People often time confuse with the question of how to power the Arduino Nano with external power supply without the USB cable. There are two solutions depending upon the power supply voltage(regulated +5V or +7V-12V) you are using as external power supply. If you have regulated +5V power supply then use the +5V pin on Arduino Nano and if the power supply is between +7V to +12V use the Vin pin as shown in the diagram below. So the two solutions are to use either +5V pin or to use the Vin pin.
For example you might have +5V regulated output voltage from LM7805 voltage regulator IC. Then you can connect the output of the voltage regulator to the +5V pin of Arduino Nano as shown in the circuit diagram below.
Here’s how you should connect the power from the LM7805 to the Arduino Nano:
- LM7805 Output (+5V) → 5V pin on Arduino Nano.
- Ground from LM7805 → GND pin on Arduino Nano.
This way, you provide a stable 5V directly to the 5V pin on the Arduino, and the onboard voltage regulator isn't used in this case. The Arduino Nano will draw power directly from the external 5V source.
However, do not connect +5V from power supply to Vin of Arduino Nano. If you connect 5V directly to the Vin pin, you bypass the onboard regulator, which may cause issues, especially if the Arduino's regulator isn't designed to handle 5V input properly.
This solution not only applies to LM7805 or similar +5V linear power supply but also +5V breadboard power supply module. Actually it is very easy to built one. The tutorial how to make diy breadboard +5V power supply shows how to make one using LM7805 regulated power supply IC. You can also make cheaper voltage supply to power your Arduino boards. For example the tutorial Power Supply for Arduino with Transistor and Zener Diode shows simple and inexpensive method to build a power supply with expensive ICs.
The second solution to power the Arduino nano with external power supply is to use +7V to +12V unregulated or regulated voltage supply and connect to the Vin pin of the Arduino Nano. This is because the Vin pin on the Arduino Nano, is designed to accept a higher voltage (typically between 7V and 12V), which is then regulated down to 5V by the onboard voltage regulator. So no need for external power supply IC.
The circuit diagram for this case is shown below.
Now compare this two methods on the diagram shown below.
You might be interested in the following online calculators for power supplies.
