Since I moved in to my current house in May, I’ve been thinking about putting a (n additional) workbench in front of the inscrutable 7ft wide projection screen (?) thing some previous tenant built in the basement. I sketched out what I wanted early summer, and drew a proper design and cut-list in September – but by then the grueling part of the break-less fall semester had started, so it never got to the top of my list. This week I finally got around to picking up the parts and building it. This has been a rate-limiting step for other projects, since it was partly needed as a home for my CNC router.
I needed some cheap little vregs recently and had run out of and/or lost all of my useful-value 780x linear parts, so I decided to look at what people in this century use.
I found some little buck boards roughly the size of a TO-220 package that looked exciting. These particular ones are QSKJ Mini DC-DC Buck Step Down Module model “QS-1205CME-3A”, Vendor page here, mine were 5pcs/$9 from Amazon.
Upon analysis they have serious issues with regulating under load, so the hunt for something decent continues, but the form-factor and advertised feature set are really compelling.
Pros:
High-efficiency high-frequency synchronous buck instead of a linear heater^H^H regulator.
Solder-jumpers for 1.8,2.5,3.3,5,9,12V or a default (fiddly, tiny) adjustment pot output so you only have to stock one device – one easy-to-cut trace to disable adjustable mode.
Tolerates 4.5-24V input as long as out < in or so.
Good stability to input voltage variation.
~0.25V drop-out.
Does appear to have a cutoff for over-current.
No perceptible ripple under various load conditions.
Cons:
Voltage regulation manages maybe 600mA at 5V before droop becomes unacceptable (<4.8v).
…and that makes it basically useless for most applications. Test data below the fold.
Maybe it could be resolved with appropriate external capacitors and/or offsetting the adjustable to regulate right at a known load or something, but not being drop-in really reduces their charm.
Anyone know of a similar offering that doesn’t suck at output regulation? (Rel: Anyone know if any of the low-end electronic loads are worthwhile? I’m not looking to spend real-lab-instrument money, but it’s come up often enough lately that I want to be able to dissipate a couple 10s of Watts through a at least stepwise-controllable resistive load).
This post is a retro post on a retro topic – a repair I did in 2017 on a monitor made in 1991. I got a question about (probably) the same problem in another venue and realized I never put it online. I managed to dig up my pictures and notes, so there is useful information to be shared.
My 12″ RGB Display is getting sad.
The end of my (2016) post about Recapping my Macintosh LC I discovered that my matching Apple 12″ Macintosh RGB Monitor ( M1296 ) was going pear-shaped, and speculated that I’d need to recap it.
I had my dear old Macintosh SE out for a health check as I slowly extract my vintage computer collection from the (unconditioned) place I’ve been keeping it at my parents house to the basement of the place I’m renting. It had a couple interesting findings that seem worth putting online, including another floppy drive rebuild and a slightly elaborate fan replacement.
I’ve been working with a number of Anycubic Linear Kossel / Kossel Plus (whatever branding they’re using when you look) 3D printers for the last couple months, including one I bought personally. While I’m overall extremely pleased with them, there are a whole bunch of notes, fixes, and improvements I feel like should be collected somewhere.
Bias-tape bound seams out looks better, even if the sewing job is obviously uneven.
Some months ago I decided I wanted to play with an IBM Selectric typewriter, and after some fuckery, obtained and started working on an example of the dual-pitch, correcting Selectric II I find most appealing. At some point there will be an extended post about that, but 1. I’m not entirely sure I know what I’m talking about yet, and 2. Too much writing at the time I was working on it. This post is not about the machine, just the cover I made for it.
Scrapheap Challenge: The world’s worst syringe pump.
Or, three hours enjoyably lost to a visit from the bad idea fairy.
My PhD advisor and I were chatting in the lab today and had an idea that it would be interesting to try to drip/jet a bit of water onto just-extruded filament, ideally in small enough quantity that it phase changed and flashed off with all the excess energy, in order to allow printing unreasonable unsupported structures.
It unfortunately doesn’t look like it will be practical, but we got a PoC-grade implementation in a few hours and it seemed worth a quick write-up to document our experiment for the interwebz.
I’ve been carrying a series of slightly-customized 3D printed bolt-type bladekeys since 2014. Despite being printed PLA, I’ve only had to print a new one once every several years – I wasn’t keeping good records but I think this is my third plastic body, second #8-32 “Chicago Binding Post,” and I upgraded the type of pocket clip at some point. I’m yet to have a catastrophic failure. The setup essentially eliminates key jingle, poking, or wear on pocket facings, while still being easy to tap check and use. The only slight downside to this setup is that when I attach a car key and put it in the vehicle, the blade-key dangles at knee height and occasionally grabs a leg hair – if I drove more I’d probably tweak how I attach the car key to fix that.
Pictures from the first one I carried in 2014, and the most recent swap out, induced by it “getting loose” and letting the stack of keys flip forward in my pocket – which turned out to be the result of several cracks in the plastic body. Plus, flexing that the bitting and labels are both obscured when closed, which I suppose is a minor security feature, especially when posting pictures on the Internet.
The first version I carried in 2014. IIRC that filament had greenish glow-in-the-dark additives.
I think this one died from a drop onto concrete, cracks in the end.
Old and new plastics.
Extensive damage to the one I’ve been carrying for the last several years.
A deeply grooved binding screw, plus a fresh one and the box, which probably represents a lifetime supply.
My current iteration.
At this point I’d buy one of the fancy ones just to support the designer, but my desired size falls in between the models they do commercially (I use 15mm W x 58 L, closest sizes are 12mm W and 19mm W). Maybe sometime I’ll get ambitious and cut one in a different material on the router.
The server that hosts this page was updated from Debian Jessie (8) through Stretch (9) and onto Buster (10) over the course of a few hours today. It involved surprisingly little suffering and should not affect functionality, please let me know if you find anything left in a broken state.
I didn’t realize how long it had been since I did any manual maintenance here, apt unattended upgrades, certbot, and a few scripts for user-installed package upgrades and backup had done such a good job maintaining things just visibly enough to know it was being taken care of that I’d let it get past-due. Most of my other individually-installed boxes are Arch rolling-release machines that require a few minutes of attention every month or two, so they don’t have the periodic major breaking maintenance issue to the same degree.
Now I can let it take care of itself again until 2022 or thereabouts.
A few notes that may be useful to others under the fold. Continue reading →
I just picked up an Aneng AN8009 DMM as an upgrade to the cheap, cheap (but surprisingly OK) Circuit Specialists branded MY-68 I’ve had as my home on-desk approxometer for ages. It’s a nice meter for $30ish, and can be readily hacked to improve its performance. I tend to point people to mid-range Uni-T DMMs when they asked for decent hobby meters, but now I might switch to one of these plus one of those little $10 Atmega328 based component testers cloned everywhere for ~$10 as basic electronics lab instruments.
The trouble with fighting for human freedom is that one spends most of one’s time defending scoundrels. For it is against scoundrels that oppressive laws are first aimed, and oppression must be stopped at the beginning if it is to be stopped at all.
