In a robot arm, small accuracy errors at the ... What if you wanted to go even less expensive than this? You could build a servo out of junk DC motors with a “3 cent” microcontroller, then.

but creating a completely custom servo motor with encoder requires some significant engineering. In the video after the break [365 Robots] takes us through the build process of a closed-loop motor ...

Raspberry Pi HATs offer small, stackable data acquisition with features like analog and digital I/O.