if else expression

the part i'm having trouble 'if else',  right below 'void loop'. looked @ couple tutorials else if, don't understand expression use. thought if purpled high, greater 0 , if low 0.

i can't fans turn off when leds off.

code: [select]

  //fade part of sketch created 1 nov 2008 david a. mellis
 //modified 30 aug 2011 tom igoe

  long secondsinms(int s){
  return s*1000l; //values expressed in seconds
 
 
}
 
  int nemled = 3;
  int nempot = a1;
  int rightrockled = 5;
  int rightrockpot = a2;
  int leftrockled = 6;
  int leftrockpot = a3;
  int purpled = 9;
  int purppot = a4;
  int fans = 4;

 
void setup() {
  pinmode(nempot, input);
  pinmode(nemled, output);                             
  pinmode(rightrockpot, input);
  pinmode(rightrockled, output);
  pinmode(leftrockpot, input);
  pinmode(leftrockled, output);
  pinmode(purppot, input);
  pinmode(purpled, output);
  pinmode(fans, output);
}

void loop() {



if (purpled > 0)
{
   digitalwrite(fans, high);
}
   
 else
{
 
   digitalwrite(fans, low);
}
   
 








 for (int fadevalue = 0 ; fadevalue <= 255; fadevalue += 1) {   
     // sets value (range 0 255):
     analogwrite(purpled, fadevalue);
     delay(30);}

     delay(3000);
     
   for (int fadevalue = 0 ; fadevalue <= 255; fadevalue += 1) {   
     // sets value (range 0 255):
     analogwrite(rightrockled, fadevalue);
     delay(30);}

     delay(3000);

   for (int fadevalue = 0 ; fadevalue <= 255; fadevalue += 1) {   
     // sets value (range 0 255):
     analogwrite(leftrockled, fadevalue);
     delay(30);}

     delay(3000);

   for (int fadevalue = 0 ; fadevalue <= 255; fadevalue += 1) {   
     // sets value (range 0 255):
     analogwrite(nemled, fadevalue);
     delay(30);}

     delay(secondsinms(15));    //temporary delay represents daytime
   
     
   

   // fade out max min in increments of 1 point:
   
   for (int fadevalue = 225 ; fadevalue >= 0; fadevalue -= 1) {   
     // sets value (range 0 255):d
     analogwrite(nemled, fadevalue);
     delay(30);}

     delay(3000);
     
   for (int fadevalue = 225 ; fadevalue >= 0; fadevalue -= 1) {   
     // sets value (range 0 255):
     analogwrite(rightrockled, fadevalue);
     delay(30);}

     delay(3000);

   for (int fadevalue = 225 ; fadevalue >= 0; fadevalue -= 1) {   
     // sets value (range 0 255):
     analogwrite(leftrockled, fadevalue);
     delay(30);}

     delay(3000);

   for (int fadevalue = 225 ; fadevalue >= 0; fadevalue -= 1) {   
     // sets value (range 0 255):
     analogwrite(purpled, fadevalue);
     delay(30);}

     delay(secondsinms(15));  //temporary delay represents night time
}

purpled 9.
that's value gave it.
9 greater zero.

you forgot read pin.

edit: it's output.

Arduino Forum > Using Arduino > Project Guidance > if else expression

arduino