speaking of displays & DPM

[Kalle Pihlajasaari]

Hi,

> >Maybe I have an odd LCD pannel (2x20, I doubt it). Mine turns black when the
> >car warms up in the sun.
> 
> Don't know -- only know what specs I am familiar with -- maybe something
> new ??  Don't think so, but maybe.  LCD specs (that I read umpteen years
> ago) say they don't work as well in the cold, get sluggish and go blank.

I was led to believe that the most sensitivity to temperature until the
very extremes was in changes to the bias/contrast voltage requited.

There are various automatic and software methods in use that measure
the temperature and change the contrast voltage to keep the display
in a useable mode for most of the temperature limits.  At the extremes
of temperature the display will go either blank or dark depending on
the failure mode (which I don't know) but is reversible until the
liquid freezes or boils I think.

Using a thermistor to check temp and then using a single pin to
generate a dutycycle PWM output for the voltages is a practical
solution if the operator cannot be trusted with tweaking a knob.

Cheers
-- 
Kalle Pihlajasaari     kalle at data.co.za
Interface Products     Box 15775, Doornfontein, 2028, South Africa
+27 (11) 402-7750      Fax: +27 (11) 402-7751