There’s something charming about the clash between obsolete and modern technology. I hadn’t heard of Numitron tubes until a few months ago (when I watched this video by Alec from Technology Connections), but I’ve been looking for an excuse to make something with Nixie tubes for a long time now, as they’re such a unique way to display data.

While the glow and the general tubiness of the Nixies and Numitrons look similar, they rely on quite different technologies. Nixies came first, arriving on the scene in the mid-1950s. Known more formally as cold-cathode displays, they use the same physics as neon lights to produce their glow. The tubes typically contain a series of stacked cathodes shaped to form the numbers zero to nine, with a mesh grid at the front that serves as the anode. When a relatively high voltage (typically around 170V DC) is applied on one of the cathodes, the neon inside the tube becomes ionised. The free electrons now flowing through the tube collide with the neon atoms that occupy the tube, transferring the kinetic energy of the free electron to one of the electrons orbiting the atom and pushing it into a higher, less stable energy level. When those electrons collapse back to their stable state, they emit a photon, giving the Nixie a warm orange glow.

Numitrons, while a later development, use a much simpler technology to display their numbers: the humble lightbulb filament. While Numitron tubes were quickly superseded by lower-current, more reliable LED seven-segment displays, for a brief period they offered a safe, low-voltage (about 5V) alternative to the Nixie tube.

...read more at raspberrypi.com