Active buzzer

A beeper with its own fixed tone: HIGH sounds it, LOW silences it — and it really sounds in your browser.

Parts in the example:

LM35
Active buzzer

The Active buzzer block as it appears on the canvas.

What it is

An active buzzer has an oscillator inside: give it power and it beeps at one fixed pitch. That is the difference from a passive buzzer, which is just a speaker and needs the code to generate the tone with tone(). The active one is the simpler part — one digitalWrite and it sounds.

In the simulator

The block draws sound waves while its GPIO is HIGH, and the browser plays a square wave at the frequency chosen in Settings (100 to 8000 Hz, 2 kHz by default). Browsers only allow sound after you interact with the page, so the buzzer is silent until your first click on Build and run.

Pins

Pin	What it is
S	signal — to a GPIO; HIGH sounds the buzzer
3V3	power — to a 3V3 symbol
GND	ground — to a GND symbol

Wiring

The circuit below is the example Thermometer with alarm — LM35 + buzzer from the lab — open it with Project → Open example… and it comes ready to run.

Active buzzer pin	Goes to
S	D26 on the board (GPIO 26)
3V3	a 3V3 symbol
GND	a GND symbol

Settings

Double-click the block's title bar to open its card, then the Settings tab. Changes apply to the running simulation right away.

Setting	Accepts	Default	Notes
Tone frequency	100 to 8000 Hz	2000 Hz	The ACTIVE buzzer has its own tone: the GPIO only turns it on and off. This is that tone.

Code

sketch.cpp

#include <Arduino.h>

const int LM35 = 32;      // 10 mV per degree Celsius
const int BUZZER = 26;
const float LIMITE_C = 30.0;

void setup() {
  Serial.begin(115200);
  pinMode(BUZZER, OUTPUT);
}

void loop() {
  // 12-bit ADC: 0..4095 = 0..3.3 V -> temp = voltage * 100
  float temp = analogRead(LM35) * 330.0 / 4095;
  bool alarme = temp > LIMITE_C;
  digitalWrite(BUZZER, alarme ? HIGH : LOW);
  Serial.printf("temp=%.1f C %s\n", temp, alarme ? "ALARM!" : "ok");
  delay(300);
}

The LM35 sensor gives a voltage proportional to the temperature (10 mV per °C); the sketch converts the ADC reading and, above 30 °C, sets the buzzer pin HIGH. Below the threshold it goes LOW.

Run it

Press Build and run. The first build of a project takes a while; after that, only what changed is rebuilt.

The simulation running: the canvas reacts and the serial monitor shows what the code prints.

Drag the LM35's temperature slider past 30 °C: the buzzer block shows the waves, you hear the tone, and the serial monitor prints “ALARM!”. Slide it back and it stops.

How the simulation models it

The buzzer follows the level of its GPIO, like an LED. The tone is a property of the part (Settings), not of the signal.
tone() and other PWM signals are not decoded: the block would just follow the fast on/off. For a musical buzzer, this is the wrong part.
The sound is quiet by design (a beep, not a concert) and stops when the simulation stops or the block is deleted.

Try this

Beep in short pulses instead of continuously: 100 ms on, 400 ms off, while the alarm is active.
Add a button that silences the alarm for 10 seconds — the “acknowledge” of a real panel.