HopeJR Arm (with Homunculus teleop) parts list

Human-scale arm with a tendon-driven dexterous hand, plus a hall-sensor exoskeleton and glove for one-to-one teleoperation in LeRobot.

Humanoidsadvanced by TheRobotStudio and Hugging Face

Total parts cost: $650 to $1,100 (cheapest listed sellers add up to about $264)

Rough estimate from servo prices found (16 SCS0009, 2 STS3250, 4 STS3215 12V, 1 SM8512BL) plus fasteners, bearings and PCBs; no official total. Covers one arm, hand and the teleop exoskeleton. The full humanoid body has no public BOM.

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 SCS0009 hand servos	16	6V, 2.3 kg.cm micro serial servo; 3 fingers with thumb, 4 for the thumb Tiny servos pull the finger tendons.	Alibaba: check price (unverified) single; BOM link AIFIT Lab: $15.00 (unverified) Switch Science: JPY 1,738.00 (unverified)
Feetech STS3250 arm servos (shoulder yaw, elbow flex)	2	12V, 50 kg.cm class, 1/345 High torque for the big arm joints.	Alibaba: check price (unverified) single; BOM link OpenELAB: EUR 75.85 (unverified)
Feetech STS3215 12V arm servos	4	12V, 30 kg.cm Remaining arm and wrist joints.	Alibaba: check price (unverified) single; BOM link Seeed Studio: $22.00 RobotShop: $31.71
Feetech SM8512BL arm servo (shoulder pitch)	1	12V, 85 kg.cm brushless; vendors list it as an RS485 servo Holds the whole arm's weight at the shoulder.	Alibaba: check price (unverified) single; BOM link AIFIT Lab: $212.00 (unverified)
Feetech FE-URT-1 USB to TTL/485 board arm bus controller	1	Talks to both the TTL and RS485 servos in the arm.	Seeed Studio: $10.00 AliExpress: check price (unverified) single; BOM link
Waveshare Serial Bus Servo Driver Board hand bus controller	1	Drives the 16 hand servos.	Waveshare: $4.99 Amazon: check price Akizuki Denshi: JPY 1,280.00
12V 5A power supply with DC adapter arm power	1	Arm servos.	Amazon: check price
5V 4A power supply hand power	1	Hand servos.	Amazon: check price
USB-C to USB-A cable, 3 m USB cables	2	Arm and hand boards to PC.	Amazon: check price
M2 screw set fasteners (hand)	1		Amazon: check price
M4 nut set fasteners (arm)	1		Amazon: check price
M4 x 65 mm screws fasteners (arm)	6	2 upper shoulder, 2 armpit, 2 wrist	Amazon: check price
M4 x 50 mm screw fasteners (arm)	1	Humeral	Amazon: check price
M4 x 45 mm screw fasteners (arm)	1	Humeral	Amazon: check price
M4 x 35 mm screw fasteners (arm)	1	Humeral	Amazon: check price
M4 x 30 mm screws fasteners (arm)	3	1 humeral, 2 lower shoulder	Amazon: check price
M4 x 25 mm screw fasteners (arm)	1	Upper elbow	Amazon: check price
M6 x 35 mm screws fasteners (arm)	4	2 elbow, 2 shoulder	Amazon: check price
M6 spacer set fasteners (arm)	1	2 elbow, 2 shoulder	Amazon: check price
Bearing 10 x 70 x 90 mm (width x ID x OD) bearings	1	Wrist	Amazon: check price
Bearing listed as 50 x 65 x 7 mm bearings	1	Shoulder; BOM column order differs here, likely ID 50, OD 65, width 7	Amazon: check price
Bearing listed as 20 x 27 x 4 mm bearings	18	Arm; likely ID 20, OD 27, width 4	Amazon: check price
Spring 15 x 0.3 x 3 mm (L x wire x OD) finger springs	1 set of 10	3 thumb, 2 fingers with thumb Returns fingers to open.	AliExpress: check price (unverified) 10 pcs; BOM link
Spring 20 x 0.3 x 3 mm finger springs	2 sets of 10	Fingers with thumb	AliExpress: check price (unverified) 10 pcs; BOM link
Braided line 0.33 mm, 63 lb tendons	1	Finger tendons.	AliExpress: check price (unverified) spool; BOM link
PTFE tube tendon guides	1	3D printer PTFE tubing Low-friction tendon routing.	Amazon: check price
Finger protectors finger pads	5	Grip surface on fingertips.	Amazon: check price
M3 screw set teleop: fasteners	1	Homunculus exoskeleton	Amazon: check price
Bearing 6 x 10 x 3 mm teleop: bearings	10	2 per upper-arm joint	Amazon: check price
20 mm velcro straps teleop: straps	6	2 forearm, 2 shoulder, 2 half-torso length Holds the exoskeleton on the operator.	Amazon: check price
3 x 2 mm diametrically magnetized N38 disc magnet teleop: encoder magnets	23	1 per joint Read by hall sensors for joint angles.	Umagnets: check price (unverified)
SS49E linear hall sensor teleop: hall sensors	28	1 per hand/wrist joint, 2 per upper-arm joint Angle sensing in the glove and exoskeleton.	Amazon: check price
JST 3-pin cables, 10 cm teleop: sensor cables	1 set of 10		AliExpress: check price (unverified) 10 pcs; BOM link
JST 3-pin same-direction cables, 15 cm teleop: sensor cables	1 set of 10		AliExpress: check price (unverified) 10 pcs; BOM link
JST 3-pin same-direction cables, 20 cm teleop: sensor cables	2 sets of 10		AliExpress: check price (unverified) 10 pcs; BOM link
JST 3-pin same-direction cables, 30 cm teleop: sensor cables	1 set of 10		AliExpress: check price (unverified) 10 pcs; BOM link
Custom connector and homunculus PCBs (assembled) teleop: PCBs	1	Order from JLCPCB with the repo's gerber, BOM and POS files Makes the exoskeleton solder-free.	JLCPCB: check price (unverified) order with repo files

Quantities follow the official HopeJR Arm (with Homunculus teleop) docs: https://github.com/TheRobotStudio/HOPEJr/blob/main/Arm/BOM.md. "Unverified" prices come from search listings or older BOMs that we could not confirm on the seller's product page.

3D printed parts

Needed. Arm and exoskeleton prints; STEP files in Arm/STEP. No threaded inserts: all joints use bolts. Files: https://github.com/TheRobotStudio/HOPEJr/tree/main/Arm/3dprint%20files

Mistakes builders make

The README mentions an STS8215 for the shoulder while the BOM lists an SM8512BL; confirm with the repo before buying the most expensive servo.
The SM8512BL is sold as an RS485 servo while the STS servos are TTL; the URT-1 board handles both.
Bearing sizes in the BOM do not all use the same column order; check each one against the CAD.
Only the arm and teleop kit have a full BOM. The whole humanoid body does not.
Exoskeleton PCBs must be ordered assembled from the gerber, BOM and POS files; no ready-made purchase link exists yet.

FAQ

How much does it cost to build the HopeJR Arm (with Homunculus teleop)?

About $650 to $1,100 in parts at current prices, Rough estimate from servo prices found (16 SCS0009, 2 STS3250, 4 STS3215 12V, 1 SM8512BL) plus fasteners, bearings and PCBs; no official total. Covers one arm, hand and the teleop exoskeleton. The full humanoid body has no public BOM..