Active buzzer, 5V, 12 mm diameter, 85 dB

This tutorial uses the Arduino Uno R3 board, powered from the computer via the USB cable. The 5 V active buzzer with a 12 mm diameter has a small oscillator inside its housing, so it emits a fixed tone on its own when DC voltage is applied.

Use it in projects for audible signals, for example confirming a button press, alarms, warnings when a threshold is exceeded, or doorbells.

How it works:

A passive buzzer is only a transducer. It needs an alternating signal from the microcontroller, and the pitch of the sound depends on the frequency of that signal. The active buzzer has an additional oscillator circuit, so for sound you apply 5 V continuously, and when the voltage is removed the sound stops. The tone has a fixed frequency of approximately 2.3 - 2.4 kHz, and the volume is at least 85 dB at 10 cm.

For this reason, the program controls the buzzer with digitalWrite(8, HIGH) for sound and digitalWrite(8, LOW) for silence. The tone() function is not necessary and does not change the pitch. The rhythm of the beeps is set by the duration the pin stays HIGH and LOW.

The rated consumption is a maximum of 30 mA at 5 V. A pin of the ATmega328P microcontroller on the Arduino Uno supports a maximum of 40 mA, and the recommended value is 20 mA. Connected directly, the buzzer is below the absolute limit but above the recommended value. For short tests, a direct connection is suitable.

For long-term operation or when you are not sure, drive the buzzer through an NPN transistor, for example 2N2222 or BC547, with a 1 kohm resistor at the base.

Wiring:

Power the Arduino Uno R3 board from the computer via the USB cable. The buzzer receives its 5 V directly from pin D8, which operates at a 5 V logic level, so you do not need a level converter. Respect the polarity, because a buzzer connected in reverse does not make any sound. The positive pin is the longer one and is marked with a + sign on the label on top.

If the buzzer has the label with the text REMOVE SEAL AFTER WASHING stuck on its top face, you can peel it off after soldering or washing, because the buzzer sounds louder without it.

Board and libraries:

In the Arduino IDE, select the Arduino Uno board at Tools > Board, from the Arduino AVR Boards package, which comes installed with the Arduino IDE. If you do not have it, add it from the Boards Manager. At Tools > Port, choose the COM or tty port of the board. The program does not use any library, so none needs to be installed.

Code:

The program below makes the buzzer emit short beeps, then a longer pause, and prints each step on the serial monitor.

/*
  Active buzzer 5 V, 12 mm - beep test
  Board: Arduino Uno (Tools > Board > Arduino AVR Boards > Arduino Uno)
  Libraries: none needed
  Wiring:
    Buzzer + (long lead, marked with +) -> Arduino D8
    Buzzer - (short lead)               -> Arduino GND (digital header, next to AREF)
*/
const int BUZZER_PIN = 8;                   // Digital pin that drives the buzzer
const unsigned long BEEP_MS = 200;          // Duration of one beep in milliseconds
const unsigned long PAUSE_MS = 300;         // Pause between beeps in milliseconds
const unsigned long LONG_PAUSE_MS = 1500;   // Longer pause after a group of beeps
int beepCount = 0;                          // Number of beeps emitted so far
void setup() {
  pinMode(BUZZER_PIN, OUTPUT);              // Set the buzzer pin as output
  digitalWrite(BUZZER_PIN, LOW);            // Make sure the buzzer is silent at start
  Serial.begin(9600);                       // Start the serial monitor at 9600 baud
  Serial.println("Active buzzer test started");
}
void loop() {
  beepCount++;                              // Count this beep
  digitalWrite(BUZZER_PIN, HIGH);           // Apply 5 V: the built-in oscillator makes the sound
  Serial.print("Beep ");
  Serial.print(beepCount);
  Serial.println(" ON");
  delay(BEEP_MS);                           // Keep the buzzer on for the beep duration
  digitalWrite(BUZZER_PIN, LOW);            // Remove the voltage: the buzzer goes silent
  Serial.print("Beep ");
  Serial.print(beepCount);
  Serial.println(" OFF");
  if (beepCount % 3 == 0) {
    delay(LONG_PAUSE_MS);                   // Longer pause after every third beep
  } else {
    delay(PAUSE_MS);                        // Short pause between beeps
  }
}

How the code works:

The constant BUZZER_PIN has the value 8 and indicates the pin to which the + pin of the buzzer is connected. The constants BEEP_MS, PAUSE_MS and LONG_PAUSE_MS set the duration of a beep, the pause between beeps and the longer pause after a group of beeps, in milliseconds. The variable beepCount counts the beeps emitted.

In the setup() function, pin 8 is configured as an output with pinMode(), then it is set to LOW so that the buzzer does not sound at startup. Also here, the serial port is opened at 9600 baud and a start message is displayed.

In the loop() function, the program sets the pin to HIGH, waits BEEP_MS, then sets it to LOW. At each beep, beepCount increases and a message is printed. After every group of three beeps there is a longer pause, and after the other beeps a short pause, so that you can clearly distinguish the rhythm.

Result:

Open the Serial Monitor in the Arduino IDE and set the speed to 9600 baud. With each message of the type Beep ON you hear a short beep, and at Beep OFF the buzzer is silent. Example output:

Active buzzer test started
Beep 1 ON
Beep 1 OFF
Beep 2 ON
Beep 2 OFF
Beep 3 ON
Beep 3 OFF
Beep 4 ON
Beep 4 OFF
Beep 5 ON
Beep 5 OFF

Common problems:

The buzzer does not make any sound. The most frequent cause is reversed polarity or a loose contact. Check that the long pin, marked with +, goes to D8 and the short pin goes to GND. Also check that the wires are well inserted into the connectors.

The buzzer sounds continuously, even after uploading the program. If the + pin is mistakenly connected to 5 V instead of D8, the buzzer receives voltage permanently. Move the wire to D8 and check that the program was uploaded.

The sound is weak or muffled. The label on the top face covers the sound opening. Peel it off after soldering and washing. Also mount the buzzer so that the opening is not blocked by the housing or by a wire.

The board resets or the pin heats up during long operation. The buzzer consumes up to 30 mA, above the recommended value of 20 mA for a pin of the ATmega328P. Drive the buzzer through an NPN transistor, for example 2N2222 or BC547, with a 1 kohm resistor at the base, with the emitter to GND, the collector to the - pin of the buzzer and the + pin to 5 V.

No messages appear on the serial monitor. Check that the speed in the Serial Monitor is 9600 baud and that the board's port is selected at Tools > Port.

Limitations and tips:

The active buzzer emits a single fixed tone, of approximately 2.3 - 2.4 kHz. For melodies or different tones, you need a passive buzzer, driven with tone().

The rated voltage is 5 V DC, and AC voltage must not be applied. Change the rhythm of the beeps through the durations BEEP_MS, PAUSE_MS and LONG_PAUSE_MS.

You can further build an alarm that sounds when a value read by a sensor exceeds a threshold, or an audible confirmation signal when a button is pressed. In this case, use the NPN transistor for long-term operation.