I promised the students earlier in the quarter that I would stay in the lab until everyone finished—that resolve was sorely tested today, on the last scheduled lab time of the quarter, as one student stayed until 9:40p.m. (the lab started at 2 p.m.). I ended up giving the student more debugging help than was probably optimal pedagogically (pointing out wiring errors, swapped resistors, and other problems—even unsoldering some wires that were incorrectly placed), but after a while I just wanted to go home. Luckily the design was ok, and only the implementation needed to be fixed, or I might have been there all night. Every group in the class got an EKG designed, soldered, and working, though it took this year’s class longer than last year’s.
I wore EKG electrodes today (as I did for Tuesday’s lab), so that students could check whether problems they were having were with inadequate electrode contact or with their amplifiers. Some of the students did have poor signals from their electrodes, possibly due to their electrode gel having dried out somewhat, possibly due to inadequate skin preparation. I’ve found that a fairly simple skin prep works for me: after my morning shower I scrub the areas where I want to apply the electrodes with a dry towel, to remove any dead skin, and apply the electrodes within a couple of minutes. The electrodes still work well 10 hours later. The packaging claims that they are good for up to 24 hours, but I don’t think I’ve ever worn them for more than 12 hours.
The T-shirts the students ordered are done, but I didn’t have time this evening to pick them up, and I won’t have time in the morning (unless I wake up very early and the store opens early), as I have to set up the bread machine in the lab before going to see the 50-minute version of Hamlet being performed by Shakes To Go. Most likely, I’ll pick up the T-shirts on Saturday and have the students come to my office on Monday to get them. Monday is the deadline for them to turn in any assignments with REDO grades, so I suspect that many will be coming to my office then anyway. (Only one student has no lab reports to redo, but I don’t know how many of the redone reports I’ll get tomorrow and how many on Monday.)