Hour meters are common for many types of machinery, because they serve a similar purpose to your car’s odometer. When time running is a more important metric than distance, an hour meter is a good choice. And because they’re common, it is easy to find hour meters in any style you can imagine — both vintage and new. This Instructables tutorial from Gautchh will show you how to convert one into a time tracker for your work or leisure activities.

You could, of course, just use an app or a stopwatch to track your time, but this is much more appealing. The idea is simple: a specific action on your computer triggers the device and it will continue ticking up until another action triggers it to stop. Gautchh provides a Python script that triggers the meter when a specific process runs or stops. The user can choose the process, which should correspond to whatever software they want to track. For it to work properly, however, that process can’t run in the background when the user isn’t actively using the software.

On the hardware side, an Arduino Nano board will accept commands from the connected PC via the serial connection and will control the hour meter. If you buy the same hour meter as Gautchh, you can follow their instructions and use their code. If you buy another model, you may need to perform some reverse-engineering to figure out the control signals and tweak the code. A simple 3D-printed enclosure houses the meter and the Arduino, putting them in a compact package that can sit unobtrusively on a desk.