Part list to make project:

1. Arduino UNO https://amzn.to/2P58O7s

2. Nixie tube 6 pcs https://amzn.to/3aHyJvX

3. Opto coupler chip TLP627

4. DC step-up module from 12VDC to 390VDC https://amzn.to/3aHyJvX

5. Breadboard https://amzn.to/3aHyJvX

6. Real time clock module DS3231 https://amzn.to/3aHyJvX

The circuit uses opto-isolation chip to control Nixie tube (using 150VDC) by Arduino (using 5VDC). By matrix connection, so we need only 16 outputs from Arduino to control 60 lights of 6 nixie tube.

The real time clock module DS3231 is used to keep the time (even turn off power), it is communicated with Arduino by I2C network.

Arduino will read real time, then turn on/off nixie lights by sequence in high frequency to make human eyes view 6 numbers as permanent

Basically, the code will get real time from module DS3231 and show to 6 nixie tube via opto-isolation chip.

Code and circuit can be downloaded here:
http://bit.ly/2tUWtMy

This is just experiment, so I made everything in bread board. Fortunately, it works at first time, no any problem

In next project, I will try to make nixie clock in MDF case with good decoration, so I can put it in my room.