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Author Topic: LCD uneven contrast and noise  (Read 819 times)
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I don't know what's going on with my LCD display. It used to work fine, but today it hasn't been. Half of the display has a much greater contrast than the other. Also, it is flickering with some weird stuff. I have gotten the LCD code to work fine before. Any advice?





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Some kind of hardware issue by the likes. Did it get dropped? Check the back, maybe poke the connections with a bit of plastic to see if one is flaky and if so, resolder it (when off).
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I think those LCDs have two driver chips (one for each lot of 8 characters) so it looks like one of the driver chips is malfunctioning.
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I built my first LCD project yesterday and i had a simular problem, it turned out to be loose wiring.
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I have been trying to push around with my finger to fix any loose connections. I see that even without the signal wires plugged in, the right half of the board is filled with blocks, while the left half is blank (which is functioning correctly) What would cause the LCD driver chips to start malfunctioning like this? How can I fix it?

- Thanks, Chow.
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I think those LCDs have two driver chips (one for each lot of 8 characters) so it looks like one of the driver chips is malfunctioning.

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I have been trying to push around with my finger to fix any loose connections.

Nicks diagnosis is probably correct (except each driver deals with 16 characters) and the malfunction is likely to be in the connections between the LCD 'glass' and the pc board.  Push down on the metal frame around your display to confirm this.

Don
« Last Edit: June 17, 2012, 03:04:23 pm by floresta » Logged

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I built my first LCD project yesterday and i had a simular problem, it turned out to be loose wiring.

I find that hard to believe.

Don
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Nicks diagnosis is probably correct (except each driver deals with 16 characters) ...

Er, yes. I meant: 8 characters wide (of course with 2 lines that is 16 in total).
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The actual glass display panel has a series of flexible "Zebra Strips" to connect the pcb to the display panel. If it wasn't making contact properly (display dropped?) it could show that same type of display, hence the 'noise'. All the information is there, just noisy so if one very slightly 'twisted' (in the direction originally twisted) the black tabs on the 'noisy end of the display the issue might go away. Regardless a 1602 display is not very expensive... $2 or $3 ( I tossed all I owned that weren't in place on test equipment I use regularly) so there is little else to go wrong, it's already broken... and inexpensively replaced 20 X 4 displays cost what 16 X 2 displays cost a year ago and good quality / easy to use GLCD's are fairly inexpensive too 320 (40 char equivalent ) X 240 (30 line equivalent) for $10 - $20 for a small one, the Adafruit 1.8" tft is easily worked with. I have been Arduino'ing for 3 months, first time using C or C++ (not that I do it well) and it took me about 3 hours to make a very nice albeit small working display for temp data output from an LM35 analog temp sensor. Granted a lot of 'comments' here and there to figure out what I needed and what I didn't... If I wasn't sure about function or method a simple // in front of a line soon told me what to do - or not what to do and I learned a great deal from it. Hard to damage anything with that method at least on an LCD display.

Doc
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If it wasn't making contact properly ... it could show that same type of display

I wish I had thought of that.

Don
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Didja Ever try to re,assemble one of those things??? successfully? I can remember 3 of them throughout the years one was a decoration till it finally fell down in an earthquake, was that one bout 20 years ago and I got so mad I tossed it rather forcefully.. Violently Threw the Da*m thing against the garage wall. It hit the wall at an angle sufficient to keep the pcb and associated wiring from falling off... and there it stayed for 3 or 4 years, a monument to that old maxim...
                                       
                                "Violence is the Last Resort of the Incompetent"
Well it is too... But Sometimes Nothing will do but...

Doc
« Last Edit: June 18, 2012, 12:08:41 am by Docedison » Logged

--> WA7EMS <--
“The solution of every problem is another problem.” -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard

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