Passive buzzer with Arduino Uno — tone(), notes and a siren

A passive buzzer is a tiny speaker: it makes whatever pitch you drive it at. With the Uno’s built-in tone() function it can play notes, melodies and sirens. That makes it the better choice over an active buzzer when you want an alarm people actually notice.

Wire I/O to D8 and power the module from 5V. The thing to plan for on the Uno is that tone() takes over Timer2. While it plays, PWM on D3 and D11 stops, and it can’t share a sketch with IRremote.

The sketch plays the Indian sargam (Sa Re Ga Ma Pa Dha Ni Sa) up and down, then a rising and falling siren — a good starting point for a doorbell or a gas alarm.

Wiring

Board quirks

• A passive buzzer has no oscillator: the Uno must send it a square wave at the note’s frequency, which is what tone() does. On plain 5 V it only clicks once.
• tone() uses the Uno’s Timer2. While a note plays, analogWrite() on D3 and D11 doesn’t work, and IRremote (also Timer2) can’t be used in the same sketch.
• Only one tone at a time on the Uno — a second tone() on another pin is ignored until noTone().
• Passive buzzers are loudest near their resonance, about 2–4 kHz. Low notes like Sa (262 Hz) sound quiet; that is the buzzer, not the code.
• Some KY-006 boards print the pins as S and − with an unlabelled middle pin. S is I/O, − is GND, the middle one is VCC.

Code

// Passive buzzer module on an Arduino Uno R3, played with tone().
// I/O → D8, VCC → 5V, GND → GND.
// tone() uses Timer2: while it plays, PWM on D3 and D11 stops working.
const uint8_t BUZZER_PIN = 8;

// Sargam in C: Sa Re Ga Ma Pa Dha Ni Sa' (Hz)
const uint16_t SARGAM[] = {262, 294, 330, 349, 392, 440, 494, 523};
const char* const NAMES[] = {"Sa", "Re", "Ga", "Ma", "Pa", "Dha", "Ni", "Sa'"};

void setup() {
  Serial.begin(9600);
  Serial.println(F("Passive buzzer on D8 - playing the sargam"));
}

void loop() {
  for (uint8_t i = 0; i < 8; i++) {
    Serial.print(NAMES[i]);
    Serial.print(' ');
    tone(BUZZER_PIN, SARGAM[i], 300);
    delay(350);  // tone() returns at once; wait for the note plus a short gap
  }
  Serial.println();
  delay(600);
  for (int8_t i = 7; i >= 0; i--) {
    tone(BUZZER_PIN, SARGAM[i], 200);
    delay(230);
  }
  Serial.println(F("Siren"));
  for (uint8_t r = 0; r < 3; r++) {
    for (uint16_t f = 600; f < 1400; f += 20) {
      tone(BUZZER_PIN, f);
      delay(5);
    }
    for (uint16_t f = 1400; f > 600; f -= 20) {
      tone(BUZZER_PIN, f);
      delay(5);
    }
  }
  noTone(BUZZER_PIN);
  delay(2000);
}

// Passive buzzer module on an Arduino Uno R3, played with tone().
// I/O → D8, VCC → 5V, GND → GND.
// tone() uses Timer2: while it plays, PWM on D3 and D11 stops working.
const uint8_t BUZZER_PIN = 8;

// Sargam in C: Sa Re Ga Ma Pa Dha Ni Sa' (Hz)
const uint16_t SARGAM[] = {262, 294, 330, 349, 392, 440, 494, 523};
const char* const NAMES[] = {"Sa", "Re", "Ga", "Ma", "Pa", "Dha", "Ni", "Sa'"};

void setup() {
  Serial.begin(9600);
  Serial.println(F("Passive buzzer on D8 - playing the sargam"));
}

void loop() {
  for (uint8_t i = 0; i < 8; i++) {
    Serial.print(NAMES[i]);
    Serial.print(' ');
    tone(BUZZER_PIN, SARGAM[i], 300);
    delay(350);  // tone() returns at once; wait for the note plus a short gap
  }
  Serial.println();
  delay(600);
  for (int8_t i = 7; i >= 0; i--) {
    tone(BUZZER_PIN, SARGAM[i], 200);
    delay(230);
  }
  Serial.println(F("Siren"));
  for (uint8_t r = 0; r < 3; r++) {
    for (uint16_t f = 600; f < 1400; f += 20) {
      tone(BUZZER_PIN, f);
      delay(5);
    }
    for (uint16_t f = 1400; f > 600; f -= 20) {
      tone(BUZZER_PIN, f);
      delay(5);
    }
  }
  noTone(BUZZER_PIN);
  delay(2000);
}

Expected serial output

Passive buzzer on D8 - playing the sargam
Sa Re Ga Ma Pa Dha Ni Sa'
Siren

Passive buzzer on D8 - playing the sargam
Sa Re Ga Ma Pa Dha Ni Sa'
Siren

Common errors