Detect car +12v using Arduino

[StealthRT]

I am looking to detect +12v from a car wire using an Arduino.

I have found the following schematic:

I know how crazy automotive voltage can get so i just want to make sure the schematic i found above will accommodate the crazy random currents that the car could produce.

Also, wouldnt i need some type of heatsink taken that i am stepping down a +12v to 5v or less? That, in my mind, would produce a pretty good amount of heat?

 

[(*steve*)]

It shouldn't produce any appreciable amount of heat and you should be able to increase the 1k resistor to 47k without a problem.

 

[StealthRT]

I got my answer in another post: