Arduino LCD only shows blue no characters

Question

I bought an LCD screen 16x2 basic stuff and I got everything hooked up correctly, verified my pins plus tested the wires twice but I can only get the backlight (I thinks it's the backlight) to show up blue. No characters at all! Not even a white rectangle... Now I tried playing with a 10k potentiometer on pin 3 but it didn't change anything. I also put a resistor of 220 ohm on the backlight voltage in and got nothing except a little dim. Running on an Arduino Nano ATmega328.

Here's my code:

#include <LiquidCrystal.h>

LiquidCrystal lcd(4,3,6,7,9,10);

void setup() {
  lcd.begin(16, 2);
  lcd.clear();
}

void loop() {
  lcd.setCursor(0,0);
  lcd.print("Hello World!");
  lcd.setCursor(0,1);
  lcd.print("Hello World!");
  delay(500);
  lcd.clear();
}

Answer 1

You should be able to see at least white blocks. Check the wiring and how voltage changes on PIN3 (contrast PIN) (I do assume you are using LCD with HD44780 driver).

It may be you need negative voltage to some specific LCD's. Especially when the LCD is powered from 3.3V. Below some solutions:

Negative volt to contrast pin

How to produce negative voltage with PWM