LCD drive with general purpose IO

[newtonisback]

Dear all,

I want to know about 7 segment "LCD" dispay's characteristics. After searching everywhere i found no solution

1. Is Each segment of LCD works like "capacitor" ?
2. How to calculate capacitance?
3. Any equivalent circuit of it?
4. If i am driving LCD with general purpose IO than what is the minimum current requirement?

Is anybody know??

 

[Surender Reddy]

Actually I didn't get you.

what is mean by "Is Each segment of LCD works like "capacitor" ?"
and which type of segment LCD your using i mean model...

 

[FvM]

If I understand right, you want to drive a 7-segment LCD display with GPIO. That's well possible.

The capacitance of LCD display segments is pretty low and doesn't cause any problems. The important point is that the voltage between segments and backplate must be DC-free. You achieve this by driving the backplate with a square wave (e.g. 30 to 200 Hz) and the segments with the same square wave, either in-phase (segment off) or out-of-phase (segment on).

It's best done in a timer interrupt.