February 5

Positive moments

Filed under: Circuits course — gasstationwithoutpumps @ 04:07
Tags: ,

After feeling a bit down yesterday about needing to reboot my teaching in the Applied Circuits course after the quiz, I went to bed early, as  I needed to get up early this morning to judge a science fair at the K–8 school where my wife works.  I managed to fall asleep, but woke up again before 3:00 a.m., with my mind still running around in circles trying to come up with ways to get the students to learn what I want them to learn in the circuits class.  I’ve been getting insomnia a lot lately, and it is not at all helpful.

When reading some mindless fantasy novel did not help me shut down the monkey chatter and get back to sleep, I got up to catch up on e-mail and blog reading (mostly mindless stuff also, though I sometimes come across a good idea on the teacher blogs).  Reading e-mail when I have insomnia is a bit dangerous, as it often results in my finding out about a missed deadline or some bureaucratic emergency I have to deal with, leading to more lack of sleep. Tonight there were no new disasters, and I managed to clean out a few old e-mails that could be handled with a short reply or simply filed and forgotten.

I spent a little time reflecting on my day, looking for positives to cheer myself up a bit. There were a few:

  • I had gotten a draft started on the lab handout for next week (the FET and phototransistor lab), and gotten a number of schematics drawn for it.  They always take me more time than they should, so getting them done put me back on schedule for this lab handout—I should be able to get it done in time to release by Thursday evening, despite having two mornings this week spent on science fair judging.
  • My son had come up to campus early for his class, so that he could debug the data logger on the Windows machines.  It has not been showing the menus the way it is supposed to, but the bug only  occurs on Windows machines, so he couldn’t debug it at home (we’re a no-Windows household).  He quickly tracked down the bug—it seems to be a bug in Tk, though not one we could find mention of on the web—he’ll be asking about it on StackOverflow. He has a workaround figured out for it, but the workaround requires some refactoring, as he had associated “quit” functionality with code for the system menu, and it is adding to the system menu that is causing Windows to suppress the menubar.  Once he gets that problem fixed, he just has one Linux bug to track down and a little more documentation to do before he’s ready for his first official release.  So I’m quite pleased with the progress he’s making on the data logger.
  • On my way into work this morning, I saw bicyclist on the bike path staring disconsolately at his derailleur.  I stopped to ask if he needed help, and he said that his chain kept slipping out of gear.  I spent a minute asking diagnostic questions: just in the lowest gear? or in all gears?  Both derailleurs or just the rear?  When he said that it was in all gears and just the rear derailleur, I guessed that the problem was the cable adjustment, and looked for the barrel adjuster to adjust the cable housing length.  There wasn’t one.  At first this confused me—who would put a cable on a shifter without a length adjustment?  Then I looked more closely at the rear derailleur and realized that it had a screwdriver-dependent adjuster, rather than a barrel adjuster.  I’d not seen that on a bike before, but the bike looked like an old one (with shift levers on the downtube) and not particularly high quality, so it may have been a cheap design that did not survive in the marketplace.  I got out the screwdriver on my Swiss Army knife and turned the adjusting screw a quarter of a turn to lengthen the housing.  We checked the derailleur and it seemed to shift ok, so I suggested he take the bike to the Bike Co-op or the Bike Church to learn how to adjust the derailleur properly and continued up the hill.  At the top I waited half a minute to ask him as he rode by whether it was shifting ok now, and he thought that it was.  The total time added to my morning commute was about 3 minutes, and doing a good deed like that lifted my mood for a couple of hours.
  • In my lab office hours after class today, one of the students who had been having a little trouble with the soldering last Thursday needed to redo the board.  The one he’d been working on last Thursday had gotten solder in a couple of the holes before the components had been added, and we had delaminated one of the traces trying to clear the holes. I was able to borrow a soldering iron from another lab (they don’t want to leave soldering irons in the lab I use, because the students in the EE circuits class can’t be trusted not to burn themselves, I guess), and the student was able to unsolder the screw connector from the old board and solder up the new board without mishaps.  I helped a bit with unsoldering the screw connector. I even had an opportunity to teach him the resistor color code, because he had forgotten what resistance value they had used (bad lab notebook keeping) and asked me if there was any way to read the markings on the resistor to determine its value.  Luckily, the colors were unambiguous on the resistor he was using (some of the markings are unclear on the blue-bodied resistors), so we could read it easily as a 4.7MΩ resistor.  I didn’t tell him the other approach, which is to measure the resistor with an ohmmeter, since that method is unreliable when the resistor is in a circuit—it is easy for other current paths through the circuit to make the ohmmeter read low (or high, in the case of a parallel capacitor).  It’s probably a good thing I didn’t suggest that, as I just checked on my hysteresis oscillator board and an in-circuit measurement there is off by a factor of five.  In any case, he managed to solder the new board up and demo it fairly quickly.  I think that leaves just one or two students who still need to demo their working soldered boards.

So despite the setback of the quiz showing me that more pseudoteaching than teaching has been taking place this quarter, I did have several positive moments yesterday. I need to remind myself of the positives more often.

I’ll work for another half hour or so tonight (either on the lab handout or on some research code), then try to get back to sleep before getting up earlier than usual to do the science fair judging.


Leave a Comment »

No comments yet.

RSS feed for comments on this post. TrackBack URI

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Blog at

%d bloggers like this: