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

HQ Sixteen: Chin Light

Setting the Handi-Quilter HQ Sixteen handlebars at a useful angle aimed the main PCB’s white LEDs at the front of the arm, rather than down at the needle:

HQ Sixteen Chin Light – off

Having caused the problem, I must fix it:

HQ Sixteen Chin Light – results

The light comes from a small chip-on-board LED affixed under the chin of the machine arm with heatsink tape:

HQ Sixteen Chin Light – detail

Yes, the pool of warm white COB LED light clashes horribly with the cool white 5 mm LEDs lighting the background (not to mention wintry daylight from the windows), but it’s sufficiently OK.

I intended to run the wiring inside the machine arm, but all the pre-existing holes I wanted to use were oiling access points or blocked by whirling shafts inside, so the wire runs along the outside:

HQ Sixteen Chin Light – wiring

The Handi-Quilter control & lighting goes through the bare gray ribbon cable to the handlebars, so I’m not too far down the stylin’ scale. The next version of the machine has round external cables, but this machine is what it is.

I mounted the 12 VDC supply to the back panel of the machine’s power box with five 3 mm holes:

HQ Sixteen Chin Light – power supply

A bag of right-angle barrel connectors will arrive shortly.

The exposed wiring at the top (the white wires carry switched 120 VAC from the PCB inside the box) seemed … unaesthetic, so I conjured a cover from the vasty digital deep:

Power Supply Cover – solid model

Which fit neatly into place on the first try:

HQ Sixteen Chin Light – supply cover fit test

That’s a trial fit, because I am not pulling the machine apart again until there’s more work to do inside.

The blurry rocker switch below the Chin Light supply controls the machine power: turn it on and everything lights up as it should.

The OpenSCAD source code as a GitHub Gist:

2024-12-18
Handi-Quilter HQ Sixteen: Handlebar LED Replacement

One string of three white LEDs in the left handlebar of Mary’s Handi-Quilter HQ Sixteen died over the past two decades:

HQ Sixteen – left LED deaders

A view minus the glare:

HQ Sixteen – left LED PCB

I replaced all 15 LEDs with new-old-stock white LEDs from my stash, while neglecting to pay close attention to the silkscreened orientation marks.

I used up a lot of solder wick while re-extracting seven of the LEDs :

HQ Sixteen – left LED PCB – orientation

The LED in the front-right corner is in the string with the two LEDs just above it, while pointing in the opposite direction. This definitely violates the Principle of Least Surprise.

Being of sound mind, I tested all the replacement LEDs before installing them:

HQ Sixteen – LED testing

Which tedious process weeded out a couple of deaders, one with its case on backwards, and a handful of completely different white LEDs evidently from a different manufacturing batch. Buying low-budget LEDs directly from a sketchy source halfway around the planet does have its downsides.

Being that type of guy, I also tested the removed LEDs. Weirdly, one of the strings had two dead LEDs, which suggests one failed short and the increased current took another LED down with it.

Two of the three strings in the central PCB had died and were replaced without incident: they all pointed in the same direction and I can deal with consistency.

2024-12-03
White LED QC Escape

Judging from the dates codes on the ICs inside, Mary’s HandiQuilter Sixteen long-arm machine is about two decades old and many of the white LEDs in the front handlebars have gone dark:

HQ Sixteen – dead handlebar LEDs

The vertiginous view looks upward into the handlebar at the top of the machine (more on this later). The PCBs run strings of three series LEDs from a 16 VDC supply with a 390 Ω ballast resistor (oddly enough, on the ground end of the string), so one failed LED takes down all three.

I decided to replace all the LEDs, on the principle they’re surely dimmer than they used to be and to take advantage of a decade or so of improvement in white LEDs (yes, I have old stock).

After discovering that the HandiQuilter engineers violated the Principle of Least Surprise by orienting adjacent LED strings in opposite directions, I found one of the strings still didn’t light up.

Pop quiz: which one of these LEDs caused the problem?

5 mm LEDs – swapped polarity

To the best of my knowledge, all 5 mm round LED packages mark the cathode lead with a flat edge. It’s easy to remember, as the cathode side of the schematic symbol has a bar: straight bar = straight edge.

Inside, the LED chip’s cathode lead is bonded to the reflective cup, with the anode lead wire-bonded to the top.

Took me a while to see what was wrong, too.

For whatever it’s worth, the backward LED works fine.

2024-11-28
Sears Microwave: Laying-On of Hands Repair

Although essentially all kitchens feature a microwave over the stove, essentially all women have difficulty reaching it. As a result, our kitchen has two microwaves: the built-in Samsung over the stove and our trusty Sears Kenmore on the counter.

We’ve had it for a while:

Sears Microwave – data plate

Apart from the turntable rollers, it’s been utterly reliable for the last two decades, until the Start button stopped working:

Sears Microwave – control panel

The membrane switch panel seems to be in good shape, with no cracks in the plastic surface. Only the Start button failed, which suggested the switch contact pad had failed and ruled out broken matrix traces on the flexible circuitry.

Back in the day, they kept casual tinkerers out of the dangerous interior:

Sears Microwave – Torx security screw

That would not be me:

Sears Microwave – security bit set

Over the course of two decades, an occasional food explosion produces a surprising amount of debris:

Sears Microwave – exhaust vent spatter

Go ahead, I dare you, show us your microwave exhaust vent.

The control panel circuit board & wiring looks like this:

Sears Microwave – control board – in place

Unplugging all the connectors proceeds as you’d expect, whereupon a single screw (out of sight to the top) releases the control assembly and pulling the whole thing upward gets it out of the cabinet:

Sears Microwave – control board

The capacitors show no signs of The Plague, but those resistors near the optoisolator (?) in the middle have a suspicious thermal plume.

The ribbon cable from the control surface goes into a connector with the usual locking collar:

Sears Microwave – control panel cable connector

The cable also has cutouts latching into tabs molded into the collar:

Sears Microwave – control panel ribbon cable – locking tabs

Removing two screws at the transformer releases the PCB:

Sears Microwave – control panel interior

Which promptly slammed the whole repair mission to a dead stop: with the entire membrane switch assembly glued to the front of the plastic shell, there is no way to get to the Start switch. Trying to peel the membrane off will most certainly destroy it.

Because all the other functions still worked, including the Add Minute button, we figured we can eke out a few more years before something else fails or the lack of one button gets intolerably annoying.

I reassembled everything in reverse order, plugged it in, and, while setting the clock, discovered the Start button once again worked perfectly.

It’s a classic laying-on of hands repair: take something apart, replace nothing, reassemble, and it works!

If the Start button is not part of the overall switch matrix, with a separate conductor through the ribbon cable, un- and re- plugging would be enough to restore a flaky contact. We’ll never know the rest of the story, although with this post as a reminder, maybe I can remember to tear the matrix apart when we scrap it out.

Somebody give me an Amen!

2024-11-25
Sonicare E5000 Toothbrush + Norelco T770 Beard Trimmer: Final Final Batteries

Although replacing the Sonicare E5000 battery six years ago was supposed to be the last time I’d do that, the poor thing died leaving most of a year’s supply of brush heads in the drawer.

Half a quartet of NiMH AA cells should keep it happy while using up that stash:

Sonicare Toothbrush – NiMH AA cells installed

The AA cells sit at a jaunty angle due to re-re-using the original contact tabs soldered into the PCB.

I’m getting pretty good at taping the case closed:

Sonicare Toothbrush – Kapton tape

Although I have no pictures to prove it, the other half of the AA cell quartet restored youthful vigor to the Norelco T770 beard trimmer. Having interior pictures made finding and popping its case latches so much easier.

If only I could change my batteries that easily …

2024-11-22
EBL Bucked Lithium AA and AAA Cells

A new kitchen scale eats a quartet of AAA alkaline cells every month, so a set of bucked lithium AAA cells make sense:

EBL AAA first charge – 2024-09-11

The cells claim 1200 mA·hr capacity, because it looks much more impressive than 1.2 A·hr, and deliver 900 mA·hr at 500 mA, likely higher than the scale’s actual load current.

The old Sony DSC-H5 works well with the light box and gets a pair of bucked lithium AA cells to replace the tired Eneloops:

EBL AA first charge – 2024-10-17

They claim 3000 mA·hr and deliver 2.5 A·hr at 500 mA: nearly perfect, considering some of the junk I’ve gotten over the years.

Now, to see how they behave in real life …

2024-10-22
SJCAM M20 Dashboard Camera: NP-BX1 Battery Deterioration

A year of limited use (a little over 3000 miles) after setting up the SJCAM M20 action camera as a dashcam in the Forester has killed the junk-as-delivered Batmax NP-BX1 battery:

Batmax NP-BX1 – 2022-H in 2024-11

Although the total capacity remains about the same as before, the voltage depression causes the camera (which expects to run from a high-voltage lithium cell) to crash immediately after the car’s USB power jack shuts off, preventing it from properly closing the video file.

Another Batmax battery from the same batch works fine, so we’ll see if it can survive for another year.

2024-10-11