Servos by joint
All servos are Feetech STS3215. The follower uses one gear ratio at every joint; the leader uses three so it holds its own weight yet moves freely. IDs count from the base.
| ID | Joint | Follower | Leader |
|---|---|---|---|
| 1 | shoulder pan | 1:345 c001-345 | 1:191 c044-191 |
| 2 | shoulder lift | 1:345 c001-345 | 1:345 c001-345 |
| 3 | elbow flex | 1:345 c001-345 | 1:191 c044-191 |
| 4 | wrist flex | 1:345 c001-345 | 1:147 c046-147 |
| 5 | wrist roll | 1:345 c001-345 | 1:147 c046-147 |
| 6 | gripper | 1:345 c001-345 | 1:147 c046-147 |
Voltage and supply
- Follower: 7.4V servos on a 5V supply (standard).
- Follower: 12V servos on a 12V 5A+ supply (optional). Optional follower-only variant. SVRC's "12V power supply" applies to this variant only (D-002).
- Leader: 7.4V servos on a 5V supply. Leader arm is always 7.4V on the 5V supply; no 12V variant exists for it (README).
Sources (21)
- lerobot/docs/source/so101.mdx#step-by-step-assembly-instructions — "The follower arm uses 6x STS3215 motors with 1/345 gearing"
- lerobot/docs/source/so101.mdx#2-set-the-motors-ids-and-baudrates — setup script names the joint and assigns id 1 bottom-up
- wiki.seeedstudio.com (retrieved 2026-09-07) — servo table: F1–F6 = ST-3215-C001 1:345
- lerobot/docs/source/so101.mdx#2-set-the-motors-ids-and-baudrates — setup script names the joint and assigns id 2 bottom-up
- lerobot/docs/source/so101.mdx#2-set-the-motors-ids-and-baudrates — setup script names the joint and assigns id 3 bottom-up
- lerobot/docs/source/so101.mdx#2-set-the-motors-ids-and-baudrates — setup script names the joint and assigns id 4 bottom-up
- lerobot/docs/source/so101.mdx#2-set-the-motors-ids-and-baudrates — setup script names the joint and assigns id 5 bottom-up
- lerobot/docs/source/so101.mdx#2-set-the-motors-ids-and-baudrates — setup script names the joint and assigns id 6 bottom-up
- 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
- 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
- lerobot/docs/source/so101.mdx#step-by-step-assembly-instructions — leader table row "Elbow Flex": motor 3, 1 / 191
- wiki.seeedstudio.com (retrieved 2026-09-07) — servo table: L3 = 1:191
- 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
- lerobot/docs/source/so101.mdx#step-by-step-assembly-instructions — leader table row "Wrist Roll": motor 5, 1 / 147
- wiki.seeedstudio.com (retrieved 2026-09-07) — servo table: L5 = 1:147
- lerobot/docs/source/so101.mdx#step-by-step-assembly-instructions — leader table row "Gripper": motor 6, 1 / 147
- wiki.seeedstudio.com (retrieved 2026-09-07) — servo table: L6 = 1:147