Leader arm · Step 3 of 26 · L-003

Plug one 3-pin cable into each motor before building

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Plug one 3-pin cable into each motor now; the cable is hard to reach once the arm is built.
src
- title — Plug one 3-pin cable into each motor before building
- lerobot/docs/source/so101.mdx#clean-parts — "It is advisable to install one 3-pin cable in the motor after placing them before continuing assembly."
- F-002 · warnings — Set IDs now: "it will be troublesome to disassemble and assemble the servo cable after assembly" (Waveshare). · Waveshare board: both jumpers on the B (USB) channel (LeRobot). · Supply voltage follows the motor variant, never a single value: 5V for the standard 7.4V STS3215; 12V 5A+ only if the optional 12V follower motors are fitted (README, D-002).
Leave the other end loose. The motors are chained together at the very end of the build.
src
- check — Every motor has one cable fitted; cables not yet daisy-chained.
- F-071 · title — Daisy-chain the motor cables and connect motor 1 to the board

Done when Every motor has one cable hanging from it.

Upstream numbers the follower's steps; this leader step is the same build step (extends F-003).

lerobot/docs/source/so101.mdx#clean-parts"It is advisable to install one 3-pin cable in the motor after placing them before continuing assembly."

waveshare.comFollower step 1: "plug the connecting wires into the two ports of servo No. 1"

Check: Every motor has one cable fitted; cables not yet daisy-chained.

You need

STS3215 motor, 1:345 gear, code C001Feetech STS3215 servo, 7.4V, 1:345 gear (C001) servo-sts3215-c001-345
approximation3D stand-in
Stand-in shape: the 3D geometry or placement is not measured from the real part.
Qty 7 is the two-arm build (6 follower + 1 leader). A 12V variant with 30 kg.cm stall exists for the follower only and needs a 12V 5A+ supply (README). Includes two horns and a 3-pin cable per the assembly texts; kit contents are not itemised upstream. Geometry: the upstream repo's own simplified body `STEP/SO100/STS3215_03a.step` (Apache-2.0, single solid drawn to the datasheet, D-007 for where they differ) with its fused horn plates cut off and the datasheet ø6 x 3.4 output boss added, posed on the embedded vendor model's transform; the vendor mesh is not redistributed.
details
STS3215 motor, 1:191 gear, code C044Feetech STS3215 servo, 7.4V, 1:191 gear (C044) servo-sts3215-c044-191
approximation3D stand-in
Stand-in shape: the 3D geometry or placement is not measured from the real part.
Geometry: the upstream repo's own simplified body STEP/SO100/STS3215_03a.step (Apache-2.0, D-007) with its fused horn plates cut off and the datasheet ø6 x 3.4 boss added, posed on the embedded vendor model's transform; the vendor mesh is not redistributed.
details
STS3215 motor, 1:147 gear, code C046Feetech STS3215 servo, 7.4V, 1:147 gear (C046) servo-sts3215-c046-147
approximation3D stand-in
Stand-in shape: the 3D geometry or placement is not measured from the real part.
Geometry: the upstream repo's own simplified body STEP/SO100/STS3215_03a.step (Apache-2.0, D-007) with its fused horn plates cut off and the datasheet ø6 x 3.4 boss added, posed on the embedded vendor model's transform; the vendor mesh is not redistributed.
details
3-pin motor cable3-pin servo bus cable servo-cable-3pin
unverifiedno source yet
Not checked yet: no public source confirms this. Treat it as a best guess and report what you find.
Used to daisy-chain motors and reach the controller board. Not itemised in the README BOM; the assembly texts assume they come with the servos. Qty 6 per arm = the six cable bodies (Component1–4, 6, 7) plus two 050375033 connector housings modelled in SO101 Assembly.step; kit-shipped count still unsourced.
details

Sources (2)

Upstream numbers the follower's steps; this leader step is the same build step (extends F-003).

lerobot/docs/source/so101.mdx#clean-parts — "It is advisable to install one 3-pin cable in the motor after placing them before continuing assembly."
waveshare.com (retrieved 2026-09-07) — Follower step 1: "plug the connecting wires into the two ports of servo No. 1"