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
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
// number of LEDs per strip
// 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) {
// Set the mood
void setup() {
digitalWrite(PIN_HEARTBEAT,LOW); // show we arrived
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
// lamp test: run a brilliant white dot along the length of the strip
printf("Lamp test: walking white\r\n");
for (int i=1; i<strip.numPixels(); i++) {
strip.setPixelColor(strip.numPixels() - 1,FullOff);;
// fill the layers
printf(" ... fill using Map array\r\n");
for (int i=0; i < LEDSTRINGCOUNT; i++) { // for each layer
for (int j=0; j < LEDSTRIPCOUNT; j++) { // spread color around the layer
// clear to black
printf(" ... clear\r\n");
for (int i=0; i < LEDSTRINGCOUNT; i++) { // for each layer
for (int j=0; j < LEDSTRIPCOUNT; j++) { // spread color around the layer
// set up the color generators
MillisNow = MillisThen = millis();
randomSeed(MillisNow + analogRead(7));
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) {
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
MillisThen = MillisNow;
view raw MultiTube.ino hosted with ❤ by GitHub

6 thoughts on “Vacuum Tube LEDs: First Light!

  1. Pretty! I like that the bases are translucent too, but it would be interesting to see one in black so most of the light is coming from the tube.

    1. I have both black and natural PETG in the drawer, cued behind the last of the cyan. I’ll start with natural (think “ceramic”) sockets, then drop a brass tube down the hole for directed light …

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