Both the Arduino Nano and Uno can be powered via their integrated USB connectors. This automatically supplies regulated 5V power to the board, allowing you to use any USB-supported power source ...

Input and Output. Each of the 14 digital pins on the Arduino Uno can be used as an input or output, using pinMode(), digitalWrite(), and digitalRead() functions. They operate at 5 volts. Each pin can ...

This expanded voltage range can make it easier to use only one power source for your entire project, especially if you're working with 24V components like relays, motors, and solenoids.

However, the input range of the DC jack is quite wide, and most input will be above 5v, so a Texas Instruments TPS62153 switch mode power supply is used to step down the voltage to 5v.