Four ways to power up the Arduino Uno

The Arduino Uno has undergone many revisions, and hence the 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 projects, it is necessary to know the following 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)
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 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 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.

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.

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