LCD not too bright / potentiometer broken?

Hi. I have problem with this project:
Project site link

I made it once and disassemble it. I bouht neat case to assemble it all over again but now for good.
I expirienced some problems with LCD. First is barely visible. It took me half of a day to doublecheck wiring… then i connected other lcd i had and result was differend. It was a tittle bit brighter when i turned potentiometer maximum to the side - but still it wasnt as bright as first assembled.

LCD 1602A

Had no problem at same powersource before at same lcd

There are two separate issues involved here.

  • One is the backlight which is powered through pins 15 and 16 and affects the blue background.
  • The other is the 'contrast' which is controlled by the potentiometer via pin 3 and affects the white characters.
    Have you checked to make sure that there is a series current limiting resistor for the backlight on your pc board? If not you may want to try a external one in series with the connection to pin 15 or 16.

Determine what happens when you turn the potentiometer from one end to the other. The characters should disappear toward one end of the potentiometer range and get very bold toward the other. The optimum setting is near that 'bold' end.

Don

Hi. I menaged to find problem and fixed it. It was a wiring! But it only solved half of the problem. One LCD works better and seccond still is barely visible... Wonder what coses that.

One is the backlight which is powered through pins 15 and 16 and affects the blue background.

I don't know. I''ll attach photos so you can tell me if i need one (I hope). I'm rookie at this stuff.

Google Drive Files

If you need more detailed photos I'll try to do them.

Cheers!

Hi,
Have you adjusted the contrast pot?

Tom… :slight_smile:

Your code and your wiring is obviously correct if one of the two displays functions properly. I am going under the assumption, not completely clear from the photographs, that you are using the same setup and just swapping the displays.

If that is the case then the most likely problem with the 'bad' display is in the soldering of its header pins to the pc board. Try reading this for some pointers on soldering.

Don

floresta:
Have you checked to make sure that there is a series current limiting resistor for the backlight on your pc board? If not you may want to try a external one in series with the connection to pin 15 or 16.

What difference would this make to readability?

What difference would this make to readability?

In the photo he provided in his original post it looked as if the very bright backlight was washing out the display making the characters appear dim by comparison.

Don

I simply cannot see that a backlight can “wash out” the display.

Easy enough to wash out the camera, which is why I always tell people here to take their pictures outside in full daylight (but not direct sun).

9459971ab2fd2855b73ddb3bfd80534375b79a3a.jpg

I’d like to know the voltage measured on the display (pins 1 and 2) and see the contrast potentiometer connections.

Good luck getting him to measure voltages. He still hasn't commented on what happens when he simply turns the potentiometer and observes the display.

Don

Quite so. But that was why I suggested the photo.