Introduction to Buzzers

​Audio feedback is a common way for electronic devices to communicate information. In Arduino projects, this is often achieved using small sound-emitting components called piezoelectric buzzers.

These devices produce sound through the vibration of a thin metal film. Inside the buzzer, a coil of wire surrounds a magnet. When electrical current passes through the coil, it creates a magnetic field that causes the metal film to vibrate rapidly, generating sound waves.

There are two primary types of these buzzers: active and passive, which differ in their internal design and how they are controlled.
  • ​An active buzzer generates the sound itself, one can actively control it to turn it on or off.
  • A passive buzzer needs a signal source that provides the sound signal.

Active buzzers

An active buzzer contains an internal oscillating circuit that produces a fixed frequency tone when a DC voltage is applied. This makes it straightforward to use, as simply connecting it to a power source will generate a continuous sound. In Arduino circuits, active buzzers are typically connected to digital pins and controlled like basic output devices.

​​This code uses digitalWrite() to turn the buzzer on and off. When the button is pressed (LOW state), the buzzer pin is set HIGH, producing sound. When the button is released, the pin is set LOW, stopping the sound.
Picture
Click the image for the simulation
Button-Controlled Buzzer 

int buzzerPin = 8;
int buttonPin = 7;

void setup() {
  pinMode(buzzerPin, OUTPUT);
  pinMode(buttonPin, INPUT_PULLUP);
}

void loop() {
  int buttonState = digitalRead(buttonPin);
  
  if (buttonState == LOW) {
    digitalWrite(buzzerPin, HIGH);
  } else {
    digitalWrite(buzzerPin, LOW);
  }
}
Exercise #1
​Try to reverse logic of code above and let buzzer to be constantly "ON" and stop only when button is pressed and held.
​Active buzzer with frequency control
However, if we were to control the frequency in an active buzzer, it requires some clever tricks involving the use delay() between on and off states.

The following code creates an Arduino program that controls a buzzer to generate two different frequencies, which can be toggled using a push button. The program initializes with the first frequency (100 Hz) active and continuously checks if the button is pressed; when pressed, it switches to the second frequency (166 Hz) and vice versa. The frequencies are generated by creating square waves with specific delay periods—5 milliseconds for the first frequency and 3 milliseconds for the second—each repeated 10 times per loop cycle to produce audible tones. A 300-millisecond delay after button detection helps prevent multiple toggles from a single press, and the use of the Arduino's internal pull-up resistor simplifies the button wiring by eliminating the need for an external resistor.

Frequency-Toggle Buzzer 

int buzzer = 8;
int buttonPin = 7;
bool useFirstFrequency = true;

void setup(){
  pinMode(buzzer, OUTPUT);
  pinMode(buttonPin, INPUT_PULLUP);
}

void loop(){
  // Check button state
  if (digitalRead(buttonPin) == LOW) {
    // Button is pressed - toggle frequency
    useFirstFrequency = !useFirstFrequency;
    delay(300); // Simple debounce delay
  }
  
  if (useFirstFrequency) {
    // First frequency: 100 Hz
    for(int i = 0; i < 10; i++){
      digitalWrite(buzzer, HIGH);
      delay(5);  // 5ms HIGH
      digitalWrite(buzzer, LOW);
      delay(5);  // 5ms LOW
    }
  } else {
    // Second frequency: ~166 Hz
    for(int i = 0; i < 10; i++){
      digitalWrite(buzzer, HIGH);
      delay(3);  // 3ms HIGH
      digitalWrite(buzzer, LOW);
      delay(3);  // 3ms LOW
    }
  }
}

Exercise #2

Modify the code to include a third frequency that cycles along with the existing two when the button is pressed. Adjust the timing delays to achieve this new frequency and ensure the button toggles through all three options in sequence (Frequency 1 → Frequency 2 → Frequency 3 → back to Frequency 1).