HOPEJr Teleop Arm
B✓ Links verified May 19, 2026
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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/LICENSEin 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
🖨 Print Files (13)
left_shoulder.stl
right_shoulder.stl
left_humeral.stl
right_humeral.stl
left_forearm.stl
right_forearm.stl
left_hand.stl
right_hand.stl
spoolcover.stl
left_exo.stl
right_exo.stl
left_glove.stl
Required Hardware
| Item | Qty | Unit Cost | Notes |
|---|---|---|---|
| Feetech SCS0009 servo | 16 | $9 | Hand fingers/thumb |
| Feetech STS3250 servo | 2 | $40 | Shoulder/elbow |
| Feetech STS3215 12V servo | 4 | $25 | Arm |
| Feetech SM8512BL servo | 1 | $80 | Shoulder pitch |
| URT-1 servo bus board | 1 | $20 | Arm bus |
| Waveshare servo driver | 1 | $15 | Hand |
| 12V 5A power supply | 1 | $20 | Arm rail |
| 5V 4A power supply | 1 | $15 | Hand rail |
| USB-C to USB-A cable 3m | 2 | $10 | Host link |
| M2 screw set | 1 | $10 | Hand fasteners |
| M4 nut + screw assortment | 1 | $15 | Arm fasteners (25-65mm) |
| M6 35mm screws + spacers | 1 set | $8 | Mount |
| Bearing 10x70x90mm | 1 | $25 | Wrist |
| Bearing 50x65x7mm | 1 | $15 | Shoulder |
| Bearing 20x27x4mm | 18 | $2 | Joints |
| 15x0.3x3mm springs (set of 10) | 1 | $5 | Tendon return |
| 20x0.3x3mm springs (set of 10) | 2 | $5 | Tendon return |
| 0.33mm steel wire (63 LB) spool | 1 | $10 | Tendon |
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