Gas station without pumps

2015 June 4

Last lab of Spring 2015

Filed under: Circuits course — gasstationwithoutpumps @ 22:50
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I spent all day today in the lab for the electronics class, from around 9:30 a.m. until the last students packed up and left at 8:30 p.m.  This was the last lab of the quarter, and I had decided to stay until all the students had left.

Most of the students got their EKG boards soldered up and working today (there may be a few who left without demoing their working boards, and the last group at 8:30 p.m. had just had some more wiring errors pointed out to them).

I’m amazed sometimes at how basically competent designers can be very careless in their wiring, rushing through the placement and soldering without carefully checking each connection. The result is a 10-minute savings in wiring time, and a 4-hour or more cost in debugging and resoldering time.

Tomorrow in class I plan to go over a couple of 1-transistor amplifier designs, but that shouldn’t take the whole time.I’ll give them some pointers to companies that sell parts and kits that might be of use to them: Digikey, Mouser, Jameco, Sparkfun, Adafruit Industries, Itead Studio, Seeedstudio, Smart Prototyping, Elecrow, OSH Park, Makershed, … . And I’ll be sure to mention some local resources: Santa Cruz Electronics and Idea Fab Labs.

I also hope to remind the students of some of the goals of the course, and try to see whether the goals have been met.  I quote from the supplemental form for the course renaming that was approved this spring (effective next year).

The Program Learning outcomes for the bioengineering program are as follows:
A bioengineering student completing the program should

  • have a broad knowledge of science and engineering disciplines including biology, chemistry, physics, mathematics, statistics, and computer science; [Not relevant to this course]
  • be able to apply their broad knowledge to identify, formulate, and solve engineering design problems; [Students passing BME 101L will be able to design simple amplifiers and RC filters for a variety of sensor-interfacing applications.]
  • be able to find and use information from a variety of sources, including books, journal articles, online encyclopedias, and manufacturer data sheets; [Students passing BME 101L will be able to find and read data sheets for a number of analog electronics parts.]
  • be able to design and conduct experiments, as well as to analyze and interpret data; [Students passing BME 101L will be able to measure signals with multimeters, oscilloscopes, and data-acquisition devices,  plot the data, and fit non-linear models to the data.]
  • be able to communicate problems, experiments, and design solutions in writing, orally, and as posters; [Students passing BME 101L will be able to write coherent design reports for electronics designs with block diagrams, schematics, and descriptions of design choices made.] and
  • be able to apply ethical reasoning to make decisions about engineering methods and solutions in a global, economic, environmental, and societal context. [Not relevant to this course]

So tomorrow I plan to ask where the students feel that they are able to design simple amplifiers and RC filters, whether they can find and read data sheets for analog parts, whether they can measure signals with multimeters, oscilloscopes, and data acquisition devices, whether they can plot the data and fit non-linear models to it, and whether they can write coherent design reports.

I had some unofficial goals for the course also: to turn a few of the students into electronics hobbyists, to encourage a few to declare the bioelectronics concentration of bioengineering, to teach some tool-using, maker skills (calipers, micrometer, soldering iron, …), and to make all of them better at attacking problems by dividing into subproblems with clear interfaces between the subproblems.  I’ll ask about those things also.

I’ll also want some detailed suggestions for the course.  (So far I’ve gotten one: fume extractors for the lab for use when soldering.)  Some things I’m curious about include

  • Should the first amplifier lab (the low-power audio amp lab) be changed to use a single power supply and solder up the board, so that the board can be used as a preamp for the class-D power amp lab later?  We could then also do an emitter follower (common collector) class-A amplifier using the preamp board.  If they solder up a pre-amp, then we could eliminate soldering the instrumentation amp for the blood pressure lab.
  • Should I redesign the prototyping board to have more room for resistors and no instrumentation amp slot, making it more suitable for the preamp lab and the EKG lab?  A new custom board is still cheaper than something like the $4 perma-proto boards from Adafruit.
  • Should I switch from 18-turn trimmer pots to 3/4-turn trimmers with shafts?  The ones with shafts tend to be easier to turn, but not as precise and the multi-turn worm gear pots.  There are 3/4-turn trimmer pots that play nicely with a breadboard, though they take up a bit more space than the worm-gear trimmers we used this year.
  • Are there tools or parts that almost no one used?
  • Are there tools or parts that should be added to the lab kit? If so, at what price do they stop being attractive?
  • Should students buy oscilloscope and voltmeter probes, like they do at UCSB, rather than having to deal with broken probes or probes locked inconveniently to equipment?
  • Should there be more practice questions in the book? (currently I have very few, with almost all the questions being part of prelab assignments)
  • Does there need to be a “what you are already expected to know” section or chapter, to review material that students are supposed to know already?
  • Which labs took up too much time for the amount of learning achieved? How can they be streamlined?
  • How much time did the course really take total for the quarter?
  • What suggestions do students have for more fun labs?

1 Comment »

  1. […] was the last day of class, and I covered almost exactly what I proposed in last night’s blog post: one-transistor amplifiers, a review of the goals of the course, and getting suggestions for […]

    Pingback by Last day of class for Spring 2015 | Gas station without pumps — 2015 June 5 @ 23:31 | Reply

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