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.
Electrical & Electronic gadgets
The weekly battery swap revealed the dismal state of the headset wires on Mary’s radio:
That’s after sorting & disentangling loose ends, ramming cables under their ties, and generally tidying things up.
Which suggested an improvement I should have done long ago:
Verily, it is written: the bigger the blob, the better the job.
Gotta glob my bike the next time around.
Update: It’s hot melt glue!
My ancient fluorescent magnifying desk lamp emerged from a box and cried out to be used, but the equally ancient 22 W fluorescent ring light was long past its prime and cried out to be replaced with something from the current millennium.
So I removed the fluorescent ballast / choke from the junction box at the lamp base:
That’s a grounded outlet in the cover plate serving as a wire termination block. The red crimp connector joins a white wire that formerly went to the ballast with the black wire going to the lamp head; you’ll note the black wire from the line cord going into the same heatstink tubing at the outlet.
The lamp head had a push-to-start switch, presumably with an internal starting capacitor or some such, but also sporting a pair of terminals behaving like a single-pole push-on / push-off switch. A bit of rewiring, of which there are no pictures, made it work perfectly with the new 13 W LED ring light:
It now sits on a bit of laboratory ironmongery weighing about as much as a small child:
Although the base has four feet, it sits perfectly flat on my (admittedly battered) surface plate because all four feet have been ground to make that happen:
Those feet will be hostile to any table / bench top outside their intended laboratory environment. Fortunately, the geometry is simple enough to build directly in LightBurn and cut from a cork disk with PSA backing suited to become a coaster:
Which fit well enough, although all four feet are just slightly different:
The new Basement Shop™ is coming together and this stuff is getting easier …
The WordPress AI came up with a plausible steampunk build:
Love those flowy feet, although the vertical rod in the back seems misplaced.
Adding “one-piece base” to the prompt produces contemporary style:
Dunno what the dingus on the lower arm might be (perhaps a spring?), but it’s got the right general idea.
With the microwave back in operation, I thought I might learn something about the failed gas sensor:
Given that much information, finding the datasheet for a Figaro TGS880 sensor didn’t require much effort. In case you were wondering, the replacement sensor has no trace of branding or identification.
The sensor element has a resistance varying with gas concentration, for a variety of test gases I hope our kitchen never contains in such abundance:
The measurement circuit:
I betcha the microwave waits for an order-of-magnitude resistance drop from whatever the starting value might be, then calls it done.
The belly band holding the steel mesh to the plastic base is no match for a Dremel slitting wheel:
As the saying goes, Sensoria est omnis divisa in partes tres:
A closer look at the sensor element:
The granular surface does not get along well with the 5× digital zoom required to fill the phone’s sensor, but you get the general idea:
The heater measured 30 Ω on the dot and the sensor was an open circuit on the 100 MΩ range. Connecting the heater to a 5 V supply dropped the sensor resistance to 800 kΩ @ 50 %RH and a warm breath punched it to about 2 MΩ. That’s with an ohmmeter because I haven’t yet unpacked the Electronics Bench, but seems far above the spec of 20-70 kΩ in air.
So it’s still a sensor, even if it’s not within spec.
The WordPress AI-generated image for this post is … SFnal:
My pictures apparently aren’t up to contemporary blog standards …
A solar yard / walkway light appeared in the far back reaches of the yard while mowing:
Yes, that’s an air bubble in the middle, so you know the light hasn’t been staying in its Happy Place™.
As the djinn in the bottle put it, “Pop the top and let’s get started”:
Those light emitting diodes around the photovoltaic cell in the middle can’t light up any more.
A little more effort with the Designated Prydriver reveals the guts:
That’s an NiMH cell, so the light has been abandoned out there for quite a few years.
The photovoltaic element still worked, but the LEDs were defunct. The corpse will be a guest of honor at the next electronics recycling event down the road from here.
Someday, our great-to-the-nth grandchildren will curse our ways …
By a quirk of fate, the Chamberlain garage door opener in our new house has the same “purple learn button” as the Sears opener in our old house, so I introduced it to our remotes and they work just fine.
I then replaced the four-button remote in my bike pack with a new single-button remote to reduce the dexterity required to hit the button:
Alas, the opener only responded when the remote was immediately outside the aluminum garage door. Checking the battery (because sometimes “new” does not mean what you think it means) reminded me we live in an age when hardware is free compared with bookkeeping:
Maybe the second button doesn’t work and this is how they monetize their QC reject pile?
I want the door to start moving when I’m at the end of the driveway, giving it enough time to get all the way up so I can bike right in. You can actually buy remote / extension antennas, although for fancier openers with SMA antenna connectors, but sometimes a little RF black magic will suffice:
The wavy wire hanging down from the opener’s rear panel is the original antenna, which might be kinda-sorta omnidirectional. The opener operates around 433 MHz= 69 cm, so a quarter-wave antenna will be 17 cm = 7 inch long; the (unbent) wire is maybe 10 inches long from the hole in the panel.
So I taped 11 inches of wire to the opener to form a very very crude Yagi-Uda antenna. It’s too long to be a director element, it’s about right (albeit in the wrong place) to be a reflector element, it might be neither.
What it does do is warp the antenna’s pattern just enough to let the remote reliably trigger the opener as I approach the end of the driveway.
Do not even begin to think about polarization mismatch from what looks like the tiny loop antenna on the remote’s PCB.
As a temporary expedient while awaiting more outlets in the basement, I screwed several hundred watts of LED strip lighting to the floor joists so I could see where I was going:
The switch seemed to run warm, which I attributed to being snuggled up against one of the LED strips, eventually became intermittent, and finally failed with the lights out.
Prying apart the snapped-together case destroyed it, but that didn’t really matter when I saw the innards:
The “intermittent” action came from the melted post on the switch actuator at the top of the photo. The “warm” came from the barely crimped black wire on the right side of the switch, which *might* have had half a dozen strands caught in the flattened crimp triangles.
I replaced it with an identical switch from the assortment that came with the lamps. That one seems to run cooler, although I doubt the crimps are really up to any reasonable quality standards.
In addition to adding basement outlets & lighting circuits, the rest of the house has some electrical wiring peculiarities; the kitchen microwave really shouldn’t share a circuit with the dining room lights.
Having had several folks ding our front doorbell in recent weeks, I thought it would be nice if the switch had a light inside and was mildly surprised it didn’t. Taking it apart revealed an even bigger surprise:
Much electronic! Many solder!
Obviously, that’s a bridge rectifier (MB6S for the curious) in the middle, with a pair of paralleled 1 kΩ SMD resistors on either side ballasting two white LEDs in series on the other side. As far as I could tell, both LEDs had stopped being diodes, most likely after one failed short and took the other down with it.
Having recently unpacked the small parts cabinet containing SMD LEDs, I could do this:
While I had the iron hot, I resoldered the fractured blobs attaching the spring contacts to their solder pads. I think the 201107 along the left edge is the PCB date code, so the switch has been in place for maybe a decade.
You gotta admit blue is distinctive:
While taking it off, I discovered it’s the second doorbell button in that spot; you can’t see the bottom screw hole and wood scar when you’re standing at the door. Unless, I suppose, you’re three feet tall, but most folks of that stature aren’t curious about doorbells.
Update: An alert reader provided more information:
I recently bought a doorbell button, Heath Zenith SL-315-1-90. […] My board is different but has the same circuit as yours. In case it’s helpful, I believe your button might be Heath Zenith SL-257-02.
That’s a perfect example of a “brand name” completely detached from its entire history and put to work doing something entirely different. AFAICT, I honored the Heath name by resoldering the poor thing.
Alas, the doorbell switch on the back door turned out to be a dead loss. Perhaps when they replaced the door, the wire got sliced just above the sill plate, leaving a stub in the basement and no way to fish a new wire to the switch. Anybody arriving via the trail from the Vassar College property out back must bang on the door to get our attention.
The Smell of Molten Projects in the Morning 