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Archive for category Home Ec

Houses Are Trouble: Trees vs. Winds

A loud crack during a windy thunderstorm announced this mess:

Driveway branch - as fallen

Driveway branch – as fallen

Some deft bow saw work cut it down to size:

Driveway branch - trimmed

Driveway branch – trimmed

Whereupon our neighbor arrived home and we dragged the carcass off the driveway.

Fortunately, it missed everything important, as have several recent branch falls in our yard. The same cannot be said for the many downed trees around the immediate area from recent storms; some folks are hurtin’ bad.

Verily, houses (and trees) are trouble!

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Ed’s Atomic Fireball Avocado Smoothie

Dump into a stick blender cup:

  • 1 tsp erythritol
  • 5 drops stevia
  • ≈2 ml mint extract
  • 1/2 tsp Vietnamese Cinnamon
  • 3+ tsp cocoa powder
  • 1/2 avocado, chunked
  • 6 fl oz whole milk to make ≈10 fl oz total

Blend thoroughly. Slurp.

Atomic Fireball Avocado Smoothie

Atomic Fireball Avocado Smoothie

Notes:

  • Another scant ounce of milk makes less of a slurry
  • More cinnamon cannot possibly be a bad thing
  • Commercial mint may be more potent

AFAICT, this is the only way to make an avocado palatable.

There is absolutely no connection with yesterday’s post.

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Monthly Science: Cheese Slicer Epoxy Coating vs. Water

Ten months ago, I cleaned the corrosion off our favorite cheese slicer:

Cheese slicer - aluminum corrosion

Cheese slicer – aluminum corrosion

After cleaning, I coated it with XTC-3D epoxy:

Cheese Slicer - epoxy coat - detail

Cheese Slicer – epoxy coat – detail

We’ve been using it daily ever since and it spends most of its life drip-drying in the dish drainer. I added a third opening to the cheerful orange measuring spoon holder just for the slicer.

A few weeks ago I noticed corrosion once again growing on the handle:

Cheese Slicer - epoxy coat - corrosion - detail

Cheese Slicer – epoxy coat – corrosion – detail

I think the rot comes from water diffusing through the epoxy, rather than gross leaks through damage or pinholes. The tip of the handle has the most corrosion, probably due to the water drop hanging there, even though it also has the thickest epoxy coating: it cured with the handle pointing downward.

Verily, rust never sleeps …

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Cheap Flashlight Boost Converter: Capacitor FAIL

A long time ago, a pair of white LED + red laser flashlights powered by an AA cell diverged: one flashlight worked fine, the other always had a dead battery. The latter ended up on my “one of these days” pile, from which it recently emerged and accompanied me to a Squidwrench Tuesday session:

Small Sun flashlight - original wiring

Small Sun flashlight – original wiring

The black wire trailing from the innards goes to the battery negative terminal, with the aluminum body providing the positive terminal connection to the wavy-washer spring contact visible atop the rear PCB inside the front shell.

The switch connects each red wire to the battery negative terminal, so there’s a color code issue in full effect. The two red wires burrow through holes in the rear PCB (shown above) and connect to the negative terminal of the laser module (the brass cylinder near the top) and the negative terminal ring on the front PCB holding the seven white LEDs:

Small Sun flashlight - original wiring - LED laser board

Small Sun flashlight – original wiring – LED laser board

Continuing the color code issue, the black wire from the laser is its positive terminal. The out-of-focus wire (an LED pin) sticking up near the top of the picture carries the positive connection to the LED ring. The red wires from the switch are the negative connections for the LEDs and laser.

Voltages applied to the LED ring and the currents flowing therein:

Small Sun flashlight - 7x white LED current vs voltage

Small Sun flashlight – 7x white LED current vs voltage

Seven LEDs at 20 mA each = 140 mA, so the voltage booster must crank out slightly more than 3.2 V. They’re not the brightest white LEDs I’ve ever seen, but suffice for a small flashlight.

A crude sketch of the PCB layout, with a completely incorrect schematic based on the mistaken assumption the SOT23-3 package was an NPN transistor:

Small Sun flashlight - schematic doodle

Small Sun flashlight – schematic doodle

Obviously, that’s just not ever going to oscillate, even if the 2603 topmark meant a 2SC2603 transistor, which it doesn’t.

A bit more searching suggests it’s a stripped-down Semtech SC2603A boost converter, normally presented in a SOT23-6 package. If you order a few million of ’em, you can strip off three unused pins, do some internal rebonding, and (presumably) come out with an SOT23-3:

Small Sun flashlight - correct schematic doodle

Small Sun flashlight – correct schematic doodle

That topology makes more sense!

Before going further, I had to rationalize the colors:

Small Sun flashlight - rewired LED laser board

Small Sun flashlight – rewired LED laser board

Soldering longer leads to the PCB allows current & voltage measurements:

Small Sun flashlight - LED current test

Small Sun flashlight – LED current test

With the LEDs and laser disconnected, the converter seems to be struggling to keep the capacitor charged:

Small Sun flashlight - V boost I 200mA-div - idle

Small Sun flashlight – V boost I 200mA-div – idle

Those purple spikes come from the current probe at 200 mA/div: maybe half an amp in 5 μs pulses at 6 kHz works out to a 15 mA average current, which is pretty close to the 11 mA I measured; it’s not obvious the Siglent SDM3045 meter was intended to handle such a tiny duty cycle.

Obviously, the output capacitor is junk and, after removing it, the AADE L/C meter says NOT A CAPACITOR. Perhaps it never was one?

Measuring the cap in the good (well, the other flashlight) suggests something around 100 nF, so I installed a random 110 nF cap from the stash. The current peaks are about the same size:

Small Sun flashlight - I 200mA-div - 110nF cap

Small Sun flashlight – I 200mA-div – 110nF cap

The cap voltage (not shown) is now nearly constant and the 50 Hz PWM rate reduces the average battery current to 100-ish μA:

Small Sun flashlight - I 200mA-div - color-grade - 110nF cap

Small Sun flashlight – I 200mA-div – color-grade – 110nF cap

Not great, but tolerable; a 1000 mA·h battery will go flat in a few months.

The LED current runs a bit hotter than I expected:

Small Sun flashlight - I 200mA-div - LED current - 110nF cap

Small Sun flashlight – I 200mA-div – LED current – 110nF cap

The bottom is about 200 mA and the average might be 350 to 400 mA.

Compared with the other flashlight:

Small Sun flashlight other - I 200mA-div - LED current

Small Sun flashlight other – I 200mA-div – LED current

So the cap is maybe a bit too small, but it likely doesn’t matter.

Done!

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Bathroom Sink Drain: Epoxy Touchup

The glaring white ring around the drain comes from Magic Porcelain Chip Fix epoxy:

Bathroom Sink Drain - Epoxy fill

Bathroom Sink Drain – Epoxy fill

What looks like a blob on the left side covers the missing chip, with the rest of the ring filled in to make it look like I knew what I was doing. The drain dried out while we were on vacation, having been scrubbed clean before we left, making for the best surface preparation I could provide.

As it turns out, our resident iron bacteria took about a week to set up shop along the bottom of the ring, producing a pair of small rust-colored dots that will inevitably spread to encompass the whole thing. They’re endemic in the plumbing, impossible to kill off, and nothing more than an unsightly nuisance.

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Rubber Soaker Hose Repair

A soaker hose leaped under a descending garden fork and accumulated a nasty gash:

Soaker Hose Splice - gashed

Soaker Hose Splice – gashed

Mary deployed a spare and continued the mission, while I pondered how to fix such an odd shape.

For lack of anything smarter, I decided to put a form-fitting clamp around the hose, with silicone caulk buttered around the gash to (ideally) slow down any leakage:

Soaker Hose Splice - Solid Model - Assembled

Soaker Hose Splice – Solid Model – Assembled

As usual, some doodling got the solid model started:

Soaker Hose Splice - Dimension doodle 1

Soaker Hose Splice – Dimension doodle 1

A hose formed from chopped rubber doesn’t really have consistent dimensions, so I set up the model to spit out small test pieces:

Soaker Hose Splice - Test Fit - Slic3r

Soaker Hose Splice – Test Fit – Slic3r

Lots and lots of test pieces:

Soaker Hose Splice - test pieces

Soaker Hose Splice – test pieces

Each iteration produced a better fit, although the dimensions never really converged:

Soaker Hose Splice - Dimension doodle 2

Soaker Hose Splice – Dimension doodle 2

The overall model looks about like you’d expect:

Soaker Hose Splice - Complete - Slic3r

Soaker Hose Splice – Complete – Slic3r

The clamp must hold its shape around a hose carrying 100 psi (for real!) water, so I put 100 mil aluminum backing plates on either side. Were you doing this for real, you’d shape the plates with a CNC mill, but I just bandsawed them to about the right size and transfer-punched the hole positions:

Soaker Hose Splice - plate transfer punch

Soaker Hose Splice – plate transfer punch

Some drill press action with a slightly oversize drill compensated for any misalignment and Mr Disk Sander rounded the corners to match the plastic block:

Soaker Hose Splice - plate corner rounding

Soaker Hose Splice – plate corner rounding

A handful of stainless steel 8-32 screws holds the whole mess together:

Soaker Hose Splice - installed

Soaker Hose Splice – installed

These hoses spend their lives at rest under a layer of mulch, so I’m ignoring the entire problem of stress relief at those sharp block edges. We’ll see how this plays out in real life, probably next year.

I haven’t tested it under pressure, but it sure looks capable!

The OpenSCAD source code as a GitHub Gist:

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Mint Extract: Results

Six weeks later, the mint seemed about as extracted as it was going to get and I now have nearly a liter of decidedly green mint extract:

Mint Extract - liquid color

Mint Extract – liquid color

Correspondingly, the leaves turned from bright green to dull brown:

Mint Extract - spent leaf colors

Mint Extract – spent leaf colors

The smaller and darker pile in the rightmost bowl came from the smaller jar (on the left) with a higher alcohol-to-leaf ratio:

Mint Extract - start - 2018-05-29

Mint Extract – start – 2018-05-29

Perhaps packing the jars before pouring in the alcohol doesn’t extract as efficiently. Or maybe, as in so many things, it doesn’t really matter.

A liter of mint extract may not be a lifetime supply, but it’ll suffice for quite a while!

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