Four-digit Nixie tube clock with automatic time sync to an NTP source using a Raspberry Pi Zero W. Tube display control and multiplexing done with an AVR ATmega328p that communicates with the Raspberry Pi through an SPI serial bus.
Software and schematics on GitHub https://github.com/eyalabraham/nixie-tube-clock
AVR ATmega328p provides necessary timing functions and display multiplexing and brightness PWM. TTL buffering for 3.3v to 5v logic level conversion. A photo resistor (LDR) is used for ambient light sensing and input to dimming.
Bottom of controller board with Raspberry Pi and 5v regulator.
High voltage power supply built according to https://threeneurons.wordpress.com/nixie-power-supply/
Nixie tube high voltage switching with transistors for anode switches and a Russian K155ID1 / 74141 equivalent BCD decoder
Passive wiring and board for Nixie tubes
IN-14 Russian Nixie tubes
Home made socked for tubes based on ideas from https://threeneurons.wordpress.com/miscellaneous-projects/improvised-tube-sockets/
Schematics and vector board wiring available as PDFs on Google drive: https://drive.google.com/drive/folders/1nii7H3NDByK19VhZ1S-wq9s5eVfae5u6?usp=sharing