Non-uniform contrast on screen NHD-C12864WO-B1TFH#-M



  • Official comment
    Engineering Support
    Community moderator

    Hi Nicolas,

    Please try the following suggestions to help improve the contrast uniformity on your display:

    • Change capacitors C302, C303, C304, and C305 from 4.7uF to 1uF
    • With the display powered on, adjust the wiper of the 10k potentiometer to increase the contrast.  There should be a "sweet spot" where all the dark pixels will look uniform.
    • This photo shows the display with 4.7uF caps and before adjusting the potentiometer:
    • This photo shows the display with 1uF caps and adjusted potentiometer:


    Also note that this display now has a more recent revision, which uses the ST7567 driver IC.  This version has notable improvements including the following:

    • Uses fewer number of pins
    • No potentiometer required.  Contrast adjustments are internally controlled by software
    • Only requires 2 capacitors

    The new version of the display is available on our website: 

  • Nicolas SAN-AGUSTIN

    Thank you for your reply.

    We followed your instructions and replaced capacitors C302 to C305 with 1 µF capacitors. We then adjusted the potentiometer, and only an extreme value enabled us to obtain a sufficiently uniform display, albeit a very dark one. Checking the display specifications, we noticed that the viewing angle of the screen was mentioned at 6:00. When viewed from this angle, the display is already more satisfactory (in any case, quite close to the second image you provided, with the exception of the black border, which for us remains white).

    So we think there's probably an error in the choice of screen. Would you happen to have another very similar reference, with the same specifications but a viewing angle so that, facing the screen, the display is both clear and uniform?

  • Engineering Support
    Community moderator

    Hi Nicolas,


    I will suggest this display as an alternative:

    This display has a higher contrast ratio and its optimal viewing angles are closer to center.


  • Nicolas SAN-AGUSTIN

    We've taken your first piece of advice, which was to use the new version of the screen. And indeed, it's much better, even when looking at the screen from the front, just with the default configuration.

    I still don't understand how we can have such a clear difference in display quality when the two drivers IC are practically identical. The only difference is in the capacitors, and yet we noticed a disparity in contrast whatever the value of the capacitors or the potentiometer.

    So the only solution I see at the moment would clearly be to use the new revision. If someone get the old version by mistake, just change it, or if you manage to find the right capacitors and resistors configuration for a uniform display, let me know. 


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