Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
The torchiere floor lamp in the sewing room suffered a catastrophic failure:
Floor lamp – failed plastic base shell
Contrary to what you might think from seeing the shattered plastic base, we didn’t use the lamp as a club or battering ram. Apparently the designer expected the thin plastic surrounding the hole to withstand all the torque produced by the long pole against the cheap concrete / mortar / grout / whatever lump in the base. As we can recall, this lamp came to us from either a yard sale or a roadside debris harvest, so I suppose the hardware outlasted any reasonable expectation.
The Basement Laboratory Warehouse disgorged the pole and base from a similar lamp, albeit sporting black paint and a smaller rod connecting its pole to its somewhat larger weight. Not being too fussy about decor, I embiggened the hole in the black base to fit the white lamp’s threaded rod:
Floor lamp – enlarging replacement base
The dust on the base shows why you shouldn’t stand motionless in the Basement Laboratory for very long.
The alert reader will have noted the cord passing through a strain relief grommet in the white base. Rather than dismantle the entire lamp, I just cut the cord, ran it through the new base weight, reinstalled the washer + nut, then crimped on a pair of solderless connectors:
Floor lamp – cord splice
The new base doesn’t offer much in the way of attachment points, so I added a cable tie to keep the strain off the connectors:
Floor lamp – cord strain relief
A strip of genuine 3M duct tape with double-thick adhesive now traps the cord inside that small channel and, given that the lamps spends most of its time standing quietly in a corner, the cord should be fine for long enough.
Obviously, you’ll pick a different keymap name than I did. All the files mentioned below will reside in the new subdirectory, which starts out with only a keymap.c file copied from the default layout.
If you had different hardware, you could specify the driver with a WS2812_DRIVER option.
QMK can also control single-color LEDs with PWM (a.k.a. backlighting), and per-key RGB LEDs (a.k.a. RGB Matrix). These functions, their configuration / controls / data, and their documentation overlap and intermingle to the extent that I spent most of my time figuring out what not to include.
The first two lines describe a single WS2812 RGB LED wired to pin B2 (a.k.a. MOSI) of the Atmel 32U4 microcontroller. The default Reset duration and Byte Order values work for the LED I used
Protip: swapping the order from GRB to RGB is a quick way to discover if the firmware actually writes to the LED, even before you get anything else working: it’ll be red with the proper setting and green with the wrong one.
Dialing the maximum intensity down works well with a bright LED shining directly at your face from a foot away.
Turning on RGBLIGHT_LAYERS is what makes this whole thing happen. The RGBLIGHT_EFFECT_RGB_TEST option enables a simple test animation at the cost of a few hundred bytes of code space; remove that line after everything works.
The last two lines remove the debugging facilities; as always with microcontroller projects, there’s enough room for either your code or the debugger required to get it running, but not both.
With those files set up, the keymap.c file does the heavy lifting:
Undefine LED_LL to enable the test mode, compile, flash, and the LED should cycle red / green / blue forever; you also need the RGB_TEST option in the config.h file.
Define LED_LL and layer lighting should then Just Work™, with the LED glowing:
White for the basic layer with all the letters
Magenta with the Fun key pressed
Cyan with the Esc key pressed
The key map code defines colors for layers that don’t yet exist, but it should get you started.
For convenience, I wadded all three QMK files into a GitHub Gist.
The LED is kinda subtle:
Atreus keyboard – LED installed
As you might expect, figuring all that out took much longer than for you to read about it, but now I have a chance of remembering what I did.
Reattaching the plate to the PCB with only three screws allows marking the hole position on the PCB, which is much easier than pretending to derive the position from first principles:
Atreus keyboard – LED marking
Despite appearances, I traced the hole with a mechanical pencil: black graphite turns shiny silvery gray against matte black soldermask. Also, the PCB trace is off-center, not the hole.
Overlay the neighborhood with Kapton tape to protect the PCB from what comes next:
Snip a WS2812 RGB LED from a strip, stick it in place with eyeballometric alignment over the target, and wire it up:
This being the season of lights, I deployed some outlet timers to turn them on at dusk and off at bedtime. The timers spend much of the rest of their lives plugged into outlets in the Basement Laboratory to keep their internal NiMH backup batteries charged, although they’re not controlling anything:
Enover outlet timer – overview
This one is labeled ENOVER, but it’s essentially identical to all the others sporting random alphabetic names; I have a few more labeled UKOKE in the same plastic case. The current crop uses a different case and has one fewer button, but don’t expect any real difference.
One of the timers had a blank display and didn’t respond to button pushes or a pin punch poked in the RESET hole, so I dismantled it to see what was inside.
Both the hot and neutral terminals had stray wire strands:
Enover outlet timer – stray wire strand
The power board had the usual missing components, suggesting it had been cheapnified after passing whatever regulatory inspection it might have endured to get a CE mark on its dataplate:
Enover outlet timer – power board – overview
The alert reader may have already noticed the mmmmm smoking gun:
Enover outlet timer – scorched diode
Incredibly, Z1 has a part number wrapped around it! A quick lookup shows a 1N4749A is a 24 V 1 W Zener diode, neatly matching the 24 V relay. The datasheet gives a 10.5 mA test current and a 38 mA maximum regulator current, with a caveat: “Valid provided that electrodes at a distance of 10mm from case are kept at ambient temperature”
The relay datasheet says 8.3 mA nominal coil current, a mere 200 mW, which is much easier to dissipate in wire wrapped around a steel core than in a little diode.
Evidently the poor diode ran rather hot before becoming a dead short, because a phenolic PCB (definitely not at ambient temperature) ought not discolor like that.
Indeed, measuring Z1 in another, still functional, Enover timer showed 25 V and a similarly discolored patch around Z1, suggesting the circuit design requires a bit more disspation from the diode than it can comfortably deliver.
I replaced it with a 1N970B from the Basement Laboratory Warehouse, rated for only 0.5 W in a seemingly identical case, buttoned the whole thing up, and left it in the middle of the concrete basement floor overnight. It wasn’t smoking and continued working in the morning, so I defined things to be no worse than before and declared victory.
Should when the next one fails the same way, I’ll epoxy a small heatsink to that poor diode and its leads to reduce its overall temperature.
For future reference, the underside of the PCB shows a distinct lack of post-soldering flux cleanup:
Enover outlet timer – power board – solder side
I swabbed it with denatured alcohol, although doing so certainly didn’t make any change to its behavior.
Memo to Self: no-clean flux is a thing.
It’s worth noting no other components show signs of overheating, despite the diode becoming a short circuit, so R1 (a big power resistor) is most likely the shunt regulator’s dropping resistor and can survive the additional power.
Should the diode fail open, the rest of the circuitry will be toast.
Because a yellow / amber LED runs at a lower voltage than blue and green LEDs, it sits atop an astable multivibrator, rather than a discrete LM3909. The battery holder has a pair of carbon-zinc “Extra-Heavy Duty” AAA cells, so corrosion and leakage pose a foreseeable hazard.
The voltage across the 100 Ω LED ballast indicates a 9 mA peak LED current, which is somewhat dim in ordinary room light:
Astable AA – Amber – LED current 100 ohm
The corresponding LED voltage says the LED runs at 2.1 V for that much current:
Astable AA – Amber – LED V
Something around 39 Ω should make it more visible.
After powering my Sony HDR-AS30V helmet camera for nearly all of this year’s riding, the Batmax NP-BX1 lithium batteries still have roughly 90% of their original capacity:
Batmax NP-BX1 – 2020-11
Those are hot off the Official Batmax charger, which appears identical to other randomly named chargers available on Amazon.
They’re holding up much better after a riding season than the DOT-01 batteries I used two years ago:
Sony DOT-01 NP-BX1 – 2019-10-29
Empirically, they power the camera for about 75 minutes, barely enough for our typical rides. I should top off the battery sitting in the camera unused for a few days, although that hasn’t happened yet.
Of course, the Batmax NP-BX1 batteries I might order early next year for the new riding season have little relation to the ones you see here.
Adding a bit of trim to the bottom of the LED spider makes it look better and helps keep the strut wires in place:
Astable Multivibrator – Alkaline – Radome trim
It’s obviously impossible to build like that, so it’s split across the middle of the strut:
Astable Multivibrator – Alkaline – Radome trim
Glue it together with black adhesive and a couple of clamps:
LED Spider – glue clamping
The aluminum fixtures (jigs?) are epoxied around snippets of strut wire aligning the spider parts:
LED Spider – gluing fixture
Those grossly oversized holes came pre-drilled in an otherwise suitable aluminum rod from the Little Tray o’ Cutoffs. I faced off the ends, chopped the rod in two, recessed the new ends, and declared victory. Might need better ones at some point, but they’ll do for now.
Next step: wire up an astable with a yellow LED to go with the green and blueboosted LEDs.