On Tuesday 04 February 2003 08:48 am, you wrote:
> michael brown wrote:
> > No offense to Roman, but he seemed to be getting it backwards.  ;-)
>
> Ha ha! Thats me. Sometimes backwards is better?

Right, like when it's winter here, you've got nice weather.  ;-)

> Re the comparator problem, try config the comparator
> with a digital output, and use 2 pots for testing,
> one on each input.

I'm going to try that here shortly, since Jinx (IIRC) confirmed usage of=20
the comparator input at 100mV.  The data sheet says you should keep the=20
input impedance below 10K, and I am using a 10K pot, so maybe that has=20
something to do with it.  I don't have a lousy 4.7K pot anywhere.  :-(

> And maybe try another PIC? :o)

Eureeka:  I just tryed a different PIC, it works right down to the low=20
millivolt range.  ;-)))  Everything is at harmony again.  ;-)  Are=20
issues like this common?  The new PIC works perfectly till you get=20
above about 4.3V.   I will keep it below 3.5 per the datasheet.  That's=20
ok with me. =20

I accidentally let the smoke out of the other one late yesterday when my=20
probe slipped.  :-O  I guess I got too tired and careless last night.  =20
The weird thing about that is that the probe shorted the *grounded* leg=20
of one of the crystal caps and the Vdd.  I'm not quite sure how that=20
resulted in the demise of the PIC since there was no DC path to the=20
PIC, but it's sure dead now, the cap is unscathed.  The circuit=20
survived with no ill effects, but that PIC is basically a space heater. =20

Since I was using a supply that had the capability to supply high=20
current, I'm thinking that a voltage surge occured and wiped it out. =20
It didn't hurt the LCD though.

Can anyone recommend better values for the charging resistor and cap. =20
I'm probably wasting allot of power using a 4.7K resistor, aren't I?

Thanks Roman

michael

> > Here is some ugly ascii art of the schematic.
> > +5V     |-------------
> >
> > |       V            |            16F628
> > |____/\/\/\/\___     |         __________________
> > |
> >                 |    |___RA2__| Comp +   Comp - |___RA1___
> >
> >        10K      V             |                 |        |
> >                Gnd     __RA3__| Charge Pin      |        |
> >
> >                        |      |_________________|        |
> >                        |
> >                        |                _________________|
> >                        |
> >                        |____/\/\/\/\____|___|(______
> >
> >                               4.7K         1uF     V
> >                                                   Gnd

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