Traffic Intersection Siren Code

Projects Programming
1

Hello, I wish to use an interrupt code to sound a siren, if a car were to pass over an LDR when the light is red I wished to have a siren sound, while still having my basic code to transition between the traffic light colours run. I plan to use two LDRs and was wondering if anyone had any suggestions, regarding how I would accomplish this.

This is the code I have so far (it hasn't worked well):

int red1= 4; // the red light at the north light is declared at pin 2
int yellow1= 5; //the yellow light at the north light is declared at pin 3
int green1= 6; //the green light at the northt light is declared at pin 4
int red2= 7; //the red light at the east light is declared at pin 5
int yellow2= 8; //the yellow light at the east light is declared at pin 6
int green2= 9; //the green light at the east light is declared at pin 7
int LDR1= 2; // the LDR at the north light is declared at analong pin 1
int LDR2= 3; //the LDR at the east light is declared at analong pin 2
int speaker1= 10; // the speaker is declared at pin 8

void setup(){
  
  Serial.begin(9600);
  
  pinMode(3,INPUT);
  digitalWrite(3, HIGH);
  attachInterrupt(LDR2, Siren1, CHANGE);
  
  pinMode(2,INPUT);
  digitalWrite(2, HIGH);
  attachInterrupt(LDR1, Siren2, CHANGE);
  
  // the leds for the north light are declared as output
  pinMode(red1,OUTPUT);
  pinMode (yellow1,OUTPUT);
  pinMode(green1, OUTPUT);
  // the leds for the east light are declared as output
  pinMode(red2, OUTPUT);
  pinMode (yellow2,OUTPUT);
  pinMode(green2, OUTPUT);
  
  pinMode(LDR1, INPUT);// LDR2 is declared as input
  pinMode(LDR2, INPUT); // LDR2 is declared as input
  
  pinMode(speaker1, OUTPUT); //the speaker pin is declared as output
  
    
}
                  
void Siren1(){
  int LDR2_Status= analogRead(LDR2);
  LDR2_Status= 0;
  
 if (digitalRead(red2)==HIGH){
   if (LDR2_Status<600){//if the LDR at the east light is <600
    tone(speaker1, 960);  //the speaker will sound the siren 
    delay(600);
    tone(speaker1, 770);
    delay(600);
    tone(speaker1,960);
    delay(600);
    tone(speaker1, 770);
    delay(600);
    tone(speaker1,960);
    delay(600);
    tone(speaker1, 770);
    delay(600);
    noTone(speaker1);
   } 
 }
  
}

void Siren2(){
  int LDR1_Status= analogRead(LDR1);
  LDR1_Status= 0;

  if (digitalRead(red1)==HIGH){
    if (LDR1_Status<600){ //if the LDR at the east light is <600
    tone(speaker1, 960);  //the speaker will sound the siren 
    delay(600);
    tone(speaker1, 770);
    delay(600);
    tone(speaker1,960);
    delay(600);
    tone(speaker1, 770);
    delay(600);
    tone(speaker1,960);
    delay(600);
    tone(speaker1, 770);
    delay(600);
    noTone(speaker1);
    }
  } 
  
}
                    
void loop(){ // declared the function changeLight
  int LDR1_Status= analogRead(LDR1);
  int LDR2_Status= analogRead(LDR2);
  LDR1_Status= 0;
  LDR2_Status= 0;
  
  
  //the north light will be green and the east light will be red
  digitalWrite(green1, HIGH);
  digitalWrite(yellow1, LOW);
  digitalWrite(red1, LOW); 
  digitalWrite(green2, LOW);
  digitalWrite(yellow2, LOW);
  digitalWrite(red2, HIGH); 
  
  //program for sounding the siren
 

  delay(35000); // the north light will be green and the east light will be red for 35 secs

  //the north light will be yellow and the east light will be red
  digitalWrite(green1, LOW);
  digitalWrite(yellow1, HIGH);
  digitalWrite(red1, LOW); 
  digitalWrite(green2, LOW);
  digitalWrite(yellow2, LOW);
  digitalWrite(red2, HIGH); 
  
  Serial.println(LDR2_Status);
 
  

  delay(10000); // the north light will be yellow and the east light will be red for 10 secs

  //the north light will be red and the east light will be green
  digitalWrite(green2, HIGH);
  digitalWrite(yellow2, LOW);
  digitalWrite(red2, LOW);
  
  digitalWrite(green1, LOW);
  digitalWrite(yellow1, LOW);
  digitalWrite(red1, HIGH); 
  
  
  delay(15000); // the north light will be red and the east light will be green for 15 secs

  //the north light will be red and the east light will be yellow
  digitalWrite(green1, LOW);
  digitalWrite(yellow1, LOW);
  digitalWrite(red1, HIGH);
  
  
  digitalWrite(green2, LOW);
  digitalWrite(yellow2,HIGH);
  digitalWrite(red2,LOW);
  
  delay(5000); // the north light will be red and the east light will be yellow for 5 secs
    
  
}
2

In general, you want ISRs to be very short and sweet. Create a global boolean variable; in the ISR, simply set that and then get out. Let the mainline handle all the other stuff.

All those delays make baby Jesus cry. When you move that stuff out of the ISR, consider restructuring it to state machines gated by millis() timing.

3

If you don't have any delay()s in your main code there will be no need to use an interrupt to detect the LDRs.

I am creating a model train control program using a Mega and I have about 20 LDRs all of which are detected just by polling. Plus 12 servos operating turnouts, a 28BYJ48 stepper motor operating a turntable, an nRF24L01+ module for wireless control of the trains and a serial connection to my PC to get instructions.

The functions delay() and delayMicroseconds() block the Arduino until they complete.
Have a look at how millis() is used to manage timing without blocking in Several Things at a Time.

And see Using millis() for timing. A beginners guide if you need more explanation.

...R