Feetech STS3215 Servo

A serial-bus smart servo from Feetech, the standard joint used in LeRobot's SO-100/SO-101 arms.

The STS3215 is a serial-bus servo (a small joint unit that packages a motor, reduction gears, a position sensor, and a control board together) made by the Shenzhen company Feetech. It measures angle with a 12-bit magnetic encoder, giving 4,096 steps per revolution, and can rotate a full 360°; multiple servos are chained together on a half-duplex serial bus, each with its own ID, and each can report back its position, speed, voltage, current, temperature, and load. It comes in two common power variants, with a stall torque of about 19 kg·cm at 7.4V and about 30 kg·cm at 12V. It's cheap, easy to buy, and simple to wire, which is why Hugging Face's LeRobot chose it for every joint on its open-source SO-100/SO-101 arms — making it the de facto standard for entering low-cost embodied AI, and it also shows up in platforms like Koch and LeKiwi. Its downside is that the plastic gears have backlash, limiting precision and stiffness.

ExampleBuilding an SO-101 requires 12 STS3215 servos (six each for the leader and follower arms); after assembly, each one gets its ID set individually before calibration.

Also called

STS3215, ST3215

Related

Servo (Smart Serial Bus Servo) · SO-100 / SO-101 Arm (LeRobot) · LeRobot (Hugging Face) · ROBOTIS DYNAMIXEL Servo · Magnetic Encoder · Backlash

Sources

Feetech STS3215 Magnetic Encoder 360° Serial bus Servo Evaluation - 飞特 (Chinese)
FeeTech 12V 30kg.cm Magnetic Encoding Servo STS3215 - RobotShop
Testing of Feetech STS3215 Servomotor: Backlash, Repeatability, and Torque - Robo9

As of

2026-09