I am actually planning on the 5 volt regulator for powering everything (the
pic and the LCD display that is going into the computer/s front bay!).  I
also immediately thought of just using a voltage divider to output a FOURTH
of the voltage off of the 12 volts, and to half the five volts.  Since the
16F877's built in A to D 's can handle up to 5 volts.  I would just use a 4*
and a 2* software multiplier to get the correct voltages back.  The LCD is
going to display temperature (using a National LM3402 temp. sensor) of the
processor and monitor the 5 and 12 volts.  (that is why I used a 16F877).  I
plan to wedge the temp sensor between the fins of the processors heatsink
near the base, and use some type of software offset to more accurately gauge
the true temperature of the AMD processor.
        My concerns were:

1. I thought I should put the 5 volt regulator for powering everything off
of the 12 volt supply.  WOULD IT BE BAD TO HANG THIS OFF OF THE 5 VOLT LINE-
BECAUSE THIS COULD DIP BELOW 5 VOLTS?  IS A 5 VOLT REGULATOR EVEN NEEDED, OR
DOES THE COMPUTER'S POWER SUPPLY DO A GOOD ENOUGH JOB OF DELIVERING 5 VOLTS
BY ITSELF????

2.  I WASN'T WORRIED ABOUT THE RESISTOR DIVIDERS DRAWING TOO MUCH CURRENT,
BUT I WASN'T SURE ABOUT USING THE PICS ADC TO MONITOR A SCALED DOWN VERSION
OF THE SAME POWER SUPPLY THAT WAS POWERING IT.  IN THEORY THE 5 AND 12 VOLTS
ARE LINKED BACK TO THE SAME POWER SUPPLY.  COULD THERE BE A PROBLEM DOING IT
THIS WAY?  IE. could a dip or spike in voltage that powers the PIC affect
the PIC's ADC in trying to measure this same voltage?

3.  FINALLY, I WANTED TO ENSURE A LITTLE ACCURACY, AND THIS MADE ME QUESTION
THE RESISTOR DIVIDER METHOD.  USING PRECISION RESISTORS....WOULD THESE BE
GOOD VALUES TO MAKE THE DIVIDERS FROM:
FOR THE 5 VOLT: GETTING 2.5 VOLTS FROM 10K AND 10k
FOR THE 12 VOLT: GETTING 3 VOLTS FROM 10K AND 30K


        THANKS FOR ALL OF YOUR HELP.  AND THANK YOU FOR HELPING ME WITH MY LITTLE
BROTHERS CHRISTMAS PRESENT....(YES, HE IS A GEEK TOO... SO HE IS SURE TO
LOVE THIS!)

*** DO YOU HAVE ANY SUGGESTIONS ON HOW TO MAKE THIS PROJECT EVEN
COOLER??????

Best Regards,
Brandon

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