Motors · Leader arm
Motor 4 · wrist flex
Wrist flex. Motor 4's joint. It bends the wrist.Source: lerobot/docs/source/so101.mdx#2-set-the-motors-ids-and-baudrates
wrist flex
Wrist flex. Motor 4's joint. It bends the wrist.Source: lerobot/docs/source/so101.mdx#2-set-the-motors-ids-and-baudratesWhich motor goes here
- Use the motor you labelled 4. It must be a STS3215 motor, gear, code C046.
1:147
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: wrist_flex · bus ID 4 · STS3215 1:147
- Default part: Feetech STS3215 servo, 7.4V, 1:147 gear (C046)
servo-sts3215-c046-147 - Standard: Feetech STS3215 servo, 7.4V, 1:147 gear (C046)
servo-sts3215-c046-147, 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-040 Fit both horns on motor 4 (wrist flex)
- L-041 Slide motor holder 4 onto the forearm
- L-042 Slide in motor 4 and fasten
- L-052 Secure the wrist to the motor 4 horns
Sources (4)
- lerobot/docs/source/so101.mdx#step-by-step-assembly-instructions — leader table row "Wrist Flex": motor 4, 1 / 147
- wiki.seeedstudio.com (retrieved 2026-09-07) — servo table: L4 = 1:147
- SO-ARM100/README.md#sourcing-parts — leader bundle footnote
- SO-ARM100/README.md#sourcing-parts — 7.4V servos; 5V power supply