Gas station without pumps

2020 April 1

Document cameras becoming unavailable

Filed under: Circuits course — gasstationwithoutpumps @ 15:29
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I decided to get a document camera for making video mini-lectures, as I suspect we may be doing at least part of Fall quarter on-line.  Based on recommendations from colleagues, I decided to get the IPEVO VZ-R camera, which I ordered last night.  Delivery was predicted to be in 3–4 weeks (it would have been another week, if I’d opted for free delivery).  If I had been in a hurry, I could have ordered the same camera from an Ebay store for another $75, with “free and fast” delivery by next week.

Both Amazon and Ebay stores seem to be out of stock today, so I probably ordered at the last possible moment.

Because I won’t have a document camera for another 3 weeks, I can’t start making videos right away, but I can set up my “studio” space, plan which topics I’ll talk about, and maybe even try writing some scripts. I’ll also have to get some colored calligraphy markers and practice writing and drawing with them, so that I don’t scrawl illegibly on my first few videos.

Just cleaning up the book room in the garage to be the studio space will be a 3-week project, as it will mean clearing a 20-year accumulation of materials from the top of my desk.  Clearing the floor and the sofa will take even more effort, as my wife has commandeered the book room for doing her job, so everything is covered with children’s books, book covers, due-date pockets, and the other paraphernalia of a children’s librarian.  We’ll also have to take turns using the desktop machine, as it is the only one with a big enough screen for video editing or even photo editing, and she needs it for her school-library blog as much as I do for creating mini-lectures.

I may end up having to get a second desktop computer and setting up the studio in the bedroom rather than the book room—that will take even more time to clean up. Though the accumulation is of shorter duration, it is denser and with fewer places to put things away.

 

2020 March 27

Day off today, planning sabbatical

Filed under: Circuits course — gasstationwithoutpumps @ 22:47
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Today was a day off for University of California, celebrating Cesar Chavez Day, though the official day for that is next Tuesday March 31.  I did a little undergraduate director work via e-mail, but mostly took it easy today.

Trader Joe’s

I started the day by bicycling to Trader Joe’s to take advantage of their first hour for seniors (I’m over 65 now, so I qualify, though I don’t think I’m at particularly high risk). The setup was that they had two lines—one for seniors and one for others, allowing people to self-identify to choose which line to join.  The cart handles were being cleaned between uses and customers were getting their hands sprayed before being let in.  They were regulating the number of people at a time in the store, but the line moved fairly quickly, as people were not lingering in the store.

Trader Joe’s has always had super-wide aisles, so social distancing in the store was easy.  I quickly grabbed the stuff I had come for (most of my TJ staples: beer, cider, port, chocolate, paper towels, and soap) and checked out quickly so that others could enter the store.  I don’t think I need to go back to TJs for a couple of weeks, as I have at least a 2-week supply now of just about everything that I ever buy there (we got laundry detergent, cereal, and toilet paper a week or two before shopping got crazy).

Mowing lawn

After I got home from shopping (and scrubbing my hands and the doorknobs I’d touched), I got out the electric lawn mower and mowed both the front yard and the back yard.  The grass (and oxalis and wild onions and all the many other plants that make up my “lawn”) had gotten pretty long, but the plants were still soft, young plants, so the mowing went fairly quickly.  I even managed to fill my 40-gallon green-waste container with blackberry vines, ivy, and chunks of the dead rosemary bush.

Having sabbatical  this spring does mean that I’ll probably be able to keep the grass cut this year, for the first time in about a decade.  No 4′-high meadow with 8′ thistles this year!  Removing all the ivy and blackberries, though, is probably beyond me—filling the 40-gallon green-waste container weekly will probably be just enough to keep the current overgrowth from getting bigger, without making an appreciable dent in the 500 square feet covered with with them.

Preparing for sabbatical

I’m going to take this weekend off (sleeping, re-reading fantasy or science fiction books) and on Monday I’ll start working on creating video tutorials for sections of my book. I’m still debating how to do the visuals for the videos: prepared slides, pen on paper with a document camera, white board in front of the computer, or tablet and stylus.

I am not fond of prepared slides as a presentation style, though I know it has become the most common style for STEM lectures, so having a set of slides to bundle with the book might make it more attractive for instructors to adopt.  My lecture style has been more of an improvisational performance, triggered by questions from the students—that will not translate well to videos with no audience, so I’m going to have to develop a whole new teaching style for myself.

I’m looking at a few document cameras on Amazon ($100–$150), though I briefly considered making a stand for my cellphone (which has a 12MP camera) instead.  I think that having a USB-attached camera with a reasonably designed arm will work better with the various software I might use for making the video than trying to jury-rig something with my cellphone, so I’d be willing to invest in the document camera—if writing on paper works for me as a lecturing style.

The closest I’ve come to using that style in the past was in Spring 2000, after I had the bike accident that necessitated removing my spleen.  I had to lecture sitting down with an overhead projector until my ribs healed—I found it much more limiting than my usual large-whiteboard lecture style, as I could not build up an information-rich surface to point back to previous items on, as I had to keep changing pages.  Whatever I do for the videos is going to have the same problem, though, as the screen is a tiny, little window that can only hold one thing at a time.

I’ll probably also have to invest in colored markers if I lecture on paper—I write somewhat more legibly with a broad chisel-tip calligraphy marker.  I’ve only used black calligraphy markers in the past (the Itoya double-header), but I see that the same company makes colored ones in the same style.

I tried a whiteboard in front of my desktop for the last (optional) lecture of BME 51A.  It was not technically very successful—lighting and contrast were problems, as well as the size of the writing on the screen being too small.  I could try a small whiteboard with a document camera, but I suspect that it will not work as well as paper and calligraphy markers.

One big advantage of the document camera is that I can put small objects (like components or breadboards) on the screen easily—I even do that in some of my live lectures.

The most expensive option is to get a tablet computer (e.g., iPad or Surface) and pressure-sensitive stylus.  I’m not convinced that I’ll be able to write all that well on them, and interfacing them to software that let’s me switch easily back and forth between a head-shot camera, a small-parts camera, preprepared images, and the stuff-drawn-on-the-tablet may be difficult.

Of course, if I’m putting together a video, I don’t have the same time constraints that a live remote lecture would have, as I can film each scene separately and edit them together.  Editing takes up a lot of time though, so I’m not sure I want to go that route, rather than recording in one continuous stretch.  (Yes, I know the quality would be better if I spent a lot of time editing, but I’m not sure I have the time to do even quick-and-dirty tutorials on all the topics.)

Another big change for me is that I’ll probably have to work from a script, rather than doing an improv lecture.  That’s because I’ll need to do closed-captioning on the videos if I post them on YouTube, as the automatic YouTube closed captioning is ludicrously bad (see YouTube closed captions are awful), and it takes forever to put in the captioning unless you have a script already prepared.

Going from big whiteboard real estate and an improv style to tiny screens and tight scripting is going to be a big change for me.  It’s a good thing I have six months to experiment with different approaches and don’t have to go live on Monday  like most of my colleagues.

Unexpected consequences

One good consequence of the sudden forced switch to remote teaching is that there has been more discussion of pedagogical tools (Canvas quizzes, document cameras, tablets, zoom, take-home exams, …) among the faculty in the past week than there has been in the previous 5 years.

Unfortunately, all the discussion has been about lecturing and high-volume remote testing, with none about teaching writing, engineering design, or hands-on lab skills, which are the topics that really need attention (but which are probably going to be sacrificed in this quarter’s remote teaching).

Lowering price of textbook

Filed under: Circuits course — gasstationwithoutpumps @ 21:21
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To make it easier for people to learn electronics at home, I’m lowering the minimum price of my book to $6 during the COVID-19 crisis.  I wish I had a ready-to-go bundle of parts and online videos to help people learn at home, but creating such videos would take me a year (though I am seriously considering starting creating such videos during my sabbatical).

Creating a bundle of tools and parts would require working with one of the companies that sells parts (Jameco, Mouser, Sparkfun, …).  The markup they would require to make it profitable for them to do the bundling is pretty high, though, so for now it is cheapest for people to order parts from distributors and tools and boards from China.

2020 March 26

Screaming op amp

Filed under: Circuits course — gasstationwithoutpumps @ 20:12
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Santa Cruz’s Museum of Art and History is having a “drawing activity” online while the museum is closed, based on their 2017 Screaming Hand Exhibit.

I’d like to see a screaming banana slug, but I can’t draw, so I  created a screaming op amp for the students in my electronics course:

I think that this circuit accurately reflects how many of the students in my class feel.

I used Digi-Key’s SchemeIt for the schematic and edited the mouth using Gimp and Inkscape from a low-quality image of a screaming-hand sticker (possibly not legally licensed) that I found with Google image search.  MAH provides a PDF file for you to start with, assuming that you will draw and color around the  printed mouth, but I find cutting and pasting SVG files in Inkscape easier.

I now have an SVG file of the screaming op amp, which I could scale up to T-shirt size, if needed.

2020 March 25

Grading done

Filed under: Circuits course — gasstationwithoutpumps @ 21:26
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I’ve finally finished my grading for Winter 2020.  It took me longer than usual—about 2 hours per paper.  Partly this was because I had some trouble focusing on work with all the COVID-19 news, partly it was because I kept getting distracted by undergrad-director duties (cancelling lab courses for next quarter and trying to get two additional courses funded and staffed with TAs), and partly it was an attempt to give the students more thorough feedback than usual, because some of them will not be taking the second half of the course.

We decided that any student who is graduating in Spring 2020 can petition to replace a cancelled lab course (like the second half of my course) with a different course that they can take (or have taken).  Reading those petitions has been one of the undergrad-director duties that has been taking up my time.  So far, most of the petitions have been acceptable—students have given pedagogic justifications for their choices that made the substitutions reasonable, even if not covering the skills that the cancelled course would have taught.  In a few cases, I’ve suggested that students revise their petitions, particularly when they’ve proposed replacing a 5-unit course with a 3-unit one.

I also ended up letting 17 of the 50 students in my course switch from graded to pass/no-pass, which is not usually something faculty can offer. Because Winter 2020 was such a disaster at UCSC (between the wildcat strike and the COVID-19 shutdown), faculty are allowed to assign P/NP grades this quarter, even if students didn’t sign up for them.  The programs in the Baskin School of Engineering usually require that all courses in the major be taken for a grade, but the BENG/BINF/BMEB majors are being allowed to have P/NP grades for Fall 2019 and Winter 2020 even in major courses.  I let the students choose whether they wanted the grade they earned or a P/NP for my course, though they only had about 3 hours to make up their minds.

The grades were lower than usual this quarter, even after I lowered the cutoffs for each grade.  Because the quarter was so stressful for students, I lowered the cutoffs much more than I usually would have.  This may come back to bite me in the fall, as there were three students who were not really doing passing work (should have gotten C-), who I passed anyway.  If they have the same sloppy approach to their work in the Fall, they will not pass BME 51B, causing their lab partners and me a lot of grief in the process.

In some ways the reports this year were better than previous years—there were fewer incorrect symbols for the NPN phototransistor and the bandpass filters were generally ok. But in some ways they were worse—there were only a few students who understood what the log-transimpedance amplifier did and reported its gain correctly, and there were many who had inconsistent component values in different schematics or between the schematic and the main body of the report. A lot of students keep making the same mistakes in report after report—apparently they never read the feedback I spend hours giving them or ignore it as unrelated to anything they do.

The writing quality remains mostly bad—though perhaps that is not so unusual for this point of the course—I think that the second quarter of the course is when most of the students begin to pay attention to the writing feedback and working on improving their writing.  There were a few students whose writing was ok on the Lab 6 reports, though nothing extraordinarily good.

One thing I’ve noticed every year in the pulse-monitor lab is that a lot of students attribute the 60Hz noise to the fluorescent lighting or to electromagnetic interference, rather than capacitive coupling. But no one has done any tests to see which was the true source. I should do some tests (black out the phototransistor with electrical tape, but keep my finger on it vs. expose phototransistor to fluorescent light with no capacitive source nearby, contrast the fluorescent light to steady light, …).

One problem will be finding old-fashioned 60Hz fluorescent lights at home—I don’t know that we have any left, as I’ve replaced all the oldest fixtures with LED lights. We still have some compact fluorescent bulbs, but they generally have high-frequency electronic ballasts to avoid the 60Hz flicker.I might have to sneak into my office at work to do the tests, if all the lights at home have higher-frequency modulation.

I may also have to do tests with a normal transimpedance amplifier, rather than a logarithmic one, as I want to see the fluctuating current added to the DC light value, rather than looking at ratios of current as we do for looking at the opacity of the finger. A fixed additional current would result in very different voltage fluctuations with different DC light levels, if I used the log-transimpedance amplifier.

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