Mark Smith has been working on a HAT for the Raspberry Pi that can drive two IN-9 or IN-13 linear Nixie tubes:
This project as described in www.surfncircuits.com came about because I needed a retro looking linear meter for my espresso maker water tank. I’m always running out of water in my espresso maker, and a cool display letting me know how much water is left and to let me know when to fill it up is definitely needed. In this project, I’ll create a HAT for the Raspberry Pi that can drive two IN-9 or IN-13 linear Nixie tubes. While I’m using this HAT as a single water meter display, this same linear display would be great for showing temperature, bar graphs, audio VU meters, even surf heights by days of the week. The Nixie Tube Power Supply, designed in an earlier blog will work perfectly to drive up to four of the IN-13 Nixie tubes or one IN-9 Nixie tube.