The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

Category: Oddities

Who’d’a thunk it?

  • 3D Printing: Peculiar Octopi Problem

    From a discussion on the Makergear 3D printer forums …

    A Makergear M2 user had a strange problem:

    Octopi claims the serial connection went down.

    LED2 was blinking red, rapidly, and LED3 was shining with a steadfast red light.

    LED2 shows the extruder heater PID loop is running and LED3 shows the extruder fan is on:
    https://reprap.org/wiki/Rambo_v1.1

    You just never noticed the blinkiness before … [grin]

    Because the extruder heater is still running, the firmware hasn’t detected a (possibly bogus) thermal runaway or any other fatal problem. It’s just waiting for the next line of G-Code, but Octopi isn’t sending it.

    Casually searching the GitHub issues, there’s a report of intermittent serial problems from last year:
    https://github.com/foosel/OctoPrint/issues/2647

    Which points to the FAQ:
    https://community.octoprint.org/t/octop … eption/228

    Look at the Octopi Terminal log to see if the conversation just before the failure matches those descriptions.

    Assuming you haven’t updated the printer firmware or anything on the Octopi, then something physical has gone wrong.

    First and least obviously, the Pi’s MicroSD card has probably started to fail: they’re not particularly durable when used as a mass storage device and “the last couple of years” is more than you should expect. Download a fresh Octopi image, put it on a shiny-new, good-quality card (*), and see if the situation improves.

    Then I’d suspect the Pi’s power supply, even though you’re using the “official rpi power supply”. All of those things contain the cheapest possible electrolytic capacitors, running right on the edge of madness, and produce bizarre errors when they begin to go bad. Get a good-quality wall wart (**), ideally with a UL rating, and see if the situation improves.

    While you’re buying stuff, get a good-quality USB cable (***) to replace the one that (assuming you’re like me) you’ve been saving for the last decade Just In Case™. Use the shortest cable possible, because longer does not equal better.

    After that, the problems get truly weird. Apply some tweakage and report back.

    (*) This is harder to do than you might think. You may safely assume all cards available on eBay and all “Sold by X, Fulfilled by Amazon” cards will be counterfeit crap. I’ve been using Samsung EVO / EVO+ cards (direct from Samsung) with reasonable success:

    https://softsolder.com/2018/10/16/raspb … sk-memory/
    https://softsolder.com/2017/11/22/samsu … ification/
    https://www.samsung.com/us/computing/me … 22y+zq29p/

    The card in question eventually failed, so having a backup card ready to go was a Good Idea™.

    (**) Top-dollar may not bring top quality, but Canakit has a good rep and costs ten bucks through Prime.

    (***) Amazon Basics cables seems well-regarded and work well for what I’ve needed.

  • COB LED Autopsy

    The intent was to wire the “5 W” COB LED to the 12 VDC supply grafted on the Juki TL-2010Q, through a suitable resistor around 18 Ω. Unfortunately, the next morning I managed to run 12 V directly to the LEDs, which produced an astonishingly bright flash of blue-white light and an opportunity for some post-mortem analysis.

    A sharp tap with a chisel popped the COB LED PCB off its heatsink:

    Destroyed COB LED - epoxy bond
    Destroyed COB LED – epoxy bond

    That’s a pretty nice thermal joint and ought to transfer as much heat as reaches the back surface. Mechanically, it yanked one of the nickel tabs right off the solder pads; obviously, I must now level up my soldering game.

    Scraping the yellow silicone filter off the PCB reveals the minuscule LEDs:

    Destroyed COB LED - excavated yellow silicone
    Destroyed COB LED – excavated yellow silicone

    You’ll recall they’re arranged in three series sets of six:

    Circular 12V COB 18 LED panel - copper layout
    Circular 12V COB 18 LED panel – copper layout

    Some probing revealed five of six LEDs in one set was still functional:

    Although a few other LEDs across the PCB survived, that’s not the way to bet when you run so much current through the poor things.

    Ah, well, that’s why I always buy a few more parts than I really need …

  • Monthly Science: Baking Powder Desiccant

    Being that type of guy, I tucked a bag of silica gel desiccant and a humidity indicator card into a #10 can of baking powder, then recorded the bag weight whenever I refilled the kitchen container:

    Baking Powder Can with Data
    Baking Powder Can with Data

    For reasons not relevant here, we pretty much stopped using baking powder a couple of years ago, so there’s a protracted silence between the last two data points:

    That last point emptied the can and, after a few days in the 60% RH basement, the bag weighed 243 g. The slope of the line suggests it’s been near 240 g for a while, although the humidity card showed the air was reasonably dry in there.

    At our current rate, we’ll open the next can in a year or so …

  • Monthly Image: Electrical Safety FAIL

    Our room in a pretty good motel (pronounced “No Pets Allowed”) had the light on the wall above the beds plugged in thusly:

    Motel outlet 1
    Motel outlet 1

    Next to the other bed was the outlet for the between-the-beds nightstand with lamp and clock radio plugs:

    Motel outlet 2 - side
    Motel outlet 2 – side

    Which looked not-so-bad from the side, but not-so-good from the top:

    Motel outlet 2 - top
    Motel outlet 2 – top

    It’s all fun and games until you grope for your metal-frame glasses in the middle of the night and they fall off the nightstand … hasn’t happened yet, but it’ll be spectacular when it does.

    I think the original beds were narrower, with more clearance around the outlets, but we’ll never know. Those Panera Bread outlets pose similar problems.

  • Squirrel Exploration

    We spotted a motion twitch outside and finally figured out what was going on:

    Squirrel in rotten branch hole - 1
    Squirrel in rotten branch hole – 1

    There must be something yummy down inside that branch scar, but you gotta keep checking your six:

    Squirrel in rotten branch hole - 2
    Squirrel in rotten branch hole – 2

    Where’s a hawk when you need one?

  • Collet Pen Holder vs. Cheap Refills

    The three collet pen holders I got a while ago came with ink cartridges:

    Collet pen holder
    Collet pen holder

    So I bought three bucks worth of a dozen pens to get pretty colors, whereupon I discovered they didn’t fit into the collet. Turns out the locating flanges aren’t in the same place along the cartridges:

    The flanges on the top cartridge have been shaved down perilously close to the ink, but it now fits into the collet.

    Bonus: a dozen fairly stiff springs that are sure to come in handy for something!

  • It’s Flat, Jim

    Aaand this front-end loader will require more than the patch kit and CO2 inflator from my bike pack before it’s back in service:

    Front-end loader with flat tire
    Front-end loader with flat tire

    The local yellow iron inventory spends most of the winter snoozing in shopping mall parking lots, waiting to clear the snowfall. It’s been a light year so far, which is fine with me.