Originally Posted by
malc-c
I don't think that would work. The regulator will simply give you a 5v supply from the 12v battery, it will never fall below 5v because the car battery would never get this low. The simple way is to use a voltage divider made by connecting two resistors accross the 12v line and then connect the pic to the junction between the two.
If you used a 58K and 41K with a 12v supply you would get 5v, however the state of a car battery is such that it's voltage will vary under charge and drain, so you would need to make allowances for that. You might find that under charge the voltage could be around 13.8v, falling to 10v under load.
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