Position drift solution

[friendlyFriend4000]

Limit switches would solve the issue of position drift: when the motor disengages, the gears move a bit releasing the string tension. That movement is not registered by the controller. Also, if someone moves the shade manually, the limits currently need to be reset because manual motion is also not registered by the MCU.

may I suggest another approach to solve the problem of position drift. Worm gears have the feature of "locking" when the motor is turned off. The downside is that the blinds will move slower, though.

[apanteleev]

Thanks for the suggestion, but your solution also has issues. The most important one is that I think it's important to be able to move the shade manually, for example in case of a power outage. Also, worm gears have much higher friction than bevel gears, which will probably make the 3d printed gears wear quicker - although I admit I have no experience with such gears.

Based on using this shade controller for almost a year, I can say that position drift is not a big issue. I didn't have to adjust the limits in months.