Can't stop the 3 pin active buzzer

Question

I was simply trying to program a buzzer with the ultrasonic HC SR04 and 128x64 OLED display. The buzzer is an active buzzer (3 pin) on a small board. The problem is that, once on, it never stops buzzing. I have used the following code which is working fine except the buzzer.

#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#define trigPin 9
#define echoPin 8
int buzzer = 12;//the pin of the active buzzer 
#define OLED_RESET 4
Adafruit_SSD1306 display(OLED_RESET);
void setup() {
Serial.begin (9600);
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);
pinMode(buzzer,OUTPUT);//initialize the buzzer pin as an output
display.begin(SSD1306_SWITCHCAPVCC, 0x3C); //initialize with the I2C addr 0x3C (128x64)
display.clearDisplay();
}
void loop() {
float duration;
float distance_cm;
float distance_in;
digitalWrite(trigPin, LOW); 
delayMicroseconds(2);
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);
duration = pulseIn(echoPin, HIGH);
distance_cm = (duration/2) / 29.1;
//distance_in = (duration/2) / 73.914;
display.setCursor(30,0); //oled display
display.setTextSize(1);
display.setTextColor(WHITE);
display.println("Distance");
display.setCursor(30,10); //oled display
display.setTextSize(1);
display.setTextColor(WHITE);
if(distance_cm<2.9)
 {
      noTone(buzzer);
      display.println("Too Close");
}
else if(distance_cm>30)
 {
      noTone(buzzer);
      display.println("Out of Range");
}
else if(distance_cm>2.9 && distance_cm<3.5 )
{
display.println(distance_cm);
display.setCursor(80,10);
display.setTextSize(1);
display.println("cm");
display.setCursor(30,20); //oled display
display.setTextSize(1);
display.setTextColor(WHITE);
display.println("Reading Data");
tone(buzzer,329);

delay(20);
noTone(buzzer);

}
else
{
 noTone(buzzer);
 display.println("Too Far");
}
display.display();
delay(500);
display.clearDisplay();
Serial.println(distance_cm);
}

I am a beginner in Arduino programming ( Although have basic knowledge in C and python). You can make any optimization of this code if you feel so. Please help.

DLSmith · Answer 1 · 2025-04-22T14:05:34.170

I think that for a passive buzzer you might take ‘noTone(buzzer);’ out of every conditional statement and place it as a default buzzer reset near the beginning of void loop() - at least before the first ‘if’ conditional. The point: move the buzzer state positively off of a silent condition when the right condition is met.

For an active buzzer, as you have, do the suggestion - but use HIGH criterion at pin output statements, and LOW at beginning of loop.

I notice also that there is a distance range not covered in the if/else tests. Not that it must matter.

Can't stop the 3 pin active buzzer

1 Answers1