Outputs and switching

Piezo buzzer with ESP32

Two parts sold under one name behave very differently. An active buzzer has its own oscillator: give it power and it makes one fixed note, around 2.3 kHz on one listed module. A passive buzzer needs a frequency from your code, so it can play alarms or melodies. If ledcWriteTone gives odd crackling or only one note, you probably have an active buzzer. Most active ones have a sealed underside, while passive ones often show bare board. Tell them apart properly with a quick test: connect 3.3 V briefly, and a steady tone means active.

Current decides the wiring. One active module lists about 25 mA at 5 V, too much to drive directly from a GPIO. Use an NPN transistor such as an S8050: buzzer + to 5V, buzzer - to the collector, emitter to GND, and the GPIO to the base through about 1 kΩ. That is also louder, since the buzzer gets 5 V. Add a flyback diode across a magnetic coil buzzer.

Code differs across core versions. Core 3 uses the pin number in ledcAttach and ledcWriteTone, and core 2 used channel numbers, so old examples can fail to compile. For a notification on a panel, keep beeps short, and offer a mute option: a buzzer that cannot be silenced gets disconnected. Several display boards have a speaker or amplifier already, so check the board page first. LCD Ultra Pro has a Beep action for a passive buzzer, and an active one only needs a rule that sets its pin on or off.

const int BUZZER_PIN = 5;              // passive buzzer

void setup() {
  ledcAttach(BUZZER_PIN, 2000, 8);
}

void loop() {
  ledcWriteTone(BUZZER_PIN, 2000);
  delay(150);
  ledcWriteTone(BUZZER_PIN, 2600);
  delay(150);
  ledcWriteTone(BUZZER_PIN, 0);         // silence
  delay(2000);
}

Use this information at your own risk. It is for general guidance only: the example code compiles, but it has not been tested on every part, and modules differ between sellers. Check the manufacturer's data before you build. Product names belong to their owners, and LCD Ultra Pro is not affiliated with them. See our Terms.