Home Ec, Machine Shop

CPAP Hose Dryer: MVP Overview

For all the usual reasons, we’re now confronted with the need to dry a freshly washed CPAP hose:

CPAP Dryer - water droplets in hose
CPAP Dryer – water droplets in hose

Those droplets might not seem like much, but I am reliably informed they produce over-humid air and sprinkle when they migrate into the mask during the night.

Commercial drying machines are available, but seem grossly overqualified and require proprietary foam filters. I wondered if simply pulling air through the hose for a few hours would work:

CPAP Dryer - dried hose
CPAP Dryer – dried hose

Why, yes, it does.

That test took two hours and another with a different hose required about five, but simply “hanging the hose up to dry” consistently produced poor results after three days, so we count a few hours as a win.

I cut the first minimally viable prototype CPAP Hose Dryer from MDF:

CPAP Dryer - overview
CPAP Dryer – overview

Stipulated: MDF is absolutely the wrong material for an air-handling project, because laser-cut MDF stinketh unto high heaven. This was the first pass using cheap material to see how well, if at all, the idea worked.

The CPAP hose goes between the fittings on the bottle and box, with air entering the bottle through a hole drilled in what was its bottom:

CPAP Dryer - filter bottle cutout
CPAP Dryer – filter bottle cutout

An air filter seemed like a Good Idea™, if only to keep ordinary room fuzz out of the bottle and hose. In this Third Pandemic Year, I could simply pull a least-favorite N95 mask from the stockpile and fit a clamp ring around it:

CPAP Dryer - filter clamp installed
CPAP Dryer – filter clamp installed

The motivation for pulling air through the tube, rather than pushing it, came when I realized I could build a much cleaner intake structure by starting with an ordinary HDPE bottle than I could possibly assemble from random parts.

So the fan in the box pulls air through the fitting on the side of the box and blows it out the swirl on top:

CPAP Dryer - fan box
CPAP Dryer – fan box

The box contains a coaxial power jack, the switch, and an 80 mm fan extricated from the Box o’ MostlyFans. I briefly considered an LED, but it’s obvious when the fan runs. The box and swirl cutting patterns come from the invaluable festi.info.

The two slots give the bottle somewhere to stand while idle. In use, the hose is sufficiently unwieldy to require standing the bottle wherever it wants to be, rather than insisting on putting it anywhere in particular.

More details to follow …

Machine Shop, PC Tweakage

Numeric Keypad Repair

Having set up a cheap wireless numeric keypad as a simple macro pad at my left hand, I eventually knocked it off the desk, whereupon the screw compressing the back of the case against the membrane switches ripped through the plastic:

Numeric Keypad - compression screw pullout
Numeric Keypad – compression screw pullout

The symptoms came down to erratic operation of a few keys that became worse as I continued tapping on the thing. Finally, with nothing to lose, I took it apart and, upon seeing the hole in the case, realized I didn’t have to cut the usual label to find the hidden screw.

Slathering the little donut with acetone and clamping things together might work for a while, but I’m sure the keypad will hit the floor again with similar results.

Instead, recruit some candidates from the Box o’ Random Screws:

Numeric Keypad - screw selection
Numeric Keypad – screw selection

Pick the screw big enough to grip the undamaged boss on the front of the case, yet short enough to compress the back again, add a small washer spanning the hole, and it’s all good again:

Numeric Keypad - screw installed
Numeric Keypad – screw installed

This only works because the keypad sits at enough of an angle to hold the screw off the desk.

That was easy …

Machine Shop, Software

Tree Frog Marquetry: FAIL

I thought this critter would look great in marquetry:

Tree frog - on trash can lid
Tree frog – on trash can lid

Posterizing the colors to represent a few shades in my Little Box o’ Veneers simplified the problem:

Tree frog - posterized
Tree frog – posterized

Applying LightBurn’s Trace tool to the various shades produced vector outlines, which I then collected together based on the veneer they should come from:

Tree Frog vector patterns
Tree Frog vector patterns

Which seemed similar to my hand-drawn doodles on a larger image:

Tree frog - sketch vs chipboard
Tree frog – sketch vs chipboard

Before committing to actual veneers, though, I cut the shapes from spraypainted chipboard on a small scale, which showed why this wasn’t going to work:

Tree Frog - auto-trace chipboard
Tree Frog – auto-trace chipboard

It’s facing the other way because I cut the chipboard from the back side, so as to keep the colors reasonably clean and bright.

Contrary to what I initially thought, the automagic tracing routine generates different nodes along a boundary between two colors depending on which side is selected by the color range. Because the nodes (and control points) don’t match exactly, adjacent pieces will have different border shapes and won’t quite match up. The missing pieces at the frog’s rump simply did not fit after the other parts soaked up all the tolerances in between.

So (I think) a better way to do this requires carefully hand-tracing the borders, then using the same path (all the nodes) for adjoining pieces. This mean duplicating the borders for each of the pieces: tedious bookkeeping and layer manipulation.

More study is needed …

Home Ec

Rodent-Approved Carrot Crop

The final garden harvest included several carrots minus their leafy tops:

Rodent-approved Carrot
Rodent-approved Carrot

I sliced that top from a rather rotund carrot and the broad tooth marks suggest a large rodent. Mary found and blocked a tunnel under the fence, so we think it was a groundhog, rather than a rabbit, but we’ll never know the rest of the story.

The rest of the carrot was fine, so the unknown critter had mmmm good taste. Unfortunately, it sampled far too many root crops as it toured the buffet, leaving Mary’s root-cellared stockpile unusually low for our winter meals.

Machine Shop, Oddities

Epson ET-3830 Duplexer Paper Jam

For the record, it is possible to get a piece of paper jammed so far inside the duplexer rollers in the back of an Epson ET-3830 Multifunction Printer / Scanner that it is not only completely invisible from the inside, but that it cannot be removed without disassembling the duplexer:

Epson ET-3830 duplexer jam
Epson ET-3830 duplexer jam

It jammed while attempting to print another batch of Geek Scratch Paper with a semilog grid, without actually duplexing the sheets. The specs say the printer can handle 4×6 paper, so I assumed 4.24×5.5 paper would be Close Enough. Apparently not.

Print ’em two-up, chop the sheets down the middle, pad and glue, and it’s all good:

OMTech CO2 laser power supply - bandwidth tests - semilog graph
OMTech CO2 laser power supply – bandwidth tests – semilog graph
Home Ec, Machine Shop, Science

Step2 Garden Seat: Seat3

Another tray becomes a replacement for the plywood on the Step2 rolling seat in the Vassar Farms plot:

Step2 Garden Seat - weathered plywood
Step2 Garden Seat – weathered plywood

I reused the old hinges, as this tray seems to be slightly thicker than the one on the home garden seat. The straight edges show it’s also somewhat smaller, but it’ll work just fine.

The bottom of the tray with its Silite logo now faces upward, because the top surface has eroded to a matte finish while supporting a bunch of plants outdoors during several summers:

Step2 Garden Seat - tray top
Step2 Garden Seat – tray top

So you can get two or three years from a painted plywood slab out in a garden, depending on how fussy you are about looks.

After two seasons, the first tray doesn’t look any the worse for wear: Silite trays really will survive the Apocalypse and be ready to serve breakfast the next day.

Home Ec, Oddities

Leaf Bag Flagwashing

The data plate at the bottom of the the leaf bags we get from the town seems intended to set expectations at a certain level:

Dano Leaf Bag - data plate
Dano Leaf Bag – data plate

Which is immediately belied by the situation at the other end of the bag:

Dano Leaf Bag - crimp line typo
Dano Leaf Bag – crimp line typo

OK, it’s just a typo that could happen to anyone, but it first appeared last year and seems to be continuing. Possibly the Town of Poughkeepsie bought a lot of bags and we’re working through the stack.

However, the built-in gashes along the sides of some bags were a new feature this year:

Dano Leaf Bag - side gashes
Dano Leaf Bag – side gashes

Perhaps a misalignment in the folder or stacker:

Dano Leaf Bag - side gash detail
Dano Leaf Bag – side gash detail

Enough bags had slices, perhaps four in some ten-packs, to justify keeping the packing tape dispenser at hand while we were shredding up a storm:

Dano Leaf Bag - side gash detail
Dano Leaf Bag – side gash detail

Which frosted Mary pretty severely, as she recycles the used bags as garden path pavers after distributing their contents as mulch, so she’ll be stripping plenty of tape next year.

Although I’m not privy to the Town’s dealings, Dano’s chart suggests the bags cost about 40¢ in truckload lots, about as much as Lowe’s charges for similar bags in retail five-packs. Surprisingly, you can also buy the same Lowe’s bags from Amazon for a lot more, suggesting some folks live much further from a Lowe’s than we do.