Lcd 20x4 contrast problem


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?

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.

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..

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.

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

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

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

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:

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

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

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

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

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:

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

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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