alan numitron clock iv6

Last update: Sat Jan 10 23:04:53 2026

README: this is the same board as the Alan numitron clock but with changes on the tubes board to host some Numitron IV6 tubes, and some additional parts to generate the high and low voltage needed.

Presentation

Principle

A clock using the low voltages Numitron IV6 tubes. They need 2 voltages, ~1v and ~20v to shine with all their blue power. So need to generate those voltages too: the high one via those inexpensive voltage boost converter of eBay, the low one with a voltage divider.
I'll also use the occasion to use those addressable WS2812B Leds that are everywhere on internet: much less hardware hassle, it goes to the mCU. And since it was busy doing nothing, that shouldn't be a problem.

Points of interrest

Usage of Numitron IV6

Sink-side driving the tubes 20v with a combo of ULN2803 (NPN darlinton array) and 74xx595 (SIPO)

Play with thoses WS2812B leds

My first blue board

Schematics

Bill of materials

Mandatory:

Numitron tubes IV6 x4

74xx595 SIPO SMD x4

ULN2803 driver SMD SOIC18 x4

Capacitor 1uF SMD1206 x1

Capacitor 22uF SMD x1

Some way to make 20~30v for the IV6 tubes

Optional:

WS2812B RGB led with 1wire x4

Resitor 470ohm SMD1206 x2 (for the colon in the middle)

Led for colon x2

Implementation

Source code

Pictures

The board as of Eagle

And the result from Seeedstudio

Links

Helpful sources

Voltage boost to 30v

Inspiration

that circuit on ebay

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