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Archive for February 10th, 2016

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:

 

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