Gas station without pumps

2016 May 5

PCB CAD tools

Filed under: Uncategorized — gasstationwithoutpumps @ 20:58
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I’ve been using Eagle for designing printed circuit boards for a few years now, and I am reasonably happy with it as a free tool. However, I’m a little annoyed by the low quality of the schematics and by the awkward creation of new footprints for components, and so I am willing to consider other tools, and am looking for recommendations for free PCB tools that are better than Eagle.

Two I’ve heard of (but not tried yet) are

  • EasyEDA , which is web-based, and
  • DipTrace, which (like Eagle) is a commercial package with a free, but limited, hobbyist version.

I’ve not used either of these yet, and I don’t have any PCB designs to do right now (nor time to do them until the quarter ends), but I’m curious whether any of my readers have tried EasyEDA or DipTrace, particularly if they can compare them with Eagle.  I’m also curious whether there are other PCB tools out there that run under both Mac OS X and Linux and that are free, easy to use, and robust.

My son and I are planning a couple of boards this summer as part of the LED theater lights project, so there will be an opportunity then to try out different PCB tools, if anyone has ones to recommend.

Democratic primary very important this year

Filed under: Uncategorized — gasstationwithoutpumps @ 20:48
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The Democratic primary is very important this year, because it gives US voters the opportunity to choose between a New Deal Democrat (Sanders) and an Eisenhower Republican (Clinton).  This is the first time since George McGovern ran in 1972 that such a choice has been offered to the US people.

The Republican party itself no longer offers serious candidates for president (and increasingly often doesn’t for other races either), so the Democratic party has taken over most of the Republican policies and positions and offers Republican candidates a place to run for office without having to associate with the clowns who have made the GOP into a circus sideshow.

Personally, I’m a progressive Democrat, so I strongly favor Sanders’s policies, but I can see a lot of Republicans voting for Clinton, whose stand on almost every issue is a late 1950s Republican position (except that Eisenhower warned us about the military-industrial complex, while Clinton supports it whole-heartedly).

Because the Republican Party is incapable this year of running a serious Presidential candidate, the Democratic primary is doubly important—it is the only chance voters will get to choose between a classic Democrat and a classic Republican.


2016 May 3

Revised pressure sensor lab went very well

Filed under: Circuits course — gasstationwithoutpumps @ 21:20
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Today I ran a revised version of the pressure sensor lab (see
Pressure-sensor lab went well, Class-D lab revision didn’t work, Blood pressure monitor, Blood pressure lab, and Blood pressure lab part 2 for descriptions of the old labs).

The revised lab included both blood pressure cuffs and breath pressure using the simplified breath pressure apparatus of Simplified breath pressure apparatus:

The ½" elbow is small enough that I can put my lips around the opening, which would have been a bit difficult with the 1" tee.

The ½” elbow is small enough that I can put my lips around the opening, which would have been a bit difficult with the 1″ tee.

To make the apparatus, the students had to drill 2mm holes in PVC elbows, so I packed up my drill press last night and hauled up the hill in my bike trailer this morning.  For those unfamiliar with Santa Cruz, that is a 3-mile ride with a fairly steady 4% slope, resulting in a climb of about 715′ (218m).  Needless to say, I went slower than usual uphill!  There is a drill press only about 150′ from the lab the students were working in, but the bureaucracy for getting the students access to the drill press is incredible (I tried, and failed, to get a dozen students access last quarter). So it was easier for me to haul my own drill press up the hill on my bike than to deal with the dysfunctional bureaucracy at UCSC to use the drill press supposedly there for student use.

I explained to each pair of students how to use a drill press, including basic safety precautions, and had them drill a 2mm diameter hole in their PVC elbows.  There were no problems with this, and I plan to do the same for the lab in future.

Each pair of students designed an instrumentation amplifier with an INA126P chip as a first stage and an op-amp as a second stage, wired it up on breadboards, checked the calibration, and recorded both breath pressure and blood cuff pressure.  A few students used extra time to play around with some toys I brought in: a hand vacuum pump, a Lego pneumatics pump, and an aquarium air pump.  One group even tried using the pressure sensor as a microphone, using a loudspeaker with a 300Hz sine wave for input (the pressure sensor could detect the 300Hz input without problems, though I suspect that it was not registering the full pressure fluctuation, as I think that the sensor has about a 200Hz bandwidth).

Most groups were done with this week’s lab in the 3 hours of today’s lab, so Thursday’s lab will consist mostly of students doing make-up work to redo old labs, with a few finishing up this week’s lab.  I expect to spend most of Thursday’s lab time grading design reports (I’m about 2 days behind—I got the design reports that were turned in a week ago done and returned yesterday, and I got the prelabs turned in yesterday done and returned today, but I haven’t started yet on the reports turned in last Friday, nor the stack of redone work turned in last week).

The instrumentation-amp lab went surprisingly well this year, despite adding the drill press.  I think that the big advantages over previous years are that they did not have to solder the inst amps this year and that they had already done a multi-stage amplifier for the microphone amp.

I think that I should rewrite the book to introduce multi-stage amplifiers as the default design (since every amplifier they do in the course is now multi-stage), and talk about how to choose the gain for each stage in general, before getting into individual labs.

One minor problem in lab today—students didn’t have the short pieces of tubing to connect up their breath-pressure apparatus.  This turned out to be my fault—I hadn’t included them on the parts list for this year!  Luckily the BELS staff had some pieces leftover from last year, and I had about 20 feet of my own tubing in the box of stuff I’d packed for the lab, so we had enough for everyone to get 6″.


2016 May 2

Sabbaticals until retirement

Filed under: Uncategorized — gasstationwithoutpumps @ 22:28
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I plan to take sabbaticals every year until I retire. Here’s how that works: for each quarter I work I get one “sabbatical leave credit”.  With the permission of my department chair (as part of the Curriculum Leave Plan each year), I can cash in the credits for sabbatical leave.  What is unusual about the UC system is that I can cash in the the credits for partial pay—9 credits gets me a quarter of sabbatical leave at full pay, 6 credits a quarter at 2/3 pay, and for n≤9, n credits a quarter at n/9ths pay.  The portion of my salary not paid to me is returned to the department, who can add it to their TAS (Temporary Academic Staffing) budget, or add it to their reserves, in the unlikely event that they have enough funding to cover all the lecturers for the year.  Taking partial-pay sabbaticals is easier for the department to cope with than taking full-pay ones, as there is no extra money for hiring replacement lecturers during full-pay sabbaticals.

As of the end of this quarter, I will have 20 sabbatical leave credits, so I could take 2 quarters off at full pay, but that’s not what I plan.  Instead I plan the following strategy, taking single-quarter, partial-pay sabbaticals every year for the next 5 years, then retiring (+1 means I’m teaching, a negative number indicates a sabbatical and how many leave credits I’ll use up):

year Fall Winter Spring credits left
2015–16 +1 +1 +1 20
2016–17 –6 +1 +1 16
2017–18 –6 +1 +1 12
2018–19 –6 +1 +1 8
2019–20 –6 +1 +1 4
2020–21 +1 –5 +1 1

I don’t have to take Fall quarters each year, but that is the quarter for which my teaching is easiest to cover by someone else, at least until I get someone trained to teach the applied electronics course.

Due to a quirk in the rules for retirement compensation, there is a significant advantage to separating from the University at the end of June, and starting retirement in July (a cost-of-living adjustment for those separated from the University but not yet retired), and I need to return from each sabbatical for at least as long as the sabbatical itself, so ending up with one credit at the end of spring is optimal use of sabbatical credits, which calls for a Winter quarter sabbatical in my last year.

I have to find someone to take over the Applied Electronics course by Winter 2021,  if I’m going to retire in summer 2021. It will also be interesting to figure out what course I’ll teach in Fall 2020, since I’ll have been out of the courses I’ve been teaching every Fall for 4 years at that point, and it might be better for me to pick up a different course.

One choice I have to make when taking partial sabbaticals is whether to “buy back” service credit for my defined-benefit retirement plan.

The defined benefit is 2.5% * years of service * (HAPC – $133*12) per year after retirement for life.   When I take partial-pay sabbatical, the “years of service” also accumulates more slowly. (HAPC is Highest Average Plan Compensation, which is the average over 36 months of base salary, excluding summer salary and stipends, for the highest-paid contiguous 36 months—taking partial-pay sabbaticals does not reduce HAPC, since it reduces % time, not base salary.)

Actually, the benefit is a bit more complicated than that, as there is a continuing 25% of the benefit to my wife, if I die before her.

As I understand it, I can buy back the service credit for 18.72% of the foregone salary—at least, that’s the Plan Normal Cost in 2016 (

The value of $1k/month for life is about $178k for someone retiring at age 66 (based on the cost of single-life annuities). Adding a 25% second-life benefit doesn’t raise the value much—maybe to $184k (25% is an unusual second life benefit, so I did not find an annuity calculator for it). More common are plans with full benefit to survivor, half benefit to survivor (2 lives treated symmetrically), or half benefit to annuity partner (lives treated asymmetrically, with no loss of benefit if partner dies, but drop in benefit if annuitant dies).

So I could buy-back 1/9 year of service for 2.08% of my annual salary, which would raise my annual income after retirement by about 0.275% of my salary.  That is a break-even time of about 91 months, substantially less than the 178 months of purchasing an annuity at age 66.  I’d have to get a 12% annual return on investment for 6 years to beat that investment, which is an unlikely return to get in the next few years.

If I’ve done my calculations right, then the service buyback is a very good investment for someone as old as me, being almost twice the return of a purchased annuity. Either I’ve done my calculations wrong (quite possible), or the leave buyback is mispriced. Since it seems that mainly senior management uses leave buyback, I can well believe that it is deliberately underpriced for old folks, as management loves giving itself perks.

For younger faculty, leave buyback might not make as much sense, since other investments are likely to grow faster than faculty salary does, and the value of the defined-benefit plan is tied to the HAPC.  Young faculty who leave UC long before retirement age get very little benefit from the defined-benefit plan, so there is higher risk associated with investing in a leave buyback.  Pre-tenure faculty should have a defined contribution plan, with the option of turning it into a defined-benefit plan when they get tenure.

2016 April 30

Sixteenth weight progress report

Filed under: Uncategorized — gasstationwithoutpumps @ 17:39
Tags: , , , , , ,

This post is yet another weight progress report, continuing the previous one. I’m doing a little better this month, going above my target range for only 5 days:

Weight is still hovering around the upper end of my self-selected target range.

Weight is still hovering around the upper end of my self-selected target range.

April saw a gradual decrease in weight, followed by a large upward spike at the end of the month.

April saw a gradual decrease in weight, followed by a large upward spike at the end of the month.

The large upward spike corresponded to a 4-day trip to Illinois for a family wedding and a 90th birthday celebration for my dad.  His birthday was months ago, but travel to Colorado in mid-winter is a difficult, so we moved the celebration to the same weekend as his granddaughter’s wedding, so that we could get everyone to come.

My exercise for April was good (averaging 4.72 miles/day bicycling), despite the trip to Illinois and having had a bad cold for the last week (flying with a bad cold is no fun).

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