Brent Brown wrote:

> The 1N4007 diode in series with the input prevents damage from
> reverse supply connection. It also stops the 1000uF cap from
> discharging if the supply voltage falls (eg. engine cranking), so if
> your circuit doesn't draw too much you have a short term UPS!

A little gotcha with this idea.

Make sure you have some sort of brownout detect on the PIC or some weird
things may crop up.

--
Best regards

Tony

http://www.picnpoke.com
Email sales@picnpoke.com