Car voltage

Will the Arduino Uno run on car voltage? When running the car is around 14.4 dc. If this is too high, what would be the best method of powering the unit in a vehicle?

14V is above the recommended 12, but below the maximum 20.

I doubt if this would be the "best" but is surely the among the easiest: use a 7809 to produce 9V.

A five volt USB adapter that plugs into the cigar lighter?

A five volt USB adapter that plugs into the cigar lighter?

This is probably the best answer; just make sure you don’t get an el-cheapo that uses something like the 7805 inside - the better ones use a switching regulator. Although, even today those are just as inexpensive.

If you just need something to run off the power - then pull the board out of the inside, desolder the contacts for the cigar lighter, and solder new wires in place. Then hook up the USB to power the Arduino.

Note that while there appears to be a 5V input beyond the USB and on-board regulator in the schematic, there seems to be debate on whether you can feed power into it or not. From what I can see, doing this may back-drive the on-board regulator, and perhaps burn it out (others have noted the same thing). Some boards (I can imagine) may add a diode (or a removable jumper) to allow for external power input. Do your research!

The reason it is best to use a pre-built solution (unless you really understand automotive power and electronics) - is because they are generally designed for adapting such devices to the noisy and varying power system of an automobile. While you may see around 14+ volts when the car is running, you’ll typically see lower than this when the car is off, and at times much, much higher voltages (generally as spikes that can only be measured using an o-scope or similar) - sometimes 100+ volts!

There’s an Atmel Application note discussing how to implement power circuits (to power their microcontrollers, of course) for an automobile; you might do well to find and read it. Until you understand what you are dealing with, though - using a pre-built solution to mitigate these issues is likely the best course of action.

Thanks for the replies. I think the usb adapter will be the way to go. Any issues with the power going to an outlet on an ignition circuit?