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Topic: HD44780 doesnt seem to work - text barely visible (Fixed) (Read 1 time) previous topic - next topic


Mar 16, 2011, 12:45 pm Last Edit: Mar 16, 2011, 03:23 pm by InToSSH Reason: 1
Hello.. i have a problem with my LCD display.. firstly i was using it with Smartie via LPT port.. it was wokring well.. but now i got an arduino board so i unsoldered it and connected it to the breadboard and then to arduino.. i checked the wiring twice and everything seems to be OK.. anyways i used a example scatch with hello world to test it.. but it doesnt seem to work.. i have to lower the contrast using 10kOhm pot to minimum.. then reset the arduino.. and then turn it to maximum.. after that it shows Hello world clearly..but the LCD gets stuck because contrast is too high.. and i have to reset it again.. if i lower the pot a little bit to not to get it stuck the text on LCD is barely visible.. and its kinda flickering and with each more character its less visible.. like the arduino cant get enough power.. i also disconnected the LED backlight and connected external power supply.. anyways its still the same.. if you had any advice i would really appreciate it :)


You haven't given us much to work with.  Some information about the display might help especially since you think there might be a power supply problem.  Specifically, what type of backlight does it have (if any) and how are you powering it?  We have had many cases of wiring and soldering that was not as good as the poster thought it was but we need a photo to check that part out.



Are you powering your LCD from Arduino? You moved the backlight to external, what if you do the same for the whole unit? That would be a good test anyway. I don't know how much current LCD takes, but why risk it.

What LCD do you have? HD44780 compatible, but do you have precise information?

The only law for me; Ohms Law: U=R*I       P=U*I
Note to self: "Damn! Why don't you just fix it!!!"


thanks for your replies.. its a 16x4 LCD MC1604B-SYL .. according to datasheet of LCD the arduinos power should be enough.. i connected external power suply to the arduino because i wasnt sure the USB is able to provide enough power for Arduino and LCD.. i completely disconnected the backlight.. i also checked the wiring between the LCD and arduino with my multimeter and its ok and stable..


well.. i just found the problem.. i noticed that when i push on the LCD the flickering changes.. so i resoldered the resistors on the LCD board.. and now it seems to be ok :) finaly..yay.. maybe the matufacture problem.. i dont know.. it was flickering some times a little bit when it was connected to my computer via LPT.. but i thought it was because of long LPT cable.. anyways thank you guys for your answers :)



So did you buy an LCD or an LCD shield? Could you provide a picture of the hardware and where you soldered, for others seeking similar answers?
Serial LCD keypad panel,phi_prompt user interface library,SDI-12 USB Adapter


Its just a LCD.. not a shield.. at the bottom side of LCD you can find 8 SMD resistors (i believe those are resistors according to code on them) and i just resoldered all of them with my soldering iron because there was a cold link.. that was the reason of flickering.. now it works just right :) im sorry i cant provide a picture because i broke my camera.. but there is not anything else to solder :)


Thanks for the details. I'm sure someone will run into this problem in the future. Now we have one more place to look for problems.
Serial LCD keypad panel,phi_prompt user interface library,SDI-12 USB Adapter

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