PROBLEM WITH IF STATEMENTS

Projects Programming
1

This is my codes:

const unsigned long sampleTime = 5000;
void setup()
{
pinMode(13, OUTPUT);
pinMode(3, INPUT);
Serial.begin(9600);
}
void loop() {

if ( digitalRead(3) == HIGH and millis() <= 5000 )
{
digitalWrite(13, HIGH);
}
if ( digitalRead(3) == HIGH and millis() > 5000)
{
digitalWrite(13, LOW);
}
if ( digitalRead(3) == LOW and millis() > 5000 )
{
digitalWrite(13, LOW);
}
if ( digitalRead(3) == HIGH and millis() > 5000);
{
millis() - sampleTime;
}
}

The problem here is, after the first if statement, the output stays low. Is there a way that I can reset the system after the second if statement? I tried to use the third and fourth if statement to restart everything but it seems its not working. Here is my original code:

void setup()
{
pinMode(13, OUTPUT);
pinMode(3, INPUT);
Serial.begin(9600);
}
void loop() {

if ( digitalRead(3) == HIGH and millis() <= 5000)
{
digitalWrite(13, HIGH);
}
else {
digitalWrite(13, LOW);
}

}

2

Okay, basics here. Do you realize that millis() will always be greater than 5000, following 5 seconds after boot time?

3

Just realized that. I am sorry I am a newbie here. So can I do the millis()-millis() in the fourth if statement?

4

Please follow the advice on posting a programming question given in Read this before posting a programming question

In particular note the advice to Auto format code in the IDE and to use code tags when posting code here

5

karlcorporal7:
Just realized that. I am sorry I am a newbie here. So can I do the millis()-millis() in the fourth if statement?

I don't see that anywhere. But this statement does a calculation and then throws the result in the garbage can:

    millis() - sampleTime;

You seem to be completely lost and just "winging it". You should read the documentation and tutorials on millis(). I get that you're a newbie, but the processor doesn't care. :slight_smile:

6 
 if ( digitalRead(3) == HIGH and millis() > 5000);
  {
    millis() - sampleTime;
  }

This is a common beginner mistake. You put a ';' at the end of the 'if' line so that is the only statement inside the 'if'. The 'if' can contain only one "statement". The ';' is a statement. The "block statement", surrounded by { and }, then isn't a part of the 'if'.

7

karlcorporal7:
Just realized that. I am sorry I am a newbie here. So can I do the millis()-millis() in the fourth if statement?

A bit more like this:

const unsigned long sampleTimeMs = 5000;
unsigned long mostRecentSampleMs;
void setup()
{
  pinMode(13, OUTPUT);
  pinMode(3, INPUT);
  Serial.begin(9600);

  // force an immediate first sample
  mostRecentSampleMs = millis() - sampleTimeMs;

}

void loop() {
  if ( digitalRead(3) == HIGH and millis()-mostRecentSampleMs <= sampleTimeMs )
  {
    digitalWrite(13, HIGH);
  }
  if ( digitalRead(3) == HIGH and millis()-mostRecentSampleMs > sampleTimeMs)
  {
    digitalWrite(13, LOW);
    mostRecentSampleMs = millis();
  }