LED board schematic

I did a series of posts about the LED boards that I designed for lighting and strobes (starting with Summer project in 2014), but I just realized in going over the posts that I never posted the schematic nor explained how the board worked. I had to dig out the Eagle files on my old laptop to find the schematic, then redo it in Scheme-It to make it look reasonable.

Schematic for the LED board. This design is version 8, and is the one I actually had made.

The resistor R1 is a current-sensing resistor, measuring the current through the nFET Q2 and the LED. When the current is high enough, the voltage on the base of Q1 becomes large enough to turn on the NPN transistor Q1, lowering the gate voltage on Q2 and starting to turn the nFET off.  When the current is low, Q1 is off and the resistor R2 pulls the gate voltage for Q2 up, turning on the nFET more strongly. The Schottky diode D1 is just there to protect the LED from large reverse voltages if the board is hooked up backwards.

Power is dissipated in 4 places: the LED itself, Q2, R1, and D1. Based on the measurements in LED board I-vs-V curve,  the current is limited to about 118mA, so the voltage on the base is about 0.555 V when Q1 starts to turn on and R1 dissipates about 65mW. There is some current going through R2 and Q1 that doesn’t go through the LED (probably about 1–2mA), depending on the voltage applied to the whole board, but it is only about 1% of the total current, so I’ll ignore it—we may have another 30mW dissipated in R2.

I probably should measure the voltages across R1, on the base of Q1, on the gate of Q2, on the drain of Q2,  and across D1 to get detailed information about where the power is really being dissipated.  I think that the voltage across the LED should be about 6V when the board is fully on, and the voltage drop across the Schottky diode should be small (maybe 0.1V for 12mW).  For board voltages before the current limitation cuts in, almost all the power goes to the LED.  At higher voltages, the extra voltage drop and power dissipation is all in Q2, with around 700mW dissipated in Q2 when the board voltage is 6V higher than where the current limitation starts and 700mW delivered to the LED. That’s about as high as I’d be willing to go for continuous lighting, even with a heat-sink on the board.

I should be able to make the measurements fairly easily with the Analog Discovery 2, and I might do so later this week. One thing I’m curious about is whether the drop in current with higher board temperature is due to changes in the characteristics of the NPN transistor or the nFET.  The nFET is dissipating most of the power, so its junction temperature is probably changing much more, though the LED and the nFET together warm up the whole board, so the NPN transistor is getting warm also.

Fifty-eighth weight progress report

This post is yet another weight progress report, continuing the previous one, part of a long series since I started in January 2015.

I’m also back to my pre-pandemic weight, after the distressing excursion into being overweight last year.

I still want to lose about 11 pounds, which would take over 2 years on my current trend.

Since mid-July, I’ve cycled an average of 2.34 miles/day, bringing my average over the last year up to 1.94 miles/day (a very small number).  I’ve averaged about 6.4k steps per day—down from earlier in the summer.  That walking has been mostly in the weekly “secret walk”  with my wife, supplemented with walks with a friend at UCSC who is trying to increase exercise.  I’ve not been blogging the secret walks much lately, as there have not been interesting routes or walks—we’ve mostly repeated walks we’ve done in the past.

I had a bunch of blood tests done last week, in preparation for my annual checkup tomorrow. Everything came out reassuringly normal. My cholesterol counts are still doing ok—the combination of rosuvastatin and ezetimibe seems to work well for me:

The only number close to a threshold is the triglycerides, but they seem to be a very noisy measurement, so I’m not concerned about it.

Arms and the Man (Jewel Theatre)

Last Sunday (2 Oct 2022) my wife and I went to see Shaw’s play Arms and the Man, produced by Jewel Theatre (at the Colligan Theater in Santa Cruz). This production was originally planned for 2019, but was cancelled by the pandemic. Before going to the play, I was pretty sure I had seen a production of it before, and my wife was pretty sure she hadn’t, but neither of us really remembered, and we could have been confusing it with some other play.

After seeing the play, we were both more firmly entrenched in our beliefs about having seen it or not seen it before, so I looked up when Arms and the Man had last been performed in Santa Cruz.  I found that Shakespeare Santa Cruz performed it in the summer of 1999 (directed by Paul Whitworth)—I’m certain that is the previous production that I saw, but it is entirely possible that my wife decided not to attend then, though she remembers the Romeo and Juliet and The Two Gentlemen of Verona that were the other two productions that season. (Our son would have been 3 years old, so there may have been some difficulty getting a baby sitter or she might just not have felt like seeing the play—I really don’t recall.)

I can’t compare the two productions, as my recollections of the previous one are too hazy, but I liked both, and think that the play is a fine one (despite some rather ludicrous caricatures of Bulgarians, Serbs, and Swiss). For an anti-war play first performed in 1894, it holds up surprisingly well in modern times.

Jewel Theatre did a fine job in all respects, from acting and directing to set design and costumes (I always like B. Modern’s costume designs).  All the actors were well cast, but I particularly liked the way that Charles Pasternak played Captain Bluntschli.  I’m glad that Pasternak is becoming a permanent addition to the Santa Cruz theater scene (he’ll be taking over as artistic director for Santa Cruz Shakespeare after the 2023 season).

I won’t bother with a detailed review of the production, as we went to the last performance, so word of mouth will not have any effect on ticket sales.  Still, it bodes well for the season that they started out with such a good production.

Oregon Shakespeare Festival 2022

My family (that is, my wife, our son, and I) went to Ashland to see five plays at the Oregon Shakespeare Festival September 21–24. This was my wife’s first trip to Ashland, though I’ve been there three or four times before, and our son at least twice more than me.

This time we were not going with a group, so we flew from SFO to MFR (Medford, Oregon).  Because the flight was midday, and United was warning people to come at least three hours early because of delays in the security line, we got a room at the last minute at a San Bruno motel.  The Hotel Aluxor is well-named, as it is certainly deficient in luxury.  If we do the trip again, we’d take the late afternoon flight and spend the extra night in Ashland instead. We took an Uber from Medford to Ashland, though the bus would have only cost $4 for the 3 of us (two seniors and one adult).

We stayed in the Stratford Inn, about ½ mile from the theaters, where our son and I have both stayed before.  Of the places I’ve stayed in Ashland, it provides the best tradeoff of comfort, convenience, and price, though I’ve only tried three places, so I may well be missing something better.

On the evening of the day we arrived, we saw The Tempest at the Allen Elizabethan Theatre (the outdoor theater). There was a very light rain at times, but we were comfortable enough with our raincoats, the throws we had brought with us, and rented pillows to sit on.  Heavy rain would have made us miserable, though, so we were lucky that the rain held off throughout the performance and the time it took us to walk back to the hotel afterwards. The theater was less than half full, but we attributed this to the day of the week (Wednesday), the rain, and the time of year (after school had started).

The play was a pretty good production of The Tempest—certainly better than the Santa Cruz Shakespeare one we’d seen five weeks earlier, though not as adventurous. The script cut very little of the dialog (leaving in some of the racism and misogyny that is usually cut), but rather surprisingly cut some of Ariel’s most famous songs.  The other major cuts were to the masque, which is almost alway cut heavily.  The projections they used for the masque were ok, but not really great (still better than the “great quotes from other plays” that Santa Cruz Shakespeare substituted). It was not such a bad thing that OSF cut Ariel’s songs, because their Ariel was not very good as an actor—he may have been an ok singer, but the sound engineer really butchered the amplification of the songs.  All in all, it was a decent production with a strong Prospero and only Ariel as noticeably poorly cast.

The next day we saw two plays: Confederates by Dominique Morisseau in the Thomas Theatre (the smallest of the three stages) and Revenge Song in the outdoor theater.

Confederates was probably the best of the productions we saw in Ashland this year, with good acting and directing, a well-written script, and a set that did not distract too much from the play.  There were a few times when we thought that they could have used the traps of Thomas stage to do set changes with a little less running around by the stage crew, but the transitions went fairly smoothly.  The contrast and parallels between the Civil-War era slave woman and the modern Black female professor were intelligently done, and the interactions between the professors and the students were realistically portrayed.

Revenge Song was not exactly what we were expecting from their description

Buckle up for a musical story about Julie d’Aubigny—a queer 17th-century rule-breaking, sword fighting, opera-singing transgressor of boundaries. It’ll be loud, it’ll be rowdy, and it’ll be hilarious! Qui Nguyen (OSF’s Vietgone and Disney’s Raya and the Last Dragon) sets this irreverent take on French history somewhere between the realms of superheroes and comic books and asks what it means to bust through your prescribed roles into who you truly are.

The description is accurate enough, but we were expecting more operatic music, rather than over-amplified rock that drowned the voices under guitars and drums and made the lyrics incomprehensible. The acting was good, and the fight choreography well done (though I think a number of the fight scenes were being done at ⅔ speed, because we had an understudy for Julie). The story itself was pretty easy to follow (despite the fake French accents) and the costuming marvelously silly. We enjoyed the show well enough, despite the sound engineer making the music painful at times (the description did warn us that it would be loud).  We felt that they would have described the show better if they had claimed it was “like Rocky Horror Picture Show with swords”—they might then have attracted a more appreciative audience.  As it was, the theater was only about a quarter full and a lot of the white-haired audience seemed to be tolerating it rather than enjoying it (though there was a contingent of dedicated fans).

On our third day we saw Once on this Island and King John, both at the Angus Bowmer Theatre.

Once on this Island was certainly the worst of the performances we saw. The sound engineer must have been completely deaf, as the music was amplified so loud that it was distorted and painful to listen to—worse even than the overamplification of Ariel in The Tempest and the instruments in Revenge Song. The story line was trite with an awkward framing story, there was essentially no dialog (just songs strung together, which were nearly incomprehensible due to the bad sound engineering), and the costumes and set looked like a high-school production. About the only good part of the show was the dancing, but that was not enough to rescue the production.

King John with an all-female-or-nonbinary cast was excellent. The play has some of the best speeches for women that Shakespeare wrote, and the cast did a vry good job with them, as well as with the male characters, though I think that the directing or acting for John could have been a bit better—the character did not seem to be consistently portrayed (some of the difficulty there is in the script). The fight scenes were highly stylized, to mixed effect. I rather liked the battle done as repetition of a very simple weaponless combat, with projection of the results on the scrim—it brought out the banality of battle and death rather than glorying in the combat. The greatsword fight with the Bastard was clumsy, though—having the Bastard grab the sword by the blade and use it like a grappling hook or halberd made no sense at all. The checkerboard battle, like the weaponless repeat, was an interesting abstract stylization of a battle scene.

Overall, we thought that Confederates and King John were excellent productions, well worth the trip; The Tempest was a workmanlike, but not exceptional production; Revenge Song was good of its kind, but did not particularly appealing to us; and Once on this Island was not worth listening to. I hope that in future Oregon Shakespeare Festival does fewer musicals (since they clearly can’t produce them well—though maybe hiring different audio engineers who were not deaf would help) and more plays like Confederates and King John.

We felt a little sorry for the cast (and the festival in general) as most of the performances we saw were to very sparse audiences (half-empty theaters or worse).  Only Confederates, in the tiny Thomas Theatre, was close to being a full house.

When going back to the airport at the end of the trip, we did take the bus, and were pleased to see how many locals used the bus for transportation.  The security line at Medford was short but slow, since they were having everyone take off belts and shoes, taking laptops out of sleeves, and generally doing the security theater like it was 2002, rather than 2022. The flight itself was uneventful, and our son got home to Richmond fairly promptly by taking BART from SFO. My wife and I had a somewhat slower trip home (BART, Caltrain, Highway 17 Express), because it was a weekend and Caltrain was running only one of the two tracks while they did repair work on the other, resulting in substantial delays.  We ended up taking 9 hours door-to-door from the Stratford Inn to home, which is not that much faster than taking a bus the whole way (which generally ran 12–13 hours, when we went with a charter group).