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Arduino LCD display contrast Answered

My LCD display is acting up. Whenever it transitions, there is a weird afterimage. i have tried turning the contrast up and down, nothing helps. Has anybody experienced this and know how to fix it?

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Downunder35mJohnM703

Reply 4 weeks ago

As with most things Amazon no real details, no schematics, no manufacturer.
But something in the listing reminds my of an old LCD controller board I used for my Mega.
Seperate brightness and contrast knobs, weird problems that no one knows about...
Try the standard LCD library for a 16x2 LCD first.
With that try if the brightness and contrast settings through code work!!
If they do it means your potentiometers are bogus and affect the disply at the wrong level.
They are there to then to adjust the max setting only once set to max by code.
Then all else is done through code alone.
But if you can not change the brightess and contrast by code you need to double check if you actually use the right voltage - 3.3V not 5V!

As you can see on their Wiki page the display contrast there is far from perfect.
If the standard libraries won't work you can try to add a resistor to the 3.3V for the backlight.
It might help, it might not though.
If you use a bread board and not soldered connection or header pins you might need to chack if you have really a proper contact.
Over time these breadboards wear out, same for the pins on the wires.


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JohnM703Downunder35m

Reply 4 weeks ago

I've been connecting the backlight to 5V with a 220 ohm resistor. I think that might be the problem. I'll try connecting it to 3.3v directly and see if that helps

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Downunder35mJohnM703

Reply 4 weeks ago

A simple resistor won't here, only 3.3V.
if the 5V not only affect the LED for the brightness then it could explain your other problems too.

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JohnM703Downunder35m

Reply 4 weeks ago

Thanks for your help! Ultimately If it didn't work, they are fairly cheap. I just prefer not to have to buy a new one

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Downunder35m

4 weeks ago

Exact model of the LCD?
Serial or parallel connection?
Code and libraries used?
Tend to say it might be a problem with your refresh but these black bloacks should not be visible in the display to start with.