Suggestion for my code

Projects Programming
1

Hello.
Maybe i could get some advices how to improve this code. Working principle should be:
If Value is less than ..., then led should light up and shine for specific time. After that it should turn off.

`
const int ledPin = 4;
int ldr=A0;//Set A0(Analog Input) for LDR.
int value=0;

int ledState = LOW;

unsigned long previousMillis = 0;

const long interval = 2000;
void setup() {

pinMode(ledPin, OUTPUT);
}

void loop() {
value=analogRead(ldr);//Reads the Value of LDR(light).

if(value<300 ){
digitalWrite(ledPin, HIGH);
unsigned long currentMillis = millis();

if(currentMillis - previousMillis >= interval)
{

	digitalWrite(ledPin,LOW);
previousMillis = currentMillis;

}

}
}

`

2

Please post your code in code tags.

This:

const long interval = 2000;

Should be:

const unsigned long interval = 2000;

If value is < 300 the light will always be on the way you have it coded. Also if the value is < 300 and then the value is >= 300 the light may not turn off.

It is likely that once the light turns on then it will stay on.

3

Ok.
So how i should correct it ?

4

It depends. Do you want the LED to always be on if the value is <300? If not, do you want the LED to turn off after the interval and not turn back on until value is >= 300 and then less than 300 again?

5

If value is less than 300, led should turn on for some time after that time it should turn off or it should turn off if value is >= 300

6

OK. When it turns off after being on should it ever turn back on again?

8

Yes. If value becomes more >=300 and after that it becomes again <300

9

OK. Then you have to remember the previous value of value. The problem always seems simple until it is fully defined.

10

This works. It could be optimized. I used a threshold to detect a change in the analog value since analogs tend to bounce.

const int ledPin = 4;
const int ldr = A0; //Set A0(Analog Input) for LDR.
const unsigned long interval = 2000;
const int threshold = 10;

int value = 0;
unsigned long previousMillis = 0;

void setup() 
{
  pinMode(ledPin, OUTPUT);
}

void loop() 
{
  unsigned long currentMillis = millis();
  static int prevValue = 2000;
  value = analogRead(ldr); //Reads the Value of LDR(light).
    
  if (abs(value - prevValue) > threshold)
  {
    if (value < 300 && prevValue >= 300) 
    {
      digitalWrite(ledPin, HIGH);
      previousMillis = currentMillis;
    }
    else if (value >= 300)
    {
      digitalWrite(ledPin, LOW);
    }
    prevValue = value;
  }
  if ((digitalRead(ledPin) == HIGH) && (currentMillis - previousMillis >= interval))
  {
    digitalWrite(ledPin, LOW);
  }
}
11

Thank you very much. I will need some time to study this code, but it works (i checked).

12

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