Gas station without pumps

2016 April 4

First week’s grading done

Filed under: Circuits course — gasstationwithoutpumps @ 22:44
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I spent all day Sunday grading the first set of lab reports.  I was expecting 24 reports of about 3 pages each, but I got 25 averaging about 5 pages each.  I think that the reports were a bit better this year than at corresponding times in previous years, but I did not get my grading done until almost midnight Sunday night, keeping me from getting much else done this weekend.

(I did manage to get my hair cut and to build a new strobe stand with room for 20 of my LED boards, which should give 1800 lumens during the flash. With a duty cycle of only 1/65, I don’t think that I need heat sinks on the boards for the strobe, as the average current should be only 40mA, though the peak current will be about 2.6A.)

In class on Monday, I gave students some group feedback on their writing, plus a couple of \LaTeX pointers, then took questions, some of which were about writing, but most were about the optimization of the fixed resistor in the voltage divider for the resistance-to-voltage converter in the thermistor lab.  I showed them how to set that up, but did not try to solve it in class.

After class, when I was making up the key (redoing all the problems—I don’t like just looking up results—refreshing my memory on how to solve the problems by resolving them is best), I ran into a little trouble doing the optimization. I used to be able to just ask Wolfram Alpha to solve the differential equation, but their newer parser seems to be much harder to convince to do anything.  I eventually gave up and used a cruder tool to just take the second derivative and solved for the resistance by hand.  That was faster than the time I wasted trying to get Wolfram Alpha to do anything useful.  (I suspect that they have deliberately crippled it, to make people pay for Mathematica.)

Monday afternoon and evening (from about 1:30 to 7:45) was spent grading the first pre-lab homework.  Again the results are a little better than previous years, but there were 9 prelabs fewer than I expected (3 students have dropped already and 6 did not do the prelab).  I hope that those who did not do the prelab were just confused about when it was due, and not starting a trend towards coming to class and lab unprepared. I also hope that no more students drop—this class is not a weed-out class, though it is a lot of work.

Back in January, Mike wanted to know where I ended up doing my grading. Sunday I did my grading in my breakfast room, with the laptop on the floor where I could get to it if I really needed to look something up, but where it was not a constant temptation to goof off.  On Monday, I worked in my office on campus, where the e-mail was a minor distraction that I checked between problems.  (For the prelabs, I graded the entire stack for problem 1, then the entire stack for problem 2, and so forth.  This makes for more consistent and faster grading than grading a student at a time, but it would be faster still if the students didn’t put their answers in random order on what they turned in.) I’ll probably continue with weekend grading in the breakfast room and prelab grading in my office until the distractions get to be too much—then I’ll look for a coffeeshop to grade in.

YouTube closed captions are awful

Filed under: Circuits course — gasstationwithoutpumps @ 13:18
Tags: , , , ,

I looked at the automatically generated closed captions on the Oscilloscope video and they were awful—pretty much just word salad. Speaker-independent voice recognition is obviously not a solved problem at Google.

I could not figure out from the captions what the text was supposed to be, so I’m definitely going to have to take an hour to edit the captions.  For your amusement, here are the automatically generated captions (with time stamps removed):


results go and circuits lab


showing this witness during a self-test
internal calibration began to overshadow

while doing this is the oscilloscope
trunk of an actual protest rally we can

make our nation of this gradually goes
to click here to lower celebration

finals where

whatever settings the previous first
layout which is probably not what you

want once it’s finished it off with
oppressed peoples historical back three

people said these are falling also know
what you want

matter whatever the last person in our
class there will help now also passed a

law received

craftspeople a suitable for calibration
single heads because we were so

impressed you’re the slap on a single
figures out what comes out is to view

that clearly see that is where color
associated with it

channel one yellow peril to this
political channel 39 channel for each

row has little to show you which channel
is for example channel two minutes later

colored chance i’m not respecting the
settings now able to accept this coupled

with 30 measures signal felt craft so
this is where signal from this marker

which is just changed it as a compliment
but this month now throws away and easy

going to take the last year which will
just show us that trust is on the screen

like this property

now to see this listing all we won’t be
using that much bandwidth and landlords

are very very important shows little
light switch when she can be set when

one asks the folks at matthews
telescopes for example tax and you still

think so it will bring up the menu by
pressing his body is still scope sent

along acts now here on the same set to

understand same problem check this
before now also watch now deciding where

around his father is cold six hits and
two bowls bowls permission to just see

they didn’t grade office he’s facing
they’re going about two-and-a-half

divisions so too cold for division

viable single with the slower larger
call for example a change is now five

balls for division and we can see the
same no only goes up by one division in

the other direction to one whole

signal goes off you might rather
increased number of major producing

science able to close at present the
many long now playing here next 10


horrible for his own vision for vertical
sets for all channels

provision a single all this way for
division last thing they apparently

because the other way to increase I’m
provision shrinking the way we did not

see one single this way every one
division so this is one killers we’re

also do this population 44122 color
calibration on the east coast is

slightly off

is it about fifteen years

channel as well you just said to
channels on here in great numbers if we

wanted to try to channel off push button
again while standing around a nice


orders probe is not properly compensated

just get there is very little space
heater which we can trust is a very

small screwdriver slotted over shooed
and other causes around the corner we

get it just right now include role is

channel on it for

which will help us all based on the
sound levels in the road below ground

connection between the microphone
amplifier board here has the microphone

in silver amplifier chip in black and
some connections on the screw terminal

we have power

5 volts red and brown and black it is
very important to always use this

convention for power and ground so that
you don’t actually connector on things

we don’t have the output signal here in
purple and everything is connected to

these heavier bands which have alligator
clips to the power supply we’re not

going to connect our protocol but we
could have to ground lead to the ground

and probably get here to center panel
which is the signal that is a kind of

difficult connection to make now it’s
connected and we can see on the screen

the output of the mic channels now just
a distraction in the range goals

overseas buyer has your rivals lot we
can also notice that occasionally take

notice cause they saw your head

only when the signal go from below 212
above 2.4 liter just this the trigger

man but other than that shows a trigger
which means it is based on a single

going from their low point for both
point to low is actually separate slope

is rising at going global

another option

trick or treating just normal several
times which will only trigger this is

more useful to wear a lot of things that
you don’t know the exact true that many


sure the level at which is to tax low on
the screen

levels for single trigger a tad bit

usually get a trigger but it’s a free
set a closer Trevor so we had a simple

Update 2016 April 6: After about 5–6 hours of work, I got the closed captions fixed, so these amusing automatic ones are no longer on the video.  Editing the captions is even more work than editing the video, so I can see why so many people don’t bother!

2016 March 31

Fifteenth weight progress report

Filed under: Uncategorized — gasstationwithoutpumps @ 22:12
Tags: , , , , , ,

This post is yet another weight progress report, continuing the previous one. I’m doing a little better this month, ging above my target range for only 6 days:

I've been fluctuating around the top of my target range, when I'd rather be in the middle of it (about 3–4 lbs less than my current weight).

I’ve been fluctuating around the top of my target range, when I’d rather be in the middle of it (about 3–4 lbs less than my current weight).


My exercise for March was a bit low (averaging just under 4.1 miles/day bicycling), but I was good about my raw-fruits-and-vegetables-for-lunch diet during the week, and did not indulge too much in sweets (except for the week of Spring break, when my son was home so we had ice cream and sorbetto in the freezer!).

PteroDAQ bug fixes

Filed under: Circuits course,Data acquisition — gasstationwithoutpumps @ 21:55
Tags: , , ,

I spent much of my lunch break today using a laptop borrowed from a student in the Applied Electronics course to debug a problem in PteroDAQ (one that I thought I had fixed on 2016 Feb 6 and again on 2016 March 30).

The problem was that on newer versions of Mac OS X, our original way for finding the serial ports and listing them in PteroDAQ (with good names) was failing, and the serial ports weren’t appearing. I fixed it for Mac 10.11.3, but that fix was breaking for most of the students in the course.  Yesterday, a student who is a friend of a student in the class suggested that the problem was just that I was only looking for USB 2 ports, and that the new USB stack used different data types for USB 3 ports.

Since I did not have any hardware with USB 3 ports (yes, I hang onto my computers for a while—the machine I’m typing this on is a MacBook Pro bought in mid-2009), I was unable to test the fix, so I released it to the class and asked them to test it.  A few students reported it working, but in the lab this morning, several students with Mac OS X computers were still unable to use PteroDAQ.  It was clearly a USB 2 vs. USB 3 problem still, since they were able to use PteroDAQ if they connected using my cable that has a USB 2 hub in it. One other student had gotten PteroDAQ to work for her by using a USB 2 hub that she had bought just for the purpose (probably a $7 or $8 one from Staples).

So instead of eating my lunch of raw vegetables, I sat with one of the laptops that was failing, uncommented some debug print statements that I had left in the code (I don’t delete debugging statements—I just comment them out, precisely for this sort of later bug fixing), and looked at the data structure for that Mac.  Apparently there are many different USB stacks for Mac OS X, with all sorts of differences. I put together ways of finding the appropriate name for the serial port using as many different methods as I could think of, based on either the child or the parent of the object in the chain that had the name I wanted.

After it was working on his computer, I handed it back to him and redid the bug fixes on my laptop and pushed them back to the bitbucket site, asking students to test the new code.  So far, everyone who has tested it has gotten it working (except for one student who seems to have a fried Teensy LC board—we were not able to get even the Arduino environment on my Mac to see his board). We don’t have any spare Teensy boards, so I suggested he order one from PJRC with the male headers already soldered on.  That makes two students (out of 48) who have had to order replacement boards (the other one soldered the male headers on the wrong side of the board, and delaminated some of the pads in attempting to correct the problem).  Perhaps next year we should order an extra 5% of Teensy LC boards, to cover for this sort of problem and have a local source for replacement boards.

I managed to finally finish my lunch after lab ended (around 5:30pm), but I’m glad to have gotten PteroDAQ working for (almost) everyone.  It is now 10pm, and time for me to prepare for tomorrow’s lecture.

Pep talk for students frustrated at the end of the first week

Filed under: Circuits course,Data acquisition — gasstationwithoutpumps @ 20:48
Tags: , , ,

Some of the students in my Applied Electronics for Bioengineers course are feeling frustrated at the end of the first week (often due to imposter syndrome, not any real inability to do the work).  I sent them the following e-mail this evening:

To the class—a number of people are feeling overwhelmed, because of the wide range of preparation that people in the class have had.  This is supposed to be a first course in electronics, but a number of people are taking it after having had other electronics courses.  If the advanced students are allowed to dominate the questions in class, I’ll never know what help the students with less preparation (that is, the students the course is intended for) need.  If you are feeling overwhelmed or out-matched in class, please ask questions!  I know that there are people feeling like they need more help, but I don’t know exactly what help they need.
I could guess at what is causing people problems, but I’m likely to guess wrong, and I don’t want to waste a lot of time on reviewing stuff that everyone in the class gets, while not spending any time on the stuff that is really needed.
In short, I’m saying that I need a lot of questions from people in the bottom quarter of the class, and I don’t think I’ve been getting them.
Going to [the group tutor]’s sections is another way to catch up to those you perceive as being ahead of you.
It looked to me like everyone pretty much got labs 1 and 2 done, and that most of the class (though perhaps not everyone) had a decent grasp of aliasing.  A bigger fraction of the class had PteroDAQ and gnuplot installed and working by Lab 2 than in any previous offering of the course—so this looks to me like a very promising start to the quarter—it may have seemed chaotic to you with not all the parts arriving on time and last-minute patches to PteroDAQ to compensate for changes in laptop operating systems, but these startup pains are normal—I expect to have them every time the course is offered.
Lab 2 was much harder than intended this year, because of the resistor assortments not including 470kΩ resistors, and I was impressed by how the class rose to the challenge, despite not having had the lectures yet that would really support the design work done (those are scheduled for week 3, I believe). I’m going to have to rewrite parts of Lab 2 to allow for the possibility of not having the right parts available.
The deal with Lab 2 was this: I had given them in the book a circuit to build that consisted of a function generator, a capacitor, a pair of resistors, and the Teensy board with the PteroDAQ software. The idea in terms of skills was for them to learn how to lay things out on bread board, collect data with PteroDAQ and do some minimal plotting with gnuplot.  The concept they were supposed to be learning about was aliasing, which I was planning to cover in lecture yesterday, but I got diverted to other equally important topics.
The problem was that the design I gave them could not be implemented, because the resistor assortments (which only arrived yesterday, so I had no idea exactly what resistors would be in the kit) did not have the specified 470kΩ resistors!  I probably should have redesigned the circuit for them and had them build a different circuit which would have worked equivalently (like using 1MΩ and 4.7µF instead of 470kΩ and 10µF), but I did not know what resistor values they did have in their kits.
Instead, on the spur of the moment, I chose to have the students come up with a design themselves that has the same (or nearly the same) RC time constant as the circuit in the book.  If I’d had an hour to think about how to handle the challenge, I might have chosen a different approach. The assignment I gave them tied in well with yesterday’s unplanned lecture—without that lecture, I would not have considered them capable of redesigning the circuit.
 I think that everyone in the class did come up with a design that let them do at least a few recordings with PteroDAQ, though they did not get as much time to explore aliasing as I had originally intended. There were several different designs students came up with, including the 1MΩ and 4.7µF design, 10MΩ and 0.47µF, putting two 1MΩ in parallel to make 500kΩ, and building the 470kΩ out of a series chain of resistors.
Having a real design challenge for this first lab was in one way a good one (it had bothered me that there was no design element in the first week of lab), but this design challenge was too much for the first week.  After lab some students were feeling overwhelmed and wanting to drop the course—even though this year’s class is well ahead of previous year’s classes (even the students who are struggling are further along than their counterparts in previous years).
Now my challenge is to convince the students who are feeling stretched to stick with the class for another week or two, so that the lectures can catch up to what they need to know and they can have a more confident base to work from.
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