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: Halogen Lamp Base

    This lamp needs a base for its (minimal) electronics:

    Vacuum Tube LEDs - plate lead - overview
    Vacuum Tube LEDs – plate lead – overview

    The solid model won’t win many stylin’ points:

    Vacuum Tube Lights - lamp base solid model
    Vacuum Tube Lights – lamp base solid model

    It’s big and bulky, with a thick wall and base, because that ceramic lamp socket wants to screw down onto something solid. The screw holes got tapped 6-32, the standard electrical box screw size.

    The odd little hole on the far side accommodates a USB-to-serial adapter that both powers the lamp and lets you reprogram the Arduino Pro Mini without tearing the thing apart:

    Vacuum Tube Lights - USB adapter cutout
    Vacuum Tube Lights – USB adapter cutout

    The sloped roof makes the hole printable in the obvious orientation:

    Lamp Base - USB port
    Lamp Base – USB port

    There’s an ugly story behind the horizontal line just above the USB adapter that I’ll explain in a bit.

    The adapter hole begins 1.2 mm above the interior floor to let the adapter sit on a strip of double-sticky foam tape. I removed the standard header socket and wired the adapter directly to the Arduino Pro Mini with 24 AWG U-wires:

    Lamp Base - interior
    Lamp Base – interior

    I didn’t want to use pin connectors on the lamp cable leads, but without those you (well, I) can’t take the base off without un-/re-soldering the wires in an awkward location; the fact that I hope to never take it apart is irrelevant. Next time, I’ll use a longer wire from the plate cap and better connectors, but this was a trial fit that became Good Enough for the purpose.

    And then It Just Worked… although black, rather than cyan, plastic would look spiffier.

    Bluish phases look icy cold:

    Vacuum Tube LEDs - halogen lamp - purple phase
    Vacuum Tube LEDs – halogen lamp – purple phase

    Reddish phases look Just Right for a hot lamp:

    Vacuum Tube LEDs - halogen lamp - red phase
    Vacuum Tube LEDs – halogen lamp – red phase

    A ring of white double sided foam tape now holds the plate cap in place; that should be black, too.

    The OpenSCAD source code adds the base to the plate cap as a GitHub gist:

    // Vacuum Tube LED Lights
    // Ed Nisley KE4ZNU January 2016
    Layout = "LampBase"; // Show Build Cap LampBase USBPort
    Section = true; // cross-section the object
    //- 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);
    ID = 0;
    OD = 1;
    LENGTH = 2;
    Pixel = [7.0,10.0,3.0]; // ID = contact patch, OD = PCB dia, LENGTH = overall thickness
    //———————-
    // 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),$fn=CapSides);
    translate([0,0,(CapSize[LENGTH] – CapTube[OD]/(2*cos(180/8)))]) // hole for brass tube holding wire loom
    rotate([90,0,0]) rotate(180/8)
    PolyCyl(CapTube[OD],CapSize[OD],8);
    }
    }
    //———————-
    // Aperture for USB-to-serial adapter snout
    // These are all magic numbers, of course
    module USBPort() {
    translate([0,28.0])
    rotate([90,0,0])
    linear_extrude(height=28.0)
    polygon(points=[
    [0,0],
    [8.0,0],
    [8.0,4.0],
    // [4.0,4.0],
    [4.0,6.5],
    [-4.0,6.5],
    // [-4.0,4.0],
    [-8.0,4.0],
    [-8.0,0],
    ]);
    }
    //———————-
    // Box for Leviton ceramic lamp base
    module LampBase() {
    Bottom = 5.0;
    Base = [3.75*inch,4.5*inch,25.0 + Bottom];
    Sides = 12*4;
    Stud = [0.107 * inch,15.0,Base[LENGTH]]; // 6-32 mounting screws, OD = ceramic boss size
    StudOC = 3.5 * inch;
    union() {
    difference() {
    rotate(180/Sides)
    cylinder(d=Base[OD],h=Base[LENGTH],$fn=Sides);
    rotate(180/Sides)
    translate([0,0,Bottom])
    cylinder(d=Base[ID],h=Base[LENGTH],$fn=Sides);
    translate([0,-Base[OD]/2,Bottom + 1.2]) // mount on double-sided foam tape
    rotate(0)
    USBPort();
    }
    for (i = [-1,1])
    translate([i*StudOC/2,0,0])
    rotate(180/8)
    difference() {
    cylinder(d=Stud[OD],h=Stud[LENGTH],$fn=8);
    translate([0,0,Bottom])
    PolyCyl(Stud[ID],(Stud[LENGTH] – (Bottom – Protrusion)),6);
    }
    }
    }
    //———————-
    // 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 == "Build") {
    Cap();
    Spigot();
    }