Posts Tagged M2

Vacuum Tube Lights: Duodecar Rebuild

You’ll recall the LED atop the 21HB5A tube failed, shortly after replacing the bottom LED and rewiring the ersatz plate lead, which led me to rebuild the whole thing with SK6812 RGBW LEDs. So I printed all the plastic parts again, because the duodecar tube socket’s pin circle can fit into a hard drive platter’s unmodified 25 mm hole, then drilled another platter to suit:

Duodecar disk drilling

Duodecar disk drilling

The hole under the drill fits the 3.5 mm stereo socket for the ersatz plate lead, so it’s bigger than before.

I’ve switched from Arduino Pro Minis with a separate USB converter to Arduino Nanos with an on-board CH340 USB chip, because the fake FTDI chips on the converters are a continuing aggravation:

21HB5A base - interior

21HB5A base – interior

Adding those wire slots to the sockets definitely helps tidy things up; the wires no longer need a crude cable tie anchoring them to the socket mounting screws.

I wanted to drive the LEDs from the A7 pin, rather than the A3 pin I’d been using on the Pro Minis, to keep the wires closer together, but it turns out that A6 and A7 can’t become digital output pins. So I used A5, although I may come to regret the backward incompatibility.

In any event, the 21HB5A tube looks spiffy with its new LEDs in full effect:

21HB5A with RBGBW LEDs - cyan violet phase

21HB5A with RBGBW LEDs – cyan violet phase

I dialed the white LED PWM down to 32, making the colors somewhat pastel, rather than washed-out.

The Arduino source code as a GitHub Gist:


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Check Your Zero

A recent OpenSCAD mailing list discussion started with an observation that the dimensions of printed parts were wildly different from the numeric values used in the OpenSCAD program that created the STL. Various folks suggested possible errors, examined the source and STL files to no avail, and were generally baffled.

Finally, a photo conclusively demonstrating the problem arrived:

Caliper - digital vs. analog scale

Caliper – digital vs. analog scale

Note the difference between the digital readout and the analog scale printed on the body.

Turns out it’s his first digital caliper: he simply didn’t realize you must close the jaws and press the ZERO button before making any measurements.

We’ve all been that guy. Right?

FWIW, our Larval Engineer can probably still hear me intoning “Check your zero” every time she picks up a caliper or turns on a multimeter. Perhaps she’ll think fondly of me, some day. [grin]

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SK2812 RGBW LED: Test Fixture

[Edit: The SK2812 in the title and elsewhere should be SK6812. If I change the title, then all the other links break. So it goes.]

An envelope of RGBW LEDs, allegedly with SK6812 controllers, arrived from halfway around the planet:

SK2812RGBW LEDs - as received

SK2812RGBW LEDs – as received

The yellow phosphor sauce poured atop the blue LED on the left that makes it glow white leaves the upper loop of two wire bonds sticking out, but I can’t fault ’em for that. The overall build quality looks better than the ill-fated WS2812 LEDs, although it’s hard to tell by looking.

I conjured a test stand from the vasty digital deep by tweaking the WS2812 mount:

SK6812 LED Array Test Fixture - Slic3r preview

SK6812 LED Array Test Fixture – Slic3r preview

Wiring up a 5×5 panel went as before:

SK2812RGBW test fixture - rear

SK2812RGBW test fixture – rear

The array test code adds another pixel channel and runs another raised sine wave with another random period, accomplished without much hackage.

With the warm-white LED at full throttle (MaxPWM = 255), the panel tends toward the pallid end of HSV space:

SK2812RGBW test fixture - front - W PWM255

SK2812RGBW test fixture – front – W PWM255

Dialing the white MaxPWM back to 32 crisps things a bit:

SK2812RGBW test fixture - front - W PWM32

SK2812RGBW test fixture – front – W PWM32

Of course, the RGBW data stream isn’t compatible with the RGB data stream, so vacuum tubes with SK6812 chips require a slightly different driver and I can’t mix the two chips on a single tube.

The Arduino source code as a GitHub Gist:

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ShopVac Hose Barb Adapter

A small ShopVac arrived with a ribbed hose carrying an absurdly long wand, so I conjured a barbed adapter with a much shorter tapered snout for the machine tools:

Vacuum hose fittings - hose barb to nozzle

Vacuum hose fittings – hose barb to nozzle

Trimming the hose end at one of the ribs makes a tidy fit:

Vacuum hose fittings - ribbed hose barb

Vacuum hose fittings – ribbed hose barb

Now I need not trip over the vacuum hose between the bandsaw bench and the sander bench…

The OpenSCAD code as a GitHub Gist:


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Tour Easy Rear Fender Clip

One of the clips holding the rear fender on my Tour Easy broke:

Rear fender clip - broken

Rear fender clip – broken

Well, if the truth be told, the fender jammed against the tire when I jackknifed the trailer while backing into a parking spot, dragged counterclockwise with the tire, and wiped that little tab right off the block. After 16 years of service, it doesn’t owe me a thing.

Although the clip around the fender sits a bit lower than it used to (actually, the entire fender sits a bit lower than it should be), you can see the tab had a distinct bend at the edge of the aluminum block supporting the underseat bag frame: the block isn’t perpendicular to the tire / fender at that point.

After devoting far too long to thinking about how to angle the tab relative to the clip, I realized that I live in the future and can just angle the clip relative to the tab. Soooo, the solid model has a rakish tilt:

Fender Clip - Slic3r preview

Fender Clip – Slic3r preview

The original design had a pair of strain relief struts where the tab meets the clip, but I figured I’ll add those after the PETG fractures.

I mooched the small bumpouts along the arc from the original design; they provide a bit of stretch & bend so to ease the hooks around the fender.

The hooks meet the clip with very slight discontinuities that, I think, come from slight differences between the 2D offset() operation and the circle() diameter; the usual 1/cos(180/numsides) trick was unavailing, so I tinkered until the answer came out right.

Despite those stretchy bumps, it took three iterations, varying the chord height by about 1.5 mm, to securely snap those hooks onto the fender:

Rear fender clip - 3D printed improvement

Rear fender clip – 3D printed improvement

Yeah, sorry ’bout the fuzzy focus on the screw head.

It’s impossible to measure the chord height accurately enough in that position and I was not going to dismount the rear tire just to get a better measurement.

You can see how the clip’s rakish tilt matches the fender’s slope, so the tab isn’t bent at all. It’ll probably break at the block the next time I jackknife the trailer, of course.

I heroically resisted the urge to run off a lower fender mount.

The OpenSCAD source code as a GitHub Gist:

The original doodle, with some measurements unable to withstand the test of time:

Rear Fender Clip - measurement doodles

Rear Fender Clip – measurement doodles


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Cheap WS2812 LEDs: Test Fixture Mount

Mounting the ungainly WS2812 LED test fixture seemed like a Good Idea to keep the electricity out of the usual conductive litter:

WS2812 array test fixture - rear

WS2812 array test fixture – rear

The solid model shows more details:

LED Test Fixture - solid model

LED Test Fixture – solid model

The power wires along the array edges slide into the rear (thinner) slot, with enough friction from a few gentle bends to hold the whole mess in place.

The knockoff Arduino Nano rests on the recessed ledge in the pit, with M2 screws and washers at the corners holding it down (the PCB’s built-in holes might work with 1 mm or 0-90 screws, but that’s just crazy talk). I soldered the power wires directly to the coaxial jack pins under the PCB; they snake out to the LEDs through the little trench. There should be another cutout around the USB connector for in-situ programming, although the existing code works fine.

The front (wider) slot holds a piece of translucent white acrylic to diffuse the light:

WS2812 array test fixture - front flash

WS2812 array test fixture – front flash

It’s painfully bright: a few layers of neutral density filter would be appropriate for a desk toy.

The array runs hot enough at MaxPWM = 255 to produce a gentle upward breeze.

It looks even better without the flash:

WS2812 array test fixture - front dark

WS2812 array test fixture – front dark

You’ll find many easier ways to get RGB LED panels, but that’s not the point here; I’m waiting for these things to die an unnatural death.

The OpenSCAD source code as a GitHub Gist:

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Bandsaw Worklight: LED Cable Clips

Adapting the sewing machine cable clips for larger USB cables:

LED Cable Clips - solid model

LED Cable Clips – solid model

The calculation positioning the posts wasn’t quite right; they now touch the cable OD at their midline and converge slightly overhead to retain it.

They’re great candidates for sequential printing:

LED Cable Clips - Slic3r - sequential print

LED Cable Clips – Slic3r – sequential print

With the basement at 14 °C, any cooling is too much: the platform heater can’t keep the bed above the thermal cutout temperature, the firmware concludes the thermistor has failed, and shuts the printer off. So I popped the four finished clips off the platform, removed the skirt, unplugged the fan, rebooted that sucker, and restarted the print.

One clip in the front keeps the cable away from the power switch and speed control directly below the gooseneck mount:

USB Gooseneck Mount - cable clip

USB Gooseneck Mount – cable clip

A few clips in the back route the cable from the COB LED epoxied directly onto the bandsaw frame away from the motor enclosure:

Bandsaw platform COB LED - cable clips

Bandsaw platform COB LED – cable clips

They’re mounted on double-sided foam tape. The COB LED on the frame isn’t anything to write home about, but you can see the foam tape peeking out around the clip base:

Bandsaw platform COB LED

Bandsaw platform COB LED

Unlike those LED filaments, it seems you can gently bend the aluminum substrate under a COB LED.

The bandsaw platform now has plenty of light: a fine upgrade!

Yeah, you can buy stick-on cable anchors, but what’s the fun in that? These fit exactly, hold securely, and work just fine.

The OpenSCAD source code as a GitHub Gist: