HOPEJr Teleop Arm

HOPEJr — Open-Source Humanoid Teleop Arm

HOPEJr is an open-source DIY humanoid robot with dexterous hands, originally designed by Rob Knight and significantly advanced by Martino Russi at Hugging Face. This program packages the Arm + Exoskeleton teleoperation kit — the most recent and most accessible entry point into the HOPEJr project.

What you're building

Two paired devices:

• Arm — a pair of humanoid arms (shoulder → humeral → forearm → hand) driven by STS8215 smart serial servos. Hands have underactuated DIP joints and opposable thumbs, with tendons driven by spools for near-linear finger position control.
• Exoskeleton — a wearable that mirrors the arm's kinematics joint-for-joint. Each DOF uses a diametric Hall encoder, so putting on the exoskeleton gives you instant 1:1 teleoperation of the HOPEJr arm with no calibration dance.

The teleop pair is wired up through a set of custom PCBs that daisy-chain motors and encoders — no soldering required for assembly.

Why it matters

Most humanoids cost $50k+. HOPEJr's design goal is explicit: produce a "DIY population of humanoid robots" cheap enough that hobbyists can build one, and use AI to close the gap that low-cost hardware creates. From Rob Knight's own words in the repo:

3D printed plastic robots offer tremendous precision but significantly lower stiffness... we know it's possible to learn how to control a bouncy system and we know they're lower cost. All that's missing are the plans and instructions to build a DIY population of humanoid robots.

What you can do with it

• Imitation learning via LeRobot — record, train, and run inference on HOPEJr episodes just like any other LeRobot-compatible robot.
• Bilateral teleop — operator wears the exoskeleton, robot arms mirror every joint in real time, including the hand.
• Dual-arm manipulation research — full underactuated hand means you can study grasping, tool use, and bimanual tasks without a six-figure robot.

Parts (this program)

• 9 arm STLs (left + right shoulder, humeral, forearm, hand, spool cover)
• 4 exoskeleton STLs (left + right exo and glove)

The full humanoid lives in the upstream repo under Humanoid/ — that's another ~160 STLs covering the torso and legs. Start here first.

Attribution & license

• Designers: Rob Knight (original humanoid) and Martino Russi / Hugging Face (current arm + exoskeleton)
• Upstream repo: https://github.com/TheRobotStudio/HOPEJr
• License: Apache 2.0 (see Humanoid/LICENSE in upstream)
• Community: WhatsApp · Discord

Links

• Upstream: https://github.com/TheRobotStudio/HOPEJr
• Project Homunculus (exoskeleton lineage): https://github.com/nepyope/Project-Homunculus
• LeRobot integration: https://github.com/huggingface/lerobot