I am trying to drive a piece of LCD glass from a weighing scale (with an aim of completely replacing the internal electronics). The exact physical characteristics of the glass are unknown but measurement of the original PCB showed it was four way multiplexed with 1/3 bias.
Anyway.... I'm using a PIC24FJ128GC006 and it works pretty well except when a lot of segments are ON there seems to be a bit of 'fade out'. I am driving the display with a 60Hz frame-rate (Type A) which is what I saw in the original.
According to the family PIC24F LCD documentation (
http://ww1.microchip.com/downloads/en/DeviceDoc/39740a.pdf) there is a recommended value of 0.47uF for VLCAP and VLBIAS1,2,3. (But on page 20 it seems to refer to 0.047uF)
I have max contrast on using the internal ladders and bias levels on the commons look spot on. I'm using Power Level B 100%.
Currently I am powering from an ICD3.
Should I be increasing/decreasing VLCAP et al? Is the glass too big to use the internal regulator?
Thanks in advance
(It looks more faded to the human eye in the middle bottom than is obvious in the camera shot)