WEEK 10 – Output Devices

Individual Assignment

Stepper Motor Control Board using XIAO ESP32-C3 and A4988 Driver

This assignment focuses on the design, fabrication, programming, and testing of an output device. For this week, I designed and fabricated a custom PCB to control a 12 V stepper motor using a Seeed Studio XIAO ESP32-C3 and an A4988 motor driver.

The idea of the system is to use a humidity sensor as an input signal. When the sensor detects a specific humidity condition, the XIAO ESP32-C3 activates the stepper motor. The motor is used to move or lift a water container toward a plant pot for a determined amount of time. This time can be adjusted in the code, allowing control over how long the watering mechanism operates.

The board was designed following the same PCB production workflow used in previous assignments: schematic design, PCB layout, fabrication with a 90 watt fiber laser machine, drilling, soldering, continuity testing, programming, and functional validation.

Final output device board with XIAO ESP32-C3 and stepper motor

Final output device board for controlling a 12 V stepper motor.

1. Assignment Objective

Main Objective

The main objective of this assignment was to design and fabricate a custom PCB capable of controlling an output device. In this case, the output device is a 12 V stepper motor controlled by an A4988 driver and commanded by a XIAO ESP32-C3.

Objective Description
Design a custom PCB Create a board to connect the XIAO ESP32-C3, A4988 driver, sensor input, and motor output.
Control an output device Use a 12 V stepper motor as the main actuator of the system.
Use a motor driver Use the A4988 driver to safely control the stepper motor from the microcontroller.
Use an external power source Power the motor with an external 12 V supply while keeping common ground with the control circuit.
Integrate a humidity sensor Use the sensor signal as a condition to activate the motor.
Fabricate the PCB Use a 90 watt fiber laser machine to engrave the copper board.
Program and validate Use Arduino IDE to program the motor movement and test the complete system.

2. Project Concept

The project is based on an automated watering concept. A humidity sensor reads the moisture condition. When the sensor detects a value below or above a defined threshold, the XIAO ESP32-C3 sends control signals to the A4988 driver. The driver then activates the 12 V stepper motor. The motor moves the mechanism for a defined time, allowing a water container to be lifted or moved toward a plant pot.

Humidity Sensor → XIAO ESP32-C3 → A4988 Driver → 12 V Stepper Motor → Water Container Movement
System Element Function
Humidity sensor Provides the input signal related to soil or environmental moisture.
XIAO ESP32-C3 Reads the sensor value and decides when the motor should move.
A4988 driver Receives STEP and DIR signals and controls the current sent to the stepper motor.
12 V stepper motor Acts as the output device that moves the watering mechanism.
12 V external power supply Provides enough power for the motor operation.
Custom PCB Integrates the control and connection system into a fabricated board.

3. Materials and Components

The components were selected to build a functional output system. The XIAO ESP32-C3 controls the logic of the system, while the A4988 driver manages the motor power stage. The external 12 V source is necessary because the motor requires more voltage and current than the microcontroller can provide directly.

Material / Component Quantity Purpose
Seeed Studio XIAO ESP32-C3 1 Main microcontroller used to read the sensor and control the motor driver.
A4988 stepper motor driver 1 Driver used to control the 12 V stepper motor.
12 V stepper motor 1 Output actuator used to move or lift the water container.
Humidity sensor 1 Input sensor used to activate the motor depending on moisture condition.
12 V external power supply 1 Power source for the stepper motor.
Copper clad board 1 Base material for PCB fabrication.
Header pins As needed Used to mount the XIAO ESP32-C3 and A4988 driver.
Screw terminal blocks As needed Used for motor and external power connections.
Capacitor 1 Recommended between VMOT and GND to stabilize the motor power supply.
USB-C cable 1 Used to program and power the XIAO ESP32-C3 logic side.
Multimeter 1 Used to check continuity and verify safe power connections.
Materials for output devices assignment A4988 stepper motor driver

4. Software Used

KiCad

KiCad was used to design the schematic and PCB layout of the custom board. The design included the XIAO ESP32-C3, the A4988 driver connections, the humidity sensor input, the motor connector, and the external 12 V power input.

Arduino IDE

Arduino IDE was used to program the XIAO ESP32-C3. The code reads the humidity sensor and activates the motor for a defined time when the sensor reaches the programmed threshold.

Laser Software

The laser software was used to prepare and send the PCB fabrication file to the 90 watt fiber laser machine.

5. Why a Driver is Needed

The XIAO ESP32-C3 cannot directly power a 12 V stepper motor because its GPIO pins only provide low-current logic signals. For this reason, the A4988 driver is required. The driver receives low-voltage control signals from the microcontroller and uses the external 12 V power supply to energize the motor coils.

Connection Type Voltage / Signal Description
Logic control 3.3 V from XIAO ESP32-C3 STEP, DIR, ENABLE, and other control signals.
Motor power 12 V external source Power used by the A4988 to drive the motor coils.
Common ground GND shared The ESP32-C3 ground and 12 V power supply ground must be connected together.

Important: The motor must not be powered directly from the ESP32-C3. The motor requires an external 12 V supply and must be controlled through the A4988 driver.

6. A4988 Driver Connections

A4988 Pin Connection Purpose
VMOT 12 V external power supply positive Motor power input.
GND Motor 12 V power supply ground Motor power ground.
VDD 3.3 V from XIAO ESP32-C3 Logic power for the driver.
GND Logic GND from XIAO ESP32-C3 Logic ground.
STEP GPIO from XIAO ESP32-C3 Receives pulses to move the motor step by step.
DIR GPIO from XIAO ESP32-C3 Controls the direction of motor rotation.
ENABLE GPIO or GND depending on design Enables or disables the driver output.
1A, 1B, 2A, 2B Stepper motor coils Output connections to the motor windings.
A4988 driver connection diagram

Connection diagram between XIAO ESP32-C3, A4988 driver, and stepper motor.

7. System Logic

The logic of the system is based on a condition. The humidity sensor provides an analog value. If the value crosses the programmed threshold, the XIAO ESP32-C3 activates the motor. The motor rotates for a defined time, which can be adjusted in the code. After the movement time ends, the motor stops.

Read Humidity Sensor → Compare with Threshold → Activate A4988 → Move Stepper Motor → Stop After Adjustable Time
Condition System Response
Humidity value does not reach threshold The motor remains stopped.
Humidity value reaches threshold The motor is activated through the A4988 driver.
Motor running time finishes The motor stops automatically.
Threshold or time needs adjustment The values are modified in the Arduino code.

8. PCB Design in KiCad

The PCB design started with the schematic in KiCad. The schematic included the XIAO ESP32-C3, the A4988 driver, the humidity sensor connector, the motor connector, and the external 12 V power input connector.

Special attention was required because the board includes both low-voltage logic signals and higher-power motor connections. For this reason, the 12 V power traces and motor output traces were designed with more care and wider routes than normal signal traces.

Schematic Design Steps

  1. Create a new KiCad project for Week 10.
  2. Add the XIAO ESP32-C3 symbol.
  3. Add the A4988 driver module footprint or pin header representation.
  4. Add a connector for the humidity sensor.
  5. Add a connector for the 12 V external power supply.
  6. Add a connector for the stepper motor coils.
  7. Connect STEP and DIR pins from the XIAO ESP32-C3 to the A4988 driver.
  8. Connect VDD of the A4988 to 3.3 V.
  9. Connect VMOT of the A4988 to the 12 V external power input.
  10. Connect all grounds together.
  11. Add a capacitor between VMOT and GND for motor supply stabilization.
  12. Run Electrical Rules Check and correct warnings.
KiCad schematic for output device board

Schematic design of the output device board in KiCad.

9. PCB Layout Design

After validating the schematic, I moved to the PCB layout. The XIAO ESP32-C3 was placed in a position where the USB-C port remained accessible. The A4988 driver was placed with enough space for ventilation and easy connection to the motor and power terminals.

The motor connector and 12 V power connector were placed near the edge of the board. This makes the wiring safer and more organized. The signal traces were separated from the motor power traces to reduce possible electrical noise.

PCB Layout Steps

  1. Assign footprints for the XIAO ESP32-C3, A4988 driver, connectors, and capacitor.
  2. Open the PCB editor in KiCad.
  3. Import all schematic components.
  4. Place the XIAO ESP32-C3 with USB access.
  5. Place the A4988 driver in a central and accessible position.
  6. Place the 12 V input connector near the board edge.
  7. Place the motor connector near the driver output pins.
  8. Route STEP, DIR, ENABLE, sensor signal, 3.3 V, and GND.
  9. Route 12 V and motor traces with wider tracks.
  10. Check clearance between power and signal traces.
  11. Run Design Rules Check.
  12. Export fabrication files.
PCB layout for output device board 3D view of output device PCB

10. Design Rules and Safety Considerations

Design Consideration Application in This Board
Separate logic and motor power 3.3 V logic traces were kept different from 12 V motor power traces.
Common ground The ESP32-C3 ground and external 12 V supply ground were connected together.
Wider power traces Motor power traces were made wider to support higher current.
Accessible USB port The XIAO ESP32-C3 was oriented to allow easy programming.
Driver ventilation Space was left around the A4988 because the driver can heat during operation.
External power protection The polarity of the 12 V input was checked carefully before powering the board.

Before powering the motor, I verified the polarity of the 12 V supply and confirmed that there was no short circuit between VMOT and GND.

11. Fabrication Equipment: 90 W Fiber Laser Machine

The PCB was fabricated using a 90 watt fiber laser machine. This machine uses a focused laser beam to remove copper from the board and isolate the conductive traces.

Because the board controls a motor, the quality of the traces is very important. Any copper bridge or incomplete isolation can affect the motor driver, the ESP32-C3, or the external power supply.

Equipment Feature Description
Machine type Fiber laser engraving machine.
Power 90 watts.
Application PCB engraving and copper isolation.
Material Single-sided copper clad board.
Critical parameters Focus, power, speed, frequency, and number of passes.
Safety Use proper protection, supervise the process, and avoid reflective exposure.
90 watt fiber laser machine

90 watt fiber laser machine used for PCB fabrication.

12. PCB Fabrication Process

Fabrication Steps

  1. Export the PCB traces from KiCad.
  2. Prepare the file for the laser software.
  3. Clean the copper board surface.
  4. Place and fix the copper board on the laser bed.
  5. Import the trace file into the laser software.
  6. Check the scale, position, and orientation.
  7. Adjust the focus of the fiber laser.
  8. Configure laser parameters.
  9. Run the engraving process.
  10. Inspect trace isolation and copper removal.
  11. Repeat the pass if necessary.
  12. Clean the PCB after engraving.
Laser setup for output device PCB Laser engraving output device PCB

13. Inspection After Laser Engraving

Inspection Point Expected Condition
Motor power traces Complete and properly isolated from other traces.
Logic traces STEP, DIR, ENABLE, and sensor lines must be continuous.
12 V and GND No short circuit between power and ground.
A4988 pads Pads must be clean and large enough for soldering headers.
Board surface The substrate must not be excessively burned.
Engraved PCB for output device

PCB after engraving with the fiber laser machine.

14. Drilling Process

After engraving, I drilled the holes required for the XIAO ESP32-C3 headers, the A4988 driver headers, the sensor connector, the motor connector, and the 12 V power input connector.

Drilling Steps

  1. Identify all holes required in the PCB.
  2. Select the correct drill bit for headers and terminals.
  3. Align the drill with the center of each pad.
  4. Drill vertically with controlled pressure.
  5. Clean dust and copper residue.
  6. Inspect all holes before soldering.
Drilling output device PCB Output device PCB after drilling

15. Soldering Process

Once the PCB was drilled and cleaned, I soldered the components. I started with the headers and connectors, then mounted the A4988 driver and XIAO ESP32-C3. The screw terminals were soldered for the 12 V input and motor output because these connections must be mechanically strong.

Soldering Steps

  1. Prepare the soldering iron and solder wire.
  2. Solder the XIAO ESP32-C3 headers.
  3. Solder the A4988 driver headers.
  4. Solder the humidity sensor connector.
  5. Solder the 12 V input terminal.
  6. Solder the stepper motor output terminal.
  7. Solder the capacitor between VMOT and GND.
  8. Inspect each solder joint.
  9. Check for solder bridges.
  10. Clean the board before testing.
Soldering Check Description
A4988 orientation The driver must be placed in the correct orientation before powering the board.
Power connector polarity 12 V and GND must be clearly identified.
Motor connector The motor coil wires must be connected to the correct A4988 outputs.
Header alignment The XIAO ESP32-C3 and A4988 headers must be straight and stable.
No solder bridges Adjacent pads must not be accidentally connected.
Soldering headers on PCB Soldering terminals on PCB
Final soldered output device board

Output device board after soldering all components.

16. Continuity and Safety Test

Before connecting the external 12 V source, I tested the PCB with a multimeter. This step was essential because the motor power circuit uses a higher voltage than the logic circuit.

Test Expected Result
3.3 V to GND No short circuit.
12 V VMOT to GND No short circuit.
STEP pin continuity Connected from XIAO ESP32-C3 to A4988 STEP.
DIR pin continuity Connected from XIAO ESP32-C3 to A4988 DIR.
Sensor signal line Connected from humidity sensor to selected analog input.
Motor outputs Connected from A4988 to motor terminal.
Continuity test on output device board

Continuity and safety test before powering the motor.

17. Arduino IDE Setup

Programming Setup

  1. Connect the XIAO ESP32-C3 to the computer using a USB-C cable.
  2. Open Arduino IDE.
  3. Select the correct ESP32 board package.
  4. Select the XIAO ESP32-C3 board.
  5. Select the correct serial port.
  6. Open a new sketch.
  7. Write or paste the motor control code.
  8. Compile the program.
  9. Upload the code to the board.
  10. Open the Serial Monitor to observe the sensor values.
Arduino IDE setup for XIAO ESP32-C3

Arduino IDE setup for programming the XIAO ESP32-C3.

18. Programming the Stepper Motor System

The code reads the humidity sensor value and compares it with a threshold. If the condition is met, the motor is activated for a specific amount of time. This time is adjustable by changing the variable motorRunTime. 

const int humidityPin = A0;

const int stepPin = 4;
const int dirPin = 5;
const int enablePin = 6;

int humidityValue = 0;
int humidityThreshold = 500;

unsigned long motorRunTime = 5000;
int stepDelay = 800;

void setup() {
  Serial.begin(115200);
  delay(1000);

  pinMode(stepPin, OUTPUT);
  pinMode(dirPin, OUTPUT);
  pinMode(enablePin, OUTPUT);

  digitalWrite(enablePin, HIGH);
  digitalWrite(dirPin, HIGH);

  Serial.println("Week 10 - Output Devices");
  Serial.println("Humidity controlled stepper motor system");
}

void loop() {
  humidityValue = analogRead(humidityPin);

  Serial.print("Humidity sensor value: ");
  Serial.println(humidityValue);

  if (humidityValue > humidityThreshold) {
    Serial.println("Condition detected. Activating motor...");
    runMotorForTime(motorRunTime);
    Serial.println("Motor stopped.");
    delay(2000);
  } else {
    digitalWrite(enablePin, HIGH);
  }

  delay(500);
}

void runMotorForTime(unsigned long duration) {
  unsigned long startTime = millis();

  digitalWrite(enablePin, LOW);
  digitalWrite(dirPin, HIGH);

  while (millis() - startTime < duration) {
    digitalWrite(stepPin, HIGH);
    delayMicroseconds(stepDelay);
    digitalWrite(stepPin, LOW);
    delayMicroseconds(stepDelay);
  }

  digitalWrite(enablePin, HIGH);
}

Note: The pins A0, stepPin, dirPin, and enablePin must be adjusted according to the final PCB design. The humidity threshold and motor running time must also be calibrated during testing.

19. Adjustable Parameters

Parameter Function How to Adjust
humidityThreshold Defines the sensor value required to activate the motor. Increase or decrease after observing real sensor values.
motorRunTime Defines how long the motor remains active. Change the value in milliseconds. Example: 5000 = 5 seconds.
stepDelay Controls the speed of the stepper motor. Lower values increase speed; higher values reduce speed.
dirPin Controls the direction of rotation. Change HIGH to LOW to reverse the motor direction.

20. Testing the Output Device

After programming the board, I tested the complete system. First, I powered only the logic side through the USB cable and checked the sensor values in the Serial Monitor. Then, I connected the external 12 V power supply to the motor driver and tested the motor response.

Testing Steps

  1. Connect the XIAO ESP32-C3 to the computer.
  2. Open the Serial Monitor at 115200 baud.
  3. Read the humidity sensor value.
  4. Adjust the threshold according to the observed values.
  5. Connect the external 12 V power supply to the board.
  6. Verify that the A4988 driver is correctly inserted.
  7. Trigger the humidity condition.
  8. Observe if the motor starts moving.
  9. Measure if the motor stops after the programmed time.
  10. Adjust motor time and speed if necessary.
Test Condition Expected Result
Sensor value below threshold The stepper motor remains stopped.
Sensor value above threshold The XIAO ESP32-C3 activates the A4988 driver.
Motor activated The stepper motor rotates and moves the mechanism.
Motor running time completed The motor stops automatically.
Humidity sensor testing Stepper motor testing

21. Application in the Watering Mechanism

The final application of this output device is related to a watering mechanism for a plant pot. The humidity sensor detects the condition that activates the system. Once the condition is detected, the motor moves for a defined period of time. This movement can be used to lift or position a water container toward the plant pot.

Since the motor running time is adjustable, the amount of movement can be modified depending on the mechanical structure, the distance to move, or the amount of water required.

Dry Condition Detected → Motor Activated → Container Moves → Water Reaches Plant → Motor Stops
Watering mechanism concept

Concept of the motor-based watering mechanism for a plant pot.

22. Problems and Solutions

Problem Possible Cause Solution
The motor does not move. No 12 V power, wrong motor wiring, disabled driver, or wrong pins. Check power supply, motor coils, STEP/DIR pins, and ENABLE state.
The motor vibrates but does not rotate. Stepper motor coils connected incorrectly. Identify coil pairs with a multimeter and reconnect them correctly.
The A4988 driver heats up. Current limit not adjusted or insufficient ventilation. Adjust current limit and allow space for cooling.
The ESP32-C3 resets when the motor starts. Electrical noise or power instability. Use common ground, add capacitor, and separate motor power from logic power.
The sensor does not activate the motor. Threshold value is not calibrated. Read real sensor values and adjust the threshold in the code.
The PCB has a short circuit. Copper bridge or solder bridge. Inspect the board, clean copper residue, and remove unwanted solder.

23. Results

The final system allowed the XIAO ESP32-C3 to control a 12 V stepper motor through an A4988 driver. The motor was activated based on the humidity sensor reading and moved for a defined amount of time.

This confirmed that the custom PCB worked as an output device board. The board integrated the microcontroller, sensor input, motor driver, external power connection, and motor output into a single fabricated system.

Final working output device board

Final working output device board controlling the stepper motor.

24. Download Files

The following buttons can be used to download the project files, including the KiCad design, fabrication files, and Arduino code for the stepper motor control system.

Download KiCad Project Download PCB Traces SVG Download PCB Outline Download Drill File Download Arduino Code

25. Evidence List

Evidence Suggested Image Path
Final hero shot images/w10/hero_shot.jpg
Materials used images/w10/materials.jpg
A4988 driver images/w10/a4988_driver.jpg
A4988 connection diagram images/w10/a4988_connections.jpg
KiCad schematic images/w10/kicad_schematic.jpg
KiCad PCB layout images/w10/kicad_pcb_layout.jpg
Fiber laser machine images/w10/fiber_laser_machine.jpg
Laser engraving process images/w10/laser_engraving.jpg
Drilling process images/w10/drilling_process.jpg
Soldering process images/w10/soldering_headers.jpg
Continuity test images/w10/continuity_test.jpg
Arduino IDE setup images/w10/arduino_setup.jpg
Motor testing images/w10/motor_testing.jpg
Final working board images/w10/final_working_board.jpg

26. Learning Outcomes

Through this assignment, I learned how to:

27. Final Reflection

This assignment helped me understand how a microcontroller can control an output device that requires more power than the microcontroller can provide directly. The A4988 driver was necessary to connect the low-power control signals of the XIAO ESP32-C3 with the higher-power requirements of the 12 V stepper motor.

The project also showed the importance of designing the PCB carefully when power and logic signals are combined. The motor power traces, common ground, driver orientation, and external power input must be checked before testing the system.

The final result was a functional output device board that can activate a stepper motor based on a humidity sensor condition, making it useful as a first prototype for an automated plant watering mechanism.

28. Conclusion

In conclusion, this assignment successfully integrated the design, fabrication, assembly, programming, and testing of an output device board. The board used a XIAO ESP32-C3 to read a humidity sensor and activate a 12 V stepper motor through an A4988 driver.

The PCB was fabricated using a 90 watt fiber laser machine and assembled through drilling and soldering processes. The final system demonstrated how an embedded board can control a physical actuator and generate movement in response to sensor data.