strange behaviour of my lcd

My LCD gives starnge letters and numbers after a while. Im using a Arduino Duemilanove. On the breadboard there was no problem at all. Now the LCD is connected with (2m long) wires to the board.

like this:

Now the LCD is connected with (2m long) wires to the board.

Well 2m is very long for high speed logic signals. You could try slowing down the pluses from the software. If you are using a library then this would mean hacking into it.

I'll try, but the first minute of so it works fine. If it doesnt work i'll use 2 arduino's and i2c.

but the first minute of so it works fine.

In that case have you tried extra decoupling at the LCD for both supply and back light.


Here are some other ideas and questions-

  1. Reconnect the LCD directly to the breadboard to make sure you didn't disrupt something there without noticing.

  2. We don't know the kind of interconnecting wire you are using, but you might try some other configuration. Ribbon cable and CAT5 come to mind.

  3. Describe the operation in a little more detail. Are you displaying a single message that is OK for a while and then gets scrambled or (more likely) are you periodically sending different messages that display correctly at first and then display as shown.

  4. Assuming the second scenario in #3 - does the deterioration occur slowly or all at once. In other words does the display start showing just a few incorrect characters at first and then gradually get worse until they are all corrupted?

  5. Is there any logic to the corrupted display? In other words when you send a specific character do you get the same (incorrect) character on the display each time?

  6. Do you have the data sheet for your specific LCD controller? At least one of the characters on your display (the one with three vertical lines) does not show up on the Character Code charts for the data sheets that I have looked at.



  1. already soldered it all together so not very easy to reconnect to my breadboard,

  2. CAT 5 utp,

  3. LCD is displaying temperatures and pressures from my dieselengine, update rate is 1 Hz, first it looks good and when I start changing the values (temperarily with a potentiometer for testing purpose)

  4. see #3, at once

  5. no, it mostly occured while I'm playing with the potentiometer.

  6. but the degree sign was made by me but the 3 lines are a bit strange....

If it doesnt work i'll use 2 arduino's and i2c.

Have you thought about using a serial LCD module? I believe that one of them also has an I2C interface. This is essentially the same solution as your 2 arduino idea except that someone has already done some of the work for you (which, on second thought, might not be an advantage...).