Barrier Gate 1.0

Note

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Kit purchase

Looking for parts? Check out our all-in-one kits below — packed with components, beginner-friendly guides, and tons of fun.

Name	Includes ESP32 board	PURCHASE LINK
ESP32 Ultimate Starter Kit	ESP32 WROOM 32E +	BUY
Universal Maker Sensor Kit		BUY

Course Introduction

In this lesson, you’ll learn how to use an ultrasonic sensor module, a digital servo motor, and LEDs with the ESP32 Board to build an intelligent barrier gate system.

When the barrier is closed, the red LED turns on. If the ultrasonic sensor module detects an approaching vehicle, the digital servo motor raises the barrier, the green LED turns on, and the vehicle is allowed to pass.

Note

If this is your first time working with an ESP32 project, we recommend downloading and reviewing the basic materials first.

• 1.1 Install Arduino IDE(Important)

• 1.2 Introduce of Arduino IDE

• 1.4 Install the Arduino Nano ESP32 Board (Important)

Required Components

In this project, we need the following components:

SN	COMPONENT INTRODUCTION	QUANTITY	PURCHASE LINK
1	ESP-WROOM-32 ESP32 ESP-32S Development Board	1	BUY
2	USB Type-C cable	1
3	Breadboard	1	BUY
4	Wires	Several	BUY
5	1kΩ resistor	2	BUY
6	Ultrasonic Sensor Module	1	BUY
7	LED	2	BUY
8	Digital Servo Motor	1	BUY

Wiring

Common Connections:

• LED

  • Green: Connect the LEDs cathode to a 1kΩ resistor then to the negative power bus on the breadboard, and the LED anode to GPIO26 on the Arduino.

  • Red: Connect the LEDs cathode to a 1kΩ resistor then to the negative power bus on the breadboard, and the LED anode to GPIO25 on the Arduino.

• Digital Servo Motor

  • Connect to breadboard’s 5V positive power bus.

  • Connect to breadboard’s negative power bus.

  • Connect to GPIO16 on the ESP32.

• Ultrasonic Sensor Module

  • Trig: Connect to GPIO19 on the ESP32.

  • Echo: Connect to GPIO18 on the ESP32.

  • GND: Connect to breadboard’s negative power bus.

  • VCC: Connect to breadboard’s 3.3V red power bus.

Writing the Code

Note

• You can copy this code into Arduino IDE.

• To install the library, use the Arduino Library Manager and search for ESP32Servo and install it.

• Don’t forget to select the board(ESP32 Dev module) and the correct port before clicking the Upload button.

// ESP32 version
#include <ESP32Servo.h>   // Use ESP32-specific Servo library (install ESP32Servo from Library Manager)

// ---------- Pin map (ESP32 DevKit v1) ----------
const int trigPin   = 19;   // HC-SR04 Trig pin (output)
const int echoPin   = 18;   // HC-SR04 Echo pin (input, level-shifted to 3.3V)
const int redLed    = 25;   // Red LED
const int greenLed  = 26;   // Green LED
const int servoPin  = 16;   // Servo signal pin (PWM capable)

Servo barrierServo;                 // Servo object
bool previousCarDetected = false;   // Record if a car was detected in last loop

void setup() {
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);          // Echo should be shifted down to 3.3V
  pinMode(redLed, OUTPUT);
  pinMode(greenLed, OUTPUT);

  // Attach servo with explicit pulse width range (adjust if needed)
  barrierServo.attach(servoPin, 500, 2500);
  barrierServo.write(0);            // Start with barrier down

  Serial.begin(115200);
  delay(100);
}

void loop() {
  long duration = 0;
  long distance = 0;

  // Send ultrasonic pulse
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Measure echo pulse (30ms timeout ~ 5m max range)
  duration = pulseIn(echoPin, HIGH, 30000UL);

  if (duration == 0) {
    // Timeout → no valid echo
    distance = 999;
  } else {
    // Convert time to distance (cm)
    distance = duration * 0.034 / 2;
  }

  Serial.print("Distance: ");
  Serial.println(distance);

  // Car detected within 15 cm
  bool carDetected = (distance > 0 && distance < 15);

  if (carDetected) {
    // Raise barrier and turn on green LED
    digitalWrite(redLed, LOW);
    digitalWrite(greenLed, HIGH);
    barrierServo.write(90);
  } else {
    // If the car just left, wait before lowering barrier
    if (previousCarDetected) {
      delay(1000);  // 1 second delay
    }
    // No car: lower barrier and turn on red LED
    digitalWrite(redLed, HIGH);
    digitalWrite(greenLed, LOW);
    barrierServo.write(0);
  }

  previousCarDetected = carDetected; // Update last state
  delay(300);                        // Small delay before next reading
}