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.

The New Hotness

  • 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),$fn=CapSides); // cos() fixes slight undersize vs cylinder
    cylinder(d1=(CapSize[OD] + 2*3*ThreadWidth),d2=CapSize[OD],h=1.5*Pixel[LENGTH],$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),$fn=CapSides);
    translate([0,0,(CapSize[LENGTH] – CapTube[OD]/(2*cos(180/8)))]) // hole for brass tube holding wire loom
    rotate([90,0,0]) rotate(180/8)
    PolyCyl(CapTube[OD],CapSize[OD],8);
    }
    }
    //———————-
    // Aperture for USB-to-serial adapter snout
    // These are all magic numbers, of course
    module USBPort() {
    translate([0,28.0])
    rotate([90,0,0])
    linear_extrude(height=28.0)
    polygon(points=[
    [0,0],
    [8.0,0],
    [8.0,4.0],
    // [4.0,4.0],
    [4.0,6.5],
    [-4.0,6.5],
    // [-4.0,4.0],
    [-8.0,4.0],
    [-8.0,0],
    ]);
    }
    //———————-
    // Box for Leviton ceramic lamp base
    module LampBase() {
    Bottom = 3.0;
    Base = [4.0*inch,4.5*inch,20.0 + Bottom];
    Sides = 12*4;
    Retainer = [3.5,11.0,1.0]; // flat fiber washer holding lamp base screws in place
    StudSides = 8;
    StudOC = 3.5 * inch;
    Stud = [0.107 * inch, // 6-32 mounting screws
    min(15.0,1.5*(Base[ID] – StudOC)/cos(180/StudSides)), // OD = big enough to merge with walls
    (Base[LENGTH] – Retainer[LENGTH])]; // leave room for retainer
    union() {
    difference() {
    rotate(180/Sides)
    cylinder(d=Base[OD],h=Base[LENGTH],$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([2*ThreadWidth,0.9*Nut[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([2*ThreadWidth,0.9*Pixel[OD],(Pixel[LENGTH] – ThreadThick)],center=true);
    }
    }
    }
    //———————-
    // Build it
    if (Layout == "Cap") {
    if (Section)
    difference() {
    Cap();
    translate([-CapSize[OD],0,CapSize[LENGTH]])
    cube([2*CapSize[OD],2*CapSize[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");
    }