Robotic arm motherboard

🦾 5-DOF Robotic Arm Modular Carrier Motherboard

Carrier PCB & Backplane · KiCad 7 / 8 · ESP32 DevKit V1 Socket · PCA9685 Module Socket · Dual VL53L1X ToF · XT30 Power

A professional 100mm × 80mm 2-layer FR4 carrier / motherboard PCB designed to interconnect the electronic modules of the 5-DOF robotic arm without hard-soldering microcontrollers or driver ICs. All commercial off-the-shelf (COTS) modules plug directly into standard 2.54mm female pin headers.

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📐 Board Overview & Specifications

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🧩 Modular Socket Architecture

1. ESP32 DevKit V1 Socket

• Dual 1×15 female socket headers spaced 22.86 mm (0.9") apart with standard 2.54 mm pitch.
• Sockets accept any standard 30-pin ESP32 DevKit V1 board.
• Dedicated antenna keepout zone ensuring zero Wi-Fi / Bluetooth attenuation.
• Dedicated breakout lines for I2C (GPIO21 SDA, GPIO22 SCL), UART (TX0, RX0), and ToF sensor shutdown (GPIO16 XSHUT1, GPIO17 XSHUT2).

2. PCA9685 16-Channel Servo Driver Module Socket & Mount

• Direct Servo Connection: RC servos (MG996R, SG90, DS3218, etc.) plug directly into the PCA9685 module's native 16×3 male header pins. No duplicate servo headers on the carrier motherboard.
• Module connects to the motherboard via a 6-pin control header: GND, OE (Active-Low Output Enable), SCL, SDA, VCC (3.3V), and V+ (Servo Power).
• Accompanied by a custom 3D-printable elevated mounting bracket (pca9685_mount_bracket.stl and pca9685_mount_bracket.scad) that secures the module cleanly above the PCB.

3. Dual VL53L1X Time-of-Flight (ToF) Distance Sensors

• 2× 5-pin headers (J_VL53_1, J_VL53_2): 3V3, GND, SDA, SCL, XSHUT.
• Allows dynamic I2C address reassignment at boot for dual-sensor LiDAR and obstacle ranging.

4. Expansion & Debug Headers

• I2C Expansion (J_I2C_EXP): 4-pin (3V3, GND, SDA, SCL) with 4.7 kΩ pull-ups.
• UART Debug (J_UART): 4-pin (3V3, GND, TX, RX).
• GPIO Breakout (J_GPIO_EXP): 10-pin header exposing spare ESP32 GPIOs for limit switches, encoders, or buttons.
• Safety Controls: Emergency Stop 2-pin header (J_ESTOP) and hardware Servo Enable 2-pin header (J_SRV_EN).
• Status LEDs: 3.3V Power (LED1), Servo V+ Active (LED2), Arm Status (LED3), Fault/Disable (LED4).

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📁 Included Files

• KiCad Design Files:
  • robotic_arm_motherboard.kicad_pcb: PCB layout (tracks, pours, footprints, silkscreen).
  • robotic_arm_motherboard.kicad_sch: Schematic with power, sockets, protection, and decoupling.
  • robotic_arm_motherboard.kicad_pro: KiCad 7/8 project configuration.
• Fabrication & Assembly:
  • robotic_arm_motherboard_gerbers.zip: Ready-to-upload ZIP for JLCPCB, PCBWay, or OSH Park.
  • production_gerbers/: Individual RS-274X Gerber layers and Excellon NC drill files.
  • BOM.csv: Complete bill of materials with references, values, and footprints.
  • robotic_arm_motherboard-pos.csv: Component pick-and-place centroid positions.
  • robotic_arm_motherboard-pcb.pdf: High-resolution vector schematic and layer plots.
• 3D Models:
  • robotic_arm_motherboard-3d.step: Full 3D CAD model of the carrier board.
  • pca9685_mount_bracket.stl: 3D printable bracket for the PCA9685 module.
  • pca9685_mount_bracket.scad: Parametric OpenSCAD source file.
• Visuals:
  • pcb_layout_diagram.svg: Dimensioned topology and socket arrangement diagram.
  • pcb_render.svg: Top layer vector render.