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Sometimes it is Just Really Easy

Many of my good friends will tell you that I am not particularly good at telling a short story. I seem to remember too many details and get obsessed with sharing them all. Once-in-a-while, I tell one of my stories and a really clever student hears it and does something amazing. Such experiences obviously do not discourage me from taking my time to get to my point. The story that I would like to tell now has two parts because telling it one time gave it a second chapter. I will begin the story at chapter two.

In my early years at RPI, the Plasma Lab (where my wonderful colleagues, students and I got to have great fun doing diagnostics for nuclear fusion experiments for 35+ years), was located in the MRC Building because we were part of what was then the EEE Division (Electrophysics and Electronic Engineering) … basically the physics side of electrical engineering. The drinking age was 18 so we regularly had a keg every Friday afternoon. Weather permitting, we drank at the loading dock, but other times in the lab. Most of the building, which also housed Materials Science and Engineering (still does) contributed in some way to the cost of the beer and everyone drank their share. This allowed everyone to wind down at the end of the week. (Note that it was possible at that time to get a temporary liquor license for on campus parties, which we did religiously every week.)

The general camaraderie led everyone to tell stories. One of the stories that I told had to do with a special experience I had as an undergrad at the University of Wisconsin. When I was a junior EE student, I worked as a researcher in a solid state lab run by Professors Al Scott and Jim Nordman. They were two great people to work for. As an undergrad, I did not work directly for either of them but rather for one of Jim’s students Juris Afanasjevs. (See their letter in the November 1967 issue of the Proceedings of the IEEE for the project I worked on.) Juris was quite the character. In addition to his talents as an engineer, he was also a good musician, playing the organ with Bach being among his favorite composers. (This is how I remember things … I have since learned too often that my memories are always a little faulty. However, I think I have most of this correct.) The EE department had a UNIVAC computer at the time, which was not heavily used because so few students and faculty knew how to program it. One day, after hours, Juris decided we should program it to play music (specifically Bach). The only outputs computers in that era produced were blinking lights, so he set out to program the lights and then connect amplifiers to them to make it possible to hear the tones produced. I had some programming skills but this was his idea and I helped only as he directed me. He was ultimately successful in producing some music which really amazed me. My point in telling the story was to show that there were always opportunities to do some fun things with technology if one had the skills, access to equipment and a willingness to do things without asking permission. We did not do anything really unsafe, but the computer was pretty expensive and not supposed to be used in this manner.

At the Friday session where I told the story was Dave Ellis, who was one of the many undergrads I recruited to work in the Plasma Lab. In Dave’s case, I hired him to help take care of our Data General Minicomputer, which was one of my responsibilities in the lab. The computer was purchased before I was hired at RPI and I had to attend two weeks of training at Data General headquarters in the Boston area to learn how best to use it and train others. This had a big impact on my computer knowledge and the minicomputer was one of the most important tools we had to do Heavy Ion Beam Probe system design. Dave was absurdly smart (his roommate John Barthel said it was like living with the answer book), and had a great career working with Steve Schoenberg at SIXNET cut short by an all-to-early death. No one who worked with Dave forgot the experience. He is really missed.

Other stories were told that day but my computer music story apparently inspired Dave. The next morning I came in to use the computer (we scheduled it 24/7 because it was so essential to our work). When I booted it up, I found some new files, one of which was called ‘Suicide,’ which you might imagine was a bit unnerving. However, when I ran it, I discovered that it played the theme song from MASH, ‘Suicide is Painless.’ (A reference to the story behind this song by Michael Bingham [another of my great students] on Facebook – see http://www.neatorama.com/2015/07/28/MASH-Notes-The-Story-Behind-Suicide-is-Painless/ – inspired me to finally write this down.) Elsewhere on the computer I found several more songs Dave had programmed, all done since we ended the party Friday night. He was the kind of student we only had to suggest something to and it would get done. All the grad students made excellent use of his talents when they were doing their simulation studies on the computer. I have always encouraged my students to be very independent, even suggesting that if they never break anything they are not trying hard enough. Dave knew this even before he came to work in the lab. He was so great to have around that we supported him as an undergrad and as a grad as her pursued two masters degrees (one in EE and one in CS). It was during this time, I think, that he started to work for Steve.

Throughout my career as an educator, I have been very fortunate to know a lot of great students. Very few had Dave’s native talent, but I have enjoyed working with everyone who grew both as engineers and people. When I was a grad student, there were other students who were absurdly bright like Dave, who really added to my own personal education. Never hesitate to find such people, especially the nice ones, and learn as much as you can. The experience, while often very humbling, is definitely worth it.

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The Tinkering Thinker

Recently, I helped to give two workshops at Universidad del Turabo in Puerto Rico on the use of personal instrumentation (e.g. Digilent’s Analog Discovery, National Instruments myDAQ and their version of Analog Discovery 2, Analog Devices ADALM 1000 …) in the teaching of circuits and electronics. In attendance were great people from all of the engineering schools on the island. They were really engaged and asked wonderful questions, even though several were uncomfortable working exclusively in English.

One of the best questions I was asked has helped me to formulate what is, I hope, a very productive way of framing the discussion of how best to educate engineers. I was trying to make the case for Experiment Centric Pedagogy (ECP), for which the guiding hypothesis is that students and instructors are more motivated and engaged and engineering education works best in a learning environment where experimentation plays a central role. This is in contrast to  the traditional STEM classroom: the lecture hall, occasionally augmented with separate labs provided as expensive limited access facilities permit.

Engineers must tinker with ideas but, unfortunately, modern technology is so complex that tinkering has generally become too difficult. (There is an excellent article on the early days of the Mobile Studio Project in the Sept 24, 2007 issue of EETimes on this topic.) Those of us old enough to have developed our interests in electronics and electrical phenomena in the 1950’s were lucky enough to work mostly with discrete components (tubes!) which allowed for a lot of tinkering and shocks and burns.

The question raised at the Turabo workshop had to do with Thinking vs Tinkering. Traditional, lecture-based instruction requires students and instructors to think their way through a subject and the questioner was concerned that student tinkering may just be a trial and error effort to find an approach that involves little or no thinking. I certainly agree that I have, for example, seen students randomly make a bunch of attempts with a spreadsheet to solve a problem without really learning what they did and why it worked. The best scenario is that they know how to repeat what they did in the same way that the work their way through a video game. However, in spite of what often happens, tinkering and thinking are not exclusive activities.

Let’s look at tinkering a little differently and ask the following questions: Can we get a tinkerer to think or can we get a thinker to tinker and which is better? That is, should our students be Thinking Tinkerers or Tinkering Thinkers? From the title of this posting, it should be obvious what I think. It is also what nearly everyone I know says (so far anyway) when I ask them to choose. Whether or not we recognize that we are asking our students to apply the scientific method, we all work hard to get our students to predict what is going to happen (hypothesis) before they do an experiment (testing). Again, what we see too often is students cranking through a task list without stopping to think about what they are doing and why. That is why thinking comes first and we have the Tinkering Thinker.

Voltage Divider Circuit (Wikipedia) & Breadboard Version (Electroschematics.com) 

An example of ECP: One of the most ubiquitous and useful circuits is the voltage divider, which I will use to show an example of ECP in action. The goal of ECP is to think our way through the process of understanding how a particular circuit works by tinkering with it both experimentally and using simulation. The process could be shown as a flow chart, but I would rather keep it more informal than that.

  1. What is a voltage divider? Look it up on Wikipedia or in a textbook. The former approach seems like the most common these days. It is also very often possible to find good videos on topics like this. I have done a bunch on the voltage divider … more on that at the end of this example.
    1. From available information, find the circuit Diagram and what it looks like when it is built? The two figures above show examples of each.
    2. What is the formula that characterizes its operation? A common question because the first thing needed is how is it analyzed or how do we use it?  In the Wikipedia, the relationship between the output and input voltages is given as  V_\mathrm{out} = \frac{R_2}{R_1+R_2} \cdot V_\mathrm{in}
  2. Build one and see what it does? Before doing any analysis, build one and try it.
    1. It has to be built correctly and data collected correctly, so some basic experimental skills are necessary. Build the circuit … connect the sinusoidal voltage source (aka function generator) … measure accurately both the input and output voltages. It is almost always necessary to measure both.
    2. How do measurements compare with the ideal formula? Are there any data features that do not agree with formula? Is the formula general enough? What happens when we add a load? What happens if it works well with 1kΩ resistors but not if it is made with 1MΩ resistors?
  3. Simulations do not show noise unless it is specifically added. Simulations are usually more ideal than experiments. Simulate it to see if there are any things left out in the ideal formula? This can be done with any version of the SPICE program. LT-Spice from Linear Systems, is a good choice because it is free.
    1. When this is done, it is seen that the simple divider seems OK. Maybe this verifies that simulation is being done properly in addition to showing us what the voltage divider does in an ideal world.
    2. Voltage dividers have no purpose unless we connect something to them to read the output voltage. Does adding a load affect its operation? It should be observed that loading does make the divider work differently, just as it did experimentally, except without the noise.
  4. Go back to the basic reference used and see how the formula is derived. What are the assumptions? Are any violated with loading?
    1. Basic analysis is based on Ohm’s Law and that the current in both resistors is the same (the resistors are in series). This is clearly not the case with a load, but, if the load resistance is 100 times R2, it will have no noticeable impact on the operation of the circuit.
    2. Analysis with load — eureka! Since adding the load resistor does not really make the analysis much more difficult (R2 is replaced by the parallel combination of R2 and the load resistor), a new formula can be derived that does a very good job of predicting the output voltage.
  5. Go back to the experiment and look at non-ideal characteristics that occur with different resistances, voltage levels, frequency, etc. Determine the limits for application of the ideal model. This and the preceding steps are addressed in a series of videos I made for my Electronic Instrumentation class. Watch the first three videos for the topics addressed here: https://www.youtube.com/playlist?list=PLZXERmYWSLA9n_ar9LJGUrSJRAUDMpzuu