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dld Wed 12 Jun 2019 at 12:14:03
Arduino i2c LCD backlight control with LDR

Arduino i2c LCD backlight control with LDR

in darkness lcd backlight can be screaming annoying brigth
auto adjust backlight intensity with an LDR

  lcd.begin(20, 4);
  lcd.setBacklightPin(3,HIGH);             // HIGH is OFF i2c control of backlight OFF
                                           // we control backlight from output D9 PWM 
                                           // Arduino i2c LCD BACKLIGHT CONTROL
int val = analogRead(0); // A0 LDR input 0...1023
val = map(val, 0, 1023, 20, 255); // map scale LDR to PWM
analogWrite(9, val); // D9 PWM output 20...255 solder wire to SMD transtistor 1 base

Serial LCD I2C backpack Module–PCF8574 i2c i/o expander
base of background light transistor connected to PWM output pin ~ D9
light control from i2c is still working => but turn it off in the code=> we control light from PWM ~ D9
others solder a wire to pin7 P3 PCF8574 ic but i think its easyer on the transistor

some do i2c LCD backligth intensity manual adjust with a potmeter on lcd backligth jumper
some connect an LDR to LCD backlight jumper, it works but i was not happy with given light intensity

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