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: Oddities

Who’d’a thunk it?

CAMtool V3.3 vs. The Fat Fingers of Death

As is my custom, the day before showtime I talked my way through a final full-up dress rehearsal, with the HP 7475A plotter and the CNC 3018XL running their demo plots. As if to justify my attention to detail, the 3018 refused to home, with its X axis motor grinding in a manner suggesting something had gone terribly wrong with its driver.

OK, I can fix that™.

Turn off the power, verify the leadscrew turns smoothly by hand, check all the connections & connectors, then pull the DRV8825 PCB to see if anything looks obviously wrong. It didn’t, so I carefully re-plugged the driver and moved the whole affair to the Electronics Workbench for further study.

I turned on the scope and Tek current probes, then turned on the 3018 power supplies, whereupon a great cloud of Magic Smoke emerged from the CAMtool board and filled the Basement Laboratory with the acrid smell of Electrical Death.

It seems I carefully and meticulously re-plugged the DRV8825 PCB into its socket exactly one pin too high, which, among other Bad Things, connects the +24 V motor power supply to the driver GND pin.

Obviously, this did not end well:

CAMtool V3.3 – blown stepper fuse

The fuse, put under considerable stress, vented smoke & debris in all directions across the board; note the jets above the white motor connector. Surprisingly, the 1 kΩ resistor just below it is in fine shape, as is the rather blackened electrolytic cap.

The fuse measures the same 150-ish mΩ as the fuses in the other two axes, but I doubt it’s actually a fuse any more.

Astonishingly, the Arduino clone on the board worked fine, so I could extract the GRBL configuration.

Memo to Self: Never plug things in with your head upside down!

2020-01-30
Alkaline Battery Packaging

Apparently, we’ve burned enough cargo aircraft and killed enough people to require careful attention to detail in battery packages:

Amazon alkaline AAA packaging

These “Ships from and sold by Amazon” alkaline AA cells arrived by UPS. They now fall under reasonable requirements to prevent shorting and damage, although the cardboard box wasn’t sturdy enough to prevent them from breaking free laterally.

One might quibble about the “Health & Personal Care Item” description, but, yeah, better battery packaging seems like a good idea.

2020-01-11
Scrap EEPROMs

A quartet of defunct 64 KB EEPROMs (*) emerged from a box of microscope doodads, so I stuck ’em under the stereo zoom scope for final pictures.

The oldest one, an MCM68764, came from Motorola with a 8313 date code. The next three, all TMS2764JL-25, came from TI with date codes in 84 and 85, so they have slightly different layouts.

MCM68764C EPROM

TMS2764JL-25 A EPROM

This one is rotated 90° counterclockwise:

TMS2764JL-25 B EPROM

TMS2764JL-25 C EPROM

The hideous compression artifacts come from the original Pixel 3a images, because they’re (digitally) zoomed in all the way, plus bonus optical distortion from the quartz windows. The chips definitely look better in person, although the (optical) magnification isn’t nearly enough to show the tiniest details.

(*) Uh, they’re just EPROMs. It’s been so long since I’ve typed it that the extra “E” just stuttered right out. That’s my story and I’m sticking with it … at least I got the image names right!

2020-01-05
Car vs. Pole: That Ain’t Gonna Buff Right Out

Spotted at the corner gas station, where they collect wrecks before harvesting their organs:

Car vs Pole

As far as we can tell, the car clipped the pole off at the base, whereupon it smashed down across the roof, leaving the trunk unscathed. The lack of blood on the airbag suggests the driver lived to tell the tale, although we’ll never know the rest of the story.

A collection of random stuff tossed on the back seat included a license plate bent into a surprisingly gentle curve.

Obligatory: And Sudden Death reference.

2020-01-04
Bird Feeder Icing

After a day of snow + sleet + ice, followed by overnight cooling, the bird feeder looked like this:

2019-12-19 – Ice on bird feeder – Day 0

The ice generally doesn’t bond across the top, so the sheets slide off separately to the front and back. This time, they stayed together and began sliding off to the side.

The next two days were unusually cold and the glacier stopped sliding:

2019-12-21 – Ice on bird feeder – Day 2

The temperature warmed enough during the day to let the glacier resume sliding, whereupon it fell and shattered on the patio.

No birds or squirrels were injured during this incident.

2019-12-29
Beware the Unit of Measure

While looking for something else, I stumbled across this Amazon offer (clicky for more dots):

Hammermill Truckload Paper

Yeah, a trailer load a’ paper. Word.

Long ago, in a universe far away, my buddy Mark One mis-read a unit of measure and ended up with a trailer load a’ Tektronix Thermal Paper. It carried a silver-based emulsion requiring constant refrigeration, so he stashed about a pallet of paper canisters under every raised floor on the IBM Poughkeepsie campus. Even though the raised floor acreage has dropped dramatically, some of it may be there to this very day.

2019-12-28
Merry Christmas

Moonrise, as seen through the pines in our yard:

Pixel 3a Night Vision – moonrise

The Pixel 3a produces exceedingly useful low-light images, mostly by having Google’s software compensate for its tiny lens and minimal light-capture area, with the downside of turning a peaceful night scene into harsh daylight.

Take the rest of the day off, OK?

2019-12-25