Circuit Documentation

Summary

This circuit is designed to control a mobile robot equipped with DC gearmotors for movement, an ultrasonic sensor for distance measurement, and a servo motor for directional scanning. The ESP32 microcontroller serves as the brain of the robot, interfacing with the L298N motor driver to control the gearmotors, reading distance data from the HC-SR04 ultrasonic sensor, and controlling the position of the SG90 servo motor. Power is supplied by a 18650 Li-Ion battery, and a rocker switch is used to turn the circuit on and off.

Component List

ESP32 (30 pin)

• Microcontroller with WiFi and Bluetooth capabilities.
• It has a variety of digital I/O pins and supports serial communication.

Gearmotor DC Wheels (Right and Left)

• DC motors with gear reduction used for driving the wheels of the robot.

SG90 Servo Motor

• A small and lightweight servo motor used for precise angular positioning.

L298N DC Motor Driver

• A dual H-bridge motor driver that can drive two DC motors or one stepper motor.

HC-SR04 Ultrasonic Sensor

• An ultrasonic distance sensor that can measure distances by emitting ultrasonic waves.

18650 Li-Ion Battery

• A rechargeable battery that provides power to the circuit.

Rocker Switch

• A simple on/off switch to control the power flow to the circuit.

Wiring Details

ESP32 (30 pin)

• D33 connected to L298N DC motor driver IN4
• D25 connected to L298N DC motor driver IN3
• D26 connected to L298N DC motor driver IN2
• D27 connected to L298N DC motor driver IN1
• D14 connected to L298N DC motor driver ENA
• D13 connected to L298N DC motor driver ENB
• GND connected to common ground net
• Vin connected to 5V power net
• D18 connected to HC-SR04 Ultrasonic Sensor ECHO
• D5 connected to HC-SR04 Ultrasonic Sensor TRIG
• D15 connected to SG90 Servo Motor PWM

Gearmotor DC Wheels Right

• PIN1 connected to L298N DC motor driver OUT4
• PIN2 connected to L298N DC motor driver OUT3

Gearmotor DC Wheels Left

• PIN1 connected to L298N DC motor driver OUT1
• PIN2 connected to L298N DC motor driver OUT2

SG90 Servo Motor

• PWM connected to ESP32 D15
• 5V connected to 5V power net
• GND connected to common ground net

L298N DC Motor Driver

• IN1 - IN4 connected to ESP32 D27, D26, D25, D33
• ENA, ENB connected to ESP32 D14, D13
• GND connected to common ground net
• 5V connected to 5V power net
• OUT1 - OUT4 connected to Gearmotor DC Wheels
• 12V connected to 18650 Li-Ion Battery Positive

HC-SR04 Ultrasonic Sensor

• VCC connected to 5V power net
• TRIG connected to ESP32 D5
• ECHO connected to ESP32 D18
• GND connected to common ground net

18650 Li-Ion Battery

• Positive connected to L298N DC motor driver 12V
• Negative connected to Rocker Switch 1

Rocker Switch

• 1 connected to 18650 Li-Ion Battery Negative
• 2 connected to common ground net

Documented Code

#include <Servo.h>

// Pin Definitions
#define trigPin 5
#define echoPin 18
#define ENA 14
#define ENB 13
#define IN1 27
#define IN2 26
#define IN3 25
#define IN4 33
#define servoPin 15

Servo myServo;

// Variables for distance measurement
long duration;
int distance;
int rightDistance, leftDistance;

// Function to calculate distance
int getDistance() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  distance = duration * 0.034 / 2;
  return distance;
}

// Motor control functions
void moveForward() {
  digitalWrite(IN1, HIGH);
  digitalWrite(IN2, LOW);
  digitalWrite(IN3, HIGH);
  digitalWrite(IN4, LOW);
  analogWrite(ENA, 250); // Adjust speed using PWM (0-255)
  analogWrite(ENB, 250); // Adjust speed using PWM (0-255)
}

void moveBackward() {
  digitalWrite(IN1, LOW);
  digitalWrite(IN2, HIGH);
  digitalWrite(IN3, LOW);
  digitalWrite(IN4, HIGH);
  analogWrite(ENA, 250); // Adjust speed using PWM
  analogWrite(ENB, 250); // Adjust speed using PWM
}

void stopCar() {
  digitalWrite(IN1, LOW);
  digitalWrite(IN2, LOW);
  digitalWrite(IN3, LOW);
  digitalWrite(IN4, LOW);
}

void turnLeft() {
  digitalWrite(IN1, LOW);
  digitalWrite(IN2, HIGH);
  digitalWrite(IN3, HIGH);
  digitalWrite(IN4, LOW);
  analogWrite(ENA, 150); // Adjust speed for turning
  analogWrite(ENB, 150); // Adjust speed for turning
}

void turnRight() {
  digitalWrite(IN1, HIGH);
  digitalWrite(IN2, LOW);
  digitalWrite(IN3, LOW);
  digitalWrite(IN4, HIGH);
  analogWrite(ENA, 150); // Adjust speed for turning
  analogWrite(ENB, 150); // Adjust speed for turning
}

void setup() {
  // Setup pins
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(IN1, OUTPUT);
  pinMode(IN2, OUTPUT);
  pinMode(IN3, OUTPUT);
  pinMode(IN4, OUTPUT);
  pinMode(ENA, OUTPUT);
  pinMode(ENB, OUTPUT);

  // Servo setup
  myServo.attach(servoPin);
  myServo.write(90); // Start servo at center position

  Serial.begin(9600);
}

void loop() {
  // Scan forward
  myServo.write(90); // Center position (looking straight ahead)
  delay(500);
  int frontDistance = getDistance();

  // If an obstacle is closer than 20 cm
  if (frontDistance < 20) { 
    stopCar();
    delay(1000); // Pause to make a decision

    // Scan left side
    myServo.write(0); // Turn servo to the left
    delay(500);
    leftDistance = getDistance();

    // Scan right side
    myServo.write(180); // Turn servo to the right
    delay(500);
    rightDistance = getDistance();

    // Decide direction based on the distances
    if (leftDistance > rightDistance) {
      turnLeft();
      delay(1000); // Adjust the delay to control turning duration
    } else {
      turnRight();
      delay(1000); // Adjust the delay to control turning duration
    }

    stopCar(); // Stop after turning
    delay(1000); // Brief pause before moving forward again
  } else {
    moveForward(); // Continue moving forward if the path is clear
  }

  delay(200); // Short delay before next loop iteration
}

This code is designed to be uploaded to the ESP32 microcontroller. It initializes the pins and sets up the servo motor, then enters a loop where it continuously checks for obstacles using the ultrasonic sensor. If an obstacle is detected, the robot will stop, scan the area with the servo motor, and then decide which direction to turn based on the distance measurements. The robot will then turn in the chosen direction, stop, and proceed to move forward again if the path is clear.