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.

Author: Ed

Torchiere Lamp Shade

A pair of torchiere lamps lit the living room for many, many years:

During their tenure, they’ve gone from 100 W incandescent bulbs to “100 W equivalent” CFL curlicues to “100 W equivalent” warm-white LED bulbs. The LEDs aren’t up to the brightness of the original incandescents, but you can get used to anything if you do it long enough.

After so many years, the plastic shades / diffusers became brittle:

Torchiere Lamp Shade - original broken — Torchiere Lamp Shade – original broken

That’s after a bump, not a fall to the floor. So it goes.

Some casual searching didn’t turn up any likely replacements. The shade measures 14 inch = 355 mm across the top, far too large for the M2’s platform, but maybe a smaller shade in natural PETG would work just as well.

ACHTUNG! This is obviously inappropriate for the original incandescent bulbs and would be, IMO, marginal with CFL tubes. Works fine with LEDs. Your mileage may vary.

OpenSCAD to the rescue:

Torchiere Lamp Shade - section — Torchiere Lamp Shade – section

That’s a section down the middle. The top is 180 mm across, leaving 20 mm of general caution on the 200 mm width of the platform. The section above the sharply angled base is 90 mm tall to match the actual LED height, thereby putting them out of my line-of-sight even when standing across the room.

I ran off a short version, corrected the angles and sizes for a better fit, tweaked the thickness to fuse three parallel threads into a semitransparent shell, and …

Torchiere Lamp Shade - M2 platform — Torchiere Lamp Shade – M2 platform

Producing what looks like thin flowerpot required just shy of seven hours of print time, as it’s almost entirely perimeter, goin’ down slow for best appearance. The weird gold tone comes from the interaction of camera flash with warm-white CFL can lights over the desk.

If you hadn’t met the original, you’d say the new shade grew there:

Torchiere Lamp Shade - no epoxy — Torchiere Lamp Shade – no epoxy

It’s definitely a Brutalist design, not even attempting to hide its 3D printed origin and glorying in those simple geometric facets.

Those three threads of natural PETG makes a reasonably transparent plate, clear enough that the bulb produced an eye-watering glare through the shade:

Torchiere Lamp Shade - no epoxy - lit — Torchiere Lamp Shade – no epoxy – lit

So I returned it to the Basement Laboratory, chucked it up in the lathe (where it barely clears the bed), dialed the slowest spindle speed (150 rpm according to the laser tach, faster than I’d prefer), and slathered a thin layer of white-tinted XTC-3D around the inside:

Torchiere Lamp Shade - lathe spinning — Torchiere Lamp Shade – lathe spinning

For lack of anything smarter, I mixed 2+ drops of Opaque White with 3.1 g of Part A (resin), added 1.3 g of Part B (Hardener), mixed vigorously, drooled the blob along the middle of the rotating shade, spread it across the width using the mixing stick, smoothed it into a thin layer with a scrap of waxed paper, and ignored it for a few hours.

If the lathe perspective looks a bit weird, it’s perfectly natural: I raised the tailstock end enough to make the lower side of the shade just about horizontal. Given the gooey nature of XTC-3D, it wasn’t going anywhere, but I didn’t want a slingout across the lathe bed.

The lit-up result isn’t photographically different from the previous picture, but in person the epoxy layer produces a much nicer diffused light and no glare.

I might be forced to preemptively replace the other shade, just for symmetry, but we’ll let this one age for a while before jumping to conclusions.

The OpenSCAD source code as a GitHub Gist:

	// Torchiere Lamp Shade
	// Ed Nisley KE4ZNU – July 2017

	/* [Build] */

	Section = false;

	Shorten = false;

	//- Extrusion parameters – must match reality!

	/* [Hidden] */

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

	function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);

	Protrusion = 0.01;

	HoleWindage = 0.2;

	//- Dimensions

	ID = 0;
	OD = 1;
	LENGTH = 2;

	/* [Dimensions] */

	ShadeThick = 1.2; // perpendicular thickness

	BaseAngle = 42; // lamp base angle wrt vertical

	BaseTopDia = 131.0; // lamp ID at top
	ShadeBaseThick = 6*ThreadThick; // horizontal bottom thickness

	SeatDepth = 10.0 + ShadeBaseThick; // shade bottom to base top

	SeatDia = BaseTopDia – 2* SeatDepth / tan(BaseAngle); // lamp ID at seating depth

	ShadeTopDia = 180.0; // top OD, limited by printer platform width
	ShadeHeight = 90.0; // height above lamp base

	ShadeHoleDia = 36.0; // central hole dia

	ShadeAngle = atan(ShadeHeight / ((ShadeTopDia – BaseTopDia)/2));
	echo(str("Shade angle: ",ShadeAngle));

	ShadeHThick = ShadeThick / sin(ShadeAngle);
	echo(str(" horiz thickness:",ShadeHThick));

	NumSides = 6*4;

	$fn = NumSides;

	//- Build it

	render(convexity=2)
	difference() {
	union() {
	cylinder(d1=SeatDia,d2=BaseTopDia,h=SeatDepth); // section within lamp base
	translate([0,0,SeatDepth])
	cylinder(d1=BaseTopDia,d2=ShadeTopDia,h=ShadeHeight);
	}

	translate([0,0,SeatDepth]) // inside of upper shade
	cylinder(d1=BaseTopDia – 2*ShadeHThick,
	d2=ShadeTopDia – 2*ShadeHThick,
	h=ShadeHeight + Protrusion);

	translate([0,0,ShadeBaseThick]) // seating base
	cylinder(d1=SeatDia – 2*ShadeHThick,
	d2=BaseTopDia – 2*ShadeHThick,
	h=SeatDepth – ShadeBaseThick + Protrusion);

	translate([0,0,-Protrusion]) // socket clearance
	cylinder(d=ShadeHoleDia,h=2*ShadeHeight);

	if (Section)
	translate([0,-ShadeTopDia,0])
	cube(2*ShadeTopDia,center=true);

	if (Shorten > 0)
	translate([0,0,(ShadeTopDia + 2*SeatDepth)])
	cube(2*ShadeTopDia,center=true);


	}

view raw Torchiere Lamp Shade.scad hosted with ❤ by GitHub

2017-08-02

Monthly Science: Final WS2812 Failures

My “exhibit” at the MHV LUG Mad Science Fair consisted of glowy and blinky LED goodness, with an array of vacuum tubes, bulbs, and the WS2812 and SK6812 test fixtures:

MHVLUG Science Fair – Chastain – highres_463020980

They look much better without a flash, honest. The cut-up cardboard box threw much needed shade; the auditorium has big incandescent can lights directly overhead.

Anyhow, what with one thing and another, the two LED test fixtures spent another few dark and cool days in the Basement Laboratory. When I finally plugged them in, the SK6812 RGBW LED array light up just fine, but three more WS2812 RGB LEDs went toes-up:

WS2812 LED test fixture – more failures

That brought the total to about 8 (one looks like it’s working) out of 28: call it a 28% failure rate. While WS2812 LEDs don’t offer much in the way of reliability, running them continuously seems to minimize the carnage.

So I wired around the new deaders and took that picture.

Flushed with success and anxious to get this over with, I sealed the tester in a plastic bag and tossed it in the freezer for a few hours …

Which promptly killed most of the remaining WS2812 chips, to the extent even a protracted session on the Squidwrench Operating Table couldn’t fix it. When I though I had all the deaders bypassed, an LED early in the string would wig out and flip the panel back to pinball panic mode.

It’s not a 100% failure rate, but close enough: they’re dead to me.

As the remaining WS2812 LEDs on the various vacuum tubes and bulbs go bad, I’m replacing them with SK6812 RGBW LEDs.

For whatever it’s worth, freezing the SK6812 tester had no effect: all 25 LEDs lit up perfectly and run fine. Maybe some of those chips will die in a few days, but, to date, they’ve been utterly reliable.

2017-08-01
Optiplex 9010: Xsetwacom vs. Dual Monitors
Having replaced the Dell Optiplex 980 (running from an eBay NOS power supply) with an off-lease Optiplex 9010, I was mildly surprised to find two Displayport outputs from the built-in Intel graphics chipset. Not being a gamer, I don’t care much about graphic performance, but plugging two 2560×1440 monitors into the jacks and having them Just Work was delightful. Indeed, Dell even managed to ~~fix~~ work around the error in the U2711 firmware requiring me to power-cycle the damned thing before booting the PC; now I can just turn the PC on and It Just Works.

Mysteriously, the incantation required to limit the Wacom tablet to the left-hand landscape monitor now uses DP1 instead of HEAD-0:
```
xsetwacom --verbose set "Wacom Graphire3 6x8 stylus" MapToOutput "DP1"
xsetwacom --verbose set "Wacom Graphire3 6x8 eraser" MapToOutput "DP1"
#xsetwacom --verbose set "Wacom Graphire3 6x8 Pen stylus" MapToOutput "HEAD-0"
#xsetwacom --verbose set "Wacom Graphire3 6x8 Pen eraser" MapToOutput "HEAD-0"
```
I’ll leave the “HEAD-0 incantations as comments, so as to have a hint the next time …
2017-07-31
Raspberry Pi vs. Music via NFS
Every now & again, streaming music from distant servers fails, for no reason I can determine. In that situation, it would be nice to have a local source and, as mplayer works just fine when aimed at an MP3 file, I tried to set up a USB stick on the ASUS router.

That requires getting their version of SAMBA working with the Raspbian Lite installed on the streaming players. After screwing around for far too long, I finally admitted defeat, popped the USB stick into the Raspberry Pi running the APRS iGate in the attic stairwell, and configured it as an NFS server.

To slightly complicate the discussion, there’s also a file server in the basement which turns itself off after its nightly backup. The local music files must be available when it’s off, so the always-up iGate machine gets the job.

On the NFS server:

Install rpcbind and nfs-common, both of which should already be included in stock Raspbian Lite, and nfs-kernel-server, which isn’t. There were problems with earlier Raspbian versions involving the startup order which should be history by now; this post may remind me what’s needed in the event the iGate NFS server wakes up dead after the next power blink.

Set up /etc/exports to share the mount point:
```
/mnt/music	*(ro,async,insecure,no_subtree_check)
# blank line so you can see the underscores in the previous one
```
Plug in the USB stick, mount, copy various music directories from the file server’s pile o’ music to the stick’s root directory.

Create a playlist from the directory entries and maybe edit it a bit:
```
ls -1 /mnt/part/The_Music_Directory > playlist.tmp
sed 's/this/that/' < playlist.tmp > playlist.txt
rm playlist.tmp
```
Tuck the playlist into the Playlists directory on the basement file server, from whence the streamer’s /etc/rc.local will copy the file to its local directory during the next boot.

On every streamer, create the /mnt/music mountpoint and edit /etc/rc.local to mount the directory:
```
nfs_music=192.168.1.110
<<< snippage >>>
mount -v -o ro $nfs_music:/mnt/music /mnt/music
# blank line so you can see the underscores in the previous one 
```
In the Python streaming program on the file server, associate the new “station” with a button:
```
         'KEY_KP8'   : ['Newname',False,['mplayer','-shuffle','-playlist','/home/pi/Playlists/playlist.txt']],
```
The startup script also fetches the latest copy of the Python program whenever the file server is up, so the new version should Just Work.

I set the numeric keypad button associated with that program as the fallback in case of stream failures, so when the Interwebs go down, we still have music. Life is good …
2017-07-30
Calculator Battery Corrosion

The display on Mary’s favorite little calculator (remember calculators?) faded away and, of course, this appeared when I popped the back:

Calculator battery corrosion

A touch of vinegar, some scrubbing, and new cells restored it to good health.

That was easy …

2017-07-29
Vacuum Tube LEDs: Knockoff Arduino Nano USB Connector

The LEDs adorning the 0D3 rectifier tube became unreliable:

0D3 Octal – 25 mm socket – raised LED

After failing to plug in a different USB power supply, a close look at the USB connector showed the problem:

Knockoff Arduino Nano – broken Mini-B connector

A bit of needle-nose tweezering extracted the culprit from the power supply’s connector:

Knockoff Arduino Nano – broken Mini-B connector – fragment

I tried applying the world’s smallest dot of epoxy to the fracture, probably slobbered epoxy along the pins while reinserting it, and the Nano still doesn’t light up.

Given that knockoff Nano boards cost a touch over two bucks delivered, it’s not clear transplanting a connector from one of the never-sufficiently-to-be-damned counterfeit FTDI USB adapters makes any sense.

2017-07-28
Vacuum Tube LEDs: Mogul Bulb Side Light

The knockoff Neopixel on the 500 W mogul-base bulb failed in the usual way, so I rebuilt it with an SK6812 RGBW LED in a round cap:

Mogul lamp socket – SK6812 LED side cap

The nice 1-¼ inch stainless socket-head cap screws replace the 1 inch pan-head screws that engaged maybe one thread due to the additional spacer between the USB port and the upper hard drive platter I added for good looks.

I tried a few iterations of an aluminized Mylar (*) disk with various sized pinholes over the RGB trio to crisp up the filament shadow, because the SK6812 LED casts a more diffuse light than the W2812 LEDs:

Aluminized Mylar pinholes for SK6812 RGBW LED

Even the ⅛ inch pinhole made the bulb too dim, so I settled for a fuzzy shadow:

500 W Mogul bulb – SK6812 RGBW LED – no pinhole – green phase

The firmware has a tweak forcing the white LED to PWM=0, because this bulb looks better in saturated colors.

(*) Here on earth, aluminized Mylar is nonconductive.

2017-07-27