Why does this code make an led glow red? - c

Question

I've written this simple piece of code for testing out my arduino and RGB led.
int redled=11;
int blueled=10;
int greenled=9;
void setup()
{
pinMode(redled, OUTPUT);
pinMode(blueled, OUTPUT);
pinMode(greenled, OUTPUT);
}
void loop()
{
digitalWrite(greenled, HIGH);
digitalWrite(blueled, HIGH);
delay(1000);
digitalWrite(greenled, LOW);
digitalWrite(blueled, LOW);
delay(1000);
}
Here is a picture:
(220Ω resistors, in case you are wondering.)
As you can see, I've coded the green and blue to blink, but after I upload it onto my arduino, the red LED actually blinks. Why is this happening? How do I fix it?
Any help would be appreciated!
UPDATE:
When I unplug the red wire altogether, the program works as expected, but now, when I plug it back in, it flashes like this:
WHITE
red
WHITE
red
What is the problem now?

Answer 1

Your problem is that you have not turned the red LED off. Off means it needs a HIGH on the pin as you have a common anode configuration, so the LED elements go on when the voltage is LOW (not HIGH).
You are flashing the blue and green outputs, but the red pin is low all the time. So that means it is on (as the common anode is at +5V). This is because blue+green+red = white (when the blue and green outputs are LOW), whereas red alone is obviously red (when the blue and green outputs are HIGH).
So add in setup():
digitalWrite(redled, HIGH);