I also have a simular project that I am working which requires HH:MM:SS
in 24 hour format.  Both of the replies that I have seen to your post refer
to the LCD driver PIC chip.  If one works out the needed segments for a 6
digit clock, 32 segments is not enough and have yet to find a 6 digit LCD
display that was multiplexed. Need about 36 segments.  I have found quite
a few 32 bit LCD drivers which is not enough unless you want to cascade
two of them together.  I did, however, come accoss something last week
that gives me hope.  My 1992 Signetics I2C data book shows a 40 seg
driver.  Part number is PCF8576.

As far as the rest of your questions, just let the PCF8576 handle it for
you. Thats what it's there for.

Michael Ghormley wrote:

> I guess this is my night to post to the PICLIST!
>
> I have a clock project that needs to display hh:mm:ss on a largish LCD
> display.  I have found a nice one at a good price (surplus -- no docs or
> markings of any kind) and got a sample to prototype.  It is a bare (no
> driver chips) LCD in a kind of huge DIP.  It would be perfect for my
> purposes.
>
> I sat down tonight to begin probing it for the pinouts when I realized
> that, while I have done any number of HD44780-based projects, I had no
> idea about driving a "raw" LCD.
>
> 1)  What voltage range is typical?  Is 5VDC sufficient?
>
> 2)  What about polarity?  Can these things be damaged by reverse
> polarity?
>
> 3)  What about series resistance?  I know these are *very* low amperage
> devices, but do I need a series resistor with each segment for some
> reason?  If so, what size?
>
> 4)  Is there going to be a chip-wide contrast pin on this thing, or is
> that up to the hardware that drives it?