Sunday, May 26, 2024

Turn Your Phone Into IR Contactless Thermometer

Since the outbreak of COVID-19, it has become essential to regularly monitor the human body temperature without coming into contact with the measuring device so that an infected person can be immediately detected without further spreading the disease (due to contact). As per the need of time, a contactless temperature measuring device such as a thermometer is required everywhere. 

So today, we will develop a smart Bluetooth-based contactless thermometer with thermal screening capability added to our phones. To transform our phones into a contactless thermometer, first we need to connect our phones to a sensor over Bluetooth for giving us the temperature reading in an app. We can also get the data from the sensor to our phone using USB. 

Bluetooth based Contactless IR thermometer

To make the device, we need the following components:


For coding, we need to install the MLX90614 library in the Arduino IDE and then include it in the code. After that, create a setup function where we will set the baud rate for the Bluetooth module.  Here, I am using a baud rate = 9600 (default). After this, create a loop function that will run repeatedly. In the loop function, we will check the sensor reading and then pass the readings to the serial using serial.println(). This ensures that when we connect the Bluetooth to the serial pin of the Arduino, the readings are transferred to the Bluetooth module.

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The OLED display code part is optional. You can either attach the OLED display or you can skip.

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Connect the components as shown in the circuit diagram. After completing it, create an app that will connect to Bluetooth and give live sensor readings to our phone. 

Connection circuit for IR Contactless Thermometer
Connection circuit for IR Contactless Thermometer

Creating the app

To do so, we have a lot of different options including MIT app inventor, Kodular, Android Studio and Eclipse. Here we are using Kodular to create the app. Firstly, open Kodular and create a new app name as per your choice. Here, I have named it Contactless IR thermometer. After that, create the app layout by adding the following components to it:

  • Bluetooth client
  • File
  • Listpicker
  • Clock
  • Image

Next go to Code Blocks and join them by selecting and dragging them into the central screen. Export it as .apk and install it in your phone.


After getting everything ready and installing the app in the phone, power the device and then switch on the Bluetooth of the phone. Now open the app, select ‘connect’ and then select the HC 05. After a successful connection, you will be able to see the temperature readings in the app. The app will also save the reading and temperature data in a text file. You can check it in the file manager.

Download Source Folder

Ashwini Sinha
Ashwini Sinha
A tech journalist at EFY, with hands-on expertise in electronics DIY. He has an extraordinary passion for AI, IoT, and electronics. Holder of two design records and two times winner of US-China Makers Award.


  1. Hi,

    Compiling done and result showing in Serial monitor but there is issue in creating aap.
    have created aap through kodular but that aap only showing Text for List_pickers and doest not show the blutooth connect, can you please share the .apk aap.

    thanks and regards
    Sushil kumar


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