The buzzer: playing notes and melodies | Our guides informaticait.it

Guide no. 38

Two wires and one command: Arduino plays “Frère Jacques”. Why you need a passive buzzer, how to write the notes and how to turn it into an alarm.

By Ada Intelisano · informaticait.it technical team

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In short

The passive buzzer goes between a pin and GND: two wires.
Every note is a number of hertz: A is 440.
tone plays a note, an array holds the melody.
One note at a time; on the UNO it interferes with PWM on pins 3 and 11.

Time: 20 minutesLevel: day fourBefore: guide no. 34

A buzzer turns the signal from a pin into a sound. With a single command, tone, Arduino plays the note you want: by the end of this guide it will play “Frère Jacques”.

1Get the parts ready

a passive buzzer (piezo): the one with no electronics inside
Arduino UNO, breadboard, two jumper wires

New word: passive or activeAn active buzzer has an oscillator inside: just give it power and it always makes the same “beeep”. A passive one plays the note Arduino sends it: that's the one you need for melodies.

2Build the circuit

The buzzer has two legs: the one marked + goes to pin 8 (blue wire), the other to the − rail, which is connected to GND. Two wires in all.

3Notes are numbers

Every note is a vibration with a certain number of oscillations per second (hertz). These are the ones we use:

C
262

D
294

E
330

F
349

G
392

A
440

New word: tonetone(8, 440, 400) plays the 440 Hz note (the A) on pin 8 for 400 thousandths of a second. noTone(8) silences the buzzer.

4Write and upload the melody

// The buzzer plays “Frère Jacques”. Passive (piezo) buzzer between pin 8 and GND.
#include <Arduino.h>

const int BUZZER = 8;        // with the ESP32 write 25

// the notes in hertz (the same as in the pitches.h file from the Arduino examples)
const int NOTE_C4 = 262, NOTE_D4 = 294, NOTE_E4 = 330, NOTE_F4 = 349, NOTE_G4 = 392, NOTE_A4 = 440;

const int MELODY[]   = {NOTE_C4, NOTE_D4, NOTE_E4, NOTE_C4,  NOTE_C4, NOTE_D4, NOTE_E4, NOTE_C4,
                        NOTE_E4, NOTE_F4, NOTE_G4,  NOTE_E4, NOTE_F4, NOTE_G4};
const int DURATION[] = {400, 400, 400, 400,  400, 400, 400, 400,  400, 400, 800,  400, 400, 800};
const int NUM_NOTES = sizeof(MELODY) / sizeof(MELODY[0]);

void setup() {
  for (int i = 0; i < NUM_NOTES; i++) {
    tone(BUZZER, MELODY[i], DURATION[i]);    // play the note for the given time
    delay(DURATION[i] * 1.2);                // wait for it to end, plus a short pause
  }
  noTone(BUZZER);
}

void loop() {
  // the melody plays only once: press RESET to hear it again
}

New word: arrayA row of values with a single name. MELODY[] holds the notes in order, DURATION[] how long each one lasts; MELODY[0] is the first.

✓ What you should seeAs soon as it's uploaded, the buzzer plays the beginning of “Frère Jacques”. To hear it again, press the board's RESET button.

If it doesn't work

No sound: is the wire on pin 8? Is the buzzer passive? With an active one you'd hear a single tone.
It plays very quietly: that's normal, small piezos aren't loud. Hold it close to your ear or rest it on a box.
It always makes the same sound, whatever the note: it's an active buzzer, you need a passive one.

5Challenge yourself

Try it yourself

Change the durations: all 200 for a fast version.
Add the pushbutton from guide no. 35: the melody starts when you press it (move the code from setup to loop).
Make an alarm: two alternating notes, 880 and 440, until you press the button.

6Two things to know

Arduino plays one note at a time, and it can't go below 31 Hz.
On the UNO, while tone is playing, PWM on pins 3 and 11 doesn't work properly: for fading LEDs use other pins (guide no. 37).

7And with the ESP32?

Same circuit with the buzzer on GPIO 25; in the sketch write const int BUZZER = 25;. The melody is the same.

✓ What you learned

a passive buzzer plays the note you give it, an active one always makes the same sound;
tone(pin, frequency, duration) plays, noTone silences;
an array keeps many values in order under a single name.

Sources: Arduino, language reference: tone() and noTone(); “toneMelody” example (pitches.h) · informaticait guides no. 34, 35 and 37