Run the loop when values change - Arduino - loops

Question

I am measuring light, temperature and humidity on a arduino uno, and have programmed the loop to run every minute. Monitoring the values on the serial monitor.
However, what i would like is the code to run once to get the values, then wait, or pause, until one of the values change, and then output this on the serial monitor.
I want to get informed of changes in the sensors immediately, not wait for a minute for the loop to run. Is there a way to do this?
Thanks.
So I would need to add an if/else function to the following code?
int lightPin = A5;
int lightok = 9;
int lighthigh = 10;
void setup()
{
Serial.begin(9600);
pinMode(lightok,OUTPUT);
pinMode(lighthigh,OUTPUT);
}
void loop()
{
delay(600000);
int lightlevel = analogRead(lightPin);
lightlevel = map(lightlevel, 0, 1023, 0, 255);
lightlevel = constrain(lightlevel, 0, 255);
Serial.print("Lightlevel: ");
Serial.println(lightlevel);
//led control for light levels
if (lightlevel < 15 || lightlevel > 125) {
digitalWrite(lighthigh, HIGH);
digitalWrite(lightok, LOW);
} else {
digitalWrite(lighthigh, LOW);
digitalWrite(lightok, HIGH);
}
}

Answer 1

You have to ways of doing this:
you can run your loop faster, say every second or half-second and only output a value to serial if the value is different from the previous one or if the difference is bigger than a specific value
you can setup interrupts run code only when something happens. But I need to know the sensor you are using to be more specific on this one.
Hope this helps! :)
EDIT
Okay, I'd do something like that :
int lightSensorPin = A5;
int lightOkPin = 9;
int lightHighPin = 10;
int currentLightLevel = 0;
int previousLightLevel = 0;
int delta = 0;
int deltaValue = 10; // needs to be changed to suit your needs
void setup() {
Serial.begin(9600);
pinMode(lightOkPin, OUTPUT);
pinMode(lightHighPin, OUTPUT);
}
void loop() {
currentLightLevel = analogRead(lightSensorPin); //read the sensor
currentLightLevel = map(currentLightLevel, 0, 1023, 0, 255); // map the value
currentLightLevel = constrain(currentLightLevel, 0, 255); // not sure this is useful
delta = abs(previousLightLevel - currentLightLevel); // calculate the absolute value of the difference btw privous and current light value
if (delta >= deltaValue) { // if the difference is higher than a threshold
Serial.print("currentLightLevel: ");
Serial.println(currentLightLevel);
//led control for light levels
if (currentLightLevel < 15 || currentLightLevel > 125) {
digitalWrite(lightHighPin, HIGH);
digitalWrite(lightOkPin, LOW);
}
else {
digitalWrite(lightHighPin, LOW);
digitalWrite(lightOkPin, HIGH);
}
}
previousLightLevel = currentLightLevel;
delay(1000);
}