Help me figure this out (noobie problem)

Projects Programming
1

Hey guys, i am playing with my arduino board and trying to get my potentiometer to turn on my RBG LED's red light (was going to eventually try to get it to go through all the colors as i rotate the potentiometer but thats a long ways away yet) and i keep getting a error when i try to compile it, i can't figure it out. Wondering if perhaps one of the more experienced persons can help me figure out whats going on here.

Heres my little project

const int RED_LED_PIN = 9;
const int GREEN_LED_PIN = 10;
const int BLUE_LED_PIN = 11;
const int DISPLAY_TIME = 100;

int redIntensity = 0;
int greenIntensity = 0;
int blueIntensity = 0;


int sensorPin = A5;
int sensorValue = 0;

void setup() {
  // initialize serial communication at 9600 bits per second:
  Serial.begin(9600);
}

// the loop routine runs over and over again forever:
void loop() {
  // read the input on analog pin 0:
  sensorValue = analogRead(sensorPin);
  // Convert the analog reading (which goes from 0 - 1023) to a voltage (0 - 5V):
if (sensorValue < 255);
redIntensity = 255 

analogWrite(RED_LED_PIN, redIntensity);
}
// print out the value you read:
  Serial.println(sensorValue);
}

and my error is this

ReadAnalogVoltagefxkk.cpp: In function 'void loop()':
ReadAnalogVoltagefxkk:35: error: expected `;' before 'analogWrite'
ReadAnalogVoltagefxkk.cpp: At global scope:
ReadAnalogVoltagefxkk:38: error: expected constructor, destructor, or type conversion before '.' token
ReadAnalogVoltagefxkk:39: error: expected declaration before '}' token
2

You have a missing ; before analogWrite, as the error states.

redIntensity = 255

should be

redIntensity = 255;

Also, the if statement just above it should not have a semicolon, but have an open brace:

if (sensorValue < 255) {
3

Thanks, i got it going now but unfortunately it just comes on soon as the arduino starts. did i miss something here? i thought the if command would only run redIntensity 255 when the sensorvalue is over 255. (i started it at 0 and the potentiometer reads 0 in the serial window.

I intended the Red LED to turn on when i got about a 1/4 turn (255) from my potentiometer....

4

your code states that if the value is less than 255, which means anything from 0 to 255, then switch it on, so it is doing what you asked it to do.
Try changing it to a range like between 240 and 260:

if ((sensorValue >= 240) &&  (sensorValue <= 260)) {
5

or try something like this:
when the sensorvalue is less than 255, turn red on to the value of the sensorvalue, otherwise switch it off:

if (sensorValue < 255);
  redIntensity = sensorValue; 

  analogWrite(RED_LED_PIN, redIntensity);
} else {
  redIntensity = 0; 

  analogWrite(RED_LED_PIN, redIntensity);
}

Maybe not the best or most efficient way, but fairly straight forward to understand.

Since you are always executing the analogWrite, you can remove that from the if statement:

if (sensorValue < 255);
  redIntensity = sensorValue; 
} else {
  redIntensity = 0; 
}
analogWrite(RED_LED_PIN, redIntensity);