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.
Who’d’a thunk it?
Trigger warning: trypophobia fuel.
Spotted on the walking path near the Vassar College golf course:
They’re everywhere:
I think the path surface rises as it freezes, then the stones sink into the loosened soil as they warm up. Other parts of the path, generally having more loam / mulch / organic material than mud & pebbles, have an obviously raised / porous / crunchy texture on bitterly cold (by my standards) days.
Surely, someone can pull a PhD thesis from similar observations …
The kitchen came with matched Samsung appliances dating back to 2018 and, on a frigid winter day, we piled the contents of the freezer on the porch and gave it a deep cleaning. While the empty freezer was cooling down from its adventure, I wondered:
The manual is strangely silent about even the existence of the coils, so evidently cleaning them wasn’t of any importance to Samsung.
Rolling the refrigerator away from the wall just enough to get the phone camera down there suggests they exist and are in need of some attention:
Rolling the refrigerator out until the door handles met the countertop across the way let me climb over the counter and worm myself into the refrigerator-sized hole behind it, bringing along a screwdriver, the vacuum cleaner snout, and a few brushes.
Removing five screws released the back cover:
Looking into the intake end of those coils (on the right):
So, yeah, I’m about to give them their first cleaning ever.
Five minutes of brushing fuzz, mostly into the vacuum, cleared a good bit of the exterior, but the interior needs more attention:
Ten minutes later:
Another five minutes:
Making the coils cleanable and putting them where they could be cleaned were obviously not bullet-item goals for Samsung’s designers.
Although the coils are not perfectly clean, I don’t know how to get them any cleaner, despite knowing even a thin layer of fuzz kills the refrigerator’s much-touted energy efficiency. Perhaps blowing them off with compressed air, then cleaning a thin layer of dust off the entire kitchen, would help.
I think the refrigerator will be happier, at least for a while.
One of our regular walks takes us up the hill on Old Sivermine Place and, being that type of guy, I tend to look at the infrastructure. The LED streetlights along the road sit atop wood poles and are obviously retrofits. Placards on some poles announce “277 V”, which means they’re fed from one leg of a three-phase 480 V wye service, making their casual mid-air wire-nut spliced connections seem … inappropriate.
Anyhow, they’re supposed to look like this:
In reality, having multiple emitters comes in handy:
Typical 12 V systems have parallel strings of three LEDs in series, so you (well, I) often see automobiles with three adjacent dead LEDs. That turned out to be true with the 15 V (-ish) LEDs in the HQ Sixteen machine I’ve been refurbishing.
These streetlights apparently have individual LED drivers, allowing single LEDs to go dark without affecting the rest. This one has five deaders, so the rot is spreading:
There seems no pattern to the failures:
Those fixtures are in order from the top of the hill downward.
Each light has its own photosensor to decide when to turn on. We don’t go walking after dusk, but at least one light will always be glowing brightly in middday; the sensors aren’t doing well, either.
Perhaps an AI / LLM has learned to write just like I do:
The same thing happened last month, although a closer look shows no human can read that fast:
These Dirac-delta pulses seem to be a new thing, with one “reader” hitting many posts, rather than many readers hitting a single post. I can’t tell if it’s a new way for search engines to scan pages or an entirely new algorithm doing the scanning.
Should you run across another blog with similar verbiage, you know where it started …
A highly effective way to bait a rat trap for garden voles:
The trap is a Victor M205 (in a 12-pack as M326) with a big yellow plastic bait pedal. The bait is pieces of walnut, secured to the pedal with generous strands of hot melt glue. The trick involves mechanically capturing the walnut by slobbering glue over & around it, forcing the vole to pull & tug while gnawing the last bit of goodness.
Which generally ends badly:
I do not begrudge the critters a fancy last meal; it’s gotta be better than their usual diet of carrots / radishes / turnips.
Voles have no qualms about eating the bait from a sprung trap with a dead compadre a few millimeters away:
They will sometimes eat the walnuts and their dead compadre.
The plastic pedals work much better than the old-style metal pedals at holding the steel arm wire. The wire slides freely on the plastic, in contrast to the previous high-friction metal-on-metal latch.
Some of the traps were entirely too sensitive and required slightly bending the tip of the arm wire upward to increase the friction on the plastic plate. Always always always handle armed traps by the wooden edges beside the kill bar, so when it accidentally snaps your fingers are nowhere near the business end.
After I figured out how to properly bait the traps and we set out half a dozen traps in the most attractive crops, Mary’s garden produced 54 dead voles over the course of 90 days, sometimes in groups of three or four at a time. While this did not prevent all the crop damage, it definitely reduced the problem.
Next year we’ll start early and probably reach triple digits by midsummer.
The same technique with Victor M035 mouse traps (in 12-packs as M035-12) is brutally effective on house mice.
Judging from the dates codes on the ICs inside, Mary’s HandiQuilter Sixteen long-arm machine is about two decades old and many of the white LEDs in the front handlebars have gone dark:
The vertiginous view looks upward into the handlebar at the top of the machine (more on this later). The PCBs run strings of three series LEDs from a 16 VDC supply with a 390 Ω ballast resistor (oddly enough, on the ground end of the string), so one failed LED takes down all three.
I decided to replace all the LEDs, on the principle they’re surely dimmer than they used to be and to take advantage of a decade or so of improvement in white LEDs (yes, I have old stock).
After discovering that the HandiQuilter engineers violated the Principle of Least Surprise by orienting adjacent LED strings in opposite directions, I found one of the strings still didn’t light up.
Pop quiz: which one of these LEDs caused the problem?
To the best of my knowledge, all 5 mm round LED packages mark the cathode lead with a flat edge. It’s easy to remember, as the cathode side of the schematic symbol has a bar: straight bar = straight edge.
Inside, the LED chip’s cathode lead is bonded to the reflective cup, with the anode lead wire-bonded to the top.
Took me a while to see what was wrong, too.
For whatever it’s worth, the backward LED works fine.
Although essentially all kitchens feature a microwave over the stove, essentially all women have difficulty reaching it. As a result, our kitchen has two microwaves: the built-in Samsung over the stove and our trusty Sears Kenmore on the counter.
We’ve had it for a while:
Apart from the turntable rollers, it’s been utterly reliable for the last two decades, until the Start button stopped working:
The membrane switch panel seems to be in good shape, with no cracks in the plastic surface. Only the Start button failed, which suggested the switch contact pad had failed and ruled out broken matrix traces on the flexible circuitry.
Back in the day, they kept casual tinkerers out of the dangerous interior:
That would not be me:
Over the course of two decades, an occasional food explosion produces a surprising amount of debris:
Go ahead, I dare you, show us your microwave exhaust vent.
The control panel circuit board & wiring looks like this:
Unplugging all the connectors proceeds as you’d expect, whereupon a single screw (out of sight to the top) releases the control assembly and pulling the whole thing upward gets it out of the cabinet:
The capacitors show no signs of The Plague, but those resistors near the optoisolator (?) in the middle have a suspicious thermal plume.
The ribbon cable from the control surface goes into a connector with the usual locking collar:
The cable also has cutouts latching into tabs molded into the collar:
Removing two screws at the transformer releases the PCB:
Which promptly slammed the whole repair mission to a dead stop: with the entire membrane switch assembly glued to the front of the plastic shell, there is no way to get to the Start switch. Trying to peel the membrane off will most certainly destroy it.
Because all the other functions still worked, including the Add Minute button, we figured we can eke out a few more years before something else fails or the lack of one button gets intolerably annoying.
I reassembled everything in reverse order, plugged it in, and, while setting the clock, discovered the Start button once again worked perfectly.
It’s a classic laying-on of hands repair: take something apart, replace nothing, reassemble, and it works!
If the Start button is not part of the overall switch matrix, with a separate conductor through the ribbon cable, un- and re- plugging would be enough to restore a flaky contact. We’ll never know the rest of the story, although with this post as a reminder, maybe I can remember to tear the matrix apart when we scrap it out.
Somebody give me an Amen!
The Smell of Molten Projects in the Morning 