Open-source Nixie Clock Project Using IN-12B Tubes
This is a 6-digit Nixie clock built around IN-12B tubes, with a custom PCB, 3D-printed enclosure, and an ESP32-C3. The idea was to build not just a nice-looking clock using old Soviet-era tubes, but a modern device that can be integrated into a smart home.
What it has:
- Flicker-Free High-Voltage Shift Register Driving — the tubes are driven using HV5222PJ without traditional multiplexing, eliminating the characteristic flicker.
- Smooth brightness control — the display can be very bright during the day or dimmed almost completely at night.
- RGB backlighting for each digit — 2 RGB LEDs are installed under each tube.
- RGB colon — the dots between the digits also have independent RGB control through AW9523B.
- ESPHome + Home Assistant — the clock can be fully integrated with Home Assistant, allowing control of brightness, colors, and effects.
- Battery-backed RTC — the clock keeps track of time even without Wi-Fi or external power.
- NTP synchronization — once connected to Wi-Fi, the time is automatically synchronized.
- USB-C for power and firmware flashing.
- Additional I2C — external sensors such as temperature, humidity, or CO₂ sensors can be connected.
- Custom PCB — all electronics are integrated onto a single board, including the high-voltage converter for powering the Nixie tubes.
- 3D-printed enclosure — the enclosure files are open source as well.
The RGB backlighting can also be used for more than just decoration. For example, you can automatically dim it at night, change the color depending on the time, or use the lighting for notifications from Home Assistant.
The entire project is available on GitHub.
The repository includes the schematics, PCB files, Gerbers, BOM, firmware, and 3D-printable enclosure files. So if you want to build your own, you can order the PCB, get the components, print the enclosure, and reproduce the entire clock.
The main components cost around $150–200, depending on where you source the tubes and other parts.