WijiBoard Wiring Diagram

This document outlines the hardware connections for the WijiBoard.

Hardware Components

Microcontroller: Tenstar Robot ESP32-C3 Super Mini
Motors: 2× 28BYJ-48 (5V Stepper Motors)
Motor Drivers: 2× ULN2003 Driver Boards
Power System:
- 4S LiPo Battery
- XH-M609 Battery Low-Voltage Disconnect Module
- 2× Buck Regulators (step-down converters tuned to 5V)

Power Connections

The system is powered by a 4S LiPo battery. To protect the battery from over-discharge, it is connected to an XH-M609 module. The output of the XH-M609 is split into two separate Buck Regulators, both tuned to output 5V.

Buck Regulator 1 (MCU Power): Dedicated to powering the ESP32-C3 Super Mini.
Buck Regulator 2 (Motor Power): Dedicated to powering both ULN2003 driver boards to prevent voltage drops or electrical noise from affecting the MCU.

Important

Common Ground: You MUST connect the Ground (GND) from the ESP32 to the Ground (GND) of the ULN2003 drivers. Even though they have separate 5V power supplies, they need a common ground reference for the GPIO logic signals to work correctly.

Component	Connection	Destination
4S LiPo	`BAT+` / `BAT-`	XH-M609 `VIN+` / `VIN-`
XH-M609	`VOUT+` / `VOUT-`	Split to IN+ and IN- on both Buck Regulators
Buck 1 (MCU)	`OUT+ (5V)`	ESP32-C3 Super Mini `5V` (used as power input)
Buck 1 (MCU)	`OUT- (GND)`	ESP32-C3 Super Mini `GND`
Buck 2 (Motors)	`OUT+ (5V)`	ULN2003 (M1) `+ / 5V` and ULN2003 (M2) `+ / 5V`
Buck 2 (Motors)	`OUT- (GND)`	ULN2003 (M1) `- / GND` and ULN2003 (M2) `- / GND`
ESP32-C3 Super Mini	`GND`	Tie to the motor ground network (Common Ground)

Motor 1 (Right Motor) Logic

Physical Location: Right side (pivot at +12.9mm)

ESP32-C3 Super Mini Pin	ULN2003 (Motor 1) Pin
GPIO 0	`IN1`
GPIO 1	`IN2`
GPIO 3	`IN3`
GPIO 4	`IN4`

Motor 2 (Left Motor) Logic

Physical Location: Left side (pivot at -12.9mm)

ESP32-C3 Super Mini Pin	ULN2003 (Motor 2) Pin
GPIO 5	`IN1`
GPIO 6	`IN2`
GPIO 7	`IN3`
GPIO 10	`IN4`

Stepper to Driver Connections

Simply plug the white 5-pin JST connectors from the 28BYJ-48 motors into the corresponding white sockets on their respective ULN2003 driver boards. The connector is keyed and only fits one way.

Schematic Overview

flowchart LR
    subgraph Power Delivery
        BATT[4S LiPo Battery] -->|14.8V| XHM609[XH-M609 Protector]
        XHM609 -->|14.8V| BUCK1[Buck Regulator 1]
        XHM609 -->|14.8V| BUCK2[Buck Regulator 2]
    end

    BUCK1 -->|5V Power| ESP[ESP32-C3 Super Mini]
    BUCK2 -->|5V Power| M1_Driver[ULN2003 M1]
    BUCK2 -->|5V Power| M2_Driver[ULN2003 M2]
    
    %% Common Ground
    ESP -. Common Ground .- M1_Driver
    ESP -. Common Ground .- M2_Driver
    
    %% Logic Signals
    ESP -- Pins 0,1,3,4 --> M1_Driver
    ESP -- Pins 5,6,7,10 --> M2_Driver
    
    %% Motors
    M1_Driver == 5-wire cable ==> M1[Motor 1 - Right]
    M2_Driver == 5-wire cable ==> M2[Motor 2 - Left]

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