68HC705V12

[FJB203 at aol.com]

In a message dated 97-04-12 12:19:33 EDT, you write:

> Does anyone know if a colour graphics LCD would be too slow for updating,
>  the ones I've worked with you could see when rewriting the display (don't
>  know if that was due to software overhead though) ?

Yes, lets try this again.  I'll add you to the list, anyone else interested
email me directly for the schematic :)

Yes, LCD displays tend to be much slower than a picture-tube style display,
however they draw less power, generally have the high-voltage generator
that's required built in, especially if using a production model, rather than
designing your own.  LCD displays are slow due to physical limitations of the
material used, not because of the video display electronics (though most of
the time PC video circuits for LCD panels are slow simply because they don't
*have* to be smoking fast because the panel is slow.

If you update the display every 1/2 second or every second, as most vehicle
digital dashes are, they are more than fast enough.  What ruins LED and LCD
displays for automotive use is brightness and sunshine.  The solution for
that is privacy glass, glass that allows only the person sitting immediately
in front of the display to be able to see it.  This type of product is about
$75US and is typically used for accountants working on high-secret numbers in
corporate america, though they can be used anywhere.  Its not safety glass
generally, so scoring and cutting it to the right size is fairly easy.  This
will prevent sunshine coming in through the windows getting into the display,
and reflecting back into the driver's eyes making the display hard to read.
 I tested this with my color Compaq notebook, and it works EXCELLENT.  So,
automotive application will be fine.

LCD's other inherent problem is going to be temperature.  Anything below
freezing is a no-no for LCD displays, as the crystals won't move, rotate, or
change color (however it works) in the cold, my Notebook has proven this in
the winter, after leaving it in my vehicle trunk overnight.  The solution is
to warn the display with either electrically heated warm air, or create a
heated glass plate and place it over the LCD display, heating it when the
temperature is low, *THEN* applying power.  Picture tubes would prevent this
I believe, however I'd worry about tube implosion in an accident.

Frederic Breitwieser
http://members.aol.com/fjb203/index.htm
Bridgeport Connecticut
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