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: Home Ec

Things around the home & hearth

DIY CPAP Mask Liner
Mary cut out a simple cloth liner for her ResMed F20 CPAP mask (a.k.a. “cushion”) and snipped away at the fabric until it felt about right. I scanned the result and turned it into a bitmap mask (which is entirely different from a CPAP mask):

Mask liner – scanned

Given that as a start:
- Import the scanned image into LightBurn
- Fair a few curves around the perimeters by hand, rather than attempting to trace the thing
- Rationalize the sizes
- Make it symmetric
- Cut a few prototypes while tweaking the fit
Which leads to a pattern like this:

CPAP Mask Liner – F20 knit – spline fit

The rectangular upper part forms a simple eyeshade that also keeps minor leaks from disturbing her sleep. Your mileage may vary, depending on how much you toss and turn during the night.

We found the fit depends on the fabric, with woven fabric requiring a taller opening:

CPAP Mask Liner – F20 knit woven – LB layout

The engraved legend verifies I used the proper design for the fabric:

Laser cut CPAP Mask Liner – F20 – knit fabric

The opening has tabs holding it in place while cutting, at least until we get this down to a routine.

Then make enough for a while:

Laser cut CPAP Mask Liner – F20 – production

The usual woodstove odor vanishes after half a day sitting atop the clothes washer. Putting them in a mesh bag and tossing them into the regular wash refreshes them after use.

The LightBurn SVG layouts as a GitHub Gist:

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2023-02-22
Shower Faucet Handle Rebuild & Tightening

The shower faucet handles have been getting looser, but once a decade seems reasonable. This time around, however, the setscrews had dug themselves so far into the splined plastic fittings that they had run out of thread:

American Standard Shower Handle rebuild – gouged setscrew sockets

Wipe out the crud, clean out what’s left with alcohol to encourage stick-to-it-ivity, and fill the cavities with JB Kwikweld epoxy:

American Standard Shower Handle rebuild – epoxy fill

When it cures, file a flat across the sockets:

American Standard Shower Handle rebuild – flatted

Reinstall in reverse order with a dot of NeverSeez on the setscrews for good measure.

Just so you don’t have to look it up, this is what the cold water faucet innards looked like a decade ago:

Shower faucet valve stem

Ought to be good for another decade, right?

2023-02-21
Flypower Wall Wart: FAIL

The IR sensor on the under-cabinet LED lights I installed half a dozen years ago became increasingly flaky. Its wall wart power supply was on the hot side of uncomfortably warm, so I had an obvious culprit.

The data plate says it’s UL Listed, which is comforting:

Flypower LED wart – data plate

The open-circuit output of a 12 VDC power supply should not look like this:

FlyPower 12V 1A – no load

The horizontal scale is 100 ms/div, so those ramps seem much more languid than you might expect from a 60 Hz wall wart.

Adding a 16 Ω load to draw maybe 750 mA got its attention:

FlyPower 12V 1A – 16ohm load

The average may be 12 V with too-large dips at the expected 120 Hz, but looky at all the hash riding the output!

No wonder the IR sensor was having such a hard time. When the LEDs are off the voltage ramps between 16 and 5 V. When it eventually turns on the supply has impossible noise levels.

So I cracked the case and extracted the electronics:

Flypower LED wart – components

Those caps over there on the left rear don’t look healthy, do they?

Flypower LED wart – failed caps

No. No, they don’t and you shouldn’t be able to see the wiring inside the inductor between them, either.

Probing the Box o’ Wall Warts produced a similar-ish wart that only required harvesting and splicing the teeny coax plug from the failed adapter to put the LED strips back into normal operation.

The identical supply for the identical LED strips on the other side of the kitchen continues to work fine and feel only warm-ish, so I’ll let it be.

2023-02-15
Laser Engraved Fabric

This is more along the lines of searing the fuzz, rather than actual engraving:

Laser Engraved Fabric – cotton knit

The top row is 15% power at 400 mm/s, the bottom is 25% power, and the fabric was a cotton t-shirt from the Box o’ Shop Wipes.

Applying the higher power to the inside of sweatpants fabric, whatever that might be:

Laser Engraved Fabric – sweatpants

Both of those were easier to see in the slanting sunlight of a later winter afternoon.

The best results come from the lowest feasible power applied at the fastest practical speed, with obvious size and complexity limitations.

I think this will most useful on a removable tag labeling a piece (perhaps cut from a larger pattern), rather than branding the piece itself.

2023-02-13
RCA Alarm Clock: Recapping

A power failure apparently pushed the ancient RCA alarm clock over the edge into a mode where it ignored its pushbuttons and displayed a time based on a hitherto unknown exoplanet. Popping the case revealed it’s been simmering in its own juices for quite a while:

RCA Alarm Clock – PCB overheat

There’s nothing obviously scorched on the underside of the PCB, although a large SMD resistor might be the source of the problem.

Having been around this block a few times, I unsoldered that big electrolytic cap with its guts protruding from the overwrap:

RCA Alarm Clock – failed cap value

Nope, that’s not really an electrolytic cap any more.

Lacking a 2200 µF cap of suitable voltage rating, but knowing cap tolerances allow for considerable windage, this worked out well enough:

RCA Alarm Clock – replacement caps

Two smaller caps measuring on the low side of OK now reside in the e-waste box.

The white diffuser over the last digit improves it in ways I do not profess to understand, but am pleased to implement:

RCA Alarm Clock – in place

It’s held in place by two strips of LSE tape to see how it reacts to prolonged shear force, no matter how gentle.

2023-02-10
Shoulder PT Pulley: Last 10% Manufacturing

Mary’s PT requires a Shoulder Pulley, so I got one that seemed better constructed than the cheapest Amazon crap. In particular, this view suggested the pulley ran on a bearing:

Slim Panda Shoulder Pulley – detail view

Which turned out to be the case, but, also as expected, the whole thing required a bit of finishing before being put in service.

It’s intended to hang from a strap trapped between an interior door and its frame. The strap was intended to attach to the block (a.k.a. “Thickened base”) through a breathtakingly awkward pair of low-end carabiners:

Slim Panda Shoulder Pulley – carabiners

Which I immediately replaced with a simple, silent, sufficiently strong black nylon cable tie:

Shoulder PT Pulley – block hardware

Rather than let the metal block clunk against the door, it now sports a pair of cork-surfaced bumper plates:

Shoulder PT Pulley – side plates installed

A doodle of the block dimensions:

Shoulder Pulley – dimension doodle

Which turned into a simple LightBurn layout:

Shoulder PT Pulley Side Plates – LB layout

The blue construction lines represent the actual block & pulley, with the red cut lines offset 2 mm to the outside to ensure the metal stays within the bumpers. It’s possible to pick the block up and whack the pulley against the door, so don’t do that.

Cut out two pieces of 3 mm MDF, two pieces from a cork coaster (covered with blue tape and cut with the paper backing up), peel-n-stick the cork to the MDF, put double-sided foam tape on the block, peel-n-stick the bumpers, then hang on the attic door.

Now it works the way it should!

The LightBurn SVG layout as a GitHub Gist:

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2023-02-07
Toilet Flush Valve Re-chaining

I don’t think I flushed the pot any more vigorously than usual, but the plastic chain snapped off at the flush valve:

Flush valve chain – broken plastic

Some rummaging in the Chain Locker produced a steel chain from a long-ago flush valve that snapped into place:

Flush valve chain – steel

Despite what you may think, I do not enjoy fiddling with this stuff, so I locked the link in place with a dab of hot melt glue:

Flush valve chain – steel glued

Having recently repaired the other pot in the house, perhaps they’ll stay fixed for a while. It could happen!

2023-02-06