Lcd 20x4 contrast problem

Using Arduino Displays
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IMG_20220511_213526
IMG_20220511_2135261920×1458 152 KB

I recently bought this 20x4 lcd display... Fact that the lcd is initializing properly as you can see black boxes so im preety sure that i did connection right.. now the problem is that ..the max contrast i could get is hardly visible im using 10k pot for v0 pin .. i have even tried to give direct gnd to v0 pin still same contrast.. is it possible that some lcd need negative voltage input to adjust contrast?

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There were some that were for use at lower temperatures that needed a negative contrast voltage. The common ones don't use a negative voltage. Usually you would have to special order them and pay extra. I have only seen one - I bought it from a surplus company.

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Thanks ... Can you tell what could be the possible problem i know without seeing connection it would b hard but as i have soldered other things also in pcb and its messy to track wires... so posting backside of pcb wont do any good.. though i have tried just comnecting vcc 5v , gnd , and V0 ...still same contrast..

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First things first.

Check that your 5 V is actually (at least) 5 V.

Do not connect the potentiometer to the 5 V - this is a longstanding and foolish mistake in circuits published (and manufactured) for use with these displays. Not connecting the potentiometer wrongly to 5 V will obviously not fix your problem, but will make contrast setting easier in general.

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Hi,
Do you get any contrast change at all when you adjust the 10K pot?

Tom... :smiley: :+1: :coffee: :australia:

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Yes.... I can lower the contrast till theres no display at all ... I think problem is with my lcd ...
Thanks :+1: tom

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Hmm.. 5v supply is not 5v slightly lower ... But i believe that should suppose to work fine.... But anyways i should consider checking.
Thanks :+1:

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Hi,
Have you tried to write to it to see if it will display characters?

Tom.... :smiley: :+1: :coffee: :australia:

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The fact that you see two (out of four) rows of black boxes means that your LCD is NOT initializing properly.

The contrast problem is another issue.

Don

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Hmm.. okay. so could it be because of faulty wiring (i have checked many times though)... Or is it because of lcd itself.. your suggestion? ..
Thanks

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Hi,
You are initalising the LCD as 20 x 4.
Can you please post your sample code?
Even the "Hello World" example that should come with the LCD library.

Tom... :smiley: :+1: :coffee: :australia:

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Hi... :sweat_smile:.. im actually using atmega32..with 16mhz crystal.... And atmel studio.. but i should try uploading test sketch with arduino..... Thanks :+1:

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In general it should, but if there actually is insufficient contrast then you probably need a higher voltage.

Well, I understand Atmel studio is not the same as the Arduino IDE, so we obviously cannot determine why it is not initialising.

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