Posts Tagged Sherline
A reasonably good silicone-wire multimeter probe set arrived last spring and has worked well enough (I thought, anyhow) for the usual voltage measurements, but recently failed while measuring a small current. We all know how this will turn out, but the details may be of some interest.
Measuring the resistance from tip to plug located the fault to the black probe, after which I poked a pin through the insulation near the plug:
The two leads near the bottom go to my shiny Siglent bench multimeter. Despite their similarity to the failed probes, I’m pretty sure Siglent has better QC (well, mostly).
The probe’s resistance was near zero from the tip (offscreen to the left) to the pin and megohms from pin to plug (on the right). Figuring the wire worked loose, I pulled it away from the plug:
Although I wouldn’t have trusted those probes anywhere near their alleged 1 kV rating, seeing that exposed copper-like substance was disconcerting.
Hacking off the strain relief bushing around the wire got closer to the fault:
And, finally, the problem becomes obvious:
Pulling a black banana plug from the heap, I decided to drill a proper hole to anchor the wire:
Which looked like this afterward:
And produced a strongly mismatched pair:
Ain’t it amazing how much fun you can have for a few bucks, all delivered by eBay? [sigh]
One cannot (or, perhaps, should not attempt to) solder parts to 14 AWG wires seated in a 3D printed battery holder base, so I cleaned up the edges of two polycarbonate scraps:
Then drilled holes to match the strut positions:
The holes fit snippets of the original wire insulation, because, after all, polycarbonate is a thermoplastic, too.
Stretch some copper wire to straighten and work-harden it, add insulation snippets, then maneuver everything in place:
I definitely need a third (and maybe a fourth) hand to hold each part, the solder, and the iron, but at least the wires won’t walk away in the middle of the process.
This seemed appropriate for a day involving toys of all descriptions…
A cast iron stove (most likely a mid-last-century reproduction rather than a Genuine Antique™) emerged from a living room recess:
The line across the lid lifter handle shows where it broke, long ago, likely while being played with. Back then, I’d done a static-display-grade fix with a dab of clear epoxy, but a better repair seemed called for; my repair-fu has grown stronger.
I expected the handle to be pot metal, so drilling a hole in both ends for a music-wire stiffener seemed reasonable:
Much to my surprise, the carbide bit skittered off the surface, leaving fine swarf standing on the end. Turns out the lid lifter is cast iron, just like the rest of the stove!
Given that much of a clue, I aligned the pieces in a pair of machinist’s vises:
Slide apart (the vises stand on a smooth glass sheet; the nubbly side is down), dab silver solder flux on the ends, capture a snippet of 40% silver solder in the gap:
Hit it ever so gently with a propane torch and slide together:
The solder flows at 1200 °F = 650 °C, roughly corresponding to the blue-gray color near the joint. The nice purple (540 °C) on the left shows where I held the flame to start, with yellows (400 °C) on both sides. Good enough, sez I, it’s going to be a static-display exhibit.
Most of the solder went to the back side, so I filed it smooth and buffed off most of the heat coloration with a stainless-steel wire wheel in the Dremel:
A little more wire-brush action left the front side looking good:
As with most of the repairs around here, it simply makes me feel better …
Now, go play with your toys!
Adapting the NP-BX1 battery holder to use SMT pogo pins worked well:
The next step is to add sockets for those 14 AWG wires:
Start by reaming / hand-drilling all the holes to their nominal size and cleaning out the pogo pin pocket.
Solder wires to the pogo pins and thread them through the holder and lid:
That’s nice, floppy silicone-insulated 24 AWG wire, which may be a bit too thick for this purpose.
The pogo pins will, ideally, seat with the end of the body flush at the holder wall. Make it so:
Dress the wires neatly into their pocket:
Butter the bottom of the lid with epoxy, clamp in place, set it up for curing, then fill the recess:
While it’s curing, make a soldering fixture for the 14 AWG wires:
The holes are on 5 mm centers, in the expectation other battery holders will need different spacing.
Solder it up and stick the wires into the base:
Jam a battery in and It Just Works™:
- Green = supply current at 20 mA/div
- Yellow = LED driver transistor base voltage
- Purple = other transistor collector voltage
- White = base – collector voltage = capacitor voltage
The measurement setup was a bit of a hairball:
For completeness, here’s the schematic-and-layout diagram behind the circuitry:
I love it when a plan comes together!
The OpenSCAD source code as a GitHub Gist:
The pips are 100 mm apart at (-50,-50) and (+50,50). Astonishingly, the laser aligner batteries are in fine shape.
I should have protected the platter before drilling all those holes:
All’s well that ends well:
It looks even better in the dark, although you’d never know it from this picture:
I wish I could engrave those patterns on already-drilled platters, but dragging a diamond point into a hole can’t possibly end well. I could deploy the Tiny Sandblaster with a vinyl mask, if I had enough artistic eptitude to lay out a good-looking mask.
The old Atom running LinuxCNC for the Sherline finally stopped booting, so I popped the Optiplex 760 off the stack and did a live-USB trial run. The latency / jitter worked out around 25 µs, slightly worse than before, but still Good Enough, and the StepConf utility coerced the motors into working OK.
What didn’t work was the old Eagle-to-HAL code defining the Logitch Gamepad as a Joggy Thing to allow smooth joystick jog control. Well, stuff changes over the course of eight years, but, in this case, the fix turned out to be a one-liner: the
probe_parport module isn’t needed nowadays.
With that out of the way, it runs fine:
The INI and HAL files defining the Sherline configuration as a GitHub Gist:
Small wipes made from worn-out cotton t-shirts absorb most shop liquids, don’t overstay their welcome after short projects, and prevent the deep emotional attachment leaving swarf in the clothes washer. Scissors cutting gets tedious, so mooch a rotary cutter and slash away:
Synthetic fabrics don’t work nearly as well as cotton, so pay attention to the labels.