Motors · Leader arm
Motor 1 · shoulder pan
Shoulder pan. Motor 1's joint, in the base. "Pan" means turning sideways, the way a camera pans; it swings the whole arm left and right.Source: lerobot/docs/source/so101.mdx#2-set-the-motors-ids-and-baudrates
shoulder pan
Shoulder pan. Motor 1's joint, in the base. "Pan" means turning sideways, the way a camera pans; it swings the whole arm left and right.Source: lerobot/docs/source/so101.mdx#2-set-the-motors-ids-and-baudratesWhich motor goes here
- Use the motor you labelled 1. It must be a STS3215 motor, gear, code C044.
1:191
Gear ratio. The number on the motor's label, such as 1:345. The motor inside turns 345 times for one turn of the output. The follower arm uses 1:345 at all six joints. The leader arm mixes 1:191, 1:345 and 1:147, so check the label before fitting a motor.Source: lerobot/docs/source/so101.mdx#step-by-step-assembly-instructions · SO-ARM100/README.md#sourcing-parts - Power it from a 5V supply; that is the supply for the standard 7.4V motor.
- Joint: shoulder_pan · bus ID 1 · STS3215 1:191
- Default part: Feetech STS3215 servo, 7.4V, 1:191 gear (C044)
servo-sts3215-c044-191 - Standard: Feetech STS3215 servo, 7.4V, 1:191 gear (C044)
servo-sts3215-c044-191, 7.4V servo, 5V supply. Leader arm is always 7.4V on the 5V supply; no 12V variant exists for it (README). - Leader arm is always 7.4V (README).
Steps for this motor
- L-010 Fit both horns on motor 1 (shoulder pan)
- L-011 Seat motor 1 in the base
- L-012 Slide the first motor holder over motor 1
- L-013 Attach the shoulder to the motor 1 horns
- L-071 Daisy-chain the motor cables and connect motor 1 to the board
Sources (4)
- lerobot/docs/source/so101.mdx#step-by-step-assembly-instructions — leader table row "Base / Shoulder Pan": motor 1, 1 / 191
- wiki.seeedstudio.com (retrieved 2026-09-07) — servo table: L1 = 1:191
- SO-ARM100/README.md#sourcing-parts — leader bundle footnote
- SO-ARM100/README.md#sourcing-parts — 7.4V servos; 5V power supply