SO-101 Builder's Pack (No Servos): Servo Adapter Board, 12 Metal Horn Sets, Cables, Power Adapter, G-Clamps + Free 3D-Print Files, for SO-ARM100 / SO-ARM101 LeRobot Arms

The SO-101 Builder's Pack is a hardware bundle for people building a LeRobot SO-ARM100 / SO-ARM101 arm from their own STS3215 servos and 3D-printed parts: the USB servo adapter, metal horns, servo cables, power adapter and desk clamps that boxed kits include but nobody sells separately, together with a free download of ArmDojo's SO-101 print files.

Everything around the servos that an SO-101 build needs and that nobody sells as one bag: the USB servo adapter, twelve metal horns, the right cables in the right lengths, a power adapter and the clamps, plus a free download of our 3D-print files. Pair it with a 12-servo STS3215 set and a roll of PLA and you have a complete leader–follower rig for a fraction of a boxed kit.

What can you use it for?

• Completing a Seeed or Feetech 12-servo set into a working leader–follower pair
• Building a second follower arm for bimanual setups
• Classroom builds where students print the parts themselves
• Replacing the miscellaneous hardware after moving a kit between labs

Who is it for?

Makers and labs who already have (or are buying) STS3215 servos and a 3D printer, and want the rest of the bill of materials in one order.

Compatibility

• Arms: SO-ARM100, SO-ARM101 (LeRobot SO-101), leader and follower
• Servos: 6 × Feetech STS3215 per arm (12 V for follower, 7.4 V mix for leader), sold separately as the SO-ARM101 12-servo set
• Software: Hugging Face LeRobot so101 configs; the Waveshare adapter appears as a serial port
• Printing: PLA or PETG, about 1 kg per pair; files download after purchase

Getting started: from unboxing to your first LeRobot dataset

1. Print the parts from the download link in your order email (leader and follower STLs, camera brackets).
2. Set the servo IDs 1–6 with the Waveshare adapter and the Feetech tool before assembly.
3. Fit the metal main + rear horns to each servo and assemble the joints following the SO-101 guide.
4. Wire the chain with the 15 / 20 / 40 cm cables, base servo to the adapter.
5. Clamp the base to the desk with two G-clamps, connect power and USB, and run LeRobot calibration.

Specifications

What's in the box

• One arm (follower or leader): 1 × Waveshare Bus Servo Adapter (A), 6 × STS3215 metal main + rear horn sets with screws, 12 × 3-pin cables (4 × 15, 4 × 20, 4 × 40 cm), 1 × 7.4 V 3 A power adapter, 2 × 2-inch G-clamps, download card for the 3D-print files
• Leader + follower pair: 2 × Waveshare adapters, 12 × horn sets, 24 × cables, 2 × power adapters (7.4 V for the leader, 8.4 V/12 V note for the follower), 4 × G-clamps, download card

Frequently asked questions

What is not included?

The servos and the printed plastic parts. Add the SO-ARM101 12-servo set from this store, print the parts from our free files, and you have a complete pair. Cameras are optional and sold separately.

Which power adapter comes in the pack?

A 7.4 V 3 A adapter for the leader arm. A follower built from 12 V STS3215-C018 servos needs a 12 V 5 A supply; if you tell us at checkout we swap the adapter.

Are the 3D files really free?

Yes. Every Builder's Pack order includes a download link to ArmDojo's SO-101 print files, licensed for personal and educational use.

Is this cheaper than a boxed DIY kit?

Servo set plus Builder's Pack comes to roughly the price of the Hiwonder DIY kit while letting you print the parts in any colour and swap in STS3250 shoulders.