Drew Pilcher wrote:
> Here's a sketch of the simplified original circuit: (the pic is a
> 16f675, forgot to mark that)
> http://img14.imageshack.us/img14/202/stripeddownoriginalpirc.jpg

These kinds of PIR sensors are very sensitive to their power inputs.  At
least you tried with the 10Kohm and 10uF filter, but that's still a ways
from what you need.  In a recent design I did with one I ended up giving it
its own LDO.  Fortunately these are small and cheap, like a Microchip
MCP1700 in SOT-23 package.

There is no attempt to filter the opamp supply, not even a decoupling cap!
C'mon, this is really basic stuff that should be taken care of before asking
2000 people for help.

There is no filtering on the 1/2 power supply input to the second stage.
This is asking for trouble.  This should have been obvious too.

Your filter frequencies are suspect.  All the high and low pass seem to be
at about 1.6Hz rolloff, which doesn't make a lot of sense unless you've got
a very special application you're not telling us about.

Each part on a real schematic has a designator, like R1 C3 etc, to make them
easy to talk about.  I would say more about your circuit, but it's too much
trouble without proper designators.  Engineers try to keep values >= 1 and <
1000 and adjust the units multiplier accordingly.  For example .1uF is
better written 100nF for more clarity and credibility.  These are simple
things I expect fixed in your next schematic.


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