OSEPP 16x2 LCD Display Turns On But Does not Display any White Boxes

Question

Circuit Wiring

This is my first ever post on here and it is due to a recent personal project i started on a Mega 2560 board. (I was attempting to build a temp and humidity sensor for which i would need to display the values on a LCD display). At first, i built the circuit according to a reference project and i noticed the LCD screen would light up only the first half of the screen (it would be lit up white boxes) img1

Then, assuming my LCD display is not working, i took everything apart and built an initialization LCD circuit.. in which i have read that it should display boxes on the top row. But, when i wire it up very basically, it just lights up but nothing happens. Can anyone tell me whether my LCD might be broken? (I have purchased 3 up till now and would hate to return to the store for ANOTHER broken LCD)

Kindly provide any advice or insight you may have to offer ( I am a complete beginner in Arduino)

I have attached all the pictures of my circuit wiring and of the LCD display.

EDIT 1: I rewired the circuit to include a resistor for contrast (V0; did not use a potentiometer because when i did use it.. it did not make any difference when changing the resistance) I also placed a 100ohm resistor for the backlight (pin A).

The code I used:

#include <LiquidCrystal.h>

const int rs = 12, en = 11, d4 = 5, d5 = 4, d6 = 3, d7 = 2;

LiquidCrystal lcd(rs, en, d4, d5, d6, d7);

void setup() { // set up the LCD's number of columns and rows:
lcd.begin(16, 2); // Print a message to the LCD. lcd.print("hello, world!"); }

void loop() { // set the cursor to column 0, line 1 // (note: line 1 is the second row, since counting begins with 0): lcd.setCursor(0, 1); // print the number of seconds since reset: lcd.print(millis() / 1000); }

Also, i have uploaded a close up picture of my LCD and there seems to be a faint 'Dark' spot towards the middle of the display.. does that imply it is damaged?

Answer 1

It is normal that these displays start up with some lines displaying as all white (and others all dark). That's just how they look before they were initialized.

However, as mentioned above, you forgot to wire the data lines. Pins 7-14 from the display need to be wired to the Arduino, typically pins 4-11. But that depends on the configuration in your sketch. It may also work with only 4 lines, then you would connect pins 11-14 from the display to the Arduino pins 4-7 and configure the display to use 4-bit mode in your sketch.

That said, there are more wiring errors in your picture. The lower pin of your potentiometer is unused, and so like this it has no use (and you cannot control the contrast of the display, also making the text, if there is any, hard to read). The bottom pin of the potentiometer must go to pin 3 of the display (remove the line that is already there).