Optical encoder bracket for Parallax Arlobot motors

thingiverse

This device holds a US Digital EM1-500 optical encoder sensor firmly in place over a US Digital HUBDISK-2-500 2" optical disk with a 5/8" bore, which is mounted to a Parallax Arlobot motor mount and wheel kit made of aluminum. It works seamlessly on both right and left motors by simply flipping it vertically. The original Arlobot encoder wheel offers 36 counts per revolution, resulting in 144 counts per revolution with quadrature decoding. In contrast, the EM encoder boasts 500 counts per revolution and 2000 counts per revolution as quadrature, delivering sub-millimeter accuracy. Unfortunately, the Parallax motor lacks a mounting bracket for the EM encoder, prompting me to design this custom bracket. The 3D printed encoder mount is securely held in place horizontally between two posts on the motor. These posts can be spaced 37mm apart with a tolerance of +/- 0.5mm. The encoder mount features a spring clip that accommodates variations in post spacing. Vertical supports at each end press between the top and bottom frames of the motor, firmly holding the encoder mount in place vertically. The encoder holes are carefully designed to be 20mm apart and have a diameter of 3mm, accommodating SAE 4-40 3/4 inch screws. The screw heads are countersunk below the encoder in the 3D printed bracket for added stability. To avoid interference with a motor mount on one side, the bracket is designed to extend only one end of the motor. Conversely, the bracket features a tab that extends beyond the motor on the other side, allowing for easy removal. It's possible that other features may interfere; in such cases, small filing or modifications should resolve any issues. Printing this design takes approximately 50 minutes on my Prusa MK2.