ARDUINO Buzzer playing sound when it shouldn't - arduino-uno

Question

So I made this kind of a temperature/humidity sensor and decided to add a fire sensor feature. So it all works fine, right? No, I also decided I want a buzzer to that. Tested it, works well, so I thrown it into my project.
Started it up [project], lit up a lighter, works fine, LEDs blink, a text is shown, buzzer plays an alarm. But then, after the fire was out, the buzzer continued to play one of two tones, even though there was no fire. Here's the code, to make it all clear:
#include <LiquidCrystal.h>
#include <dht.h>
LiquidCrystal lcd(7, 6, 5, 4, 3, 2);
dht DHT;
#define FLAME 13
#define DHT11_PIN 8
#define ALARM A5
const int a9 = 9, a10 = 10, a11 = 11, a12 = 12;
byte z[8] = {
B00100,
B00000,
B11111,
B00001,
B00010,
B00100,
B11111,
B00000,
};
byte st[8] = {
0b00110,
0b01001,
0b01001,
0b00110,
0b00000,
0b00000,
0b00000,
0b00000,
};
void setup(){
lcd.begin(16, 2);
lcd.createChar(0, st);
lcd.createChar(1, z);
Serial.begin(9600);
pinMode((a9, a10, a11, a12), OUTPUT);
pinMode(FLAME, INPUT);
pinMode(ALARM, OUTPUT);
}
void loop() {
// Flame sensor code for Robojax.com
int fire = digitalRead(FLAME);// read FLAME sensor
if(fire == HIGH)
{
analogWrite(a9, 255);
analogWrite(a10, 255);
lcd.setCursor(5, 0);
lcd.print("Po");
lcd.print(char(1));
lcd.print("ar!");
tone(ALARM, 4300);
delay(150);
analogWrite(a9, 0);
analogWrite(a10, 0);
lcd.clear();
tone(ALARM, 3500);
delay(150);
} else {
lcd.createChar(0, st);
int chk = DHT.read11(DHT11_PIN);
lcd.home();
lcd.print("Temp.: ");
lcd.print(DHT.temperature);
if(DHT.temperature >= 20.00 && DHT.temperature < 25) {
analogWrite(a11, 255);
delay(750);
analogWrite(a11, 0);
delay(750);
} else if(DHT.temperature >= 25 && DHT.temperature < 30) {
analogWrite(a10, 255);
delay(250);
analogWrite(a10, 0);
delay(250);
} else if(DHT.temperature >= 30) {
analogWrite(a9, 255);
}
lcd.print(char(0));
lcd.print("C");
lcd.setCursor(0, 1);
lcd.print("Wilg.: ");
lcd.print(DHT.humidity);
if(DHT.humidity >= 45.00 && DHT.humidity < 60.00) {
digitalWrite(a12, HIGH);
delay(250);
digitalWrite(a12, LOW);
delay(250);
} else if(DHT.humidity >= 60.00) {
digitalWrite(a12, HIGH);
}
lcd.print(" %");
delay(750);
}
delay(200);
}
So, what I mean is that even though fire is changed from HIGH to LOW and other part of the code is executed, the buzzer continues to play.
What am I doing wrong?

Answer 1

Check the documentation for tone:
A duration can be specified, otherwise the wave continues until a call
to noTone().
So, you probably need to reset your tone on every loop beginning before checking the values of the sensors (or explicitly invoke notone on the LOW branch), or use the 3-arg version of tone.
I have no idea how tone and delay might interact, though.
I'd probably make the actual tone sounding routine its own task. The idea is that you would start the alarm task and then reset it when appropriate. But for now make sure your state is reset at the beginning of every loop, or each branch resets anything it has to explicitly, if tasks sound too advanced.
Make sure you learn the basic "print" debugging in the Arduino world. Simple write logging to the serial port where it can be read on the IDE is invaluable.
Finally: use functions! If you put everything in loop your programs will get unreadable as they grow. For example, if you have some state you want to reset every time (e.g., running tasks like tones, values, flags) then create an init() function that loop calls first so any given loop has good starting state.

Answer 2

Limitations of the Piezo Buzzer
Here are some things to consider when using the piezo buzzer:
You can’t use tone() while also using analogWrite() on pins 3 or 11