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.

Month: March 2016

Vacuum Tube LEDs: Knockoff Neopixel Failure
The knockoff Neopixel epoxied atop the big incandescent bulb just failed:

Vacuum Tube LEDs – ersatz heatsink plate cap

It stopped changing colors and began blinking high-intensity bursts of the RGB LEDs. Which was interesting, I’ll grant you, but didn’t produce the desired, ah, mood.

Differential diagnosis:
- Reboot that sucker: fail
- Shot of circuit cooler: fail
- Failing LED with known-good Arduino Pro Mini: fail
- “Failing” Arduino Pro Mini with known-good LED: work
Looks like a permanent WS2812B controller failure this time around.

It’s been plugged into a Kill-a-Watt meter that reports it ran for 415 hours and used 150 W·h of energy, for an average 360 mW dissipation. I think the actual power falls well below the meter’s lower limit, so I doubt the accuracy, but it’s a whole bunch less than a nightlight and much more interesting.

Now, to break that epoxy bond without breaking the bulb …
2016-03-10
Vacuum Tube LEDs: Octal Tube on a CD

Mounting an octal tube socket in a CD requires nothing more than printing one from the same OpenSCAD code that produced the Noval socket:

Vacuum Tube Lights – octal socket – Slic3r preview

Then apply a 1-1/8 inch Greenleee punch to a randomly chosen scrap CD, match-drill two screw holes, push the knurled inserts into the socket, and screw everything together:

Octal socket in CD – screw detail

I totally forgot about the raised ring around the central hole, so the OpenSCAD source code now moves the screws outward to 47 mm OC for a bit of head clearance. The 6-32 screws don’t look nearly so large next to that big Bakelite base.

The 2.36 mm tube pins fit perfectly into the (square!) socket holes without reaming.

This 6SN7GTB would definitely benefit from a ersatz plate cap with an LED shining down on the mica spacer; fortunately, the getter flash is on the side, not the top. You can see the plate cap atop the adjacent duodecar tube diffracted in the grooves, so a CD “chassis” will add some pizzazz to a rather drab tube:

$Octal socket in CD - LED diffraction$
Octal socket in CD – LED diffraction

In person, you see distinct RGB spots, not a continuous spectrum.

This tube has a completely broken-off base spigot (the keyed cylinder around the evacuation tip), so (I think) more light gets through the base than from a cut-off spigot end. Perhaps the plate cap will add enough light to turn the base LEDs into an accent.

2016-03-09
Vacuum Tube LEDs: Fire in the Noval

Replacing the original Noval socket in the string with the platter-friendly version, bracing the wiring with duct tape, balancing it on my desk, and firing it up:

Noval socket – red phase

The green phase looks nice, too:

Noval socket – green phase

Those screws are too big.

The getter flash covers the entire top of the tube; shining an LED down through the evacuation tip won’t work and even a laser doesn’t do much. That saves me the trouble of trying to create a cap that doesn’t wreck the tube’s good looks.

I originally planned to use white / natural PETG for the socket, but the more I see of those things, the more I think black is the new white. The sockets should vanish into the background, to let the tubes (and their reflections) carry the show.

The (yet to be designed) base must vanish under the platter edge, too, which puts a real crimp on its overall height. I’m not sure how to fit an Arduino Pro Mini and an FTDI board beside the existing socket; perhaps this calls for a unified socket-base design held on by those screws, rather than a separate socket inside a base enclosure.

Even though I know the tubes are inert and cool, I still hesitate before removing them from their sockets with the Neopixels running: you simply do not unplug a hot, powered device!

2016-03-08

Vacuum Tube LEDs: Noval Tube on a Platter

Replacing the hex nut traps with knurled insert cylinders slims the ends of the socket:

Noval Socket - knurled inserts - bottom - Slic3r preview — Noval Socket – knurled inserts – bottom – Slic3r preview

Making the raised part of the socket fit the 25 mm ID of a hard drive platter swells the midsection of the socket~~, but the platter won’t need any machining or punching~~:

Noval Socket - knurled inserts - top - Slic3r preview — Noval Socket – knurled inserts – top – Slic3r preview

The octal and duodecar sockets will require a punch to open up the platter hole and all sockets require two drilled clearance holes for the screws. Given that I’ll eventually do this on the Sherline, maybe milling the hole for the bigger tubes will be faster & easier than manually punching them.

I moved the screw centers to 35 mm (from the historically accurate 28 mm) to accommodate the larger center, not that anybody will ever notice, and enlarged the central hole to 7.5 mm (from 5.0 mm) to let more light into the tube base.

The support structures inside the (now much smaller) knurled insert cylinders might not be strictly necessary, but I left them in place to see how well they built. Which was perfectly, as it turns out, and they popped out with a slight push:

Noval socket - knurled inserts - support structures — Noval socket – knurled inserts – support structures

They’re just the cutest little things (those are 0.100 inch grid squares in the background):

Noval socket - support structures — Noval socket – support structures

Anyhow, the knurled inserts pressed into their holes with a slight shove:

Noval socket - installing knurled insert — Noval socket – installing knurled insert

The chuck jaws were loose on the screw cutoff stud and stopped at the surface, putting the knurled inserts perfectly flush with the socket:

Noval socket - knurled inserts - installed — Noval socket – knurled inserts – installed

The surface looks very slightly distorted around the inserts, although it’s still smooth to the touch, and I think the PETG will slowly relax around the knurls. Even without heat or epoxy, they’re now impossible to pull out with any force I’m willing to apply to the screws threaded into them. Given that the platter screws will (be trying to) pull the inserts through the socket, I think a dry install will suffice for my simple needs.

Match-mark, drill #27 6-32 clearance holes, and the screws drop right in:

Noval socket - installed — Noval socket – installed

Those stainless steel pan-head 6-32 screws seem a bit large in comparison with the socket. Perhaps I should use 4-40 screws, even though they’re not, ahem, historically accurate.

The tube pin holes get hand-reamed with a #53 drill = 1.5 mm. That’s a bit over the nominal 1.1 mm pin diameter, but seems to provide both easy insertion and firm retention. For permanent installation, an adhesive would be in order.

Buff off the fingerprints, stick the tube in place, and it looks pretty good:

Noval socket - tube on platter — Noval socket – tube on platter

Yeah, those screws are too big. Maybe a brace of black M3 socket head screws would look better, despite a complete lack of historicity.

Now to wire it up and ponder how to build a base.

The OpenSCAD source code as a GitHub Gist:

	// Vacuum Tube LED Lights
	// Ed Nisley KE4ZNU February 2016

	Layout = "Socket"; // Cap LampBase USBPort Socket(s) (Build)FinCap
	DefaultSocket = "Noval";

	Section = false; // cross-section the object

	Support = true;

	//- Extrusion parameters must match reality!

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

	HoleWindage = 0.2;

	Protrusion = 0.1; // make holes end cleanly

	inch = 25.4;

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

	//———————-
	// Dimensions
	// https://en.wikipedia.org/wiki/Tube_socket#Summary_of_Base_Details
	// punch & screw OC modified for drive platter chassis plate
	// platter = 25 mm ID

	T_NAME = 0; // common name
	T_NUMPINS = 1; // total, with no allowance for keying
	T_PINBCD = 2; // tube pin circle diameter
	T_PINOD = 3; // … diameter
	T_PINLEN = 4; // … length (overestimate)
	T_HOLEOD = 5; // nominal panel hole from various sources
	T_PUNCHOD = 6; // panel hole optimized for inch-size Greenlee punches
	T_TUBEOD = 7; // envelope or base diameter
	T_PIPEOD = 8; // light pipe from LED to tube base
	T_SCREWOC = 9; // mounting screw holes

	// Name pins BCD dia length hole punch env pipe screw
	TubeData = [
	["Mini7", 8, 9.53, 1.016, 7.0, 16.0, 25.0, 18.0, 5.0, 35.0], // punch 11/16, screw 22.5 OC
	["Octal", 8, 17.45, 2.36, 10.0, 36.2, (8 + 1)/8 * inch, 32.0, 11.5, 39.0],
	["Noval", 10, 11.89, 1.1016, 7.0, 22.0, 25.0 , 21.0, 7.5, 35.0], // punch 7/8, screw 28.0 OC
	["Duodecar", 13, 19.10, 1.05, 9.0, 32.0, (4 + 1)/4 * inch, 38.0, 12.5, 39.0], // aka Compactron
	];

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

	Pixel = [7.0,10.0,3.0]; // ID = contact patch, OD = PCB dia, LENGTH = overall thickness

	Nut = [3.5,5.2,7.2]; // socket mounting nut recess — threaded insert
	NutSides = 8;

	BaseShim = 2*ThreadThick; // between pin holes and pixel top
	SocketFlange = 2.0; // rim around socket below punchout
	PanelThick = 1.5; // socket extension through punchout

	FinCutterOD = 1/8 * inch;
	FinCapSize = [(Pixel[OD] + 2FinCutterOD),30.0,(10.0 + 2Pixel[LENGTH])];


	//———————-
	// Useful routines

	module PolyCyl(Dia,Height,ForceSides=0) { // based on nophead's polyholes

	Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);

	FixDia = Dia / cos(180/Sides);

	cylinder(r=(FixDia + HoleWindage)/2,h=Height,$fn=Sides);
	}

	//———————-
	// Tube cap

	CapTube = [4.0,3/16 * inch,10.0]; // brass tube for flying lead to cap LED

	CapSize = [Pixel[ID],(Pixel[OD] + 3.0),(CapTube[OD] + 2*Pixel[LENGTH])];

	CapSides = 6*4;

	module Cap() {

	difference() {
	union() {
	cylinder(d=CapSize[OD],h=(CapSize[LENGTH]),$fn=CapSides); // main cap body
	translate([0,0,CapSize[LENGTH]]) // rounded top
	scale([1.0,1.0,0.65])
	sphere(d=CapSize[OD]/cos(180/CapSides),$fn=CapSides); // cos() fixes slight undersize vs cylinder
	cylinder(d1=(CapSize[OD] + 23ThreadWidth),d2=CapSize[OD],h=1.5*Pixel[LENGTH],$fn=CapSides); // skirt
	}

	translate([0,0,-Protrusion]) // bore for wiring to LED
	PolyCyl(CapSize[ID],(CapSize[LENGTH] + 3*ThreadThick + Protrusion),CapSides);

	translate([0,0,-Protrusion]) // PCB recess with clearance for tube dome
	PolyCyl(Pixel[OD],(1.5*Pixel[LENGTH] + Protrusion),CapSides);

	translate([0,0,(1.5*Pixel[LENGTH] – Protrusion)]) // small step + cone to retain PCB
	cylinder(d1=(Pixel[OD]/cos(180/CapSides)),d2=Pixel[ID],h=(Pixel[LENGTH] + Protrusion),$fn=CapSides);

	translate([0,0,(CapSize[LENGTH] – CapTube[OD]/(2*cos(180/8)))]) // hole for brass tube holding wire loom
	rotate([90,0,0]) rotate(180/8)
	PolyCyl(CapTube[OD],CapSize[OD],8);
	}

	}

	//———————-
	// Heatsink tube cap


	module FinCap() {

	CableOD = 3.5; // cable + braid diameter
	BulbOD = 3.75 * inch; // bulb OD; use 10 inches for flat

	echo(str("Fin Cutter: ",FinCutterOD));
	FinSides = 2*4;

	BulbRadius = BulbOD / 2;
	BulbDepth = BulbRadius – sqrt(pow(BulbRadius,2) – pow(FinCapSize[OD],2)/4);
	echo(str("Bulb OD: ",BulbOD," recess: ",BulbDepth));

	NumFins = floor(PIFinCapSize[ID] / (2FinCutterOD));
	FinAngle = 360 / NumFins;
	echo(str("NumFins: ",NumFins," angle: ",FinAngle," deg"));

	difference() {
	union() {
	cylinder(d=FinCapSize[ID],h=FinCapSize[LENGTH],$fn=2*NumFins); // main body

	for (i = [0:NumFins – 1]) // fins
	rotate(i * FinAngle)
	hull() {
	translate([FinCapSize[ID]/2,0,0])
	rotate(180/FinSides)
	cylinder(d=FinCutterOD,h=FinCapSize[LENGTH],$fn=FinSides);
	translate([(FinCapSize[OD] – FinCutterOD)/2,0,0])
	rotate(180/FinSides)
	cylinder(d=FinCutterOD,h=FinCapSize[LENGTH],$fn=FinSides);
	}

	rotate(FinAngle/2) // cable entry boss
	translate([FinCapSize[ID]/2,0,FinCapSize[LENGTH]/2])
	cube([FinCapSize[OD]/4,FinCapSize[OD]/4,FinCapSize[LENGTH]],center=true);
	}

	for (i = [1:NumFins – 1]) // fin inner gullets, omit cable entry side
	rotate(i * FinAngle + FinAngle/2) // joint isn't quite perfect, but OK
	translate([FinCapSize[ID]/2,0,-Protrusion])
	rotate(0*180/FinSides)
	cylinder(d=FinCutterOD/cos(180/FinSides),h=(FinCapSize[LENGTH] + 2*Protrusion),$fn=FinSides);

	translate([0,0,-Protrusion]) // PCB recess
	PolyCyl(Pixel[OD],(1.5*Pixel[LENGTH] + Protrusion),FinSides);

	PolyCyl(Pixel[ID],(FinCapSize[LENGTH] – 3*ThreadThick),FinSides); // bore for LED wiring

	translate([0,0,(FinCapSize[LENGTH] – 3ThreadThick – 2CableOD/(2*cos(180/8)))]) // cable inlet
	rotate(FinAngle/2) rotate([0,90,0]) rotate(180/8)
	PolyCyl(CableOD,FinCapSize[OD],8);

	if (BulbOD <= 10.0 * inch) // curve for top of bulb
	translate([0,0,-(BulbRadius – BulbDepth + 2*ThreadThick)]) // … slightly flatten tips
	sphere(d=BulbOD,$fn=16*FinSides);
	}

	}


	//———————-
	// Aperture for USB-to-serial adapter snout
	// These are all magic numbers, of course

	module USBPort() {

	translate([0,28.0])
	rotate([90,0,0])
	linear_extrude(height=28.0)
	polygon(points=[
	[0,0],
	[8.0,0],
	[8.0,4.0],
	// [4.0,4.0],
	[4.0,6.5],
	[-4.0,6.5],
	// [-4.0,4.0],
	[-8.0,4.0],
	[-8.0,0],
	]);
	}


	//———————-
	// Box for Leviton ceramic lamp base

	module LampBase() {

	Bottom = 3.0;
	Base = [4.0inch,4.5inch,20.0 + Bottom];
	Sides = 12*4;

	Retainer = [3.5,11.0,1.0]; // flat fiber washer holding lamp base screws in place

	StudSides = 8;
	StudOC = 3.5 * inch;
	Stud = [Nut[OD], // 6-32 tapped brass insert
	min(15.0,1.5*(Base[ID] – StudOC)/cos(180/StudSides)), // OD = big enough to merge with walls
	(Base[LENGTH] – Retainer[LENGTH])]; // leave room for retainer


	union() {
	difference() {
	rotate(180/Sides)
	cylinder(d=Base[OD],h=Base[LENGTH],$fn=Sides);
	rotate(180/Sides)
	translate([0,0,Bottom])
	cylinder(d=Base[ID],h=Base[LENGTH],$fn=Sides);
	translate([0,-Base[OD]/2,Bottom + 1.2]) // mount on double-sided foam tape
	rotate(0)
	USBPort();
	}
	for (i = [-1,1])
	translate([i*StudOC/2,0,0])
	rotate(180/StudSides)
	difference() {
	cylinder(d=Stud[OD],h=Stud[LENGTH],$fn=StudSides);
	translate([0,0,Bottom])
	PolyCyl(Stud[ID],(Stud[LENGTH] – (Bottom – Protrusion)),6);
	}
	}
	}

	//———————-
	// Tube Socket

	module Socket(Name = DefaultSocket) {

	NumSides = 6*4;

	Tube = search([Name],TubeData,1,0)[0];
	echo(str("Building ",TubeData[Tube][0]," socket"));
	echo(str(" Punch: ",TubeData[ID][T_PUNCHOD]," mm = ",TubeData[ID][T_PUNCHOD]/inch," inch"));
	echo(str(" Screws: ",TubeData[ID][T_SCREWOC]," mm =",TubeData[ID][T_SCREWOC]/inch," inch OC"));

	OAH = Pixel[LENGTH] + BaseShim + TubeData[Tube][T_PINLEN];
	BaseHeight = OAH – PanelThick;

	difference() {
	union() {
	linear_extrude(height=BaseHeight)
	hull() {
	circle(d=(TubeData[Tube][T_PUNCHOD] + 2*SocketFlange),$fn=NumSides);
	for (i=[-1,1])
	translate([i*TubeData[Tube][T_SCREWOC]/2,0])
	circle(d=2.0*Nut[OD],$fn=NumSides);
	}
	cylinder(d=TubeData[Tube][T_PUNCHOD],h=OAH,$fn=NumSides); // boss in chassis punch hole
	}

	for (i=[0:(TubeData[Tube][T_NUMPINS] – 1)]) // tube pins
	rotate(i*360/TubeData[Tube][T_NUMPINS])
	translate([TubeData[Tube][T_PINBCD]/2,0,(OAH – TubeData[Tube][T_PINLEN])])
	rotate(180/4)
	PolyCyl(TubeData[Tube][T_PINOD],(TubeData[Tube][T_PINLEN] + Protrusion),4);

	for (i=[-1,1]) // mounting screw holes & nut traps / threaded inserts
	translate([i*TubeData[Tube][T_SCREWOC]/2,0,-Protrusion]) {
	PolyCyl(Nut[OD],(Nut[LENGTH] + Protrusion),NutSides);
	PolyCyl(Nut[ID],(OAH + 2*Protrusion),NutSides);
	}

	translate([0,0,-Protrusion]) { // LED recess
	PolyCyl(Pixel[OD],(Pixel[LENGTH] + Protrusion),8);
	}

	translate([0,0,(Pixel[LENGTH] – Protrusion)]) { // light pipe
	rotate(180/TubeData[Tube][T_NUMPINS])
	PolyCyl(TubeData[Tube][T_PIPEOD],(OAH + 2*Protrusion),TubeData[Tube][T_NUMPINS]);
	}
	}

	// Totally ad-hoc support structures …

	if (Support) {
	color("Yellow") {
	for (i=[-1,1]) // nut traps
	translate([i*TubeData[Tube][T_SCREWOC]/2,0,(Nut[LENGTH] – ThreadThick)/2])
	for (a=[0:5])
	rotate(a*30 + 15)
	cube([2ThreadWidth,0.9Nut[OD],(Nut[LENGTH] – ThreadThick)],center=true);

	if (Pixel[OD] > TubeData[Tube][T_PIPEOD]) // support pipe only if needed
	translate([0,0,(Pixel[LENGTH] – ThreadThick)/2])
	for (a=[0:7])
	rotate(a*22.5)
	cube([2ThreadWidth,0.9Pixel[OD],(Pixel[LENGTH] – ThreadThick)],center=true);

	}
	}

	}

	//———————-
	// Build it

	if (Layout == "Cap") {
	if (Section)
	difference() {
	Cap();
	translate([-CapSize[OD],0,CapSize[LENGTH]])
	cube([2CapSize[OD],2CapSize[OD],3*CapSize[LENGTH]],center=true);
	}
	else
	Cap();
	}

	if (Layout == "FinCap") {
	if (Section) render(convexity=5)
	difference() {
	FinCap();
	// translate([0,-FinCapSize[OD],FinCapSize[LENGTH]])
	// cube([2FinCapSize[OD],2FinCapSize[OD],3*FinCapSize[LENGTH]],center=true);
	translate([-FinCapSize[OD],0,FinCapSize[LENGTH]])
	cube([2FinCapSize[OD],2FinCapSize[OD],3*FinCapSize[LENGTH]],center=true);
	}
	else
	FinCap();
	}

	if (Layout == "BuildFinCap")
	translate([0,0,FinCapSize[LENGTH]])
	rotate([180,0,0])
	FinCap();

	if (Layout == "LampBase")
	LampBase();

	if (Layout == "USBPort")
	USBPort();

	if (Layout == "Socket")
	if (Section) {
	difference() {
	Socket();
	translate([-100/2,0,-Protrusion])
	cube([100,50,50],center=false);
	}
	}
	else
	Socket();

	if (Layout == "Sockets") {
	translate([0,50,0])
	Socket("Mini7");
	translate([0,20,0])
	Socket("Octal");
	translate([0,-15,0])
	Socket("Duodecar");
	translate([0,-50,0])
	Socket("Noval");
	}

view raw Vacuum Tube Lights.scad hosted with ❤ by GitHub

2016-03-07

Vacuum Tube Prices, Then and Now

Quite by coincidence, a Pile o’ Stuff disgorged a 1975 Radio Shack Catalog listing three dense pages of vacuum tubes, including a 21HB5A:

Radio Shack 1975 Catalog – 21HB5A Tube Listing

These days, you buy New Old Stock 21HB5A tubes from eBay for about the same in current dollars with shipping:

eBay – 21HB5A Tubes

I should stock up and light up!

Vacuum Tube LEDs – IBM 21HB5A Beam Power Tube – green violet phase

2016-03-06
Command-Line CD Ripping, Redux
A slight improvement to my two-step manual CD ripping process, with the intent of avoiding any thoughts about abcde:
```
cdparanoia -B -v ; eject cdrom
```
Ejecting the CD after cdparanoid finishes with it provides a visual cue for the next step.

Set up the disk number and maximum number of tracks, then unleash lame:
```
d=1
tm=19
for t in $(seq -w 1 $tm) ; do lame --preset tape --tt "D${d}:T${t}" --ta "Michael Lewis" --tl "The Big Short" --tn "${t}/${tm}" --tg "Audio Book" --add-id3v2 track${t}.cdda.wav D${d}-${t}.mp3 ; done
rm track*
```
The $(seq -w 1 $tm) expansion generates a list of zero-filled numbers for the tracks.

There’s surely a one-liner to extract $tm, the maximum track number, from the track* files, but I’ll leave that for later.

You can increment the disk number with let "d++" if the ripping goes smoothly. If not, that’s fraught with peril, because you (well, I) will do it once too often.

Iterate for each CD in the set, washing & primping as needed for good results.

And that’s that, at least for a while…
2016-03-05
Streaming Player: Wireless Keypad

Moving the streaming media player control panel across the Sewing Room for E-Z access:

Wireless Keypad – colored labels

Stipulated: garish labels that don’t fit the keys well at all.

I need more than one stream for testing; the only one that matters is Classical.

The keypad uses the same 2.4 GHz ISM band as the Raspberry Pi’s Wifi radio, which means holding a key down (which should never happen) puts a dent in mplayer’s cache fill level. Even absent that interference, the WiFi link seems more than a little iffy, probably because it’s at the far end of the house and upstairs from the router.

Other WiFi devices report that 2.4 GHz RF has trouble punching through the intervening fifty feet of hardwood floor (on the diagonal, the joists amount to a lot of wood) and multiple sets of doubled wallboard sheets; the RPi probably needs a better radio with an actual antenna. I did move the WiFi control channel away from the default used by the (relatively distant) neighbors, which seemed to improve its disposition.

2016-03-04