read the tutorial
Blueprint is a pre-configured template on the Blynk IoT platform, that will help you create a fully functional project in a few minutes. It already includes mobile and web dashboard UI, working firmware, and a tutorial to help you connect your device to the Blynk IoT platform and control it from the app!

On this page you can review the blueprint to have an idea of the ready project you are going to get. Sign up for a free account on the Blynk IoT platform to try it out.


This blueprint is a quick-start tutorial for connecting a classical Arduino board to Blynk using Ethernet. You will be able to control the built-in LED using a switch button on the web or mobile dashboard. You can use this blueprint with Arduino Uno, Leonardo, Mega, and similar boards.


  • Blynk Console and Blynk App for web and mobile dashboards
  • Arduino IDE or PlatformIO to upload a firmware
  • Arduino Leonardo / Uno / Mega board
  • Ethernet Shield
  • USB cable

1. Prepare Your Hardware Before Flashing

  1. Connect Ethernet Shield to the Arduino board
  2. Connect Arduino board to the computer with a USB cable
  3. Insert Ethernet cable to Ethernet Shield It should look like this:
Hadrware connection

2. Prepare Required Software

  1. Install Arduino IDE or PlatformIO
    If you are using Arduino IDE, follow the next steps (skip for PlatformIO)
  2. Install Blynk library
  3. Install Ethernet library
  4. Select the correct board and port in the Tools menu
  5. Create a new sketch

3. Prepare the Firmware and Upload It to Your Device

We need to include TemplateID and AuthToken (unique identifier of your device) in the sketch.

  1. Click on the Activate device action in the Template Home tab (this tab should open automatically once you've pressed the Use Blueprint button)
  2. Follow the proposed steps to prepare and upload the code
  3. Once the code is successfully uploaded the device dashboard will open automatically

Check the Troubleshooting section at the end of this tutorial if you have issues uploading the firmware

4. Testing

  1. Open your device Dashboard on web and on mobile
  2. You should be able to turn an LED on and off using Switch on web and a button on mobile dashboard
  3. The LED on a dashboard should indicate the state of the LED on your device

If it doesn't work as described

  1. Reboot the device and see if it helps
  2. Delete your device and try connecting it again considering the recommendations from the Troubleshooting section at the end of this tutorial

5. Dashboard Breakdown

Widgets are used to display and visualize data, and interact with your device from the web dashboard and mobile app. In order to connect data to a widget, a specific datastream should be assigned to a widget. You can create datastreams in the widget settings or in the Datastream tab of a Template. Below you can find datastream and widgets used in this project.

Datastream V0 - an LED state
Name: LED
Web widgets: Switch (to control an LED), LED (to show an LED on / off state)
Mobile widgets: Button (to control an LED), LED (to show an LED on / off state)


Congratulations! You have successfully connected Arduino board to Blynk and now can control a built-in LED from the web dashboard and app. By following this tutorial, you have gained experience working with the Arduino hardware, Arduino IDE, Blynk Console and Blynk App. You can now expand on this project to incorporate sensors or controllers.

Next Steps


  • Make sure you have the latest Blynk Library installed
  • Make sure all other used libraries are up to date
  • Check that all the dependencies and configurations are correct
  • Check your sketch for errors. Click the Verify button to compile your sketch without uploading it
  • Check your board and port selections (if you are using Arduino IDE)
  • Check your connections. Your board needs to be connected with a data USB cable (charge-only cables will not work). Make sure the cable is fully inserted in the port on each end. Try a different USB cable, and avoid hubs and other adapters if possible. Remove connections to the board pins, especially the 0 (RX) and 1 (TX) digital pins.
  • Check that your Ethernet cable is not damaged and the connection is stable

Related Links

Blynk Troubleshooting guide

More pre-built IoT projects

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