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.
The keypad for the garage door opener didn’t cooperate one cold evening, so the first thing to check is the battery:
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 …
Lacking a loading dock, I built a level unloading platform in the driveway:
The OMTech 60 W laser cutter arrived inside a generous supply of plywood obviously intended for practice cutting and engraving:
Knowing the crate wouldn’t fit through our “36 inch” basement door, we stripped the cutter down to the crate’s steel-framed baseplate:
I raised the cutter (using the foot-pad screws) enough to slide 3/4 inch planks under the casters so we could roll it over the lip of the crate base.
The specs say it’s 34 inches wide, but, not at all to our surprise, that’s just the cabinet. The hinges on the access hatches and the lid handle make it just over 35 inches wide, which we slowly and carefully verified would not fit through the 34 inch door opening:
Raising the lid to get the handle out of the way, then pushing gently inward on the sides, eased it through without damage to either the cabinet or the door frame:
Standing on the plank let me raise the outer end enough to roll it forward and lower the casters onto the planks inside the door.
It vents through a long-disused flue straight up the chimney:
The supplied aquarium pump circulates five gallons of distilled water to cool the laser tube. My simple test patterns so far haven’t dumped much heat into the water:
The doily on the left shows 9% power cuts right through paper. Dot Mode fires the laser every 0.25 mm (in this case) for a specified number of milliseconds to reduce the total energy; 3 ms produces dark dots, 1 ms is a pale brown, and 2 ms looks pretty good.
More tinkering is in order …
Concerted rummaging in the Basement Warehouse produced some rather old acrylic sheets:
Washing with detergent and denatured alcohol cleaned off a lot of grunge, but the yellow tint says it’s been around for a while. In fact, It Came With The House™ when we bought it three decades ago.
One sheet was a status board in an automobile machine shop:
So, yeah, that might be 70-year-old acrylic.
A long-delayed bench cleanup united these two HP 09872-60066 digitizing sights:
I’ve used the one on the right (above) with my HP 7475A plotters, but the other sight obviously won’t fit:
The metal-shell version is advertised as “09872-60066 Calibration Pen for fit HP DesignJet 2000CP 2500CP 2800CP 3000CP 3500CP 3800CP Original New” which makes absolutely no sense, as those were inkjet and laser printers with (AFAICT) no need for a “calibration pen”. Because nobody with those printers will buy (or even look for) a widget they can’t use, the price is surprisingly low, compared to the real ones occasionally found on eBay.
My guess: somebody halfway around the planet found a pile of Genuine HP plastic snap boxes, filled them with knockoff sights vaguely similar to the original (perhaps intended for a different plotter?), and marketed them with the usual (lack of) attention to veracity.
Anyhow, we find our contestants standing in the light on a micropositioner under the microscope:
The old sight (genuine HP plotter) has a clean field of view:
With a tidy dot in the middle:
The new (to me, anyhow) sight has rather coarse hexagonal light pipes with gaps at the edges:
The spot at the middle is raggedly machined / drilled, with a bottom sufficiently un-flat to prevent focusing on the whole thing at once:
I have a vague project in mind to turn the new (craptastic) sight into an optical alignment punch, but the spot seems a bit too large for that.
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:
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.
The rivet holding the lace eyelet in place disintegrated:
A flat head 6-32 screw fit neatly inside the original grommet, making it flush on the side that matters and putting a stylin’ nyloc nut in full view.
When the only tool you have is a Basement Shop, pretty nearly everything looks like a project … and is fixable, too!
The Huion tablet on my desk has its USB cable sticking straight out of the left side, whereupon it must loop around to burrow under the shelf under my monitor on its way to the port on the back of the PC case. The loop snagged on all the clutter atop the desk and I finally got around to Fixing That Problem:
Of course, it wasn’t quite that simple.
Right angle USB Mini-B connectors are still a thing:
Which is a “left angle” adapter and which is a “right angle” adapter depends on which supplier you ask and how much you trust their descriptions / product photos, so you should get a set containing both: it’s the only way to be sure.
The one on the right (a “right angle”) shows a bit of carving, which came after the completely unsurprising discovery that the stylin’ curves on the side of the tablet collided with the rectangular adapter:
Some diligent X-Acto knife work carved away enough of both the adapter and the tablet case to snugly join them:
The hackery over on the far right fits around the USB cable’s molded connector. I simply cut away any parts that touched until the adapter seated firmly in the USB socket and the cable exited parallel to the edge.
Part of this involved not carving deeply enough into the adapter or cable connector to expose the internal wiring. I assumed the tablet didn’t have anything vital immediately inside that fancy curve, so that’s where I dug deepest.
Stick adapter + cable to the tablet with good-quality electrical tape and now the cable points directly to where it should go.
Declare victory and move on!
The Smell of Molten Projects in the Morning 