Motors · Leader arm
Motor 2 · shoulder lift
Shoulder lift. Motor 2's joint. It raises and lowers the upper arm.Source: lerobot/docs/source/so101.mdx#2-set-the-motors-ids-and-baudrates · lerobot/docs/source/so101.mdx#joint-2
shoulder lift
Shoulder lift. Motor 2's joint. It raises and lowers the upper arm.Source: lerobot/docs/source/so101.mdx#2-set-the-motors-ids-and-baudrates · lerobot/docs/source/so101.mdx#joint-2Which motor goes here
- Use the motor you labelled 2. It must be a STS3215 motor, gear, code C001.
1:345
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_lift · bus ID 2 · STS3215 1:345
- Default part: Feetech STS3215 servo, 7.4V, 1:345 gear (C001)
servo-sts3215-c001-345 - Standard: Feetech STS3215 servo, 7.4V, 1:345 gear (C001)
servo-sts3215-c001-345, 7.4V servo, 5V supply. Leader arm is always 7.4V on the 5V supply; no 12V variant exists for it (README).
Steps for this motor
- L-014 Add the shoulder motor holder
- L-020 Fit both horns on motor 2 (shoulder lift)
- L-021 Slide motor 2 in from the top and fasten
- L-022 Attach the upper arm to the motor 2 horns
Sources (4)
- lerobot/docs/source/so101.mdx#step-by-step-assembly-instructions — leader table row "Shoulder Lift": motor 2, 1 / 345
- wiki.seeedstudio.com (retrieved 2026-09-07) — servo table: L2 = 1:345
- SO-ARM100/README.md#sourcing-parts — leader bundle footnote
- SO-ARM100/README.md#sourcing-parts — 7.4V servos; 5V power supply