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: Electronics Workbench

Electrical & Electronic gadgets

LED Light Switch: FAIL 2

Another switch for the temporary basement LED light strips failed the same way:

T8 LED power switch – failure 2

As always with such things, I suspect the only reason it has a UL mark on the back is because somebody else hasn’t missed theirs yet.

So I got a three-pack of inline switches with cute little indicator lights and set about replacing all of them:

Inline T8 power switch – internal

These switches carry absolutely no regulatory approval markings, although they do claim to carry 10 A at 250 V, which I take with another load of salt.

At least here in the US-of-A, a 240 VAC outlet has two “hot” wires carrying 120 VAC 180° out of phase, which means both conductors must be switched. Despite the voltage rating, only the L path goes through the clicky switch, with the N path along a strap just below the switch toggle. Using it on a 240 VAC circuit will kill you stone cold dead should you assume whatever it controls is turned off.

I secured the Line and Neutral conductors with crimp connectors, rather than just wrapping the 20 AWG wires around the screw terminals, because the case halves join without perimeter nesting: a bare millimeter of air in the gap between the halves separates the terminals from my fingers. A layer of good electrical tape on each side improved that situation, but not by much.

The complete lack of strain relief clamping on the cords prompted me to route the wires around the screw bosses. After a function check, squirts of hot melt glue anchored the two cords somewhat better.

Aaaaand I secured that loose strap on the right with an (identical to the others!) screw from the Tray o’ Random Screws. The other switches had both screws installed, so this one must have been a QC escape.

They suffice for the purpose, but … caveat emptor!

2024-07-02
IWISS SN-2549 Crimping Tool Instructions

Because I needed to know which of the four dies in the jaw of my IWISS SN-2549 crimper was the right one for 24 AWG ribbon cable:

IWISS SN-2549 JST Crimper Manual

It turns out either of the two middle slots should work, but the crimps look better in the smaller one.

Admittedly, the instructions are thin on technique, but I only wrecked four pins while retraining my crimping hand. The key trick is indexing the insulation fingers on the step inside the jaw, thus putting the socket box or the male pin outside where it won’t get smashed flat. Squishing those fingers from their normal splayed condition into a rectangular shape helps fit them into the jaw against the step.

Living in the future where the right crimping tool doesn’t cost five Benjamins is great …

2024-06-18
Baofeng UV-5 Wiring Plate Globbery

The weekly battery swap revealed the dismal state of the headset wires on Mary’s radio:

Baofeng wiring plate – loose wires

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:

Baofeng wiring plate – globbed

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!

2024-05-29
Magnifying Desk Light: LED-ifying & Base Refooting

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:

Magnifying Ring Light – ballast removed

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:

Magnifying Ring Light – LED ring installed

It now sits on a bit of laboratory ironmongery weighing about as much as a small child:

Magnifying Ring Light – on base

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:

Magnifying Ring Light – foot plan view

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:

Magnifying Ring Light – cork foot cutting

Which fit well enough, although all four feet are just slightly different:

Magnifying Ring Light – cork foot

The new Basement Shop™ is coming together and this stuff is getting easier …

The WordPress AI came up with a plausible steampunk build:

Magnifying Ring Light – WP AI image 1

Love those flowy feet, although the vertical rod in the back seems misplaced.

Adding “one-piece base” to the prompt produces contemporary style:

Magnifying Ring Light – WP AI image 2

Dunno what the dingus on the lower arm might be (perhaps a spring?), but it’s got the right general idea.

2024-05-23
Samsung Microwave Gas Sensor Teardown

With the microwave back in operation, I thought I might learn something about the failed gas sensor:

Figaro TGS880 – base

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:

Figaro TGS-880 Gas Sensor – response plot

The measurement circuit:

Figaro TGS-880 Gas Sensor – 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:

Figaro TGS880 – opening

As the saying goes, Sensoria est omnis divisa in partes tres:

Figaro TGS880 – teardown

A closer look at the sensor element:

Figaro TGS880 – interior

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:

Figaro TGS880 – element detail

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:

Figaro TGS-880 Gas Sensor – AI generated image

My pictures apparently aren’t up to contemporary blog standards …

2024-05-14
Solar Yard Light Debris

A solar yard / walkway light appeared in the far back reaches of the yard while mowing:

Solar yard light – bubble

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”:

Solar yard light – cover off

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:

Solar yard light – components

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 …

2024-05-09
Garage Opener Antenna Director

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:

Garage Opener – one 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:

Garage Opener – interior

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:

Garage Opener – crude antenna director

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.

2024-05-07