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Beginner build

How to build SO-101

6-DoF desktop robot arm · Beginner

Build the SO-101, The Robot Studio and Hugging Face's LeRobot arm with Feetech STS3215 servos and simpler wiring than the SO-100, about $121 per arm.

Start the buildProject files
Difficulty
Beginner

Mostly printed parts and plug-in servos. Good first build.

Build time
1–2 weekends

Our estimate, part-time

Parts cost
$121

≈$121 per arm (source BOM)

Degrees of freedom
6

Apache-2.0

What is SO-101?

The SO-101 is the second-generation Standard Open arm from The Robot Studio and Hugging Face, and it's LeRobot's default starter arm. It's usually built as a pair: a follower that does the work and a leader you move by hand.

Compared with the SO-100, it routes the wiring so the cables don't snag at the joints, drops the step of removing gears from the leader's servos, and gives the leader motors different gear ratios so it holds its own pose. Many vendors sell parts kits, printed frames or assembled arms.

Versions and forks

  • SO-100
  • LeKiwi and XLeRobot use SO-101 arms
  • Wrist-camera mounts

SO-101 specifications

DoF
6 (5 + gripper)
Follower servos
6 × STS3215, 12 V, 1/345
Leader servos
STS3215, 1/147, 1/191, 1/345 mix
Software
LeRobot
License
Apache-2.0

Figures as published by the project. See Sources below.

Bill of materials

PartQtyNotes
STS3215 (follower)6
STS3215 mixed ratios (leader)6
Motor control board2
USB-C cables2
Power supplies2
Clamps4
Printed frames—
Where's the full bill of materials?

The full BOM, with exact quantities and vendors, lives in the project's own files. Prices change often, so treat $121 as a ballpark from the project. Start at the project repository.

Tools you'll need

  • 3D printer
  • Small Phillips screwdriver
  • LeRobot

Step-by-step build overview

Electronics & wiring overview

Each arm runs one STS3215 bus into a USB-C adapter board with its own supply. The new cable routing avoids pinch points.

DC power supplypower sourceLaptop / PChigh-level controlEncoderssensingMicrocontrollerreal-time controllerServo bus adapterdrivers / busFeetech STS3215 bus s…6 joints / motors
PowerData / commandsSensor feedbackOverview only. Follow the project's own schematic for pinouts and voltages.

Software

LeRobot

LeRobot covers setup, calibration, teleop, recording to the Hub and training.

Tips from the bench

  • ☕ Label the leader servos by gear ratio.
  • ☕ Consider the raised leader base from the optional parts.

SO-101 FAQ

How is it different from the SO-100?

Better wiring, no gear removal for the leader, and updated leader motors.

Can I buy one assembled?

Yes, from vendors such as Seeed, WowRobo and PartaBot.

What software does it use?

LeRobot.

Sources

Written by Bots n' Beans from the project's own documentation. Check the sources for the latest revision before you buy parts.

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