Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Running continuously for three months made the air filters look like this (with an unused filter on top for comparison):
Basement Air Filter Box – 3 months – A
I have not stretched the image contrast, so the new filter isn’t the pure white in the top picture, but it’s still about the same white as the cardboard frame. The floor is, indeed, painted gray.
Looking at the pleats in the other direction to show I’m not making it up:
Basement Air Filter Box – 3 months – B
The inside surface of the filters has the same gray appearance. The fans are, unsurprisingly, immaculate.
Totally did not expect that!
The filters sport a MERV 13 rating and snag “most smoke” from the passing air, so they’ve been collecting any fumes not sucked out of the laser cutter, along with whatever arises from other Basement Shop™ activities.
So I’ll buy another set of filters, build another box, and see what accumulates during the next three months.
It’s a W5W “parking light” in the same fixture as the melty halogen high-beam bulbs (used as daytime running lights at half power), so it gets toasted on those occasions when we drive somewhere.
The adhesive holding the LED strip to the aluminum shell fossilized and came loose:
White W5W Parking Light – failed adhesive
Now that I know what to look for, I’d get LED bulbs with chips soldered directly to the PCB, although it’s not obvious what holds the PCB to the aluminum frame.
As long as the voltage limit is over about 10 V, it will (likely) never matter, as the LED forward drop doesn’t vary much with temperature. Setting it to something sensible keeps it out of the way.
The middle trimpot apparently sets a voltage for a comparator to light an LED when the battery current drops below that level as it reaches full charge.
Although the regulator touts its high efficiency, it does run hot and a heatsink seemed in order:
LED Garage Light – heatsink
Stipulated: the fins run the wrong way and it’s sitting in the updraft from the main heatsink. It’s Good Enough™.
The switch on the top comes from the collection of flashlight tailcap switches and controls the 12 V input power. It’s buried up to its button in a generous dollop of JB Kwik epoxy, which seemed the least awful way to get that done.
The solid model looks about like you’d expect:
LED Lamp Driver case – switch housing – show solid model
The OpenSCAD code exports the (transparent) lid as an SVG so I can import it into LightBurn and laser-cut some thin acrylic. Two tape snippets hold the lid in place pending more power-on hours, after which I’ll apply a few dots of cyanoacrylate adhesive and call it done.
The case builds in two pieces that glue together to avoid absurd support structures:
LED Lamp Driver case – switch housing – build solid model
A 3D printed adapter goes between the desk lamp arm and the lamp heatsink bolt:
LED Lamp Driver case – arm adapter – solid model
The OpenSCAD source code files for the case and adapter arm as a GitHub Gist:
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Mary’s current quilt project has a corner design with an essentially infinite number of 45° triangles, which another custom ruler will simplify:
45° Quilting Ruler – finished
That’s the end result of several iterations, proceeding from doodles to sketches to increasingly accurate laser-cut prototypes:
45° Quilting Ruler – prototypes
A “ruler” in quilting parlance is a thing guiding the sewing machine’s “ruler foot” across the fabric (or, for sit-down machines, the fabric under the foot) in specific directions:
45° Quilting Ruler – in use
That’s a practice quilt on scrap fabric: quilters need prototypes, too!
The foot is 0.5 inch OD, within a reasonable tolerance, which accounts for the slot width in the ruler. It’s also intended to run against 1/4 inch thick rulers, which accounts for the thickness of that slab of acrylic.
The engraved lines & arcs are on the bottom of the ruler to eliminate parallax errors against the fabric, so the bottom is upward and the text is mirrored for the laser:
45° Quilting Ruler – cutting
Although fluorescent green acrylic may have higher visibility, clear seems adequate for the fabric in question:
45° Quilting Ruler – colored fabric
I very carefully trimmed the arcs against the ruler outline using LightBurn’s Cut Shapes, which turned out to be a Bad Idea™, because the high-current pulse as the laser fires causes a visible puncture wound at the still-to-be-cut edge:
45° Quilting Ruler – edge damage
Those are not straight lines and the plastic isn’t bent!
A closer look:
45° Quilting Ruler – edge damage – detail
The arcs without wounds started from their other end and stopped at the edge, which is perfectly fine.
The wounds are unsightly, not structural, but the next time around I’ll extend the markings a millimeter beyond the edges into the scrap material.
The overall design looks busier than it is, because I put different features on different layers in case they needed different settings:
Mary picked up a pair of Star quilting rulers from the Quilting Guild’s “exchange” table:
Star quilting ruler – finished
They’re 1/4 inch laser-cut acrylic slabs dating back to the turn of the millennium, when laser cuttery wasn’t nearly as common as today. Apparently, the (now long gone) Gadget Girls had a problem with their laser: the larger star had eight of its ten lines not cut completely through the acrylic. The protective paper on the back had small perforations along a few of the lines, but nothing for most of them.
Well, I can fix that.
Lay the slab on the platform and lock it in place so it cannot move:
Star quilting ruler – laser setup
That’s with the original bottom side facing upward, so the laser beam will hit the uncut part of the lines.
Focus the laser atop some scrap 1/4 inch acrylic, then verify the red dot pointer is exactly concentric with the CO₂ beam by firing a test pulse, as in this punched card:
Red dot vs printed target vs laser spot alignment
Adjust as needed.
Jog the laser to put the red dot pointer exactly at a star point:
Star quilting ruler – laser point alignment
Hit Get Position in the Laser window so LightBurn knows where the laser head is located.
I’ve added the targets I normally use for LightBurn’s Print and Cut alignment to its Art Library, so I dragged one to the workspace, then hit Move to Laser Position to snap the target directly onto that point of the star.
Repeat for vertices along the star, then draw a multi-segment line = path between the target centers:
Star Ruler Re-cutting – LightBurn layout
That’s one continuous path from the upper right, counterclockwise around the star, ending in the center right. The missing pair of lines (and the vertex between them) were already cut, so I didn’t need to locate them.
The camera view shows the alignment, although IMO the camera simply isn’t capable of such finicky alignment:
Star Ruler Re-cutting – LightBurn layout overlay
As a confidence builder, I selected each target, moved the laser to that point, then fired a test pulse to verify the hole hit the vertex. In most cases, I couldn’t see the hole because it was within the original cut.
My 60 W laser can’t cut through 1/4 inch = 6 mm acrylic in a single pass, so I use a 10 mm/s @ 60% pass to get most of the way through and a 20 mm/s @ 60% pass to complete the cut. That seemed excessive for a mostly cut path, but a single 20 mm/s @ 60% pass didn’t completely clear the uncut sections.
So I used the normal two-pass cut and the star lifted right out:
Star quilting ruler – victory
Happy dance!
Although it is not obvious from the pictures, the star is not symmetric: it fits into the sheet in only one of its ten possible orientations. I will never know if that was a deliberate stylin’ decision or the result of hand layout before CAD spread throughout the land.
I managed to locate the vertices so accurately that the repeated cuts left edges indistinguishable from the original cuts on the two free sides, which was a pleasant surprise.
Mary promises to do something with those stars when she’s done with her current project(s). She may want the slab of acrylic around the large star trimmed into a smaller and more manageable decagon, in which case I will suddenly have a bounty of thick fluorescent green acrylic.
Of late, the magnetic stirrer mixing my morning cocoa occasionally doesn’t start spinning when I turn it on, which calls for some investigation.
Removing the four obvious screws concealed under the rubber feet and prying off bottom cover reveals the trivial innards:
Magnetic stirrer – interior
The speed adjustment pot holds the little circuit board in place, with the green LED setting its jaunty angle.
The motor spins a pair of neodymium magnets:
Magnetic stirrer – magnet holder
I expected a gearbox instead of the direct drive setup.
Perhaps those whirling neodymium magnets have been slowly demagnetizing the motor’s internal (alnico?) magnets.
The motor brushes seem to be a pair of stiff wires, rather than carbon blocks, contacting the commutator, the wear from which may account for motor’s decreasing startup enthusiasm. Even though I didn’t expect a BLDC motor, this one may have been overly cheapnified.
Perhaps kickstarting the motor with the steel fork I use to fish the stirrer magnet out of the mug will get the thing going.
Having recently filed our income taxes, this email came as a mild surprise:
IRS Audit email
The From field seemed a bit sketchy, but, hey, maybe the IRS subcontracted their email vendor after having lost much of their staff in the name of efficiency.
The Smell of Molten Projects in the Morning 
