Sheath Your Blades!

Trigger warning: gore.

A week ago I milled a stack of cursor blanks, then engraved a test hairline on a scrap cursor to make sure everything was ready:

Cursor V-bit setup
Cursor V-bit setup

After raising the spindle a few inches, I reached across the table, peeled the tape, and, as I pulled my hand back with the finished cursor, snagged the back of my left index finger on the V bit.

So. Much. Blood.

Urgent Care PA: “You may have nicked the tendon. Get thee hence to the Hospital Trauma Center.”

Trauma Center MD: “See that white fiber down in there? That’s the extensor ligament. Looks OK and should heal fine.”

Me: “Urp.”

Trauma Center MD: “Unless you’re one of the 20% who get an infection.”

Me: “Unless I’m one of the few who contract an MRSA infection, then just up and die.”

Trauma Center MD: “Well, yes, there’s that. If the wound swells or smells bad, come back here quickly.”

Dutchess County is now on the trailing edge of the Omicron wave, but the Trauma Center is attached to the Emergency Room and had a steady stream of customers arriving by ambulance. While being entirely content to not be their most urgent case, I had plenty of time to examine the wide variety of instruments parked in the room with me:

Nameless Hospital Cart
Nameless Hospital Cart

I’m on a ten-day regimen of surprisingly inexpensive Amoxicillin + Clavulanate Potassium capsules, which is apparently what it takes to knock down a potential infection these days.

Five days later, it looks like I should pull through:

Lacerated Left Index Finger
Lacerated Left Index Finger

So I hereby swear a mighty oath on the bones of my ancestors to always sheath my blades. You should, too.

But we all knew that last week, didn’t we?

Google Play Store Ad Bidding Delay

Being that type of guy, I turn my phone off during the night while it’s charging, turn it on for the next day’s adventures, and check the Google Play App Store to see which apps will get updates.

The vast machine learning / AI / whatever analyzing my every move still hasn’t figured out my morning ritual, so it desperately tries to sell me crap:

Google Play Store - app ad delay
Google Play Store – app ad delay

My guess: those blank spots are placeholders for app ads, but, while the phone is busy scanning for malicious apps, the ad bidding process doesn’t complete fast enough to update the display before I see it.

FWIW, I had the Genuine NYS Covid-19 app installed for a while, but I very rarely go anywhere or see anybody, so it seemed to offer no net benefit.

Schauer Solid State Battery Charger: Digital Meter Retrofit

The Forester’s battery has been on life support from an ancient Schauer “Solid State” charger (which may have Come With The House™) for the last year:

Schauer battery charger - analog ammeter
Schauer battery charger – analog ammeter

A remote Squidwrench session provided an opportunity to replace its OEM ammeter with a cheap volt-amp meter:

Schauer battery charger - digital meter
Schauer battery charger – digital meter

The charger is “solid state” because it contains silicon electronics:

Schauer battery charger - solid state components
Schauer battery charger – solid state components

That’s an SCR implanted in the aluminum heatsink. The other side has a Motorola 18356 house number, a date code that might be 523, and the word MEXICO. The company now known as NXP says Motorola opened its Guadalajara plant in 1969, so they could have built the SCR in either 1973 or 1975; it’s not clear who manufactures what these days.

The black tubing contains at least one part with enough value to justify the (presumably) Kovar lead; nowadays, it would be a “gold tone” finish. It’s probably a Zener diode setting the trickle-charging voltage, joined to the resistor lead in the crimped block. I don’t know if the glass diode is soldered to the Zener, but I’m reasonably sure if the third lead came from a transistor tucked inside the sleeve, we’d read about it on the charger’s front cover.

In an ideal world, a digital meter would fit into a matching rectangular hole in the front panel, but that’s not the world we live in. After wrestling my gotta-make-a-solid-model jones to the floor, I got primal on a random slab of soft-ish plastic sheet:

Schauer battery charger - bezel nibbling
Schauer battery charger – bezel nibbling

There’s nothing like some bandsaw / belt sander / nibbler action to jam a square peg into a round hole:

Schauer battery charger - bezel test fit
Schauer battery charger – bezel test fit

It’s actually a firm press fit; whenever something like that happens, you know the project will end well.

Hot melt glue FTW:

Schauer battery charger - digital meter wiring
Schauer battery charger – digital meter wiring

The new meter’s (heavy) red-black leads go to the same terminals as the old meter’s wires, paying attention to the polarity. I splurged with insulated QD terminals on the old wires where a joint was needed.

The meter’s thin red lead expects to see a power supply under 50 V with no particular regulation requirements, so I used the same flying-component design as the rest of the charger:

Schauer battery charger - meter power supply
Schauer battery charger – meter power supply

The meter draws basically no current, at least on the scale of an automotive battery charger, so the 220 µf cap holds pretty nearly the peak 18 V half-wave rectified from the center tap by a 1N5819 Schottky diode.

Those two squares riveted to the back panel are genuine selenium rectifiers, from back in the day when silicon power diodes weren’t cheap and readily available. They also limit the charger’s peak current and have yet to emit their incredibly foul stench upon failure; you always know exactly what died when that happens.

Selenium rectifiers were pretty much obsolete by the early 1970s, agreeing with a 1973 date code. Schauer might have been working through their stockpile of obsolete rectifiers, which would have been sunk-cost-cheap compared to silicon diodes.

The meter’s thin black lead goes to the power supply common point, which turns out to be where those rectifiers meet. The larger black wire goes off to the meter’s fat black lead on the other side of the aluminum heatsink, joining it in a new insulated QD terminal.

The meter’s thin yellow wire is its voltage sense input, which gets soldered directly to the hot lead of the SCR.

The meter indicates DC voltages and currents, which definitely isn’t the situation in the 100 Ω power resistor shown in the second picture.

The voltage:

Schauer battery charger - voltage waveform
Schauer battery charger – voltage waveform

And the current at 20 mA/div, showing why silicon replaced selenium:

Schauer battery charger - current waveform
Schauer battery charger – current waveform

Yes, the current does go negative while the rectifiers figure out what to do next.

The charger seems a little happier out in the garage:

Schauer battery charger - in use
Schauer battery charger – in use

The battery holds the voltage steady at 13.7 V, with the charger producing 85 mV blips every second or so:

Schauer battery charger - float V pulse
Schauer battery charger – float V pulse

Those blips correspond to 3 A pulses rammed into the battery:

Schauer battery charger - float A pulse - 1 A-div
Schauer battery charger – float A pulse – 1 A-div

They’re measured across a 1 Ω series resistor that’s surely limiting the maximum current: 18 V from the transformer minus 13.7 V on the battery minus other IR losses doesn’t leave room for anything more than 3 V across the resistor. I wasn’t going to haul the Tek current probes out to the garage just for the occasion.

Opening the Forester’s door to turn on all its LED interior lights bumps the meter to about 1 A, although the truth is more complicated:

Schauer battery charger - loaded A pulse - 1 A-div
Schauer battery charger – loaded A pulse – 1 A-div

The average current is, indeed, just under 1 A, but in this situation the meter’s cool blue number seems more like a comfort indicator than anything particularly reliable.

All I really wanted from the meter was an indication that the trickle charger was trickling, so I disconnected Tiny Scope, declared victory, and closed the garage door.

Ed’s Low-Effort High Traction Bread

Being that type of guy, perhaps I snug the plastic film over the top of the mixing bowl a bit too securely:

Yeast at work
Yeast at work

The dough descends from my High-Traction Bread, prepared with my low-effort version of the NY Times no-knead recipe.

The current dramatis personae:

  • 2 cups whole wheat flour (coarse grind OK)
  • 1 cup bread flour
  • ½ cup rye flour
  • ½ cup whey protein (dry milk powder OK)
  • 1 tsp yeast
  • 1 tsp salt
  • 1-½ cup warmish water

Let the mixer work on the dry ingredients for a while, then slowly pour the water into the bowl. The dough will (probably) become a thick batter, which is perfectly OK. Cover with plastic wrap as above, let it sit from afternoon until the next morning, plop the dough / batter on a floured silicone sheet, chivvy it into a lump, cover with the wrap, let it sit for a couple more hours.

Fire the oven to 450 °F, get the pot crazy hot, plop the lump inside, cook 25 minutes covered and 10 more uncovered, dump on a rack, slice off a QC sample, slather with butter, enjoy.

Makes a 700 gram = 24 ounce loaf lump: 1600 kcal, 320 g carb, 90 g protein. A serving might be a scant two ounces: 135 kcal, 26 g carb, 7 g protein.

Not keto-oid, but it’ll keep you warm in the Basement Laboratory.

You may safely ignore all recommendations concerning exact times, temperatures, and suchlike; this ain’t no damn fainting-flower souffle.

You could get used to it …

Handle With Care – FRAGILE – Thank You

I wonder if somebody took careful aim at this particular corner:

FRAGILE package damage
FRAGILE package damage

Well, it arrived in a more-or-less timely manner, unlike some packages and letters we’ve both sent and received of late. Tracking data suggests packages can vanish for days at a time, teleport to distant sorting centers, and sometimes loop between centers.

The USPS may simply have run out of people willing to work under the current conditions.

Blog Summary: 2020

You can’t make up results like this for a techie kind of blog:

Blog Top Post Summary - 2020-12-31
Blog Top Post Summary – 2020-12-31

Given my demographic cohort, bedbugs suddenly seemed downright friendly.

Overall, this blog had 109 k visitors and 204 k page views. The ratio of 1.8 pages / visitor has been roughly constant for the last few years, so I assume most folks find one more interesting post before wandering off.

My take from the increasing volume of ads WordPress shovels at those of you who (foolishly) aren’t using an ad blocker continues to fall:

Blog Ad Summary - 2020-12-31
Blog Ad Summary – 2020-12-31

The CPM graph scale seems deliberately scrunched, but the value now ticks along at 25¢ / thousand impressions, adding up to perhaps $250 over the full year. Obviously, I’m not in this for the money.

The ratio of five ads per page view remains more or less constant. Because Google continues to neuter Chrome’s ad blocking ability, I highly recommend using Firefox with uBlock Origin.

WordPress gives me no control over which ads they serve, nor where they put ads on the page. By paying WordPress about $50 / year I could turn off all their ads and convert the blog into a dead loss. I’m nearing their 3 GB limit for media files on a “free” blog, so the calculation may change late next year.

Onward, into Year Two …

Straightening Armature Wire

Although I was blithely unaware when I bought some useful-looking surplus, it turns out 1/16 inch armature wire works really well to seal our homebrew masks around our noses. Mary added a narrow passage along the top edge of her slightly reshaped Fu Mask pattern to retain the wire and I provided 4.5 inch lengths of straightened wire:

Armature wire - stock vs. straightened
Armature wire – stock vs. straightened

The wire comes off the roll in dead-soft condition, so I can straighten (and slightly harden) it by simply rolling each wire with eight fingertips across the battered cutting board. The slightly wavy wire shows its as-cut condition and the three straight ones are ready for their masks.

Although nearly pure aluminum wire doesn’t work-harden quickly, half a year of mask duty definitely takes its toll. This sample came from my biking mask after the edges wore out:

Armature wire - work-hardened
Armature wire – work-hardened

We initially thought using two wires would provide a better fit, but more metal just made adjusting the nose seal more difficult after each washing. The wire has work-hardened enough to make the sharper bends pretty much permanent; they can be further bent, but no longer roll out under finger pressure.

Although we’re not yet at the point where we must reuse wires, I took this as an opportunity to improve my annealing hand: heat the wire almost to its melting point, hold it there for a few seconds, then let it cool slowly. The usual technique involves covering the aluminum with something like hand soap or permanent marker ink, heat until the soap / marker burns away, then let it air-cool. Unlike steel, there’s no need for quenching or tempering.

Blue Sharpie worked surprisingly well with a propane torch:

Armature wire - annealed straightened
Armature wire – annealed straightened

As far as I can tell after a few attempts, the pigment vanishes just below the annealing temperature and requires another pass to reach the right temperature. Sweep the flame steadily, don’t pause, and don’t hold the wire over anything melt-able.

Those wires (I cut the doubled wire apart) aren’t quite as soft as the original stock, but they rolled straight and are certainly good enough for our simple needs; they’re back in the Basement Laboratory Warehouse for future (re)use.