Repurposed Russian IV-25 Tubes for Giant VFD Display

It’s always interesting to see what people can create using repurposed materials, and Tony P’s (from idyl.io) giant VFD display is no exception. Tony made his display using a surplus of 75 Russian IV-25 tubes, which can be had by the truckload for ridiculously low prices. Be forewarned though as Tony found out, with any surplus stock, some may not work or are missing parts such as leads.

Each IV-25 tube contains seven small segments and was intended to make bar graph displays, but when stacked side-by-side, they create an 84-pixel display that can double as a scrolling marquee. Tony construct his display using twelve tubes for every section, each with a custom PCB driver board, each with three SN75518 chips with 40-pin DIPs.

To hold the segments together and the tubes aligned in a fixed position, Tony designed brackets using Tinkercad, and 3D-printed them out using a Prusa i3 MK3 printer and painted them matte black, which gives them high contrast when the tubes are lit. As for the rest of the electronics, the display is controlled through an ESP32 module along with an SN74LVC8T245 3.3V to 5V logic converter, 20V boost converter, and 5V buck converter — all stapled together on a protoboard.

As for software, Tony designed a utility that transforms a pixel font into a series of bytes, which allowed him to create a simple text scroller and clock, complete with transition effects. Tony’s VFD Display is still a work in progress, and he hopes code as much software as he can for the ESP32 module before he connects it to a proper motherboard.