hackaday.io/project/158779-de…
Dexter is an open-source robotic arm mostly made with a 3D printer. It uses 5 NEMA-17 stepper motors to control its 5 axes along with harmonic drives on 3 of them. We put quadrature optical encoders on each axis since stepper motors don't have encoders and they sometimes skip if not strong enough. Having these encoders allows the FPGA microcontroller on Dexter to poll the sensors fast enough and correct the motor's position in real time. Thanks to our gateware, we can poll each axis 5 million times per second, creating a 200 nanosecond feedback loop. Dexter is licensed under GPL3 so the design can be reproduced and modified at will. All of our files are on our OnShape, GitHub, and Thingiverse and a link to the building manual is in the build instructions.