> > i need to connect a pic to my car, using the 12v car battery...umm i
assume i can't just wire up the car battery to like a 7805 to control the
voltage..or maybe im wrong...Suggestions?


It works for hobby projects.
Add a series fuse before the reg, and a 15V or maybe 18V zener across power
in front of the reg.
This protects you from overvoltage surges, and reverse voltage transients.
If you have more than about 100uF on the 05 output, then add a diode from
input to output on the 05, such that it's normally reverse biased.  Taking
the 78XX or 340-XX reg inputs to ground suddenly (like during an alternator
spike) can kill the reg otherwise. They aren't designed to withstand any
voltage on the output larger than the input.

The auto industry has standards for such things, but this is a practical
minimum.
Don't forget the input and output caps on that 7805 or you may end up with
an AM broadcast station for free!