Arduino - Temperature - Send Email Notification

We are going to learn how to use Arduino to send a notification to you via email when the temperature exceeds a threshold. We will use Arduino, the waterproof DS18B20 temperature sensor, and Ethernet Shield.

Alternatives: by making a small modification in the Arduino code:

Hardware Required

1×Arduino UNO or Genuino UNO
1×USB 2.0 cable type A/B
1×Temperature Sensor DS18B20
1×4.7 kΩ resistor
1×Arduino Ethernet Shield 2
1×Ethernet Cable
n×Jumper Wires
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About DS18B20 Temperature Sensor and Sending Email

If you do not know about the DS18B20 temperature sensor (pinout, how it works, how to program ...) and how to send email from Arduino, learn about them in the following tutorials:

Wiring Diagram

  • Stack Ethernet Shield on Arduino Uno or Mega
  • Connect the temperature sensor to Arduino as below writing diagram
    • With breadboard
    • Arduino Temperature Sensor Wiring Diagram

      Image is developed using Fritzing. Click to enlarge image

    • Without breadboard
    • Arduino DS18B20 Wiring Diagram

      Image is developed using Fritzing. Click to enlarge image

    • Real wiring
    • Arduino one wire temperature sensor Wiring Diagram

      Image is developed using Fritzing. Click to enlarge image

What we need to do

We need to do to main tasks:

  • Create an Applet on the IFTTT website
  • Write Arduino code that makes an HTTP request to the Applet when the temperature exceeds a threshold

How it works

When the temperature exceeds a threshold:

  • Arduino makes an HTTP request to IFTTT Applet we created,
  • The IFTTT Applet will send an email to the email address.

The email address, email subject, and email content are specified when we create the IFTTT Applet.

How To Create an IFTTT Applet

  • Create an IFTTT account and Login to IFTTT.
  • Go to IFTTT Home page and click the Create button
  • Arduino create IFTTT applet
  • Click the Add button
  • Arduino adds IFTTT applet
  • Search for Webhooks, and then click the Webhooks icon
  • Arduino IFTTT Webhooks
  • Click the Receive a web request icon
  • Arduino IFTTT Webhooks Service
  • Click the Connect button
  • Arduino
  • Type an event name. You can give any name you want and memorize it to use later. The event name is a part of URL that Arduino will make request to. In this tutorial, we use a name send-email. And then click Create trigger button
  • Arduino Webhooks create trigger
  • Click the Add button to add the action
  • Arduino IFTTT create action
  • Search for email, and then click the Email icon
  • Arduino  Email service
  • Click the Send me an email icon
  • Arduino send me an email
  • Click the Connnect button
  • Arduino Connects to email
  • Input your email address and then click the Semd PIN button
  • Arduino
  • You will receive an email, get the PIN from email and input to Web UI to do verification
  • After that the email subject and content editor appears
  • Arduino email subject and content editor
  • You can give any subject and content for the email. The below are example
  • Arduino
    • Subject:
Temperature from Arduino
  • Content:
Outside Temperature: {{Value1}}°C<br> Measured Time: {{OccurredAt}}<br> <br> <br> Take care of yourself!<br> Arduino Uno
  • Click the Create Action button
  • Click the Continue button
  • Arduino
  • Click the Finish button
  • Arduino

Now you succeeded to create an IFTTT Applet for your Arduino. The next step is to get the IFTTT Webhooks key, which is used to authenticate and identify your Arduino.

  • Click the Documentation button
  • Arduino IFTTT Webhooks documentation
  • You will see the Webhooks key as below
  • Arduino IFTTT webhooks key
  • Copy and wire down your Webhooks to use on Arduino code.

Now, We just need to write Arduino code that makes an HTTP request to the below URL:


  • In the URL, the send-email is the event name we used:
    • If you already used this name for another Applet, you can give it any other name.
    • If you use another name, please replace the send-email by your event name
  • Webhooks key is generated by IFTTT. Please keep it secret. You can change it by regenerating it on the IFTTT website.

Before writing Arduino code, We can test the IFTTT Applet by doing:

  • Open a web browser
  • Copy the below link:
  • Paste it on the address bar of the web browser
  • Replace XXXXXXXXXXXXXXXXXXXXX with your Webhooks key.
  • Press the enter key on your keyboard. You will see the browser display the message as below image.
  • Arduino IFTTT applet test
  • And you will receive an email.

Arduino Code

/* * Created by * * This example code is in the public domain * * Tutorial page: */ #include <SPI.h> #include <Ethernet.h> #include <OneWire.h> #include <DallasTemperature.h> #define TEMP_THRESHOLD 27 // °C #define SENSOR_PIN 13 // Arduino pin connected to DS18B20 sensor's DQ pin OneWire oneWire(SENSOR_PIN); // setup a oneWire instance DallasTemperature DS18B20(&oneWire); // pass oneWire to DallasTemperature library // replace the MAC address below by the MAC address printed on a sticker on the Arduino Shield 2 byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED }; EthernetClient client; int HTTP_PORT = 80; String HTTP_METHOD = "GET"; char HOST_NAME[] = ""; String PATH_NAME = "/trigger/send-email/with/key/XXXXXXXXXXXXXXXXXXXXX"; // change your Webhooks key bool isSent = false; void setup() { Serial.begin(9600); Serial.println("TEMPERATURE MONITORING via EMAIL STARTED!"); // initialize the Ethernet shield using DHCP: if (Ethernet.begin(mac) == 0) { Serial.println("Failed to obtaining an IP address using DHCP"); while (true); } DS18B20.begin(); // initialize the sensor } void loop() { DS18B20.requestTemperatures(); // send the command to get temperatures float temperature = DS18B20.getTempCByIndex(0); // read temperature in Celsius Serial.print("Temperature: "); Serial.print(temperature); // print the temperature in Celsius Serial.println("°C"); if (temperature >= TEMP_THRESHOLD) { if (isSent == false) { // to make sure that Arduino does not send duplicated emails sendEmail(temperature); isSent = true; } } else { isSent = false; // reset to send if the temperature exceeds threshold again } } void sendEmail(float temperature) { // connect to IFTTT server on port 80: if (client.connect(HOST_NAME, HTTP_PORT)) { // if connected: Serial.println("Connected to server"); // make a HTTP request: String queryString = "?value1=" + String(temperature); // send HTTP header client.println("GET " + PATH_NAME + queryString + " HTTP/1.1"); client.println("Host: " + String(HOST_NAME)); client.println("Connection: close"); client.println(); // end HTTP header while (client.connected()) { if (client.available()) { // read an incoming byte from the server and print it to serial monitor: char c =; Serial.print(c); } } // the server's disconnected, stop the client: client.stop(); Serial.println(); Serial.println("disconnected"); } else {// if not connected: Serial.println("connection failed"); } }

Quick Steps

  • Stack Ethernet Shield on Arduino
  • Do wiring as above image
  • Connect Arduino to PC via USB cable
  • Open Arduino IDE, select the right board and port
  • On Arduino IDE, Go to Tools Manage Libraries
  • Arduino add library
  • Search “OneWire”, then find the OneWire library by Paul Stoffregen
  • Click Install button to install OneWire library.
  • Arduino onewire library
  • Search “Dallas”, then find the DallasTemperature library by Miles Burton.
  • Click Install button to install DallasTemperature library.
  • Arduino Dallas Temperature library
  • Copy the above code and open with Arduino IDE
  • Click Upload button on Arduino IDE to upload code to Arduino
  • Put the sensor on hot and cold water, or grasp the sensor by your hand
  • You will receive an email notification as below
  • Arduino Gmail temperature
  • The log on Serial Monitor as below:
  • COM6
    TEMPERATURE MONITORING via EMAIL STARTED! Temperature: 26.06°C Temperature: 26.06°C Temperature: 26.31°C Temperature: 26.69°C Temperature: 27.13°C Connected to server HTTP/1.1 200 OK Date: Mon, 22 Nov 2021 04:22:50 GMT Content-Type: text/html; charset=utf-8 Content-Length: 50 Connection: close X-Powered-By: Sad Unicorns X-Robots-Tag: none X-Top-SecreTTT: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX ETag: W/"32-jD2lq/0l+3wF/XXXXXXXXXXXXX" Congratulations! You've fired the send-email event disconnected Temperature: 28.06°C Temperature: 28.31°C Temperature: 28.50°C
    Autoscroll Show timestamp
    Clear output
    9600 baud  

Code Explanation

Read the line-by-line explanation in comment lines of source code!

Video Tutorial

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