3. Electronics Design

3.1 Control Architecture

The control system is centered around a Seeed Studio XIAO ESP32-C3 microcontroller programmed with Arduino firmware. Two A4988 stepper drivers are used to control the NEMA17 motors — one for the winding axis and one for the pitch control. Inputs include a beam break sensor for detecting spool rotations, a limit switch for pitch axis homing, and a 4-button interface to navigate the OLED menu.

3.2 Wiring Overview

• Stepper Motor 1 (Spool) → A4988 → Step/Dir → MCU
• Stepper Motor 2 (Pitch) → A4988 → Step/Dir → MCU
• Beam Break Sensor → Digital Pin (interrupt)
• Limit Switch → Digital Pin (homing)
• OLED Display → I2C (SDA/SCL)
• 4 Tactile Buttons → Digital Inputs with pull-up
• Power Supply → 12V DC input → onboard 5V regulator

3.3 PCB Design

The custom PCB was designed in KiCad and manufactured with a compact 2-layer layout. The board includes:

• Headers for 2x A4988 stepper drivers
• Screw terminals for 12V power and motor outputs
• I2C header for OLED display
• JST or header pins for sensors and buttons

3.4 Safety and Cable Management

• A rocker switch is included between the 12V supply and the main board for safety
• Color-coded wires with heat shrink tubing provide safe and clean routing
• All sensor wires are removable for maintenance/debugging

3.5 Electronics BOM

Component	Qty	Specification	Notes
Microcontroller	1	Seeed XIAO ESP32-C3	Arduino-compatible, Wi-Fi
Stepper Motor Drivers	2	A4988	For NEMA17 control
NEMA17 Stepper Motors	2	1.8° step	Spool and pitch axes
Power Supply	1	12V 3A	Main power source
Beam Break Sensor	1	KY-010 or TCRT5000	Spool rotation counter
Limit Switch	1	Mechanical	Pitch axis homing
OLED Display	1	0.96\", SSD1306, I2C	Menu interface
Tactile Buttons	4	6mm push buttons	User input navigation
Custom PCB	1	2-layer KiCad	All-in-one control board
Header Pins / JSTs	~20	2.54 mm	Sensor and driver connectors
Wires	1 set	22 AWG	Signal and power
Heat Shrink Tubing	Various	-	Insulation and labeling