Arduino randomly freezes during runtime?

Question

I'm currently trying to create a traffic simulation project on Arduino, where it can change lights, open a gate, and turn on street lamps based on light. If anybody could help me diagnose why my arduino is behaving this way, that'd be extremely appreciated. Here is my code, if it helps you understand.

//Libraries Used
#include<Servo.h>
//Variable Declaration
int red1 = 10;
int yellow1 = 9;
int green1 = 8;
int red2 = 13;
int yellow2 = 12;
int green2 = 11;
int debug = 3;
int PIR = 5;
int button1 = 2;
int buttonState = 0;
int light = 0;
unsigned long previousTime = 0;
unsigned long currentTime = 0;
int currentState = 0;
int currentPIR = 0;
int pirState = LOW;
Servo servo;
void setup()
{
 pinMode(red1, OUTPUT);
 pinMode(yellow1, OUTPUT);
 pinMode(green1, OUTPUT);
 pinMode(red2, OUTPUT);
 pinMode(yellow2, OUTPUT);
 pinMode(green2, OUTPUT);
 pinMode(debug, OUTPUT);
 pinMode(PIR, INPUT);
 pinMode(button1, INPUT);
 servo.attach(4);
 servo.write(90);
}
void loop()
{
 currentPIR = digitalRead(PIR);
 if(currentPIR == 1){
 servo.write(180);
 }else{
 servo.write(90);
 }
 buttonState = digitalRead(2);
 light = analogRead(A0);
 if(light > 100){
 digitalWrite(debug, HIGH); 
 }else{
 digitalWrite(debug, LOW);
 }
 if(buttonState == HIGH){
 if(currentState == 3){
 digitalWrite(debug, HIGH);
 currentState++;
 }
 }
 //Using millis() instead of delay(), so program doesn't pause completely.
 currentTime = millis();
 changeLights();
}
void changeLights(){
 if(currentState == 0){
 //Red, Green
 digitalWrite(red2, LOW);
 digitalWrite(red1, HIGH);
 digitalWrite(green2, HIGH);
 asyncDelay(4000);
 }
 else if(currentState == 1){
 //Red, Yellow
 digitalWrite(green2, LOW);
 digitalWrite(yellow2, HIGH);
 asyncDelay(2000);
 }
 else if(currentState == 2){
 //Red, Red
 digitalWrite(yellow2, LOW);
 digitalWrite(red2, HIGH);
 asyncDelay(750);
 }
 else if(currentState == 3){
 //Green, Red
 digitalWrite(red1, LOW);
 digitalWrite(green1, HIGH);
 asyncDelay(4000);
 }
 else if(currentState == 4){
 //Yellow, Red
 digitalWrite(green1, LOW);
 digitalWrite(yellow1, HIGH);
 asyncDelay(2000);
 }
 else if(currentState == 5){
 //Red, Red
 digitalWrite(yellow1, LOW);
 digitalWrite(red2, HIGH);
 asyncDelay(750);
 }
}
void asyncDelay(int delayTime){
 if(currentTime - previousTime == delayTime){
 currentState++; 
 previousTime = currentTime;
 if(currentState == 6){
 currentState = 0;
 }
 }
}

• jsotola: add debugging code to your sketch

Answer 1

You should replace:

if(currentTime - previousTime == delayTime){

with

if(currentTime - previousTime >= delayTime){

There is always a chance that, since you are using a servo which is quite intensive with interrupts, that millis() may skip a beat and that statement can never be true.

• Bill Bai: Thank you! I don't know why I hadn't thought of this before, but thank you for such a simple fix! I will accept your answer as solved in a few minutes when it allows me to, but thank you so much, I've been so confused over this the whole day.
• Majenko: @BillBai You should confirm it fixes it - it's only a suggestion...
• Bill Bai: yup, I confirmed it worked, and it's been working for a few minutes already - rather than the 20 seconds max as before.