lcd problem


my code works on the 16x2 lcd, but when i replace it by the 20x4 one nothing appears on the screen. shall I make changes to the code or wiring?

Definitely check the wiring. If you replace a 16x2 LCD with a 20x4 LCD, it will still display characters but will just use the first two lines.

The wiring is identical and the same code will work for both so don't mess with it after you get the 16x2 running. Just connect the 20x4 in it's place and readjust the contrast and you should see the same text on the first two lines.

Once it is working you can change the lcd.begin() statement.

If that doesn't work then you may have an extended temperature range device that requires a negative voltage on pin 3.