/*
  Project Title: Automatic Gate Using Ultrasonic Sensor & Servo Motor

  Description:
  This project reads distance from an ultrasonic sensor and controls a servo motor
  to simulate an automatic gate or barrier. When an object is detected within 15 cm,
  the servo rotates to 90 degrees (open position). Otherwise, it stays at 0 degrees (closed).

  Developed by: Your Name
  Organization: VoltACDC Lab
  Date: 30 May 2025
  Version: 1.0

  Hardware Requirements:
  - Arduino UNO/Nano/Mega
  - Ultrasonic Sensor (HC-SR04)
  - Servo Motor (SG90 or similar)
  - Jumper Wires
  - Power Source (5V)

  Library Required:
  - Servo.h (Built-in Arduino library)

  Circuit Connections:
  - HC-SR04 TRIG  -> Digital Pin 2
  - HC-SR04 ECHO  -> Digital Pin 3
  - Servo Signal  -> Digital Pin 9
  - VCC and GND   -> 5V and GND (common ground)

  License:
  Free to use for educational and non-commercial use.
  Contact developer for commercial licensing.

  Note:
  - You may adjust the distance threshold (currently 15 cm) based on your requirement.
  - Make sure the servo gets enough power if it behaves erratically.
*/

#include <Servo.h>

// Pin Definitions
#define TRIG_PIN  2
#define ECHO_PIN  3
#define SERVO_PIN 9

Servo myServo;

// Function: Read distance from ultrasonic sensor (in cm)
long readDistanceCM() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  long duration = pulseIn(ECHO_PIN, HIGH);
  long distanceCM = duration * 0.034 / 2;
  return distanceCM;
}

void setup() {
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  myServo.attach(SERVO_PIN);
  myServo.write(0); // Start at 0 degree (closed gate)
  Serial.begin(9600);
}

void loop() {
  long distance = readDistanceCM();

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

  // If object is within 15 cm, open gate
  if (distance > 0 && distance < 15) {
    myServo.write(90); // Open position
  } else {
    delay(500);        // Optional delay before closing
    myServo.write(0);  // Closed position
  }

  delay(100); // Debounce delay
}