Feetech STS3215 serial bus servo
by Feetech. Used in 7 builds listed here.
Where to buy
Seeed Studio: $20.00 Seeed Studio: $21.99 Seeed Studio: $20.00 Seeed Studio: $22.00 RobotShop: $34.32 RobotShop: $31.71 OpenELAB: EUR 23.57 Akizuki Denshi: JPY 3,200.00 Alibaba: check price (unverified) single; BOM link
Specs
| interface | TTL half-duplex serial bus, daisy-chained 3-pin |
| encoder | 12-bit magnetic, 4096 steps per turn |
| case | standard size, dual-axis horns |
| voltage_classes | 7.4V class (4 to 7.4V) and 12V class (6 to 12.6V) |
Variants (pick the right one)
- code: C001, voltage: 7.4V, gear: 1/345, stall_torque: 19.5 kg.cm at 7.4V, typical_use: SO-101 follower, SO-101 leader shoulder lift, SO-100, Moss
- code: C044, voltage: 7.4V, gear: 1/191, stall_torque: 27.4 kg.cm at 7.4V (vendor sheets), typical_use: SO-101 leader base pan and elbow
- code: C046, voltage: 7.4V, gear: 1/147, stall_torque: 14.4 kg.cm at 7.4V, typical_use: SO-101 leader wrist flex, wrist roll, gripper
- code: C047 / C018, voltage: 12V, gear: 1/345, stall_torque: 30 kg.cm at 12V, typical_use: SO-101 Pro follower, LeKiwi 12V, XLeRobot, HopeJR arm
Mistakes to avoid
- Gear ratio is not printed on most retail listings; check the C-code (C001, C044, C046, C047) before you buy.
- 7.4V servos run from a 5V supply in the LeRobot docs; never feed them 12V.
- New servos all ship as ID 1. Set IDs one at a time with only that servo on the bus.
- RobotShop's 7.4V listing does not name the gear ratio; its 19 kg.cm rating matches C001.
Builds that use it
SO-100 (SO-ARM100)
The original LeRobot leader and follower arm pair; now deprecated in favor of SO-101 but uses the same servos.
SO-101 (SO-ARM101)
Low-cost 3D printed 6-DOF arm pair (leader plus follower) for teleoperation and imitation learning with LeRobot.
Moss v1
Metal-bracket STS3215 leader and follower arms for LeRobot; still supported but deprecated in favor of SO-100/SO-101.
LeKiwi
Three-wheel omnidirectional base carrying an SO-101 arm, with a Raspberry Pi 5 and two cameras, for mobile manipulation.
XLeRobot
Dual-arm household mobile robot built from two SO-101 arms, a LeKiwi-style base and an IKEA cart, starting near $660.
HopeJR Arm (with Homunculus teleop)
Human-scale arm with a tendon-driven dexterous hand, plus a hall-sensor exoskeleton and glove for one-to-one teleoperation in LeRobot.
Open Duck Mini v2
A 42 cm 3D printed biped inspired by Disney's BDX droid, walking with reinforcement learning policies on a Pi Zero 2W.