Create a TinkerCAD simulation

Create a Fritzng simulation

Serial setup

• The Arduino starts communication with the computer or HC-05 Bluetooth module at 9600 baud.

• This lets it receive characters like '1', '2', '3', etc.

Serial.begin(9600);

Pin setup

• Pins 9, 10, and 11 are used to control the RGB LED colors.

• Pin A0 is used as the buzzer output.

• These are set as INPUT in the sketch, but they should actually be OUTPUT since we’re driving LED and buzzer (a small mistake in code).

pinMode(9, INPUT);

pinMode(10, INPUT);

pinMode(11, INPUT);

pinMode(A0, INPUT);

Listening for Bluetooth / Serial data

• Inside loop(), the Arduino checks if there is any data coming from Serial.

• If yes, it reads one character into the variable command.

if (Serial.available()) {

    command = Serial.read();

Command cases

• Depending on the character received, the Arduino changes the LED color and makes the buzzer beep at a certain frequency.

For example:

• '1' => Red LED, buzzer at 600 Hz

• '2' => Green LED, buzzer at 800 Hz

• '3' => Blue LED, buzzer at 1000 Hz

• '4'=> Yellow (Red+Green), buzzer at 1200 Hz

• '5' =>Cyan (Green+Blue), buzzer at 1400 Hz

• '6' => LED off, buzzer silent

switch (command) {

  case '1':

    setColor(255, 0, 0);  // red

    tone(A0, 600);

    break;

  ...

  case '6':

    setColor(0, 0, 0);    off

    noTone(A0);

    break;

setColor() function

• This function writes values to the LED pins using PWM (analogWrite).

• Each color (red, green, blue) is given a value between 0–255.

• The combination creates the visible color.

void setColor(int red, int green, int blue) {

  analogWrite(10, red);   // Green

  analogWrite(9, green);  // Red

  analogWrite(11, blue);  // Blue

I used a switch–case statement because my program needs to react to different values of the same variable (command). Instead of writing a long chain of if and else if conditions to check whether command is '1', '2', '3', and so on, the switch–case structure organizes these options neatly in separate blocks. This makes the code easier for me to read, understand, and maintain, since each case clearly shows what happens for that specific input. It also makes the program slightly more efficient, because the Arduino can jump directly to the matching case rather than checking every condition in sequence. Overall, it’s the best choice when I have multiple clear options tied to one variable.