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

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

… 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

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

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

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

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.

2016-11-24
Kitchen Chair Leg Glide

A stick in the ground marking a repair:

Kitchen chair leg glide

The white plastic glide / slide / foot / cap / whatever is molded around a simple nail that broke a divot out of the foot. Fortunately, I caught it before the nail gouged the kitchen floor.

Under normal conditions, I’d replace the foot from my heap, but, my heap having become somewhat depleted, I swapped in another chair, chipped out the broken plastic, undercut the divot, filled it with JB Kwik epoxy, gooshed the foot in place, and taped it until it cured.

We’ll see how long this lasts …

2016-11-23
Hair Dryer Fuzz

Mary reported that her hair dryer didn’t have nearly as much oomph as in the Good Old Days. After a struggle to remove the rear cover (with no affordance to turn in the direction required to release the hidden latches), this appeared:

Hair dryer inlet fuzz

One snort from the shop vacuum returned it to the Good Old Days.

That was easy…

2016-11-19
Scale Cover Repair

You can only drop a small kitchen scale so many times before the plastic cover / weighing tray breaks:

Magnum scale cover – glued and clamped

The trick was to anchor the cover to the glass plate with the big clamp so that the smaller clamps could exert force straight down on the edge, without flipping the lid due to the bevel. With that all set up: apply IPS #4 to the broken edges, insert pieces, apply clamps, wait overnight.

For the record, my morning mug o’ green tea starts with 4 (-0.0 +0.4) g of leaves…

2016-11-17
Money For Nothing: Gfk MRI TV Survey

This arrived a week ago:

GfK MRI postcard

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

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.

2016-11-13
Phishing Knows No Bounds

This appeared on The Mighty Thor’s phone during a Squidwrench meeting:

BofA Phishing

“To maintain a secure banking environment” seems diagnostic of a scam.

Discouragingly, some of our banks still send emails with clicky links using third-party mail servers, so checkonlineinfo.com doesn’t seem any more suspicious than, say, Schwab’s customercenter.net.

A pox on their collective backsides!

2016-11-09
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

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

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.
2016-11-07