Arduino Nano - LED

This tutorial instructs you how to use Arduino Nano to control an LED. In detail, we will learn:

Hardware Preparation

1×Arduino Nano
1×USB A to Mini-B USB cable
1×220 ohm resistor
1×Jumper Wires
1×(Optional) 9V Power Adapter for Arduino Nano
1×(Recommended) Screw Terminal Adapter for Arduino Nano

Or you can buy the following sensor kits:

1×DIYables Sensor Kit (30 sensors/displays)
1×DIYables Sensor Kit (18 sensors/displays)
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Overview of LED

The LED Pinout

LED has two pins:

  • The Cathode(-) pin: should be connected to the negative of power supply
  • The Anode(+) pin: should be connected to the positive of power supply via a resistor
LED pinout

How It Works

The below table shows the LED state according to how the power connects to LED's pin

LED cathode(-) pin LED anode(+) pin Condition LED state
GND VCC via a resistor ON
GND PWM via a resistor ON, variable brightness
VCC GND any burned! cautious!
How LED works

As shown on the above table, by generating a PWM signal to the anode (+) of an LED, the brightness of the LED varies in accordance with the PWM value. This has been explained in detail in Arduino Nano fade LED tutorial.


  • For most of LED, a resistor is required to protect LED from the current. There are two options to place the resistor: between the anode(+) and VCC, or between the cathode(-) and GND. The value of the resistor depends on the specification of the LED.
  • Some kinds of LEDs have a built-in resistor. In this case, the resistor is not required.

Arduino Nano - LED

When an Arduino's pin is set up as a digital output, it can be programmed to have either a GND or VCC voltage. Connect the Arduino's pin to the anode(+) pin of the LED with a resistor. This will enable us to control the LED's state through programming.

Wiring Diagram

The wiring diagram between Arduino Nano and LED

This image is created using Fritzing. Click to enlarge image

How To Program

  • Set up an Arduino pin as a digital output using the pinMode() function. For example:
pinMode(5, OUTPUT);
  • To turn OFF the LED, program the pin to GND using the digitalWrite() function:
digitalWrite(5, LOW);
  • To turn ON the LED, program the pin to VCC by using the digitalWrite() function:
digitalWrite(5, HIGH);

Arduino Nano Code for controlling the LED

The below is a complete code for Arduino Nano that controls the LED

/* * This Arduino Nano code was developed by * * This Arduino Nano code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * */ #define LED_PIN 5 // The Arduino Nano pin connected to LED // The setup function runs once on reset or power-up void setup() { // initialize digital pin as an output. pinMode(LED_PIN, OUTPUT); } // The loop function repeats indefinitely void loop() { digitalWrite(LED_PIN, HIGH); // turn the LED on (HIGH is the voltage level) delay(1000); // wait for a second digitalWrite(LED_PIN, LOW); // turn the LED off by making the voltage LOW delay(1000); // wait for a second }

Detailed Instructions

  • Connect an Arduino Nano to a computer using a USB cable.
  • Open the Arduino IDE, select the appropriate board and port.
  • Copy the code above and open it with the Arduino IDE.
  • Click the Upload button on the Arduino IDE to compile and upload the code to the Arduino Nano.
How to upload code to Arduino Nano
  • Check out the outcome: The integrated LED will alternate between being ON and OFF at regular intervals of one second.

Code Explanation

Check out the line-by-line explanation contained in the comments of the source code!


The code above makes use of delay(). This function prevents Arduino Nano from carrying out other operations while the delay is in effect. If your project necessitates completing certain tasks, it is best to avoid blocking Arduino Nano by utilizing the non-blocking method for Arduino.

Video Tutorial

Additional Knowledge

  • Arduino Nano pins 0 through 13 and pins A0 through A5 can be utilized as an output pin to control an LED. Pin A6, A7 are used for the analog input only
  • At one moment, a pin can only handle one job. If you have already used it for something else (e.g., digital input, analog input, PWM, UART...), you should NOT use it as a digital output to control an LED. For instance, if we use the Serial.println() function, we should NOT use pins 0 and 1 for any other purpose since they are used for Serial.
  • This tutorial demonstrates how to use the output pin of an Arduino Nano to control an LED. We can use this code to switch ON/OFF any apparatus, including large machines.
  • For devices/machines that require a high power supply (greater than 5v) and/or high-current consumption, it is necessary to use a relay between the output pin and the device/machine. Further information can be found in the Arduino Nano - Relay tutorial.

Function References


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