Day 11: Buzzer — Make Noise and a Simple Melody

Hi Anish! Today your Arduino starts making sound. We’ll connect a piezo buzzer — a tiny speaker that can play tones — and learn how to play single beeps, long beeps, and even a short melody. By the end, your board can sing.

What you need today

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• Arduino Uno + USB cable
• Breadboard
• 1 piezo buzzer (passive buzzer — looks like a small black cylinder with a hole)
• 2 jumper wires

Passive vs active buzzers

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There are two kinds of buzzers in most kits:

• Active buzzer — has a built-in circuit. Apply power and it just beeps at one fixed sound. Useful but boring.
• Passive buzzer — you send it different frequencies and it plays different notes. This is what we want. More flexible.

If your kit has both, the passive one usually has a hole on top (where sound comes out) and the active one is sealed. When in doubt, try both — whichever one plays different notes with the code below is the passive one.

Passive buzzers have a + side (usually marked with + on top) and a − side. The + leg is positive, − is GND.

The circuit

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graph LR
    PIN8["Pin 8"] --> BZp["Buzzer +"]
    BZp --> BZn["Buzzer −"]
    BZn --> GND["GND"]

Wiring:

1. Jumper from pin 8 to the + leg of the buzzer.
2. Jumper from the − leg of the buzzer to GND.

That’s it. No resistor needed for a buzzer (though some people add one for safety — not required).

Part 1: Simple beep

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void setup() {
  pinMode(8, OUTPUT);
}

void loop() {
  tone(8, 1000);    // Play a 1000 Hz tone on pin 8
  delay(500);
  noTone(8);        // Silence
  delay(500);
}

Upload. You should hear: beep (half a second), silence (half a second), beep, silence, forever.

What is tone()?

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tone(pin, frequency) tells Arduino to send a square wave to the pin at the given frequency (in Hz, which is “cycles per second”). The buzzer’s membrane vibrates at that frequency and you hear a pitch. Higher numbers = higher pitch.

• tone(8, 200) — very low, almost a rumble
• tone(8, 1000) — middle, a clear tone
• tone(8, 4000) — high squeak

What is noTone()?

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noTone(pin) stops the sound. That’s all. You need it because tone() by itself keeps playing forever until you tell it to stop.

You can also call tone(pin, frequency, duration) with three arguments — Arduino plays the note for that many milliseconds and then stops on its own. We’ll use that style in the melody below.

Part 2: Rising pitch siren

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void setup() {
  pinMode(8, OUTPUT);
}

void loop() {
  // Sweep from low to high
  for (int freq = 200; freq <= 2000; freq += 10) {
    tone(8, freq);
    delay(5);
  }
  noTone(8);
  delay(500);
}

Upload. You hear a rising siren — 200 Hz up to 2000 Hz in tiny steps. That’s a for loop where the counter freq goes up by 10 each time (freq += 10 is shorthand for freq = freq + 10). Day 4’s for-loop idea, applied to sound.

Part 3: Play a short melody

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Let’s play the first few notes of Twinkle Twinkle Little Star. Each note is a specific frequency.

Twinkle Twinkle goes: C C G G A A G (“Twinkle twinkle little star”)

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void setup() {
  pinMode(8, OUTPUT);
}

void loop() {
  tone(8, 262, 400);  // C
  delay(450);         // wait a bit longer than the note
  tone(8, 262, 400);  // C
  delay(450);
  tone(8, 392, 400);  // G
  delay(450);
  tone(8, 392, 400);  // G
  delay(450);
  tone(8, 440, 400);  // A
  delay(450);
  tone(8, 440, 400);  // A
  delay(450);
  tone(8, 392, 800);  // G (longer — it's a held note)
  delay(850);

  delay(2000);        // big pause before repeating
}

Upload. You should hear the opening line of Twinkle Twinkle. Not a symphony, but recognizable.

Why tone(8, 262, 400) with 3 arguments?

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The third number (400) tells tone() how long to play the note — 400 milliseconds in this case. After 400ms the sound stops automatically. No noTone() needed.

Why delay(450) instead of delay(400)?

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Because if you delay(400) right after a 400ms note, the next note starts the instant the first one ends — notes blend into each other with no gap. The extra 50ms gives a tiny pause so you can hear individual notes clearly.

Try this

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1. Faster melody. Change all the 400s to 200s and all the 450s to 250s. Twinkle Twinkle, espresso edition.
2. New melody. Mary Had a Little Lamb: E D C D E E E (all the same length). Look up the frequencies above and write the tone calls.
3. Use variables. Make int noteLength = 400; at the top and use it in every tone call. Changing one number changes the whole tempo. (This is Day 4’s variable idea, applied to music.)
4. Two-tone siren. Alternate between 500 Hz and 1000 Hz every 200ms. Sounds like an ambulance.

Storing notes in arrays

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If you do Challenge 2 above, you’ll notice it’s tedious to write 7 tone() calls. Here’s a fancier way using an array — a variable that holds a list of numbers.

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int melody[] = {262, 262, 392, 392, 440, 440, 392};
int noteCount = 7;

void setup() {
  pinMode(8, OUTPUT);
}

void loop() {
  for (int i = 0; i < noteCount; i++) {
    tone(8, melody[i], 400);
    delay(450);
  }
  delay(2000);
}

• int melody[] = {262, 262, 392, ...}; — this creates a variable called melody that holds a list of numbers. The [] after the name means “this is an array.”
• melody[0] is the first number (262), melody[1] is the second (262), melody[2] is the third (392), etc. Arrays are indexed from 0, just like for-loop counters.
• Inside the for loop, melody[i] grabs the ith note and plays it.

Arrays are the right way to handle “lots of things of the same kind.” You’ll use them constantly from here on.

What you learned today

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• What a piezo buzzer is (active vs passive)
• tone(pin, frequency) — play a pitch on a pin
• tone(pin, frequency, duration) — play for a set time
• noTone(pin) — stop playing
• Frequency = pitch. Higher Hz = higher note.
• Musical notes as Hz values (C = 262, G = 392, A = 440, etc.)
• += — shorthand for “add to variable” (freq += 10 is freq = freq + 10)
• Arrays — int melody[] = {...}; — a variable that holds a list

What is next

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Day 12 — your first motor. A servo motor can rotate to any angle you pick. We’ll sweep it back and forth like a wagging tail, and then use the potentiometer to control it with a knob.

Great work, Anish. Now your Arduino can beep, sing, and tell you stories.