For voltage, it should be as simple as running the input voltage into a s=
imple=20
voltage divider and then into a PIC pin.  You'd need an external Vref sou=
rce=20
though.  For example, a simple way would be to divide the say 5V power in=
 2=20
using 2 equal-value resistors, then run that into an ADC channel.  And us=
e an=20
external voltage reference a bit higher than 2.5V.  This way you have som=
e=20
headroom to measure say 5.5V input (=3D 2.75V at the ADC channel).  I lik=
e to=20
use 4.096V references for simpler math.

For current, add a small dropping resistor as a current-sense resistor (d=
o=20
this after the voltage divider), and then amplify that with an op-amp, th=
en=20
send that to another ADC channel.  Power (should be minimal) for the op-a=
mp=20
can be compensated for in code if you wish.

Cheers,
-Neil.



On Wednesday 24 March 2004 04:45 pm, Rfiles scribbled:
> Hi all,
>
> I was wondering whats the best way to measure the current and voltage o=
f na
> circuit the simple way possible, without any specialized chip, for exam=
ple
> using a pic and his ADC. I did a search on google but no usefull thing =
was
> found.
>
>
> Regards,
> Ricardo Reis

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