Build the JARY-Bot

The JARY-Bot is an open source educational humanoid. The mechanical structure is 3D printed from files you can download, and the electronics, actuators and hardware come from the Bearbot component kit. Read this whole page before ordering filament — printing is the longest part of the project.

Assign servo bus IDs in this order so the firmware defaults match your build: left leg 1–6, right leg 7–12, left arm 13–15, right arm 16–18 (only 15 actuators are used; unused IDs are skipped in the default configuration).

• 2.0 / 2.5 mm hex drivers
• Small Phillips screwdriver
• Soldering iron with a heat-set insert tip
• Flush cutters and needle-nose pliers
• Digital multimeter
• USB-C cable and a computer
• Calipers (for checking printed tolerances)
• Heat gun or lighter for heat-shrink

1. 01

   Prepare the printed parts

   Deburr every part, clear support material and test-fit each servo body before assembly. Install all M3 heat-set inserts with the soldering iron, keeping them perpendicular to the surface.

2. 02

   ID and centre every servo

   Before mounting, connect each ST3215 to the driver board one at a time, assign its bus ID from the joint map and drive it to its centre position. A servo mounted off-centre cannot be corrected later without disassembly.

3. 03

   Build the legs

   Assemble each leg from the hip outward: Hip Yaw, Hip Roll, Hip Pitch, Knee Pitch, Ankle Pitch, Ankle Roll. Fit nylon washers on rotating faces and use removable threadlocker on the horn screws only.

4. 04

   Assemble the pelvis and torso

   Join both legs to the pelvis, then mount the torso. Route the leg servo bus cables up through the pelvis before closing the torso — leave slack for full hip travel.

5. 05

   Build the arms

   Assemble Shoulder Pitch, Shoulder Roll and Elbow Pitch per side, mount the shoulder brackets to the torso and route each arm bus cable inside the shoulder.

6. 06

   Head, camera and IMU

   Fit the OV5640 into the head housing and connect its ribbon to the ESP32-S3. Mount the MPU6050 rigidly near the centre of the torso with its axes aligned to the robot frame.

7. 07

   Install electronics and power

   Mount the ESP32-S3, servo driver, buck converter and capacitor in the torso. Wire the battery through the XT60, fuse and switch before anything else.

8. 08

   Bench test before standing

   With the robot supported off the floor, power up and sweep every joint through its range. Only stand the robot once every joint direction and limit is verified.

• Battery → XT60 → fuse → main switch → power distribution.
• Servo bus power comes straight from the 7.4 V rail; place the 2200 µF capacitor at the distribution point.
• Buck converter drops 7.4 V to a clean 5 V rail for the ESP32-S3 and camera. Never power 15 servos through the controller board.
• All grounds must be common: battery, buck output, servo bus and controller.
• Servo driver connects to the ESP32-S3 over UART (TX/RX crossed, shared ground).
• MPU6050 uses I²C (SDA/SCL + 3.3 V + GND); keep the run short and away from power wires.
• Check polarity with a multimeter before the first connection — a reversed battery will destroy the controller.

• LiPo batteries can burn: charge in a fireproof bag, never leave charging unattended and never use a swollen pack.
• Fifteen servos can move fast and pinch — keep fingers clear of joints when powered.
• Always power down before connecting or disconnecting a servo on the bus.
• Work over a soft surface and hold or suspend the robot during the first standing tests.
• Adult supervision is required for soldering, heat-set inserts and battery handling.

The JARY-Bot is open source: the printable STL files, firmware and build documentation are shared so you can print, build, modify and learn from the robot. Send us a message and we will point you to the current release of the files and the license terms.