GELLO only drives an existing industrial or research arm and does nothing on its own.
GELLO is a family of small 3D-printed leader arms from UC Berkeley that mirror the joint layout of a full-size robot arm, so moving the GELLO by hand drives the real robot. Each joint holds a cheap Dynamixel servo used mainly as an encoder, and designs exist for Franka, UR5, xArm, YAM, Lite6, AR4 and FR3 arms. It is used to collect demonstrations for robot learning.
At a glance
| Parts cost | $280 (2023) parts list · Parts list totals in the project doc, from $272 for the UR5 version to $288 for the YAM version source ↗ |
|---|---|
| Difficulty | 2/5 Easy · Screws servos to printed links with a short guide. Software setup and the target robot are the real work. |
| Build time | About 30 minutes to assemble (printing extra) source ↗ |
| Tools needed | 3D printer, small Phillips screwdriver |
| Motors | 7 Dynamixel XL330-M288-T (arm) and 1 XL330-M077-T (gripper trigger), used mostly as encoders |
| Controller | ROBOTIS U2D2 with power hub, 5V supply, PC running gello_software |
| Sensors | Servo encoders |
| Published | ✓ Parts list✓ CAD/STL✓ Assembly guide✗ Wiring✓ Software✓ Video GitHub + Google Doc (parts list with prices and assembly steps) + project website + timelapse build video |
| Activity | Last update 2026-09-14 · 551 GitHub stars · The mechanical repo has 342 stars, and the community has added designs for more arms |
| Kits | None known |
Licenses
| Design files | MIT (gello_mechanical repo, STL files) source ↗ |
|---|---|
| Code | MIT source ↗ |
| Documentation | CC BY-SA 4.0 (website footer) source ↗ |
Builder notes
Practical points from the project's issue tracker, forum and docs, each linked to its source.
- GELLO is a controller only. It needs a matching full-size arm (Franka, UR5, xArm and so on) as the follower, which costs far more than the GELLO itself. source ↗
- Since the servos act as encoders, cheaper or easier-to-find XL330-M077 units can replace M288s. Lower gearing gives smoother wrist joints, while higher friction helps steady the base joints. source ↗
- Source CAD is only shared by email on request, and several builders asking for SolidWorks files to adapt GELLO to other arms waited a long time. source ↗
- The Dynamixel screws strip easily, so the guide advises a well-fitting screwdriver. source ↗
- The Trossen braided 450 mm cable listed in the UR5 parts list is no longer available. source ↗
Other arms plans
- MeArm · $40 · difficulty 1/5
- SO-101 arm · $230 · difficulty 2/5
- EEZYbotARM MK2 · $100 (2018) · difficulty 2/5
- Thor arm · $390 · difficulty 4/5
- reBot-DevArm (Seeed Studio) · $1,500 · difficulty 4/5
- OpenArm · $6,500 · difficulty 5/5
- Koch v1.1 arm · $480 (2024) · difficulty 2/5
- ROBOTIS OpenMANIPULATOR-X · $1,600 · difficulty 2/5
- BCN3D Moveo · $430 · difficulty 4/5
- PAROL6 · $970 · difficulty 4/5
- Faze4 robotic arm · $1,000–$1,500 (2020) · difficulty 4/5