Without a doubt, the NixiChron, Nixie tube clock is the quintessential example of original Nixie clock design. Approximately one thousand were produced, and when a rare example comes up for sale, it sells far in excess of its original price.¬†Unfortunately the designer passed away several years ago, and the original microcontroller cannot be replaced. Also, many features common on today’s Nixie clocks are not available on the NixiChron.

The impetus for this project was to design a replacement microcontroller, adding many new features to the NixiChron, and to offer a replacement for original microcontrollers.

Only two small, reversible modifications are necessary to install the NixiChron AVR upgrade, and then it is simply installed in the microcontroller socket.

Features of the upgrade not available with the original microcontroller include:

  • Optional RGB LED lighting with a variety of interesting effects. Brightness and color of each intelligent APA102 RGB light is individually controlled, and custom colors can be set for each hour. Optional RGB LED scrolling with digits. Commonly available light strips are used.
  • Three configurable override periods with independent settings for start and end times, Nixie brightness, RGB LED brightness, RGB colors and patterns, and colon patterns. Each period can be enabled for weekdays, weekends, or both. Period override button restores standard settings for user selectable time period.
  • Real time clock with accuracy to approximately one second per week.
  • Original NIXIECHRON GPS receiver is supported, or substitute an Adafruit, Ublox, or other, TTL level GPS. GPS is no longer required.
  • Automatic time zone setting for Daylight Saving Time. Tables are not used! Month, week, day of week, and time, are used to calculate time changes, for easy updating as rules change.
  • Scrolling date display with three selectable date formats.
  • Scrolling temperature using original sensor, or add a BME280 weather sensor to display temperature, pressure, and humidity.
  • Optional ambient light sensor increases brightness at user configurable setting.
  • Optional PIR sensor enables display only when motion is sensed.
  • Configurable cathode anti-poisoning routing helps to keep tubes in good condition.
  • Option to add two additional buttons for easier setting.
  • Morse code time announcements.

Alarms are not supported because we hate them on Nixie clocks, and no chimes. The 1PPS LED and AM/PM neon are supported.

RGB LED strips, buttons, PIR sensor, ambient light sensor, and other parts to implement additional options are not included, but are easily available.



The NixiChron AVR is completely assembled and tested. The price is $159 plus $10 for USPS Priority shipping. Sales tax is charged for orders shipped within Florida. Contact us for international orders.