Lcd 16x2 with glitch on text

Hi Ardu-fiends!

It’s the first time that i notice problems with lcd, I’ve already played with this stuff with more complex board without having any problems.

But now I’m using a Arduino clone (Here the link http://www.gravitech.us/arna30wiatp.html) from a few days and it was working with an old LCD with green backlight, but somehow it has started to loose contrast only on the right side of display and on the startup phase the common black blocks on the first line was shown only on the right part with 8 char on the first line and the other 8 on the bottom line.

Anyway since it was working I thought to replace lcd with a brand new and tested before one with blue backlight but the same controller and size.

In the first try the image in attachment is appeared on my display.

I’ve checked twice all the soldering and connection in general, I’ve also disconnected the ethernet and the RFID reader from the circuit without any success.

Someone have found tha same issue in other way?? and please someone have an idea of how to solve??

Thanks a lot to everybody have the patience to help me :slight_smile:

nlubello:
it was working with an old LCD with green backlight, but somehow it has started to loose contrast only on the right side of display and on the startup phase the common black blocks on the first line was shown only on the right part with 8 char on the first line and the other 8 on the bottom line.

Faulty display, possibly connections in the “Zebra strip”.

nlubello:
Someone have found the same issue in other way?? and please someone have an idea of how to solve??

Beats me. Another faulty display? How unlucky can you get?

OTOH, put a 100 nF capacitor between pins 1 and 2 (GND and Vcc) and see if it gets better.

Please don't talk to me about lucky =(

I'll will try with the last one that i know exactly that it's working.

There is any way to fix those two displays???

Try the capacitor. Lack of decoupling has been known to cause bizarre behaviour.

Other than the problems with the "Zebra strip", if the display itself genuinely is faulty, it is generally unfixable, but it still likely that there is some problem with the configuration.

Ok I will try with 100nF capacitor welded directly on LCD 1 and 2 pins!

Thanks!

Interesting - which language do you speak?

Referring to "welding" where in English the actual term is "soldering", seems to be a common mistranslation on the Chinese websites.

Sorry, I'm not Chinese but I'm Italian.

I always spend my time on mechanical forums and those was the only word in my mind to tell what I have to do.

Welding is the "Hard" sense of melting metals (both workpiece and filler material) like wiki can confirm http://en.wikipedia.org/wiki/Welding but soldering suit much better our work with elettronics because of lower temperature wich melt only the filler material without damaging our precious workpiece (Arduino and company).

So I'm really sorry for this mistake :) but coming back in-topic I have some news.

I've fit a strip pin on LCD to test it on the breadboard with the HelloWord example on another arduino board (same 328p but on Arduino uno form factor) and the "blue" display works well rather than the "green" one, that one is completely broken.

Now I have to try if the arduino nano board have some problems or the issue was related to the messy wiring of the previous assembly

I've also put an capacitor for decoupling as suggested!

Thanks for your support.

That problem has absolutely nothing to do with your wiring. The caracters are generated internally in the display, so wiring cannot make a line defective.

Defect zebra-strip, 100% sure.

I have never seen a LCD display that didn't have the proper decoupling caps built-in, so my bet is that the zebra-strip is faulty.

// Per.

Zapro: I have never seen a LCD display that didn't have the proper decoupling caps built-in, so my bet is that the zebra-strip is faulty.

My bet too. That's funny - must be different in Denmark - because I have a bag of various common ones here and (not going through the whole bag but looking at a couple of different models) I don't recall ever seeing any capacitor at all on them.

Can't be hiding under the display because it is solid plastic "light pipe".

While i agree that not all LCD displays have decoupling caps, i could quicky find some that did.

Looking at the internals of the HD44780 i cannot see why a missing or insufficent decoupling of the controller could make a single line dim/missing, while the operation of the display pertains.

// Per.

LCD.JPG

Zapro: While I agree that not all LCD displays have decoupling caps, I could quickly find some that did.

Yeah, but I am kind of presuming we are talking on this forum about the sort people get from eBay, Sparkfun, Adafruit, etc.

Now dim is one thing and we know about problems when the connection to the "slave" chip is defective, but outright display scrambling - crook characters and failure to access the second line and such - does seem a plausible result from major transients on the power line.