Problem with LCD GDM1602K


I am here to report a problem that I've with a LCD. When I connect these pins:

1 - GND
2 - +5V
3 - Contrast (10k)
15 - +5V
16 - GND

it's supposed to display the rows and columns (2x16) very clear but it doesn't happen. Here's the image of what It displays.

Does anyone know what happens here? Is the LCD broken or something?

If anyone can help me I'd very pleased.

How did you connect the contrast POT?
For testing purposes try connecting Pin3 to GND as well and see if there's a difference.

I conected it with a potentiometer like this schematic shows:

But I noticed something weird, when I connect pin 1 and 2 (closed circuit) isn't it supposed to be on?

And in the schematic does not connect the pins 15 and 16. If I do not connect them the LCD doesn't turns on.

The LCD has a backlight which has to be connected separately (pins 15-16). The backlight can be on or off, it won't affect what the LCD displays, it will simply be very difficult to see anything on it without direct light.
When you don't have the contrast set properly you won't see anything on the display itself.
Try the following diagram and see if you see the top row with solid blocks.
*Click to resize.

Yeah! It appeared. The top row has solid blocks. Now how can I make solid both rows? Potentiometer maybe?


I’ve made the same circuit but putting a 47k potentiometer instead of connecting the contrast pin drect to the GND. And this is the result:

And now what I have to do next?

Now connect all the other pins following the schematic you posted earlier, and run the hello world sketch.

If anyone can help me I'd very pleased.

One thing you could do is scan through the other threads that mention 'LCD' in the title. The various devices that are out there, regardless of their configuration (rows and columns) or manufacturer, are more similar than than they are different.

You will find my generic step by step approach to getting an LCD to work in another nearby thread, but here it is again:

(1) If the module has a backlight then get it working properly. This involves only pins 15 and 16 on your LCD module. Make sure to use a current limiting resistor if there is none on the LCD module.

(2) Get the power and contrast working properly. This involves pins 1, 2, and 3 on your LCD module. You should be able to see blocks on one row of a two row display and on two rows of a four row display.

NOTE: The Arduino has not been used yet, except as a possible source for the power needed for the first two steps. Do not try to go any further until this is working. If you don't see the blocks then no amount of program code will help.

(3) Connect the LCD R/W pin (pin 5) to GND.

(4) Connect the six control and data wires between your LCD module and your Arduino.

(5) Upload your sketch and it should work.

If you still don't get a display then make sure that your wiring matches the numbers in the descriptor (or vice versa).

//LiquidCrystal lcd(RS, E, D4, D5, D6, D7);
LiquidCrystal lcd(7, 8, 9, 10, 11, 12); // put your pin numbers here

If you get a display but it is garbled or has some other problems then try again with a 'static' sketch, one that displays a simple message on the top row of the display and then stops. All of your code should be in setup() and loop() should be empty between the brackets.