Em 24/04/2014 19:59, IVP escreveu:
>> For a long time now you just connect the Vo pin to GND via a
>> trim-pot or a controlled current sink.
> I think the only time I ever fitted a trimpot, as per the datasheet,
> was the first time I used an HD44780-type alphanumeric. Then
> realised how ridiculous a waste it was. Now I either tie Vo to
> 0V or, for best contrast, a 47R/4k7 divider to raise Vo to just
> above 0V
>
> Joe


We use a lot of modules (10s a month) and the contrast adjustment varies
from manufacturer to manufacturer and from lot to lot, there is not a
single value that suits all.

We have just a couple designs that use a trim-pot, all the others adjust
the contrast and back-light intensity by PWM.

And you don't need a resistive divider, the module has an internal
resistor to VCC, you just need to add a resistor to GND. If using a
trim-pot, you can leave the positive extremity open, you will save a
little current.

And tying the Vo pin to ground (almost?) always result in a too dark
background, the LCD can be read only at very shallow angles.


Isaac

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