My latest little project was to build something out of a handful of old HP 5082-7302 numeric indicators and my home-made breadboarded (almost) Arduino. These displays are very easy to use once you get past the errors in (some versions of) the datasheet. That is fortunate because they stopped making them a long time ago and there isn’t much information or libraries available for controlling them.
The result was a timer that counts up from zero and with a button for resetting it, and a pair of Arduino libraries. The first library, HPNumberDisplay, can control an array of HP5082-7300/7302 (and probably 7340) displays. The second library, TimeCounter, can count (increment/decrement) time by arbitrary amounts. All source code for the libraries are available here.
I also recorded a short demo using my old camera. The quality could be better. Some day I will buy a proper camera.