I built the circuit on a breadboard using an Arduino UNO, RGB LED, buzzer, and a Bluetooth module. After wiring the components according to my Tinkercad design, I tested the circuit step by step to make sure each part worked. The Arduino was programmed in Arduino IDE C language and the uploaded code made the buzzer beep and RGB LED light up when I sent “A” from my phone, and turned everything off when I sent “B” like it shows in the video

•  First, the code checks if there is any incoming data from the Serial, 

Then there are two main conditions:

 Condition 1: if data == 'A'

• If the phone sends the letter A:

  1. The buzzer turns on briefly, then off.

  2. The red LED turns on briefly, then off.

  3. The blue LED turns on briefly, then off.

  4. Finally, the green LED stays on.
     
     

Condition 2: if data == 'B 

• If the phone sends the letter B:

  • All components (red, green, blue LEDs and the buzzer) turn off.
    
    

char data = '\0';

#define RED 13

#define GREEN 12

#define BLUE 11

#define BUZZER 10

void setup() {

  Serial.begin(9600);                                          

  pinMode(RED, OUTPUT);

  pinMode(GREEN, OUTPUT);

  pinMode(BLUE, OUTPUT);                                 

  pinMode(BUZZER, OUTPUT);

  digitalWrite(RED, LOW);

  digitalWrite(GREEN, LOW);

  digitalWrite(BLUE, LOW);

  digitalWrite(BUZZER, LOW);

}

void loop() {

  if (Serial.available()) {

    data = Serial.read();

    if (data == 'A') {

      digitalWrite(BUZZER, HIGH); delay(200);

      digitalWrite(BUZZER, LOW);

      digitalWrite(RED, HIGH); delay(200);

      digitalWrite(RED, LOW);

      digitalWrite(BLUE, HIGH); delay(200);

      digitalWrite(BLUE, LOW);

      digitalWrite(GREEN, HIGH);

    }

    else if (data == 'B') {

      digitalWrite(RED, LOW);

      digitalWrite(GREEN, LOW);

      digitalWrite(BLUE, LOW);

      digitalWrite(BUZZER, LOW);

    }

  }

}

video of the wiring