Arduino Code LED failure to alternate

Question

Traffic light just stays on red rather than alternating. Wanted it to stay on for 10s then off for 10s, continuing ad infinitum. Dont want to use the delay function cos need to do other stuff while the LED continues to alternate. Thanks

int red = 10;  // red traffic light LED on pin 10
int redcounter;


// the setup routine runs once when you press reset:
void setup() 
{                
  // initialize the digital pin as an output.
  pinMode(red, OUTPUT);     

  digitalWrite(red, LOW);
  redcounter = 0;
}

// the loop routine runs over and over again forever:
void loop()
{
  redcounter = redcounter +1;
  if(redcounter==1000)
  {
     redcounter=0;
     if(digitalRead(red)==HIGH)
     {
       digitalWrite(red, LOW);
     }     
     if(digitalRead(red)==LOW)
     {
       digitalWrite(red, HIGH);
     } 
 }

Emilien · Accepted Answer · 2014-11-03 12:44:03Z

1

You try to read a port which is configured as an OUTPUT. I don't know if this is supposed to work, but it would be more clear if you simply use another port as INPUT and feedback the signal you want to check in that port. I'm not sure however if it makes much sense to check the state of a signal you generate yourself (?). Moreover your redcounter is just "Active waiting", and arduino provides a delay function which does exactly that.

int red=10;
int signal=11;

void setup()
{                
    pinMode(red, OUTPUT);   
    pinMode(signal, INPUT);   
    digitalWrite(red, LOW);
}

void loop()
{
    delay(1000);
    if(digitalRead(signal)==HIGH)
    {
        digitalWrite(red, LOW);
    }      
    if(digitalRead(signal)==LOW)
    {
        digitalWrite(red, HIGH);
    }  
}

answered Nov 3, 2014 at 12:44

Emilien

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Comments

Maciej Baranowski · Accepted Answer · 2014-11-03 12:16:45Z

0

Use elseif instead of if here:

 if(digitalRead(red)==HIGH)
 {
   digitalWrite(red, LOW);
 }     
 else if(digitalRead(red)==LOW)
 {
   digitalWrite(red, HIGH);
 }

In your old solution every time red turned low, it was turned high a moment later.

answered Nov 3, 2014 at 12:16

Maciej Baranowski

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6 Comments

user3062510 Over a year ago

have tried several values for 'if(redcounter==1000)' as well but no difference

Maciej Baranowski Over a year ago

Can you provide whole code? There's possibility that setup is not called, therefore redcounter is not initialised?

Maciej Baranowski Over a year ago

use redcounter>=1000 instead of redcounter==1000.

user3062510 Over a year ago

Whole code has been provided, Arduino automatically runs whatever is under the setup function first before running the loop

user3062510 Over a year ago

Good ideas but the LED still remains on

|

djUniversal · Accepted Answer · 2014-11-03 13:38:56Z

Two issues in your code are that digitalread will not read an output pin and if you use an increment counter you won't be able to accurately denote time. Sorry if I missed a bracket or something I was doing this on the mobile app. Use this:

int red = 10; // red traffic light LED on    pin 10
int redcounter;
boolean pinState = false;
int delayTime = 10000;

// the setup routine runs once when you press reset:
void setup() {
    // initialize the digital pin as an output.
    pinMode(red, OUTPUT);
    digitalWrite(red, LOW);
    redcounter = millis();
}

// the loop routine runs over and over again forever:
void loop() { 
    if((millis() - red counter) > delayTime) {
        redcounter=millis();

        if(pinState) {
            digitalWrite(red, LOW);
            pinState = false;
        }
        else {
            digitalWrite(red, HIGH);
            pinState = true;
        }
    }
}

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