Oppie wrote:
"Robert Baer" wrote in message
net...
Oppie wrote:
What you did in digital was the equivalent of ignoring the common
mode range of an opamp. Both are parameters that are very easy to
miss if you don't watch closely.

I did not ignore the common mode range; note the biasing puts the
inputs exactly in the middle: 2.5V of the 5V supply.
And at 10 amps input, the drive to the 10K is 1V so at a gain
setting near 2, all is linear for a drive to the MCU as a "hi" for
overcurrent tripping.
As long as the opamp is running in the linear region (as noted in
example), it is well within the common mode range.

I did not say you violated anything with the common mode range. Only
meant to say that some designers (and designer wanabes) miss what appear
to be obscure inconsequential bits... like what type of buffer is on a
digital input port. My record is not perfect in that respect and I've
been an engineer for 30+ years smile
Yes; if i were to learn how to program these PIC beasties, i would
take some care in the choosing of ports and add a few niceties: serial
I/O query of machine state along with unique machine number.