Arduino Time-based Relay Control: Automates relay based on IST hours with a manual override button. Includes status LED & serial feedback using TimeLib.h

TimeScheduledRelayControl_v1.ino

#include <TimeLib.h>

const int relayPin = 7;  
const int buttonPin = 2;  // Button for manual override
const int ledPin = 13;    // On-board LED to indicate relay status

// Adjustable start and end times
int startTime = 4;   // 4 AM
int endTime = 19;    // 7 PM

bool manualOverride = false;  // Flag to track if lights are manually overridden

void setup() {
  pinMode(relayPin, OUTPUT);
  pinMode(buttonPin, INPUT_PULLUP);  // Use internal pullup for button
  pinMode(ledPin, OUTPUT);

  digitalWrite(relayPin, LOW); 
  attachInterrupt(digitalPinToInterrupt(buttonPin), toggleLight, FALLING);  // Interrupt for button press
  
  Serial.begin(9600);
  Serial.println("System Started");
}

void loop() {
  int currentHour = hour() + 5; // Add 5 for IST
  int currentMinute = minute() + 30; // Add 30 minutes for IST
  
  if (currentMinute >= 60) {
    currentMinute -= 60;
    currentHour += 1;
  }

  if (currentHour >= 24) { 
    currentHour -= 24;
  }

  if (!manualOverride) {  // If not manually overridden
    if (currentHour >= startTime && currentHour < endTime) {
      turnOnLight();
    } else {
      turnOffLight();
    }
  }

  delay(60000);  
}

void turnOnLight() {
  digitalWrite(relayPin, HIGH);
  digitalWrite(ledPin, HIGH);  // Indicate relay status
  Serial.println("Light Turned ON");
}

void turnOffLight() {
  digitalWrite(relayPin, LOW);
  digitalWrite(ledPin, LOW);   // Indicate relay status
  Serial.println("Light Turned OFF");
}

void toggleLight() {  // Interrupt service routine for button press
  if (manualOverride) {  // If currently overridden
    manualOverride = false;
  } else {
    manualOverride = true;
    digitalWrite(relayPin, !digitalRead(relayPin));  // Toggle light state
    digitalWrite(ledPin, !digitalRead(ledPin));      // Indicate relay status
  }
  delay(200);  // Debounce delay
}