How to design a smart, contactless temperature-measurement gun

Contactless temperature-measurement guns became popular during the Covid pandemic. Several places used this device to ensure safety protocols. However, one of the drawbacks of the contactless temperature measurement guns available today is that they measure body temperature — not the distance of the body (object) from the sensor.

The body’s distance from the sensor is the most important factor in correct temperature measurement. The sensor used for contactless temperature measurement in such guns can only read the temperature of the surface of an object (the human body in this case) accurately if the object distance is less than 5 cm. If we measure the body temperature from 10 or 15 cm away, there’s the possibility of an error and inaccurate reading.

To ensure the correct temperature reading, we must keep the gun sensor less than 5 cm away from the body. In this project, we will create a smart contactless temperature gun with some modifications and enhancements in the sensor and software part to ensure its accuracy in measuring the correct human body temperature that considers distance as a parameter.

The gun will measure the distance of the body first and, when the body is less than 5 cm away, it will then measure its temperature. It does not measure the temperature directly but, instead, it measures distance. If the body is away from the gun sensor, it gives a message to come closer, and when the body is within 5 cm range, it measures the body temperature. This provides accurate reading and rectifies the problem of reading the wrong body temperature.

We call it a “smart” contactless temperature measurement gun because it measures the distance and takes the body temperature reading multiple times, providing an accurate average value. It also reads the body temperature beyond the normal range, providing an alert notification.

This gun is built using contactless temperature measurement sensor MLX90614 from Melexis, UDM sensor HC SR04, Arduino, NANO, and OLED. The body temperature measured with the gun is compared with a conventional digital thermometer.

Software program
The program is responsible for performing all the following tasks

It measures object distance (body) using the UDM sensor
It measures body temperature using the MLX sensor
It displays distance and body temperature on an OLED
It gives an alert indication via an LED and a buzzer if the body’s temperature is high

The program is written in C programming language using Arduino IDE, and it’s compiled and uploaded into the Arduino microcontroller internal FLASH.