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

OMTech 60 W Laser: Improved Lighting

The OMTech 60 W laser arrived with an LED strip light under the gantry:

OMTech 60W laser – OEM lighting

That works reasonably well, if only because the pool of light travels with the gantry, but it’s always behind the area where you’re (well, I’m) setting up the Thing To Be Cut. An overhead can lamp with a warm-white CFL bulb contributes the yellowish foreground lighting, although I cast a big shadow when leaning into the cutter.

Adding three COB LED strips along the sides definitely improved the situation:

OMTech 60W laser – COB LED strips

The glare will require shades along their top, but that’s in the nature of fine tuning.

I got 24 V COB LEDs to match the cutter’s power supply and reduce the overall current along the strips, but upon further inspection the OEM power supply seems under-specified for its job. The XY stepper drivers each draw 3.5 A peak, the Z (they call it U) axis driver is set for 5.1 A peak, and the knockoff RuiDa controller also runs at 24 V with an unspecified current.

Rather than stress the OEM supply, some rummaging in the Big Box o’ Wall Warts produced the 24 V 2 A power brick shown in the first picture. The previous owner had cut off the no-doubt specialized connector, so I had no qualms about splicing in a 5.1 mm coaxial power plug.

On the other end, I amputated the AC line plug, crimped on a pair of ferrules, and inserted them into the AC power barrier strip inside the electronics bay:

OMTech 60W laser – LED power supply

Yes, that little smudge in the middle of the brick is an Genuine Embossed Apple logo, so you know it’s gotta be good.

2022-03-28
Garage Door Opener Battery Life

The keypad for the garage door opener didn’t cooperate one cold evening, so the first thing to check is the battery:

Garage Door Opener battery change

Given that it lacks a scrawled date, it’s the original battery dating back to late 1998 when I replaced the defunct opener that Came With The House™.

It was down to 8.3 V on that sunny afternoon and, surely, not nearly enough in the dark of a wintry night.

Even I can’t complain about that kind of battery life …

2022-03-18
Dual Thermocouple Meter Backlight Override

A cheap dual thermocouple meter, utterly devoid of branding, arrived:

It seems suitable for a semi-permanent laser cooling water monitor, particularly because it can perform arithmetic to show the difference between the inlet and outlet temperatures. The minuscule clock face at the center top of the display shows it’s in auto-power-off mode, which can be defeated by a Vulcan Nerve Pinch while turning it on.

Having a large backlit display was a selling (well, buying) point and the instructions have this to say about its operation:

Dual Thermocouple meter – backlight instructions

The instructions say nothing about defeating the backlight timeout. The description is technically correct, because the two seconds before it goes dark is “within 30 seconds”, but I’d rather have a nicely lit display that’s on all the time.

Five screws hold the back cover in place, with no nasty prying required to pull it apart, and the build quality is about what you’d expect for a cheap meter. The circuitry fits on a single PCB and perhaps the thermistor over on the right serves as the cold junction compensation:

Doodling the backlight circuit layout suggests it’s pretty simple, even without filling in the component values:

I replaced the transistor base resistor with a somewhat larger 4.7 kΩ SMD part and added a flying wire to jam the transistor on all the time:

The IC is a serial EEPROM with its VCC and ground pins in the usual places, so, when the power to the EEPROM goes on, the backlight turns on and stays on.

The meter draws a bit over 8 mA with the backlight running, which means the trio of AAA cells won’t last all that long. When things settle down, I’ll conjure a simpleminded power supply running from a convenient voltage inside the laser cabinet.

2022-03-14
Wireless Numeric Keypad vs. AmazonBasics AAA Alkaline: Another Data Point

Looks like a trend to me:

Wireless keypad – 6 year battery

Of course, past performance does not guarantee future results, because Amazon surely has gone through more white-label suppliers in the last half-dozen years than I can count.

2022-03-04
Work Glove Security Tags

Having worn my work glove collection to exhaustion, the fanciest two pairs in a new selection came with elaborate security tags:

Elaborate Security Tag dissection

Finding a standard tag inside inside the fancy shell shouldn’t come as any surprise, but I’m surprised the retail loss ratio for a pair of $20 gloves can support that much hardware.

I went through the self-checkout area and didn’t do anything special, so either those lanes don’t have tag scanners or the tags are security theater.

2022-03-03
Fluorescent Shop Light Ballast Caps

It never ceases to amaze me that these capacitors appear in the AC power line circuits inside old-school fluorescent shop lights:

Shop light ballast cap

It really is a capacitor:

Shop light ballast cap A – test

Its sibling from the other end of the fixture had more ESR:

Shop light ballast cap B – test

Both were likely within spec, whatever that means.

I have no idea what’s lurking inside the tidy LED tubes now living in that same fixture, of course.

2022-02-24
Underwriter’s Knot

Found inside a fluorescent desk lamp being salvaged for possible use as an LED task lamp:

Fluorescent Desk Lamp – Underwriters Knot

It’s one of the few Underwriter’s Knots I’ve ever seen in the wild. Many recent (i.e., built in the last half-century) lamps pass the cords through a plastic clamp or depend on simple bushings, with some just ignoring the problem.

This anonymous lamp sports the usual Made in China sticker, but also features a genuine-looking UL sticker complete with elaborate holograms, so it may well have been sold by a reputable company. IIRC, it came from a trash can in a Vassar College hallway, back when in-person meetings were a thing; perhaps Vassar required known-good electrical hardware.

2022-02-11