Numitron Clock

A post apocalyptic Numitron clock based on Arduino Nano and DS3231

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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

    Jelto10/26/2020 at 18:11 0 comments

    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: 


    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:

    stty -F /dev/ttyUSB0 -hupcl
    echo -n "201026w191020x" > /dev/ttyUSB0

  • Creating the case

    Jelto10/25/2020 at 18:13 0 comments

    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.

  • Replacing tubes

    Jelto10/25/2020 at 18:00 0 comments

    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.

  • Soldering the second pair of Numitrons

    Jelto10/25/2020 at 17:55 0 comments

    The next step was to solder the next pair of Numitrons to the PCB.

    Due to the usage of simple shift registers, the PCBs can be chained together.

  • Soldering the first Numitron pcb

    Jelto10/25/2020 at 17:49 0 comments

    The first step was to solder the Numitron tubes to the pcbs. The PCBs are quite simple and just consist of a pair of shift registers, two tubes and a diode. I found the pcb here.

    After soldering the tubes I connected the Arduino and created the mapping for each number. The mapping can be found in the linked Github repository. The idea is to map the right bitmapping to each number for one tube:

    byte digit[10]= {B00100001, B11111001, B00010101, B10010001, B11001001, B10000011, B00000011, B11110001, B00000001, B11000001};

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