i have just started programming my Arduino Uno and working through basic programs.
i have played around with my 2IC LCD PCF8574T displaying the Hello World!

now i have just completed making happy faces. my question i need help with is why i cannot adjust the back light, i can only turn it on and off.

the I2C board has a jumper which keeps the BL on all the time and i have read articles on the web were i need to remove this. that done the program does not turn it on or off.


//1st Arduino experiment LCD 
// by craig Wilson 22/05/2015
#include <Wire.h> 
LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);
byte smiley[8] = {
int z=1;
void setup() 
 // ------- Quick 3 blinks of backlight  -------------
  for(int i = 0; i< 3; i++)
  lcd.backlight(); // finish with backlight on 
  // put your setup code here, to run once:
lcd.createChar(0, smiley);

void loop() {
  // put your main code here, to run repeatedly: