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Four ways to power up the Arduino Uno

The Arduino Uno has undergone many revisions, and hence the Arduino power supply circuit has evolved to an almost foolproof design. In this project, we will learn about the four different ways in which we can power up the Arduino Uno. While making any Arduino projects, it is necessary to know these techniques, since there are instances when flexibility with regards to the power supply is required.

Things required to power up the Arduino Uno

We are going to need the following apparatus to learn how to switch on the Arduino Uno.

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Images (Things required to supply power to the Arduino Uno)
Arduino Uno power cable USB
Standard A-B USB cable
AC - DC adapter barrel plug for Arduino Uno
9V adapter
Battery and female to male cables
9V Battery with connector and female to male jumpers

What is the procedure to power up the Arduino Uno?

Modern Arduino Uno boards allow the board to have more than one source of power to be connected simultaneously. An intelligent switching circuitry ensures that the highest available voltage is selected and sent to the onboard voltage regulator and eventually powers up the board. We have covered the core Arduino Uno power supply schematic in detail here.

We can power up the Arduino using power supplied from the computer via a USB cable and/or by using external power sources.

1. Using USB cable

An Arduino Uno powered up using a USB cable
An Arduino Uno powered up using a USB cable

The USB port of the Arduino Uno can be connected to a desktop/laptop. If the connection is enumerated, i.e. the computer recognizes the device, the current supplied to the board is 500mA at 5V. If the connection is not enumerated, 100mA is supplied at 5V.

USB Enumeration
It is the process by which the host computer identifies a device to load the appropriate driver and learns the capabilities of the device

2. Using an AC to DC adapter plugged into the barrel connector

Arduino Uno power jack or barrel connector
The barrel connector is 2.1mm in diameter. The center pin is positive, and the outer sleeve is grounded.
Power up the Arduino using AC-DC adapter
Arduino Uno powered up using 9V AC-DC adapter

The barrel connector can be supplied with an input of 7-12V. This is regulated to 5V by the onboard voltage regulator, and the board is powered on.

3. Using 5V input

Power up Arduino using battery
A voltage regulator can be used to supply fixed 5V input to power up the Arduino

It is possible to power up the Arduino using the 5V and GND pins, provided that the input given is steady and regulated 5V. The 5V pin bypasses the voltage regulator and all the safety measures present on the Arduino Uno, so if the input exceeds 5V (5.5 is the maximum upper limit), the board can be damaged. It is generally advised to avoid powering up the Arduino Uno using this method.

4. Using batteries greater than 5V

Power up Arduino using 9V battery (unregulated)
Connection layout to supply power to the board using a 9V battery

Connect a 9V battery with the positive terminal connected to the Vin pin and the negative terminal connected to the GND pin. The Vin port allows an input between 7 and 12 Volts, but we recommend to use a 9V battery. Depending on your application you can input 12V too but make sure the current values stay around 500mA.

5. Bonus method: Using a battery shield

This method is suggested by a reader in the comments section below and I think it’s worth adding to the main post.

There’s this nifty little Arduino Uno shield that holds two batteries. You can just plug it into the sockets of your Arduino Uno and you’re set. The battery/power pack shield can be charged using a simple micro USB cable. It outputs a steady 5V that you can use to power up your Arduino. You can use either the USB B cable or a simple jumper cable to get the 5V supply.

power or battery shield for arduino uno

Moreover, depending on how long your batteries last, you can make your project wireless and portable. Surely that’s a great feature. You can get the battery shield on Amazon over here. Ali express might have some cheaper options that you might want to check out too.

Precautions to be undertaken before switching on the Arduino Uno

  • If the barrel connector and an AC-DC adapter are being used to power up the Arduino, make sure that the output of the adapter is between 7-12V. Although the rated input can exceed to as much as 20V, it is safe to stay within the recommended range to protect the voltage regulator from excessive heating. Also, see to it that the GND and Vin pins are not shorted.
  • But if you are using the 5V and GND pins to power up the Arduino, it is imperative that the 5V input is stable and steady.
  • If the Vin/5V and GND pins are being used to power up the Arduino, double-check the polarity because if the GND and 5V/Vin pins are mixed up, it can potentially damage the Arduino board.


If the Arduino Uno fails to be recognized by the host computer, it’s possible that it won’t draw enough current. To fix this, try to use a USB 2.0 port if you were using a USB 3.0 port. In addition to that, you can also try changing the USB cable. However, if none of these work, you can manually install the Arduino Uno.

This article is a part of our free Arduino Course for beginners. An excellent progression from powering up your Arduino is to connect an LCD with the Arduino and display your first HelloWorld.c program. Or you can just interface a DC motor or a temperature and humidity sensor with the Arduino. Check out our Arduino IDE and Arduino programming guides too.

If you face any issues in switching on your Arduino Uno, let us know in the comments and we will try to troubleshoot your issues.

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  1. hye can i know the set up from arduino uno to switch button , voltage regulator, to lipo battery like the picture on number 3. i want to power up my circuit like sensor and servo motor by using micro hydrogenerator 5v.

    1. Can you show me some documentation of what you are trying to achieve? I can’t understand the setup you have described.

  2. Hi, I am running a simple sketch to see how I could use capacitive sensors for my project but when I connect the Arduino to 9V battery through Gnd and Vin and remove the USB connection the sketch does not run. It says Error opening serial port ‘COM3’ (Port not found). This only makes sense as the Arduino is no longer connected throught the USB. My question is – is there some obvious thing that I need to change i to be able to run the Arduino with the battery? The light on the board does come on when I connect the battery just the sketch won’t compile. Thank you in advance!

    1. How can you compile/upload the sketch without being connected to the computer? You need to upload your “executable”and compiled sketch to the Uno and then you can remove the USB and power using the 9V battery. If you have any queries let me know. Your issue seems easily fixable.

  3. You should now know the most common ways to power your circuit and how to figure out which way is best for you depending on your your project’s specific requirements. You can make a better judgment now based on current, voltage, connector, and mobility considerations for your project. Check out these other great tutorials to monitor, control, or power your project!

  4. Arduino is one of my favorite open source hardware hacking platform for hobbyists, designers, and artists? Arduino gonna be a big thing in the future. Umair I want a little favor from your end I am looking for best arduino courses online over the web. I try to find it but I am little confused which one is good for professional level. Can you help me out. Link is in the website coloum. Do reply and please help me.

      1. Hi Umair! Nice tutorial, I have a question. I am making a data logger using the Arduino UNO board. However, I want to power it from both 9V Battery or the power adopter. Like if I need to transport my board to a place where I don’t have wall plug available I can still make it work using the battery.


        1. Maybe you can design an independent power supply source that packs a battery as well as an AC-DC converter. You can have power out pins for both the sources. So one circuit board, two power sources, two power outputs. Choose according to your convenience. What do you think?

          1. @Naeen Ahmad – I think there might be a better solution for you.
            There exist two Arduino expansion boards, one with a holder for a 16340 battery, and one that can hold 2 16340 batteries.
            I consider it ‘the fifth way to power up an Arduino-Uno’. The dual version has 32 pins that fit into the female sockets of the Uno, thus cascading all 32 Arduino-Uno pins.
            The single battery version is wired directly to a few Uno pins. They can be used as a 16340 battery charger
            (they both have a 5V USB-Micro input-port for charging, as well as a 5V regulated USB-B output). They also have a very handy on-off switch 🙂
            Depending on the quality of your batteries you can have a good amount of power available to power your Uno and also drive your externals.
            I made a pic that I uploaded to Imgur at http address: i.imgur(.)com/65XNFol.jpg (remove the 2 parentheses).
            You can buy them online everywhere (like Aliexpress) for around $ 2,50 US. Good luck with your projects!

            1. Hans that is an excellent suggestion! I will add your advice to the main post with due credits so that everyone can benefit from it. Thanks!