Passive buzzer explained — how tone() plays notes on Arduino

#What it is

A passive piezo buzzer is a small round speaker, 12 mm across, with two legs. It has no sound of its own: it clicks each time its pin changes between HIGH and LOW. Make the pin change fast and regularly, and the clicks join into a note. Arduino's tone() function does exactly that, at any frequency you ask for. See it in 3D.

#How it works inside

Inside the black case is a thin metal disc with a layer of piezo crystal on it — a material that bends a tiny bit when a voltage is put across it. Every time the pin goes HIGH the disc bends one way; every time it goes LOW it springs back. Each bend pushes the air, and pushes in the air are sound.

The frequency — how many times per second the pin flips — is the note you hear. More flips per second, higher note:

At 440 Hz one full HIGH-then-LOW wave takes 1 ÷ 440 ≈ 2.3 ms. Double a frequency and you get the same note one octave higher: 440 Hz → 880 Hz.

#Passive or active?

If your buzzer beeps when you simply put 5 V on it, it is an active one.

#The pins

#How to wire it to an Arduino

This is the wiring of the play a tune project:

1. Push the buzzer into the breadboard. Its legs are about 7.6 mm apart, so they land three columns apart.
2. Pin 8 → the + leg.
3. The − leg → GND.

Any digital pin works, not only the ~ pins — tone() makes its own fast signal.

#Example code

The exact code of the tune project — it plays "Ode to Joy" from two arrays:

const int BUZZER = 8;
// "Ode to Joy" (Beethoven): E E F G G F E D C C D E E D D
const int NOTES[] = { 330, 330, 349, 392, 392, 349, 330, 294, 262, 262, 294, 330, 330, 294, 294 };
const int BEATS[] = { 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2 };
const int COUNT = 15;
const int BEAT = 300; // ms

void setup() {
  Serial.begin(9600);
}

void loop() {
  for (int i = 0; i < COUNT; i++) {
    int ms = BEATS[i] * BEAT;
    tone(BUZZER, NOTES[i], ms - 30);
    Serial.println(NOTES[i]);
    delay(ms);
  }
  delay(1500);
}

• NOTES[] holds each note's frequency in Hz; BEATS[] how many beats it lasts.
• tone(BUZZER, NOTES[i], ms - 30) plays the note for a little less than its beat — the 30 ms gap keeps two equal notes from blurring into one.
• delay(ms) waits for the beat; tone() itself does not wait.
• To stop a note started without a duration, call noTone(BUZZER).

Play in 3DRun the code · press the parts · turn it around

#Common mistakes

• Silence with digitalWrite(8, HIGH). A passive buzzer needs a changing signal. Use tone().
• Notes run together. Without a gap, two equal notes sound like one long one. Play each slightly shorter than its beat.
• A very quiet buzzer. Very low notes (under about 100 Hz) are weak on a small piezo. Try 400–4000 Hz.
• Nothing in the 3D lab. Sound is off by default — switch it on in the toolbar.

#Check yourself

#Questions people ask

#What is the difference between an active and a passive buzzer?

An active buzzer has its own oscillator and beeps at one pitch when you give it power. A passive buzzer needs a changing signal, like tone(), but can play any note.

#Does a buzzer need a resistor on Arduino?

A small passive piezo buzzer passes almost no current, so it is usually wired straight to the pin and GND. A magnetic (coil) buzzer is different and needs a transistor.

#How do I play two notes at once?

tone() can only play one note at a time on an UNO. Play them one after another quickly, or use two Arduinos.

#How do I make the buzzer stop?

Give tone() a duration in milliseconds as the third number, or call noTone(pin).

#Where it is used

Play music in the play a tune project. In the 3D lab the buzzer also becomes an eight-key mini piano, and rings the bell of the strength tester.

Last updated 2026-10-29