Several years ago I decided to build a 6-digit nixie clock. As a hobby project it took quite some time for me. I hope this guide will provide some helpful information at key points if you have limited access to PCB printing or component markets.
Before beginning:
- Find a reliable tube supplier for your location.
- Select a tube model and find it's datasheet, check voltage range.
- Choose a suitable high voltage power supply design or board. Generally 170V is enough for most of the tubes.
After some research I found a tube vendor which can deliver to Turkey. I purchased a dozen IN-12A nixie tubes and IN-12 / IN-15 / IV-22 sockets. If I remember correctly I paid 2.5 USD for one tube and 1.0 USD for one socket. I bought them in March 2018, today (July 2021) tubes are 12.0 USD, sockets are 2.0 USD.
Nearly one month later I received the package with 4 extra tubes. They were covered in dirt, some of them had mud between their pins. Even today I am not sure if they are salvaged from some Soviet era contaminated scrapyard.
I soldered a 555 timer power supply from basic components. I couldn't find exact parts from local sources and bought 2-3 different inductors, at some point the circuit reached max 180V. First supply board worked for a long time until I shorted it accidently, made a second board with spare parts and added a static cooler to the MOSFET.
This is a personal design choice, you can make one from basic parts or purchase a card from some vendor. If you are concerned about voltage range or you don't have abundant time and patience I recommend buying one.
First supply board with extra symbol tubes
9V IN -> 170V OUT
Second board with cooler
After constructing a sufficient power supply I designed a very redundant tube driver group. High voltage power supply can't run multiple tubes simultaneously, so multiplexing the current is a necessity. There are several methods, I wanted to create some modular high voltage drivers for future projects back then and designed a modular one. Duplicated the driver for each tube. I could have selected a more compact design with much less components, but I didn’t want to permanently connect all 6 tubes to one single board. Again this is a personal design choice.
In my case for every digit 4 bits are needed, I used a pair of CD74HC238E 3-to-8 line decoders for every tube and used high voltage transistors to enable the nixie tube's specific pin/number.
Wired up an Arduino Uno (video)
All 6 boards
I completed the digit drivers and started to implement the main board for MCU. I decided to use an Arduino Mega with an external clock. Simply distributed the pins to cable connections. Until this point I used jumpers or crocodile cables to connect boards together and used breadboards for Arduino IO connections, after completing the main board I pressed flat ribbon cables for every connection.
Normally specialized IDC crimping tools are used for cable connectors, but I used a cheap bench clamp. Tip: small rubber sheets can prevent fractures on connectors
I strongly recommend using properly insulated connections while working with high voltage!
Connected tubes to driver boards with these isolated socket/connectors. Original tube sockets are the best option for maintainability.
Fully assembled. March 2018 to October 2018.
Desk for scale
This is the easy part, at least you can't electrocute yourself.
Arduino Mega just simply applies voltage to each digit. Refreshing all tubes with a proper frame rate creates a solid view. Additionally I used a sound sensor for clock display activation.
Final result
