SO-ARM100 Track Axis

Summary

This project is related to the SO-ARM100 robot arm and LeRobot

It provides an additional axis, using the same STS3215 servo.

The carriage comes in 2 Versions: 1) Direct Drive (best for leader with encoders or higher precision) 2) Additional gear for twice the speed

Hardware

• 1 x FeeTech STS3215 Servo (same as SO-ARM100)
• 8 x 624 Bearing (ID: 4mm / OD: 13mm / H: 5mm)
• 8 x M4 10mm or 12mm machine screws for bearings
• 6 x M3 6mm or 8mm screws for motor bracket
• 4 x drywall screws to mount arm to slide (holes are 3.2mm)
• M3 wood screws to mount rails to wooden base

The "Fast" version with additional gear additionally needs:

• 2 x 624 Bearing (ID: 4mm / OD: 13mm / H: 5mm)
• 1 x 4mm rod, ca. 35mm, longer is fine

Drive Gear Specs

• Modulo: 1.5
• Pressure Angle: 20
• 18 Teeth
• Height: 14mm

Code

The servo can give current feedback. This is used to home the axis and find the length of the track. A small python program demonstrates this and also shows how to keep track of multiple servo rotations.

• Find end of track
• Find home position
• Move to 10% and 90% of track length
• Move to middle

Images

Video: https://youtu.be/PuqxYcexV3M