If - Else

Using Arduino Programming Questions
1

Hi all

I am trying to test IF - ELSE.

This is what I wrote

const int readPin = 8;

void setup() {
pinMode (11, OUTPUT); // Yellow
pinMode (readPin, INPUT);
pinMode (12, OUTPUT); // Red

}

void loop(){
if digitalRead (readPin, HIGH);

{
digitalWrite (11, HIGH);// Yellow LED on
}
else
{
digitalWrite (12, HIGH);// Red LED on
}

}

what happens at the moment is that pin 8 is not connected to a 5V pin but the yellow LED is on and the Red is off.

Could you please help me to find what's wrong?

Thanks a lot guys :slight_smile:

2

if digitalRead (readPin, HIGH);Delete the trailing semicolon.

3

And because you made it just an input and not connect it it's floating. A pin that's not connected does not mean it's low, it's like undefined, it can be high or low. To overcome that, use pinMode(readPin, INPUT_PULLUP). This will pull a pin high when it's not connected. So connect the pin to GND to make it switch :wink:

4

if digitalRead (readPin, HIGH);

Lose the semicolon and the HIGH, add some parentheses and USE CODE TAGS.

5

Ok, thank you guys

This is how I re-wrote it

void setup() {
pinMode (11, OUTPUT); // Yellow
pinMode (8, INPUT); //jumper to GND
pinMode (12, OUTPUT); // Red
pinMode(8, INPUT_PULLUP); //Thanks for the tip :slight_smile:

}

void loop(){
if (digitalRead (8)==HIGH) // jumper not connected to GND

{
digitalWrite (11, HIGH);// Yellow LED on
digitalWrite (12, LOW) ;//Red LED off
}
else
{
digitalWrite (12, HIGH);// Red LED on
digitalWrite (11, LOW);//Yellow LED off
}

}

it works :slight_smile:

6

. . . and that's why I asked you to USE CODE TAGS.

const byte YELLOW = 11;
const byte RED = 12;
const byte JUMPER = 8;

void setup() 
{
  pinMode (YELLOW, OUTPUT);
  pinMode (RED, OUTPUT);
  pinMode(JUMPER, INPUT_PULLUP);
}

void loop()
{
  int jumperVal = digitalRead (JUMPER);
  digitalWrite (YELLOW, jumperVal);
  digitalWrite (RED, ! jumperVal);
}
7

AWOL:
. . . and that's why I asked you to USE CODE TAGS.

const byte YELLOW = 11;

const byte RED = 12;
const byte JUMPER = 8;

void setup()
{
  pinMode (YELLOW, OUTPUT);
  pinMode (RED, OUTPUT);
  pinMode(JUMPER, INPUT_PULLUP);
}

void loop()
{
  int jumperVal = digitalRead (JUMPER);
  digitalWrite (YELLOW, jumperVal);
  digitalWrite (RED, ! jumperVal);
}

I'm sorry AWOL, I tought CODE TAGS were the desctiptions after //

Thanks! :slight_smile: