Author: Ed

Vacuum Tube LEDs: First Light!

A test lashup to see how it all works, with an ersatz plate cap atop the IBM 21HB5A Beam Power tube on the far right end:

Vacuum Tube LEDs - test lashup — Vacuum Tube LEDs – test lashup

Those sockets must mount in a chassis, not flop around loose on the cable.

I hacked the code out of the Hard Drive Platter Mood Light; there’s a lot to not like about what’s left and I must rethink the overall structure. The colors now run an order of magnitude faster than the Platter Mood Light, with a 90° phase angle between successive Neopixels.

The mica spacers in the 12AT7 Dual Triode tube (second in the sequence, Noval socket) look cool & crystalline:

Vacuum Tube LEDs - Noval tube - blue phase — Vacuum Tube LEDs – Noval tube – blue phase

When the red phase comes around, it becomes a firebottle:

Vacuum Tube LEDs - Noval tube - red phase — Vacuum Tube LEDs – Noval tube – red phase

With a touch of fire in its hole, the IBM 21HB5A Beam Power tube looks just flat-out gorgeous, despite that translucent blue plate cap:

Vacuum Tube LEDs - IBM 21HB5A Beam Power Tube - violet amber phase — Vacuum Tube LEDs – IBM 21HB5A Beam Power Tube – violet amber phase

Cool green works pretty well:

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

If you wait long enough, it’ll probably turn True IBM Blue.

This worked out even better than I expected!

The Arduino source code as a GitHub gist:

	// Neopixel lighting for multiple vacuum tubes
	// Ed Nisley – KE4ANU – January 2015

	#include <Adafruit_NeoPixel.h>

	//———-
	// Pin assignments

	const byte PIN_NEO = A3; // DO – data out to first Neopixel

	const byte PIN_HEARTBEAT = 13; // DO – Arduino LED

	//———-
	// Constants

	#define UPDATEINTERVAL 25ul
	const unsigned long UpdateMS = UPDATEINTERVAL – 1ul; // update LEDs only this many ms apart minus loop() overhead

	// number of steps per cycle, before applying prime factors
	#define RESOLUTION 100

	// phase difference between tubes for slowest color
	#define BASEPHASE (PI/4.0)

	// number of LED strips around each tube
	#define LEDSTRIPCOUNT 1

	// number of LEDs per strip
	#define LEDSTRINGCOUNT 5

	// want to randomize the startup a little?
	#define RANDOMIZE true

	//———-
	// Globals

	// instantiate the Neopixel buffer array

	Adafruit_NeoPixel strip = Adafruit_NeoPixel(LEDSTRIPCOUNT * LEDSTRINGCOUNT, PIN_NEO, NEO_GRB + NEO_KHZ800);

	uint32_t FullWhite = strip.Color(255,255,255);
	uint32_t FullOff = strip.Color(0,0,0);

	struct pixcolor_t {
	byte Prime;
	unsigned int NumSteps;
	unsigned int Step;
	float StepSize;
	float TubePhase;
	byte MaxPWM;
	};

	// colors in each LED
	enum pixcolors {RED, GREEN, BLUE, PIXELSIZE};

	struct pixcolor_t Pixels[PIXELSIZE]; // all the data for each pixel color intensity

	byte Map[LEDSTRINGCOUNT][LEDSTRIPCOUNT] = {{0},{1},{2},{3},{4}}; // pixel IDs around each tube, bottom to top.

	unsigned long MillisNow;
	unsigned long MillisThen;

	//– Figure PWM based on current state

	byte StepColor(byte Color, float Phi) {

	byte Value;

	Value = (Pixels[Color].MaxPWM / 2.0) * (1.0 + sin(Pixels[Color].Step * Pixels[Color].StepSize + Phi));

	// Value = (Value) ? Value : Pixels[Color].MaxPWM; // flash at dimmest points
	// printf("C: %d Phi: %d Value: %d\r\n",Color,(int)(Phi*180.0/PI),Value);

	return Value;
	}


	//– Helper routine for printf()

	int s_putc(char c, FILE *t) {
	Serial.write(c);
	}

	//——————
	// Set the mood

	void setup() {

	pinMode(PIN_HEARTBEAT,OUTPUT);
	digitalWrite(PIN_HEARTBEAT,LOW); // show we arrived

	Serial.begin(57600);
	fdevopen(&s_putc,0); // set up serial output for printf()

	printf("Multiple Vacuum Tube Mood Light with Neopixels\r\nEd Nisley – KE4ZNU – January 2016\r\n");

	/// set up Neopixels

	strip.begin();
	strip.show();

	// lamp test: run a brilliant white dot along the length of the strip

	printf("Lamp test: walking white\r\n");

	strip.setPixelColor(0,FullWhite);
	strip.show();
	delay(500);

	for (int i=1; i<strip.numPixels(); i++) {
	digitalWrite(PIN_HEARTBEAT,HIGH);
	strip.setPixelColor(i-1,FullOff);
	strip.setPixelColor(i,FullWhite);
	strip.show();
	digitalWrite(PIN_HEARTBEAT,LOW);
	delay(500);
	}

	strip.setPixelColor(strip.numPixels() – 1,FullOff);
	strip.show();
	delay(500);

	// fill the layers

	printf(" … fill using Map array\r\n");

	for (int i=0; i < LEDSTRINGCOUNT; i++) { // for each layer
	digitalWrite(PIN_HEARTBEAT,HIGH);
	for (int j=0; j < LEDSTRIPCOUNT; j++) { // spread color around the layer
	strip.setPixelColor(Map[i][j],FullWhite);
	strip.show();
	delay(250);
	}
	digitalWrite(PIN_HEARTBEAT,LOW);
	}

	// clear to black

	printf(" … clear\r\n");

	for (int i=0; i < LEDSTRINGCOUNT; i++) { // for each layer
	digitalWrite(PIN_HEARTBEAT,HIGH);
	for (int j=0; j < LEDSTRIPCOUNT; j++) { // spread color around the layer
	strip.setPixelColor(Map[i][j],FullOff);
	strip.show();
	delay(250);
	}
	digitalWrite(PIN_HEARTBEAT,LOW);
	}

	delay(1000);

	// set up the color generators

	MillisNow = MillisThen = millis();
	if (RANDOMIZE)
	randomSeed(MillisNow + analogRead(7));
	else
	printf("Start not randomized\r\n");
	printf("First random number: %ld\r\n",random(10));

	Pixels[RED].Prime = 7;
	Pixels[GREEN].Prime = 5;
	Pixels[BLUE].Prime = 3;
	printf("Primes: (%d,%d,%d)\r\n",Pixels[RED].Prime,Pixels[GREEN].Prime,Pixels[BLUE].Prime);

	unsigned int TubeSteps = (unsigned int) ((BASEPHASE / TWO_PI) *
	RESOLUTION * (unsigned int) max(max(Pixels[RED].Prime,Pixels[GREEN].Prime),Pixels[BLUE].Prime));
	printf("Tube phase offset: %d deg = %d steps\r\n",(int)(BASEPHASE*(360.0/TWO_PI)),TubeSteps);

	Pixels[RED].MaxPWM = 255;
	Pixels[GREEN].MaxPWM = 128;
	Pixels[BLUE].MaxPWM = 255;

	for (byte c=0; c < PIXELSIZE; c++) {
	Pixels[c].NumSteps = RESOLUTION * (unsigned int) Pixels[c].Prime;
	Pixels[c].Step = (RANDOMIZE) ? random(Pixels[c].NumSteps) : (3*Pixels[c].NumSteps)/4;
	Pixels[c].StepSize = TWO_PI / Pixels[c].NumSteps; // in radians per step
	Pixels[c].TubePhase = TubeSteps * Pixels[c].StepSize; // radians per tube

	printf("c: %d Steps: %d Init: %d",c,Pixels[c].NumSteps,Pixels[c].Step);
	printf(" PWM: %d Phi %d deg\r\n",Pixels[c].MaxPWM,(int)(Pixels[c].TubePhase*(360.0/TWO_PI)));
	}


	}

	//——————
	// Run the mood

	void loop() {

	MillisNow = millis();
	if ((MillisNow – MillisThen) > UpdateMS) {
	digitalWrite(PIN_HEARTBEAT,HIGH);

	for (byte c=0; c < PIXELSIZE; c++) { // step to next increment in each color
	if (++Pixels[c].Step >= Pixels[c].NumSteps) {
	Pixels[c].Step = 0;
	printf("Cycle %d steps %d at %8ld delta %ld ms\r\n",c,Pixels[c].NumSteps,MillisNow,(MillisNow – MillisThen));
	}
	}

	for (int i=0; i < LEDSTRINGCOUNT; i++) { // for each layer
	byte Value[PIXELSIZE];
	for (byte c=0; c < PIXELSIZE; c++) { // … for each color
	Value[c] = StepColor(c,-i*Pixels[c].TubePhase); // figure new PWM value
	// Value[c] = (c == RED && Value[c] == 0) ? Pixels[c].MaxPWM : Value[c]; // flash highlight for tracking
	}
	uint32_t UniColor = strip.Color(Value[RED],Value[GREEN],Value[BLUE]);
	if (false && (i == 0))
	printf("L: %d C: %08lx\r\n",i,UniColor);
	for (int j=0; j < LEDSTRIPCOUNT; j++) { // fill layer with color
	strip.setPixelColor(Map[i][j],UniColor);
	}
	}
	strip.show();

	MillisThen = MillisNow;
	digitalWrite(PIN_HEARTBEAT,LOW);
	}

	}

view raw MultiTube.ino hosted with ❤ by GitHub

2016-02-11

Vacuum Tube LEDs: Ersatz Tube Sockets

Even vacuum tubes destined to be decorations need sockets:

Vacuum Tube Bases - solid models — Vacuum Tube Bases – solid models

They’re entirely plastic, of course, but they match the dimensions of “real” tube sockets pretty closely. The bosses around the pins have hard-inch dimensions, so you (well, I) can unleash Genuine Greenlee Radio Chassis Punches on sheet metal.

All the key dimensions come from a table, so you can build whatever sockets you need. These four seem to cover the most common relics of the Hollow State Empire:

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,        11/16 * inch,  18.0,  5.0, 22.5],
    ["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,          7/8 * inch,  21.0,  5.0, 28.0],
    ["Duodecar", 13,   19.10, 1.05,    9.0,  32.0,         1.25 * inch,  38.0, 12.5, 39.0],
];

Given that the tubes lack electrical connections, I omitted the base keying: plug them in for best visual effect.

The hole through the middle passes light from a knockoff Neopixel on a 10 mm OD PCB:

Vacuum Tube LEDs - Octal base - top — Vacuum Tube LEDs – Octal base – top

Seen from the bottom, each base traps a pair of 6-32 nuts for chassis mounting and has a Neopixel press-fit in the middle:

Vacuum Tube LEDs - Duodecar base - bottom — Vacuum Tube LEDs – Duodecar base – bottom

Those recesses require support structures:

Vacuum Tube Bases - solid models - support — Vacuum Tube Bases – solid models – support

The Miniature 7-pin socket has the least space for the 10 mm OD Neopixel PCB and shows the thin layer between the bottom of the pin holes and the top of the openings.

Vacuum Tube Base - Mini7 - solid model section — Vacuum Tube Base – Mini7 – solid model section

You see half of the eight holes in the “7 pin” socket, because it has the eighth hole where a standard socket has a gap between pins 1 and 7.

Somewhat to my surprise, punching the support spiders out with a 6-32 stud (grabbed in the drill press) worked perfectly:

Vacuum Tube Base - nut trap overhang - detail — Vacuum Tube Base – nut trap overhang – detail

They look like I intended to build tiny decorations:

Vacuum Tube Base - support structure - detail — Vacuum Tube Base – support structure – detail

The cookies held on tenuously, then released with a loud bang! as I gradually increased the pressure. A PETG support structure in a blind recess wouldn’t pop out nearly so well.

The OpenSCAD source code as a GitHub gist:

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

	Layout = "Sockets"; // Cap LampBase USBPort Socket(s)

	Section = true; // 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

	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, 11/16 * inch, 18.0, 5.0, 22.5],
	["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, 7/8 * inch, 21.0, 5.0, 28.0],
	["Duodecar", 13, 19.10, 1.05, 9.0, 32.0, 1.25 * inch, 38.0, 12.5, 39.0],
	];

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

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

	Nut = [3.5,8.0,3.0]; // socket mounting nut recess

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

	//———————-
	// 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);
	}

	}

	//———————-
	// 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 = [0.107 * inch, // 6-32 mounting screws
	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 = "Mini7") {

	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),$fn=NumSides);
	for (i=[-1,1])
	translate([i*TubeData[Tube][T_SCREWOC]/2,0])
	circle(d=2*Nut[OD],$fn=NumSides);
	}
	cylinder(d=TubeData[Tube][T_PUNCHOD],h=OAH,$fn=NumSides);
	}

	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
	translate([i*TubeData[Tube][T_SCREWOC]/2,0,-Protrusion]) {
	PolyCyl(Nut[OD],(Nut[LENGTH] + Protrusion),6);
	PolyCyl(Nut[ID],(OAH + 2*Protrusion),6);
	}

	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 == "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

2016-02-10

Sears Sewing Table Hinge Covers

The extension surfaces on the Sears sewing table in the Basement Sewing Room unfold from the top, leaving the hinges exposed:

Alas, quilts snag on the squared-off ends of the hinges, a situation that is not to be tolerated…

This protective cap isn’t as small as we’d like, but it must be that thick to cover the hinge, that long to cover the squared-off ends, and that wide for symmetry:

Sears Sewing Table Hinge Cover - solid model — Sears Sewing Table Hinge Cover – solid model

Two neodymium magnets fit in the holes and secure the cover to the all-steel “bronzed” hinges:

Sears Sewing Table - hinge covers — Sears Sewing Table – hinge covers

We’re not sure how well that will work in the long term, but early returns seem promising.

It could be slightly narrower left-to-right and maybe fewer vertices should be oriented differently.

The OpenSCAD source code as a GitHub gist:

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

	//- Extrusion parameters must match reality!

	ThreadThick = 0.20;
	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

	Hinge = [7.0,52.0,6.0];

	TopThick = 3*ThreadThick;
	PlateThick = Hinge[2] + TopThick;

	NumSides = 8*4;

	//———————-
	// 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);
	}

	//———————-
	// Build it

	difference() {
	hull()
	for (a=[0:7])
	rotate(a*360/8)
	translate([Hinge[1]/2,0,0])
	scale([1.5,1.5,1])
	sphere(r=PlateThick,$fn=NumSides);
	hull()
	for (k=[-1,1])
	translate([0,Hinge[1]/2,k*(Hinge[2] – Hinge[0]/2)])
	rotate([90,0,0]) rotate(180/8)
	PolyCyl(Hinge[0],Hinge[1],8);

	for (i=[-1,1])
	translate([i*Hinge[1]/2,0,-Protrusion])
	PolyCyl(4.8,2.5 + Protrusion,8);

	translate([0,0,-PlateThick])
	cube(2*[Hinge[1],Hinge[1],PlateThick],center=true);
	}

view raw Sewing Table Hinge Covers.scad hosted with ❤ by GitHub

2016-02-09

Raspberry Pi: Jessie Lite Setup for Streaming Audio
As a first pass at a featureless box that simply streams music from various sources, I set up a Raspberry Pi with a Jessie Lite Raspbian image. I’m mildly astonished that they use dd to transfer the image to the MicroSD card, but it certainly cuts out a whole bunch of felgercarb that comes with a more user-friendly interface.

I used dcfldd (for progress reports while copying) and verify the copied image:
```
sudo dcfldd statusinterval=10 bs=4M if=/mnt/diskimages/ISOs/Raspberry\ Pi/2015-11-21-raspbian-jessie-lite.img of=/dev/sdb
sudo dcfldd statusinterval=10 bs=4M if=/dev/sdb of=/tmp/rpi.img count=350
truncate --reference /mnt/diskimages/ISOs/Raspberry\ Pi/2015-11-21-raspbian-jessie-lite.img /tmp/rpi.img
diff -s /tmp/rpi.img /mnt/diskimages/ISOs/Raspberry\ Pi/2015-11-21-raspbian-jessie-lite.img
```
That fits neatly on a minuscule 2 GB MicroSD card:
```
df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/root       1.8G  1.1G  549M  67% /
devtmpfs        214M     0  214M   0% /dev
tmpfs           218M     0  218M   0% /dev/shm
tmpfs           218M  4.5M  213M   3% /run
tmpfs           5.0M  4.0K  5.0M   1% /run/lock
tmpfs           218M     0  218M   0% /sys/fs/cgroup
/dev/mmcblk0p1   60M   20M   41M  34% /boot
```
Set the name of the Raspberry Pi to something memorable, perhaps streamer1.

Disable IPV6, because nothing around here supports it, by tweaking /etc/modprobe.d/ipv6.conf:
```
alias ipv6 off
```
Enable the USB WiFi dongle by adding network credentials to /etc/wpa_supplicant/wpa_supplicant.conf:
```
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1

network={
 ssid="your network SSID goes here"
 psk="pick your own"
}
```
Nowadays, there’s no need for a fixed IP address, because after adding your public key to the (empty) list in ~/.ssh/authorized_keys, you can sign in using a magic alias:
```
ssh -p12345 pi@streamer1.local
```
I have absolutely no idea how that works, nor how to find out. If it ever stops working, I’m doomed.

The Raspberry Pi Model B+ has “improved” audio that, to Mary’s ears, comes across as pure crap; even my deflicted ears can hear low-level hissing and bad distortion at moderate volumes. An old Creative Labs Sound Blaster USB box sidesteps that problem, but requires a tweak in /etc/asound.conf to route the audio to the proper destination:
```
# Make USB sound gadget the default output

pcm.!default {
 type hw card 1
}
ctl.!default {
 type hw card 1
}
```
ALSA then seems to default to the wrong channel (or something), although this tweak in the middle of /usr/share/alsa/alsa.conf may not be needed:
```
#pcm.front cards.pcm.front
pcm.front cards.pcm.default
```
Good old mplayer seems to handle everything involved in streaming audio from the Interwebs.

Set up blank /etc/mplayer/input.conf and ~/.mplayer/input.conf files to eliminate kvetching:
```
# Dummy file to quiet the "not found" error message
```
Set up ~/.mplayer/config thusly:
```
prefer-ipv4=true
novideo=true
#ao=alsa:device=hw=1.0
ao=alsa
format=s16le
#mixer-channel=Master
softvol=true
volume=25
quiet=true
```
The commented-out ao option will force the output to the USB gadget if you want to route the default audio to the built-in headphone jack or HDMI output.

Telling mplayer to use its own software volume control eliminates a whole bunch of screwing around with the ALSA mixer configuration.

The quiet option silences the buffer progress display, while still showing the station ID and track information.

With that in hand, the Public Domain Project has a classical music stream that is strictly from noncommercial:
```
mplayer -playlist http://relay.publicdomainproject.org/classical.aac.m3u
```
Send them a sack of money if you like them as much as we do.

By contrast, the local NPR station comes across as talk radio:
```
mplayer http://live.str3am.com:2070/wmht1
```
You can’t feed nested playlists into mplayer, but fetching the contents of the stream playlists produces a one-station-per-line playlist file that one might call RadioList.txt:
```
http://relay.publicdomainproject.org:80/classical.aac
http://relay.publicdomainproject.org:80/jazz_swing.aac
http://live.str3am.com:2070/wmht1
```
So far, I’ve been manually starting mplayer just to get a feel for reliability and suchlike, but the setup really needs an autostart option with some user-friendly way to select various streams, plus a way to cleanly halt the system. A USB numeric keypad may be in order, rather than dinking around with discrete buttons and similar nonsense.

There exists a horrible hack to transfer the stream metadata from mplayer onto an LCD, but I’m flat-out not using PHP or Perl. Perhaps the Python subprocess management module will suffice to auto-start a Python program that:
- starts mplayer with the default playlist
- parses mplayer’s piped output
- updates the LCD accordingly
- reads / translates keypad input
This being a Pi, not an Arduino, one could actually use a touchscreen LCD without plumbing the depths of absurdity, but that starts looking like a lot of work…
2016-02-08
Raspberry Pi Model B+ Reset Connector

Turns out Raspberry Pi boards have provision for a Reset switch, but you gotta dig for it. On the Model B+, it’s labeled RUN:

Raspberry Pi BPlus – RUN header

Soldering in that 2-pin header and plugging a pushbutton switch on a short cable will suffice until I get around to thinking of / scrounging a suitable case.

Poking the button forces a power-on reset, which you shouldn’t do with the RPi running, lest you trash the filesystem. After shutting down with sudo halt, however, the switch does exactly what’s needed: restarts the CPU from scratch.

The RPi draws little enough power that there’s no point in actually pulling the plug; stressing that Micro-B connector is definitely a Bad Idea.

2016-02-07
Hollow State Electronics: Desk Decorations

I did a lightning talk / show-n-tell last Tuesday at the MHV LUG meeting and covered one end of a table with the Neopixel-lit bulbs & vacuum tubes & hard drive platters I’ve been playing with:

MHVLUG – Hollow State Decorations – Lightning Talk

Some of the posts won’t go live for a week, but here’s a peek into the future:

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

Dang, that came out well…

2016-02-06
Vacuum Tube LEDs: Halogen Lamp Success

The Neopixel-illuminated halogen lamp looks much, much better than I expected:

Vacuum Tube LEDs – halogen lamp – red phase

The ceramic ring screws down around the socket shell and pulls it up against the base; the threads have only as much precision as required to keep it from falling off. I may need to add a leveling shim just so I don’t have to explain why it’s always crooked.

2016-02-05

Author: Ed

Vacuum Tube LEDs: First Light!

Vacuum Tube LEDs: Ersatz Tube Sockets

Sears Sewing Table Hinge Covers

Raspberry Pi: Jessie Lite Setup for Streaming Audio

Raspberry Pi Model B+ Reset Connector

Hollow State Electronics: Desk Decorations

Vacuum Tube LEDs: Halogen Lamp Success