# Gas station without pumps

## 2021 November 24

### Contract signed with publisher!

Filed under: Circuits course,Uncategorized — gasstationwithoutpumps @ 10:31
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I’ve just signed a contract with World Scientific Publishing to publish my Applied Analog Electronics textbook.  They first contacted me on 2021 Oct 7 expressing an interest in the book, we met on Zoom on Oct 20, and they had a proposed contract to me by Oct 26, and we had a few back-and-forth rounds of negotiations.  The final contract was sent to me on Nov 19, I signed Nov 21, and they signed Nov 24. So the full process took about 48 days.

Here is the contract:

The most surprising thing in the contract is that they are continuing to let me sell the PDF through Leanpub (and my own web site, if I ever create one).  The royalties per book for Leanpub sales are higher than I’ll get from World Scientific Publishing, and the price will most likely be lower.

I did not use a lawyer in negotiating the contract—I contacted 4 lawyers who specialize in book contracts, but even the cheapest of them was too expensive, as I don’t really expect to make much money on this publishing deal.  I did use two online books:

Now I just have to get the 250MB of source files to the publisher and fill out the promotional questionnaire.  They may want me to make some small changes (like changing the title page).  When they are ready to publish, I’ll have to register the copyright also.

I’ll post here again when the book becomes available in paper.

## 2021 September 27

### Next book edition almost done

Filed under: Circuits course — gasstationwithoutpumps @ 13:50
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Eleven days ago, I said

Now all I have to do for the next release of the book is do the standard final checks (page breaks, spell checks, and URL checks).  This will probably take me another week.

I have now gotten the page breaks fixed and checked all the URLs (only 8 of the 215 distinct URLs needed fixing).  I last checked them about a year ago, so that is a link-rot rate of only 4%/year (a half-life of about 18 years).  In the process of fixing the page breaks, I noticed and fixed a few minor typos, as well as tightening the text in a couple of places (to improve the page breaks).  I found one instance of “the the” with my tandem-word checks (probably introduced since the last released edition).

I still have to do the spell checks.

I did release one new video last night: https://youtu.be/vLece-VKfkQ, which talks about providing a constant current for electroplating (see the post Controlling current if you don’t want to waste time watching an 11-minute video).

## 2021 September 16

### Last to-do note in book done

Filed under: Circuits course — gasstationwithoutpumps @ 10:46
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I’ve finally removed the last to-do note from the text book. This one was an explanation of the threshold voltage for FETs as the transition between the subthreshold conduction, where the on-resistance has exponential behavior with $V_{gs}$ and the on-region, where it is roughly constant.

I don’t like copying graphs from datasheets for the textbook, so I needed to measure the values myself to make a plot. My first attempt, using the PMV20XNE nFETs that we used for the past few years in class, was a failure.  The typical on-resistance is only 23mΩ, which is too small for the crude measuring setups and low currents that I could get with the Analog Discovery 2.  I ended up mainly measuring the resistance of the test setup, with errors larger than the value I was trying to measure, so I couldn’t even subtract off the short-circuit measurement.

I tried again with a low-power nFET (a 2N7000), using a constant load resistor of 150Ω (so the maximum power dissipation in the ¼-W resistor would be $(5V)^2/150\Omega = 167mW$).

I controlled with the gate voltage with waveform generator, and measured both the drain-source voltage and the drain current. I used the oscilloscope tool and averaged both within a sweep and across many sweeps to reduce noise.

Because the Analog Discovery 2 has only 2 measurement channels, I had to manually copy the measurements into a file for gnuplot, as there was no way to record the waveform generator output with the measurements in a single file (well, there might be with the scripting capabilities of Waveforms 3, but I’ve not explored them much).

I noticed some pretty large offsets when measuring small voltages, so I did open-circuit and short-circuit measurements and used them to subtract off offsets (with the understanding that the current for the open circuit would be about 150µA, because of the 1MΩ impedance of the Channel 1 measuring the open-circuit voltage).

The corrections make a big difference at the low end, where on-resistance is comparable to the resistance of the measurement instrument and test currents are tiny. The correction at the high end is smaller, but still noticeable. The transition from the exponential behavior of subthreshold conduction to the on-region is pretty clear. (Click to enlarge)

Now all I have to do for the next release of the book is do the standard final checks (page breaks, spell checks, and URL checks).  This will probably take me another week.

## 2015 March 30

### First day of S15 circuits class: demo failure

Filed under: Circuits course — gasstationwithoutpumps @ 16:23
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I went into the class with a fairly short to-do list—much shorter than last year’s. I managed to cover the following:

1. Went over syllabus .I showed them the syllabus and managed to go over scheduling of labs, partner work, and online texts, but did not get to some of the boilerplate about cheating and about disability services.  Oh well, it is enough that the boilerplate is on the syllabus.
2. Demoed pressure sensor  with PteroDAQ on KL25Z board. I hooked everything up and it didn’t work. I fixed one problem of a loose wire (using the jeweler’s screwdriver, but it still didn’t work. I did manage to show them PteroDAQ and used gnuplot to show them a pressure trace I had recorded in the BME88A demo last quarter.
3. Reading the book and doing design well before lab.
4. Assigning reading due tomorrow and Thursday.
5. Partners changing every week, so no one gets a free ride for very long and no one has to suffer with a freeloader.

I was thinking that I’d use the chalkboard a lot, so I used the small screen in the classroom (this classroom is ridiculously over-equipped with projectors, even having a project for a screen at the back of the classroom) rather than the big one, which covers most of the chalkboard. But I ended up using the projector to show them parts of the book and to use the document camera to show the KL25Z board and instrumentation amp protoboard, and barely used the chalkboard at all.

The rearrangement of the labs, with soldering on Tuesday, sampling and aliasing on Thursday, and the thermistor labs next week does give me a little leisurely start-up than last year, as I don’t have to get to Ohm’s law and Kirchhoff’s current law until the voltage-divider lecture on Friday.

Overall, I’m fairly happy with how the first day of class went, despite the demo failure.  I’ll debug the demo and show them either in lab tomorrow or in class on Wednesday.  I just hope I haven’t fried the instrumentation amplifier with static—they’re expensive and I don’t know whether I have any spares on hand.

Update 2015-Mar-30 17:58:  When I got home I checked out the board to figure out what might be wrong.  After probing for a while with the voltmeter, I determined that the wire that had come loose from its screw terminal and that I had fixed in class was not the only wire that had come loose.  The one next to it had also come loose.  It still looked ok, but wasn’t making contact.  Opening the screw terminal, reinserting the wire, and tightening it down again fixed the problem.

## 2014 June 12

### Starting on book for circuits lab—scheduling labs

Filed under: Circuits course — gasstationwithoutpumps @ 23:59
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In Revised plan for circuits labs I provided a tentative schedule for the applied circuits course and lab, which I ended up not really following (dropping the FET measurements, moving the sampling lab after the loudspeaker lab, and swapping the order of the pressure sensor and the class-D amplifier).

I’m now trying to turn the course lab handouts into a book (which means adding everything that was previously just in lectures), and I’m trying to rearrange the lab schedule to fit better into the 10-week quarter and to flow a little better pedagogically.

In this post, I’ll ignore the lecture component, but just look at a possible reordering of the labs.  Squeezing the KL25Z soldering and both halves of the thermistor lab was too much, and the sampling and aliasing lab did not work well late in the quarter, so I’ll strip the filter design out of the sampling lab and simplify it a bit to get it in the first week, and move the thermistor lab fully to the second week.  I’ll have to squeeze somewhere else, and I think that the best bet is the hysteresis lab, which took far longer than it should have.  I still want to have data-analysis Wednesdays, and reports due on Fridays.