Home-made spindle encoders can be as simple as a slotted disc with 3 x opto sensors (like:
www.amazon.co.uk/YOUMILE-Optocoupler-Sen...rduino/dp/B07TZ78N8W
)
You need to make one slot a bit deeper so that only the index sees it, and arrange the others around the perimiter so that they are N + 0.25 apart. (not N + 0.5 as I once did when making an encoder)
