Numitron Clock
1 year ago | Blogs | by: Jelto

The case consists of a empty 1HE server power supply. To make it a bit more interesting I added some handles, mesh and elements I scraped from an old case I found on the flea market. By assembling the case of the clock I managed to break two of the tubes. The case was quite tight and caused some pressure on the glass tubes.


Luckily I had two spare tubes so I replaced them and added more space in the case. However unsoldering the broken glass tubes was quite stressful.


This project is a Numitron Clock based on an Arduino Nano, a DS3231 RTC, some ws2812b RGB LEDs and four shift registers to drive the Numitron tubes. The clock was built as a cheap and easy alternative to a Nixie clock.


The clock consists of:

  • Arduino Nano
  • Arduino Breakout Shield with terminals
  • DS3231 real-time-clock
  • 6x WS2821 RGB leds
  • 4x Numitron tubes IV-9
  • 4x Shift registers 4049N
  • Old 1HE server power supply

Set the time over serial

To keep the design simple I decided to adjust the time only with a serial command. Most of the logic comes from the DS3231_set example code. The Arduino listens on the serial connection with 9600 baud. It accepts the following string: YYMMDDwHHMMSSx

YY= two digit year (example '20')

MM=two digit month (example '10')

DD=two digit day (example '26')


HH=two digit hour (exampel '19')

MM=two digit minute (example '10')

SS=two digit second (example '20')

x=sparator at the end

Full example would be:


for the 26th of October 2020, 19:10:20

To set the date with a Linux computer just type:

1 year ago | Blogs | by: Jelto

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