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: Science

If you measure something often enough, it becomes science

  • Wearable Electronics: Connections

    Although I’m not the type of guy who thinks twinkly LEDs will enhance his apparel, one of Mary’s quilting thread sources had a closeout deal on their “wearable electronics”, including a large cone of stainless steel thread / yarn:

    Stainless steel thread
    Stainless steel thread

    … CR2032 lithium cells & holders, plus assorted LEDs on small PCBs.

    The usual advice for connecting the thread seems to involve knotting it through the PCB holes, then sewing it to the backing fabric. Alas, I’m bad with knots and the stainless steel yarn isn’t all that cohesive:

    Emerald LED - Stainless steel thread - knotted
    Emerald LED – Stainless steel thread – knotted

    The holder has an even smaller hole, but Mary gave me a needle threader that helped:

    CR2032 - Stainless steel thread - knotted
    CR2032 – Stainless steel thread – knotted

    Some advice found on The InterTubes suggests using copper crimp beads (perhaps with solder) to prevent the thread from completely unraveling and keep the thread loop tight around the PCB hole:

    Rose LED - Stainless steel thread - Crimp bead - Wire Glue
    Rose LED – Stainless steel thread – Crimp bead – Wire Glue

    Beadworkers use crimping pliers that leave a tidy dent; I mashed the beads with a needlenose pliers and called it good.

    The LEDs seem to be white LEDs with filters or, perhaps, blue / violet LEDs with different phosphors: their forward voltages look more blue than red or green. Everybody in this field depends on the minor miracle that lithium cell voltages match blue LED forward drops closely enough that you can get away without a ballast resistor.; the cell’s 20-ish Ω internal resistance doesn’t hurt in the least. An interesting white paper (SWRA349) from TI explores the effect of current on cell capacity and how to size a parallel capacitor that reduces the peak battery current.

    The black gunk is Wire Glue, which costs about five bucks for a lifetime supply in a small jar (or nigh onto 15 bucks via Amazon Prime) and is basically carbon powder in a water-based binder. Apply a dab to the connection and the water evaporates to leave the carbon + binder behind.

    That works better on joints that don’t move, which is precisely what you don’t have in a wearable electronic situation. You can see the crumbling Wire Glue after the trip back from a Squidwrench meeting:

    CR2032 - Stainless steel thread - Crimp bead - Wire Glue
    CR2032 – Stainless steel thread – Crimp bead – Wire Glue

    I also picked up a Permatext Rear Window Defogger repair kit (09117, if you’re looking) that seems to be a staggeringly expensive way to get a tenacious high-current conductive adhesive. More on that later.

    The yarn runs 3.5 Ω/ft, much lower than Adafruit’s three-ply yarn (10 Ω /ft), and suggests itself for flexible connections, EMI gaskets, and suchlike.

    Those LEDs are taped to the kitchen window, where they cast a cool light over the table, with the battery holders sitting on the sash. I’d just replaced some data logger CR2032 cells, so they’re running from nearly dead lithium batteries.

    For future reference: 2.77 V and falling, pushing less than 2 mA through the LEDs.

  • Compose Key Sequences for Useful Unicode Characters

    If you activate a Compose key on your keyboard:

    Compose key selection
    Compose key selection

    Then you can insert Unicode characters without memorizing their hex values. Of course, you must memorize the Compose key sequences. Fortunately, they’re more-or-less mnemonic for the ones I occasionally use, which are hereby cherrypicked from that list.

    Press-and-release the Compose key (right-Win), then type the characters as shown to get the symbol in quotes:

    • o c “©” copyright # COPYRIGHT SIGN
    • o o “°” degree # DEGREE SIGN
    • o r “®” registered # REGISTERED SIGN
    • t m “™” U2122 # TRADE MARK SIGN
    • s m “℠” U2120 # SERVICE MARK
    • . . “…” ellipsis # HORIZONTAL ELLIPSIS
    • . – “·” periodcentered # MIDDLE DOT
    • . = “•” enfilledcircbullet # BULLET
    • + – “±” plusminus # PLUS-MINUS SIGN (∓ MINUS-PLUS is U2213)
    • x x “×” multiply # MULTIPLICATION SIGN
    • < < “«” guillemotleft # LEFT-POINTING DOUBLE ANGLE QUOTATION MARK
    • > > “»” guillemotright # RIGHT-POINTING DOUBLE ANGLE QUOTATION MARK
    • c / “¢” cent # CENT SIGN
    • – – . “–” U2013 # EN DASH
    • – – – “—” U2014 # EM DASH
    • < – “←” U2190 # LEFTWARDS ARROW
    • | ^ “↑” U2191 # UPWARDS ARROW
    • – > “→” U2192 # RIGHTWARDS ARROW
    • | v “↓” U2193 # DOWNWARDS ARROW
    • = > “⇒” U21D2 # RIGHTWARDS DOUBLE ARROW
    • ? ! “‽” U203D # INTERROBANG
    • p o o “💩” U1F4A9 # PILE OF POO
    • m u “µ” mu # MICRO SIGN
    • d i “⌀” U2300 # DIAMETER SIGN
    • 1 4 “¼” onequarter # VULGAR FRACTION ONE QUARTER
    • 1 2 “½” onehalf # VULGAR FRACTION ONE HALF
    • 3 4 “¾” threequarters # VULGAR FRACTION THREE QUARTERS
    • 1 1 0 “⅒” U2152 # VULGAR FRACTION ONE TENTH (and similar)
    • ^ 1 “¹” onesuperior # SUPERSCRIPT ONE (also 0 2 3 + -…)
    • _ 1 “₁” U2081 # SUBSCRIPT ONE (also 0 2 3 + -…)
    • e ‘ “é” eacute # LATIN SMALL LETTER E WITH ACUTE
    • e ` “è” egrave # LATIN SMALL LETTER E WITH GRAVE

    Producing Greek letters requires a “dead_greek” key, so it’s easier to start with bare hex Unicode values at U0391 (Α) and U03b1 (α) and work upward until you find what you need:

    • U03A3 Σ uppercase sigma
    • U03a9 Ω uppercase omega
    • U03C3 σ lowercase sigma
    • U03c9 ω lowercase omega
    • U03c4 τ lowercase tau
    • U03c0 π lowercase pi
    • U0394 Δ uppercase delta
    • U03F4 ϴ uppercase theta
    • U03B8 θ lowercase theta
    • U03D5 ϕ phi math symbol
    • U03A6 Φ uppercase phi
    • U03C6 φ lowercase phi

    Odds and ends:

    • U00a0 | | non-breaking space
    • U2007 | | figure space (invisible digit space)
    • U202F | | narrow space
    • U2011 ‑ non-breaking hyphen
    • U2030 ′ prime (not quote)
    • U2033 ″ double-prime (not double-quote)
    • U2018 ‘ left single quote
    • U2019 ’ right single quote
    • U201C “ left double quote
    • U201D ” right double quote
    • U2245 ≅ approximately equal
    • U2264 ≤ less-than or equal
    • U2265 ≥ greater-than or equal
    • U221A √ square root
    • U221B ∛ cube root
    • U221C ∜ fourth root (yeah, right)
    • U221D ∝ proportional to
    • U2300 ⌀ diameter
    • U25CA ◊ lozenge

    If you set the keyboard layout to US International With Dead Keys, maybe you (definitely not I) could remember all the dead keys.

  • Monthly Image: Potholes in Wappinger Creek at Red Oaks Mill

    The Mighty Wappinger Creek runs low after months with very little rain and we saw more of the rocky streambed than any time in recent memory:

    Wappinger Creek - streambed at Red Oaks Mill - 2016-09-23
    Wappinger Creek – streambed at Red Oaks Mill – 2016-09-23

    Much of the deteriorated Red Oaks Mill Dam stands high and dry:

    Wappinger Creek - Red Oaks Mill Dam - 2016-09-23
    Wappinger Creek – Red Oaks Mill Dam – 2016-09-23

    Just upstream from the bridge, you can see how water carves potholes into the rock:

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    Back in the day, my parents took us to see the far more impressive Susquehanna River potholes (*) near Harrisburg. They range from finger-size pits up to craters large enough to comfortably hold an adult. I’m sure one of their photo albums, now tucked in our closet, contains similar pictures of those holes.

    Searching for red oaks mill dam will turn up previous posts and pictures for comparison.

    (*) Exploration of the pages linked there will show how, with sufficient mental effort, one can force-fit a non-erosion-based explanation of eroded potholes to match a pre-conceived timeline and narrative. Your opinion of that narrative and the effort required to fit evidence into it may differ from mine.

  • Money For Nothing: Gfk MRI TV Survey

    This arrived a week ago:

    GfK MRI postcard
    GfK MRI postcard

    You cannot imagine my excitement when the actual survey arrived, complete with a crisp $5 bill:

    GfK MRI Survey
    GfK MRI Survey

    These folks are cheapskates; Nielsen paid better, although I haven’t gotten anything further from them.

    It didn’t take long to fill out; my fat Sharpie slashed through the NO columns at a pretty good clip. I did attach a note saying we didn’t have a TV and regarded all TV programs as crap, just in case they didn’t get the message.

    Now they know.

    FWIW, I did not fill out the form that would enter us in a drawing for one of five $500 prizes, because that would let them associate my name with my response without fattening my wallet. The survey itself probably encodes my identity, even though it didn’t have any obvious bar codes or other ID; they could simply print the questions in a unique order in each survey.

  • Cast Iron Pan Seasoning: Low-woo Results

    The original cast-iron seasoning recipe, after half a dozen iterations of flax seed oil & high-temperature baking, produced disappointing results:

    Wagner cast iron skillet - washed - top
    Wagner cast iron skillet – washed – top

    The key point of seasoning seems to require heating the oil enough to polymerize its molecular thingies, with (IMO) pretty nearly everything else boiling down to woo.

    Since that rusting incident, I’ve done this after every use:

    • Wipe the pan clean with the same hot soapy water I use for everything else
    • Remove crud with the same Scotchbrite / sponge pad I use for everything else
    • Rinse and wipe dry with the sponge side of the pad
    • Set stove timer for 3 minutes
    • Put pan on simmer burner, set to high flame
    • Continue cleanup until timer sounds
    • Set stove timer for 3 minutes
    • Wipe half a dozen drops of flax seed oil around pan with cotton cloth scrap
    • Continue cleanup until timer sounds
    • Turn off simmer burner
    • Wipe pan with that oily cotton scrap

    The pan reaches about 300 °F after 3 minutes. The “opening the pores” thing is woo, but a completely dry pan doesn’t spit back and that’s a major plus.

    The pan tops out at a bit over 400 °F after a total of 6 minutes. There’s no smoke, no excitement, just a hot pan on the back burner.

    Given that I’m washing the pan anyway, the whole “seasoning” operation adds maybe two minutes to the process. By now, it’s entirely automatic.

    Nota Bene: Set the timer before turning on the burner and before adding the oil, because you will become distracted and will not remember the pan quietly heating on the back burner. You have been warned.

    After two months of doing that about once a day:

    Wagner Cast Iron Skillet - Low Woo Seasoning
    Wagner Cast Iron Skillet – Low Woo Seasoning

    Granted, it looks about the same as the previous results, but this uniform dull black coating repels water, doesn’t rust, loves oil, wipes clean without scouring, and the daily omelet doesn’t stick hardly at all. Obviously, the key difference is that I’ve polymerized a gazillion coats of oil, rather than half a dozen.

    Although I have no idea whether I’m exposing us to lethal free radicals created by the polymerization process, I doubt anybody else knows anything on that subject with regard to their own seasoning technique, so we’re pretty much even. As with most such worries, It Doesn’t Matter.

    Next, I’ll just wipe the pan and let it dry in the rack. That coating should eventually wear off, at least in the high-traffic areas; let’s see how little maintenance it requires.

     

  • Discrete LED Aging After Two Decades

    While at another Vassar concert, I noticed a manufacturing date stamp on one of the LED exit signs in Skinner Hall:

    Exit Sign - Manufacturing date
    Exit Sign – Manufacturing date

    I like the “Replacement lamp not applicable” line. I wonder how recently they’ve tested the battery for the projected 90 minutes of backup time…

    These old LEDs show the expected brightness variations:

    Exit Sign - LED aging
    Exit Sign – LED aging

    So, now you know what your discrete LEDs will look like after two decades of continuous use. That’s if anybody (else) still uses discrete LEDs, of course.

  • Kitchen Spatula Search

    A long long time ago, we bought a kitchen spatula that’s served us well ever since:

    Spatula Search - original
    Spatula Search – original

    To give you an idea of how old that poor thing is, the back of the handle bears a Japan stamp. I’ve re-set the rivets several times, the blade has rusted as badly as you think, and we recently, very reluctantly, decided it has passed its best-used-by date.

    The 3 x 4.5 inch blade is 19 mil = 0.45 mm plated carbon steel, stiff enough to remain flat and springy enough to bend a little, with a 9 inch = 230 mm steel handle ending in a plastic overmold.

    These days, it’s essential to the cutting, flipping, and serving of the morning’s omelet-like substance, made of eggs, bacon, veggies, green leafy things, plus this-and-that, in the cast-iron pan. Mary chops the disk into quarters with the reasonably sharp edge, maneuvers the reasonably bendy blade under each quarter, flips them over, tops with bacon & cheese, pauses for consolidation & melting, then pops them onto plates. Yum!

    Omelet in cast-iron pan
    Omelet in cast-iron pan

    So we set out to buy a replacement.

    Here’s what we’ve tried and rejected so far:

    Spatula Search - overview
    Spatula Search – overview

    I’ve used this one for many years to flip pancakes on a succession of non-stick griddles, a service at which it excels. The edge isn’t sharp enough to cut the green-and-leafy and the completely inflexible blade cannot be maneuvered under the omelet quarters:

    Spatula Search - heavy solid plastic
    Spatula Search – heavy solid plastic

    This one gets deployed for burgers and their ilk, also in the cast-iron pan. The blade, although sharp enough, is completely rigid:

    Spatula Search - heavy slotted metal
    Spatula Search – heavy slotted metal

    On the other paw, a slightly concave 7 mil = 0.18 mm spring steel blade is much too thin and, well, springy. Although very sharp, you cannot apply enough cutting force without suddenly bending the blade and, if the omelet quarter isn’t positioned exactly right, the blade will bend underneath it and dump breakfast on the stovetop. The alert reader will notice a missing weld between the blade and the bottom wire handle:

    Spatula Search - thin spring steel
    Spatula Search – thin spring steel

    This very thin plastic blade has similar problems with poor cut-ability and excessive flexibility:

    Spatula Search - thin springy plastic
    Spatula Search – thin springy plastic

    This one looked really promising and worked almost perfectly. Regrettably, its nylon blade bears a 400 °F rating and the bottom of the omelet reaches nearly 450 °F. You can see what happens to the reasonably sharp edge as it scrapes across the pan:

    Spatula Search - heavy slotted nylon
    Spatula Search – heavy slotted nylon

    The omelet cooks at the temperature it cooks at, which part of the specifications is not subject to further discussion.

    So, we’re stumped. Having trawled the usual online and big-box stores, we’ve been unable to find a replacement. Simple steel blades aren’t available. Trendy silicone-bonded stainless steel blades combine the worst of all worlds: won’t cut and won’t flip. Pretty nearly anything you don’t see above seems obviously unsuitable for our simple needs: too big, too small, or too melty.

    We’ll consider all recommendations and suggestions! Thanks …