Arduino, Sensor

Build Your Own Portable Contactless Temperature Reader

by Idris
March 18, 2020

Arduino, Contactless Temperature Reader, Corona Virus, Covid-19

Measure your surrounding (e.g. people nearby) temperature with contactless reader.

Introduction

Covid-19 have been declared as pandemic. One of the early symptoms of corona virus was fever, and we are advised to reduce the direct contact. So, I try to develop a portable contactless temperature reader using ESP32 and Arduino platform. Later, you can improve the code to implement IoT in the application.

Before proceed to the tutorial, please go through following tutorial first on how to install and edit the library.

Interface LSM9DS1 9DOF IMU With TTGO T-Display ESP32 – Install TFT_eSPI library and edit.
Send Sensor Data to Adafruit IO Using ESP32 – Install MLX90614 library.

Video

This video shows how to build your own Portable Contactless Temperature Reader using Arduino platform.

Hardware Preparation

This is the list of items used in the video.

TTGO T-Display ESP32

MLX90614 Non-Contact Infrared Temperature Sensor

14500 Li-Ion Battery 3.7V 600mAh

1xAA Battery Holder

Mini Slide Switch (PCB)

Donut Board (Big) 10x24cm

Straight Female Header 1×40 Ways

If you have Snapmaker or Ender3, you can access ? TinkerCAD 3D file,
export to .stl and print your casing.

Sample Program

This is Arduino sample program for ESP32 board. Before compile, please install following libraries through Library Manager:

TFT_eSPI by Bodmer Version 1.4.20
MLX90614 Library by Adafruit Version 1.0.1

/*

  Tutorial: Build Your Own Portable Contactless Temperature Reader

  Hardware:

  – TTGO T-Display ESP32

    https://my.cytron.io/p-ttgo-t-display-esp32-1.14-display-module-presolder-header?tracking=idris

  – MLX90614 Non-Contact Infrared Temperature Sensor

    https://my.cytron.io/p-mlx90614-non-contact-infrared-temperature-sensor?tracking=idris

  External libraries:

  – TFT_eSPI by Bodmer Version 1.4.20

  – Adafruit MLX90614 Library by Adafruit Version 1.0.1

  Created by:

  18 Mar 2020    Idris Zainal Abidin, Cytron Technologies

*/

#include <TFT_eSPI.h>

#include <SPI.h>

#include <Wire.h>

#include <Adafruit_MLX90614.h>

#define ADC_PIN 34

#define VREF    1100

#define BUTTON1 35

#define BUTTON2 0

#define FF17 &FreeSans9pt7b

#define FF21 &FreeSansBold9pt7b

#define ROW1 0,16

#define ROW2 0,38

#define ROW3 0,60

#define ROW4 0,82

#define ROW5 0,104

#define ROW6 0,126

Adafruit_MLX90614 mlx = Adafruit_MLX90614();

TFT_eSPI tft = TFT_eSPI();

float ambientCelsius = 0.0;

float objectCelsius = 0.0;

float objectCelsiusTotal = 0.0;

long prevMillis = 0;

int interval = 1000;

void setup()

{

  pinMode(BUTTON1, INPUT_PULLUP);

  pinMode(BUTTON2, INPUT_PULLUP);

  Serial.begin(115200);

  Serial.println();

  Serial.println("Build your own Portable Contactless Temperature Reader for Covid-19");

  Serial.println();

  tft.init();

  tft.setRotation(1);

  tft.fillScreen(TFT_BLACK);

  tft.fillRect(0, 0, 240, 43, TFT_DARKGREY);

  tft.setFreeFont(FF21);

  tft.setTextColor(TFT_BLACK);

  tft.setCursor(ROW1);

  tft.print("      Portable Contactless");

  tft.setCursor(0, 35); // Row 2

  tft.print("      Temperature Reader");

  tft.setTextColor(TFT_WHITE);

  tft.setCursor(ROW3);

  tft.print("         Battery:");

  tft.setTextColor(TFT_CYAN);

  tft.setCursor(ROW4);

  tft.print("   < Press button to read >");

  tft.setTextColor(TFT_WHITE);

  tft.setCursor(ROW5);

  tft.print("         Celsius:");

  tft.fillRect(0, 112, 240, 23, TFT_MAROON);

  tft.setTextColor(TFT_BLACK);

  tft.setCursor(0, 128); // Row 6

  tft.print("   #Covid19             by Idris");

  mlx.begin();

}

void loop()

{

  if (millis() – prevMillis > interval) {

    int adc = analogRead(ADC_PIN);

    float batteryVoltage = ((float)adc/4095.0)*2.0*3.3*(VREF/1000.0);

    tft.fillRect(140, 48, 100, 20, TFT_BLACK);

    if (batteryVoltage > 4.2) {

      tft.setTextColor(TFT_BLUE);

      tft.setCursor(140, 60);

      tft.print("Charge");

    }

    else {

      batteryVoltage = constrain(batteryVoltage, 3, 4); 

      float batteryPercent = ((batteryVoltage – 3) / 1) * 100;

      if (batteryPercent < 50) {

        tft.setTextColor(TFT_RED);

      }

      else if (batteryPercent < 80) {

        tft.setTextColor(TFT_YELLOW);

      }

      else {

        tft.setTextColor(TFT_GREEN);

      }

      tft.setCursor(150, 60);

      tft.print((int)batteryPercent);

      tft.print(" %");

    }

    prevMillis = millis();

  }

  if (digitalRead(BUTTON2) == LOW) {

    objectCelsiusTotal = 0.0;

    for (int i = 0; i < 20; i++) {

//      ambientCelsius = mlx.readAmbientTempC();

      objectCelsius = mlx.readObjectTempC();

      objectCelsiusTotal += objectCelsius;

      delay(50);

    }

    objectCelsius = objectCelsiusTotal / 20;

    tft.fillRect(140, 92, 100, 14, TFT_BLACK);

    tft.setTextColor(TFT_GREEN);

    tft.setCursor(150, 104);

    tft.print(objectCelsius);

  }

}