Renaming Bluetooth HC-05 module

****[HC05] Rename the HC05 Bluetooth Module Using AT Command

Controlling Arduino with Bluetooth

Connect Arduino Uno to Android Via Bluetooth

Control an Arduino with Bluetooth - Projects

If above links are too confusing, try this:

#include <SoftwareSerial.h>

SoftwareSerial BTSerial(10, 11); // RX, TX

String receivedText = "";  // Variable to store incoming Bluetooth text

void setup() {
  Serial.begin(9600);
  BTSerial.begin(9600);
  Serial.println("Bluetooth serial started. Waiting for messages...");
}

void loop() {
  // Read characters from Bluetooth
  while (BTSerial.available()) {
    char c = BTSerial.read();

    if (c == '#') {    // Make sure the end of every message from mobile app must have "#"
      if (receivedText.length() > 0) {
        Serial.print("Received: ");
        Serial.println(receivedText);
      }
    } else {
      receivedText += c; // Append character to message
    }
  }
  
  if (receivedText == ""){
	  digitalWrite(3,HIGH); //switch on LED on pin 3
	  delay(5000); //5s delay
  }
  else{
	  digitalWrite(3,LOW); //switch off LED on pin 3
  }
  
  receivedText = ""; // Clear for next message
}