SO-100 (SO-ARM100) parts list
The original LeRobot leader and follower arm pair; now deprecated in favor of SO-101 but uses the same servos.
Robot armsbeginner by TheRobotStudio and Hugging Face
Exploded view
Tap any part to see where to buy it. Diagram is schematic, not to scale.
Every part you need
| Part | Qty | Spec | Where to buy |
|---|---|---|---|
| Feetech STS3215 7.4V (C001, 1/345) leader and follower servos | 12 | 7.4V, 19.5 kg.cm stall; SO-100 uses the same servo in all 12 joints; official BOM lists $15/unit (6-pack link) One servo type for both arms keeps ordering simple. | Seeed Studio: $20.00 OpenELAB: EUR 23.57 Akizuki Denshi: JPY 3,200.00 RobotShop: $34.32 Alibaba: check price (unverified) single; BOM link |
| Waveshare Bus Servo Adapter (A) / Serial Bus Servo Driver Board servo bus controller | 2 | USB to TTL bus board with DC jack; Waveshare part 25514; official BOM lists $10.6/unit on Amazon Connects the servo chain to your computer over USB and feeds servo power. | Waveshare: $4.99 Amazon: check price Akizuki Denshi: JPY 1,280.00 The Pi Hut: GBP 4.80 (unverified) |
| USB-C cable, 2-pack USB cables | 1 | USB-A or USB-C to USB-C data cable One cable per controller board to the PC. | Amazon: check price |
| 5V power supply, 5.5x2.1 mm barrel servo power | 2 | 5V barrel supply as linked in the BOM; use a 12V 5A+ supply only if you buy 12V servos Powers the 7.4V STS3215 chain (5V is what the docs use). | Amazon: check price Amazon: check price |
| Table clamps 4-pack mounting | 1 | Small trigger or C clamps Holds the arm base to the desk so it does not tip. | Amazon: check price |
| Precision screwdriver set tools | 1 | Needs Phillips #0 and #1 The M2 and M3 screws use #0 and #1 heads. | Amazon: check price |
Quantities follow the official SO-100 (SO-ARM100) docs: https://github.com/TheRobotStudio/SO-ARM100/blob/main/SO100.md. "Unverified" prices come from search listings or older BOMs that we could not confirm on the seller's product page.
Kits (fewer orders, check what they leave out)
| Kit | Price | Includes | Leaves out | Buy |
|---|---|---|---|---|
| SO-ARM100 Low-Cost AI Arm Servo Motor Kit (no printed parts) Seeed Studio | $200.00 | Servo motors, adapter board, cables | 3D printed parts. Page marks it discontinued and out of stock. | Seeed Studio: $200.00 |
3D printed parts
Needed. PLA+, 0.2 mm layers. SO-100 leader needs gears removed from some servos to make it backdrivable; SO-101 avoids this. Files: https://github.com/TheRobotStudio/SO-ARM100/tree/main/STL/SO100
Mistakes builders make
- SO-100 is deprecated. The same 12 servos also build an SO-101, but SO-101's leader wants three different gear ratios, so you would need 6 new leader servos.
- The old two-arm BOM link sold 6-packs that came bundled with an older driver board the project no longer uses; the single-servo link was cheaper per servo.
- If you buy 12V servos, swap the 5V supply for a 12V 5A+ supply.
- Waveshare ST3215 servos and the Waveshare driver board work with the same LeRobot code as Feetech-branded parts, per the maintainers.
FAQ
How much does it cost to build the SO-100 (SO-ARM100)?
About $232 to $330 in parts at current prices, Two arms. Low end is the legacy BOM total ($232); high end uses US retail servos. Excludes printing, computer, cameras, shipping. SO-100 docs are marked deprecated; new builders should print SO-101 parts..
Do I need a 3D printer for the SO-100 (SO-ARM100)?
Yes. PLA+, 0.2 mm layers. SO-100 leader needs gears removed from some servos to make it backdrivable; SO-101 avoids this.
Is there a kit for the SO-100 (SO-ARM100)?
Yes: Seeed Studio. Check what each kit leaves out before ordering.
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SO-100 (SO-ARM100) vs AR4 (MK5)
SO-100 (SO-ARM100) vs BCN3D Moveo
SO-100 (SO-ARM100) vs Koch v1.1
Last checked 2026-10-25. Sources: github.com · github.com · github.com · github.com · www.seeedstudio.com · www.seeedstudio.com · www.waveshare.com