Problem connecting LCD 16x2 screen to Arduino uno

Other Hardware Displays
1

Hi,

I get my arduino uno since 2 week and and learning on the web how to use it correctly.
I also get an LCD 16x2 screen (http://www.kibuck.com/fr/65-module-lcd-bleu-216.html).

I directly goes on arduino tuts to learn how to use it ! (http://www.arduino.cc/en/Tutorial/LiquidCrystal)

I followed the connection on the plan, checked and double checked it.

My first question is : why does we have to put a potentiomer ? and to wich position do i have ton put it, i mean totally open, close, halfe.

When i connect the last wire to the 5v pin the only things that happen to my lcd screen is the first line is fulled with black.
I mean instead of a character all the pixel are on. And also there is no backlight on.

I'm sure that all the wire are connected and the only way to have this reaction on the lcd screen is when the potentiometer is on the max size.

I posted 3 pictures below :

http://dib258.be/files/IMG_3923.JPG
http://dib258.be/files/IMG_3924.JPG
http://dib258.be/files/IMG_3925.JPG

And the code used is the same that in the arduino tuts.

Thanks in advance !

Edit : the only wire who's not connected (the red one) is the one for the 5v pin. I disconnected it so it's not the error ^^

2

My first question is : why does we have to put a potentiomer ? and to wich position do i have ton put it, i mean totally open, close, halfe.

When i connect the last wire to the 5v pin the only things that happen to my lcd screen is the first line is fulled with black.
I mean instead of a character all the pixel are on. And also there is no backlight on.

I'm sure that all the wire are connected and the only way to have this reaction on the lcd screen is when the potentiometer is on the max size.

The potentiometer is used to adjust the 'contrast' and it must be adjusted properly otherwise the characters will not be visible. When the potentiometer is set to one extreme it will apply 5 volts to pin 3 and the display will be blank. When the potentiometer is set to the other extreme it will apply 0 volts to pin 3 and the display will be very dark. Typically the voltage will be around 0.5 volts for a good display.

If the display shows only a single row of 'blocks' then it means that the display controller has not been properly initialized. This will happen if code is not correct or if there is a problem with your connections. Since the tutorial code known to work this leaves your connections (the six wires between the LCD and the Arduino). Your LCD terminals look suspiciously clean, how is the LCD module connected to the breadboard?

The backlight is not on because you have not connected pins 15 and 16. You typically need a series resistor and you will need the datasheet for your display to determine the proper value.

You might want to try using the tutorial at Arduino Tutorial - connecting a parallel LCD.

Don

3

dib258:
Edit : the only wire who's not connected (the red one) is the one for the 5v pin. I disconnected it so it's not the error ^^

The lcd needs to be powered when the UNO does the initializing (sending commands to tell it in your case to work in 4 bit mode).