I would like to use the power from my car to power the UNO board, but the instructions say that the input voltage should be between 7 and 12 volts. The voltage from my port in the car is 13.8 volts. Will this damage my board?
The problem with supplying that voltage to the input jack is that the 5V regulator has to drop over 8V which severely limits the current that the 5V regulator can supply before it overheats and shuts down. To stay under the recommended 1W dissipation the current draw, at that voltage, must stay under about 100 mA. The Uno itself uses around 50mA of that so there is not much left for your circuit. Another issue is the potential for higher voltage spikes on automobile power. I have used 12V to 5V car chargers connected to the 5V input on car projects. That bypasses the 5V regulator and they are made to handle the environment.
There are inductive spikes, reverse conditions, load dumps and other nasty things that occur on the automotive 12v supply. Arduino is not designed to survive these conditions. I have seen some work for a while but it would not be reliable and will eventually fail. It would be better to use a 12v-usb power supply which should have some of the protection built in use the Arduino usb cord that came with it.
Thanks for the idea. I have an adapter that plugs into the lighter port and you can pick the output voltage it provides. THANKS!
I have used 12V to 5V car chargers connected to the 5V input on car projects. That bypasses the 5V regulator and they are made to handle the environment.
You mean like this?