Thanks Mark!

I was considering laying a limit switch flat along the outer edge of the disk, and use a notch to catch the limit switch roller. But I'm liking the hall sensor even more:
- no moving parts,
- impervious to dirt or light seepage,
- can sit directly on the PCB,
- lower cost,
- and waaaay less bulky.


Going to try this hall sensor:
https://www.digikey.ca/en/products/d...ULPGM/12165112

And these magnets:
https://www.digikey.ca/en/products/d...c/8189/5400498