Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
The aperiodic monotile discovery prompted some reverse engineering, snapping a path to regular hexagons for the proper lengths and angles without mathing too hard:
Aperiodic tile – hexagon overlay
The resulting red path is the “hat” monotile, here shown as a PNG for neatness:
Aperiodic monotile
With SVG hat in hand, I laid and cut a trial puzzle based on the sample shown in the paper:
Aperiodic tile layout
Which looked promising enough to add a few rings around that layout and turn it into an actual, albeit low budget, puzzle:
Aperiodic tile puzzle – starting
The paper notes that one can build mutually incompatible patches, which is the state I immediately blundered into:
Aperiodic tile puzzle – progress
The upper and lower left halves cannot be combined to extend rightward, as the middle section is incompatible with both. I began growing patches from the upper and lower right corners, hoping to use them to rectify the left half, but producing a small un-fillable situation in the middle:
Aperiodic tile puzzle – incorrect layout
Obviously, I need a cheat code. I’m resolutely not looking at the source layout for a while.
It’s basically ten identical identical spacers cut from 3 mm plywood, with a side benefit of dramatically reducing my scrap plywood stash, then skewered by a pair of absurdly long 4 mm self-tapping metal screws into holes drilled half an inch into the ¾ inch solid wood cabinet floor.
It clears some clutter atop the microwave and, at least to my deflicted ears, sounds much better. At some point I must screw the Raspberry Pi under the cabinet, too, but that awaits further rearrangement.
Confirming the diagnosis, the cool white LEDs worked fine with the light turned on:
Miroco floor lamp – all-LED mode fail
With nine spare SI2306 transistors in hand from the last time in this rodeo and minus the sticky adhesive foam covering the PCB, replacing the other driver transistor was no big deal, whereupon the lamp once again worked the way it should:
Miroco floor lamp – restored warm LEDs
While I was in there, I spotted a dent in the input filter cap:
Miroco floor lamp – OEM capacitor
Most likely I squished a wire between the cap and the U-shaped steel strut joining the two halves of the pole. I relocated the replacement cap off the circuit board into an open space with a bit more room:
Miroco floor lamp – recapped
The fragile wires running to the lamp head got their own sheet of silicone tape (not shown here) to isolate them from the U-strut:
Miroco floor lamp – LED wiring
Tuck all the wires back inside, snap the housing together, and it should be good for another uhh half year or two.
It’s hard to be sure about such things, but I now have eight spare transistors …
The “live hinge” on my overnight eyeglass case shattered when it hit the floor (these things happen), which prompted me to finish a longstanding project of replacing the inadequate / worn out padding in my most-used cases to reduce rattles while in my pocket.
I’d long ago cut craft foam sheets to fit some of the cases, so I started by scanning a sample:
Zenni case pad
Admittedly, black foam on a white background isn’t much to look at, but it did fit one of the cases pretty well.
Rotate the image to make things simple, convert it into a monochrome bitmask, import it into LightBurn, fair some Bezier curves around it, duplicate and tweak for the other not-quite half of the case:
Zenni eyeglass case pads – LB Layout
I ended up with several different versions for various cases, but you get the general idea:
Zenni eyeglass case pads – installed
They’re all cut from 2 mm EVAfoam sheets which, despite the “vinyl” in their name, do not contain chlorine and are suitable for laser cuttery.
Some of the deeper case halves required strips of adhesive sheet to secure the foam, but most sheets dry-fit in place.
The four control “buttons” on the SmartHeart kitchen scale are copper-foil tabs that sense the presence of your finger though about 5 mm of white plastic and glass:
SmartHeart 19-106 Kitchen Scale – top view
The main failure mode seemed to come from the microcontroller locking up and refusing to recognize any of the buttons, most annoyingly the On/Tare button, while continuing to measure whatever weight was on the scale with whatever zero point it chose. Recovery involved waiting until the thing timed out and shut itself off.
The two buttons on the left select Kilocalories for any of the various foods arrayed around the display. Depending on how it jammed during startup, it might display the Kilocalorie value for, say, sugar, while ignoring all button presses. As the manual does not mention any way to return to weights after activating the Kilocalorie function, other than turning it off, it’s not clear recognizing the other buttons would be much help.
Because we have no use for those functions, I unsoldered the wires to those sensor pads and it no longer jams in that mode:
SmartHeart 19-106 Kitchen Scale – PCB detail
The alert reader will note the PCB legend says I have unsoldered the ON/OFF and UNIT wires. If one believes the silkscreen, the PCB dates back to 2015, so it now carries a reprogrammed microcontroller with functions that no longer match the silkscreen.
The overall soldering quality resembles mine on a bad day.
With those out of the way, the scale still jammed and refused to recognize the remaining two buttons. I wondered if it was somehow sensing ghost fingers over both sensors and waiting for one to vanish, so I added a shield ring around the power tab:
SmartHeart 19-106 Kitchen Scale – shielded sensor
That reduced the sensitivity of both sensors to the point where they pretty much didn’t work, without reducing the number of jams.
So I tried increasing the sensitivity of the power tab by replacing it with a larger copper foil sheet:
SmartHeart 19-106 Kitchen Scale – larger sensor
That definitely got its attention, as it will now respond to a finger hovering half an inch over the glass, as well as a finger on the bottom of the case: it can now turn on and jam while I pick it up.
More tinkering is in order, but it’s at least less awful in its current state than it was originally, so I can fix a few other things of higher priority.
The health plan I use pays $100 toward the year’s over-the-counter healthcare stuff, although with a caveat: you can only buy the stuff from a specific website. As you might expect, what’s available consists of no-name generic products with absurdly high sticker prices and, just to rub it in, the hundred bucks gets paid in quarterly use-it-or-lose it installments.
Seeing as how it was free, I got a kitchen scale:
SmartHeart 19-106 Kitchen Scale – top view
It has two catastrophically bad design features:
Terrible battery life
Overly sensitive controls
It runs from a pair of series-connected CR2032 non-rechargeable lithium coin cells. Which would be fine, except that the blue LED backlight stays on for 30 seconds after each button touch and draws about 10 mA.
The battery lifetime is best measured in days.
The four control “buttons” on either side of the backlit LCD are touchless sensors using copper foil stickers:
SmartHeart 19-106 Kitchen Scale – NP-BX1 retrofit
The alert reader will spot those the empty CR2032 coin cell contacts over on the left and a pair of NP-BX1 batteries in the middle.
I figured there was no need to keep feeding it coin cells while I played with it, so I conjured a holder from the vasty digital deep. Normally, that would be an OpenSCAD solid model suited for 3D printing, but in this case the lithium cells exactly filled the space between the PCB and the bottom of the case, so it became a 2D design neatly suited for laser cuttery.
Kitchen scale – NP-BX1 holder – LB layout
I planned to stick the orange cutout (in 1.5 mm acrylic) as a stabilizer around the pogo pins making contact with the cell terminals from the red cutout (in 3 mm acrylic), but just melting the pins into the acrylic seemed sufficient for the purpose. Strips of adhesive sheet saved from the margins of previous projects affix the holder (not the cells!) to the scale’s upper glass layer.
As far as I can tell, the scale is perfectly happy running on 7.4 V, rather than 6.0 V. The PCB has two terminals marked +3V and +6V, so it probably depends on which LEDs they use for backlights:
SmartHeart 19-106 Kitchen Scale – PCB detail
The alert reader will notice a peculiarity concerning the sensor pad connections along the top edge.
The Smell of Molten Projects in the Morning 
