Like many people I enjoy the look of nixie tubes. I was looking for controllers for them, but really all that's available is the 74141 which is mostly only available second hand or from old russian stockpiles. I wanted something that added a bit more control for these old tubes that might be a bit simpler to work with.
The circuit was simple enough. A bunch of NPN transistors and an atmega 328. I've set it up to be able to use I2C for control and broke out a few extra I/O pins. The transistors I decided to try out are the MMBTA42. rated to 300V so they should be able to handle the voltage in nixies without a problem.
To get started however, I needed a power supply so I wipped up something with parts from the junk pile. It's a 240VAC step-up transformer with a pair of 0A2 tubes in series to give me a 150 volt and 300 volt tap at about 20mA total. Good enough for prototyping with my IN-2 tubes.
Also its super safe. Who cares if mains and 300V rails are floating all over the place.
The boards came in and I got lots of SMD soldering practice. On a completely unrelated note, I think my next project is going to be a reflow oven.
I wipped up some quick arduino code to cycle through all the digits to test the circuit design and everything worked out just fine. Now I need to clean up the code, add in some of the functionality I'd been planning and work on the next revision.