MLX90615 infrared thermometer and LinkIT example

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In this example we take a look at an MLX90615 IR thermometer, we will connect this to a LinkIT one. There will be 2 examples to look at which are written using the Arduino IDE

The MLX90615 is a miniature infrared thermometer for non-contact temperature measurements. Both the IR sensitive thermopile detector chip and the signal conditioning ASIC are integrated in the same miniature TO-46 can.

The infrared thermometer comes factory calibrated with a digital SMBus output giving full access to the measured temperature in the complete temperature range(s) with a resolution of 0.02 °C. The sensor achieves an accuracy of ±0.2°C within the relevant medical temperature range. The user can choose to configure the digital output to be PWM.

Features and benefits

Factory calibrated in wide temperature range: -20 to 85°C for sensor temperature and -40 to 115°C for object temperature
High accuracy of 0.5°C over wide temperature range (0..+50 C for both Ta and To)
Medical accuracy of 0.2°C in a limited temperature range
Measurement resolution of 0.02°C
SMBus compatible digital interface for fast temperature readings and building sensor networks
Customizable PWM output for continuous reading
3V supply voltage with power saving mode

Parts List

 

Amount Part Type
1 MLX90615 Digital Infrared Temperature Sensor for Arduino GY Series Module
1 LinkIt ONE MT2502A wireless 2503 development board

Connection

An easy device to connect, simple I2C sensor that requires 3.3v and GND.

linkit and mlx90615 layout
linkit and mlx90615 layout

 

Test Code

This particular example comes from the following library which I installed – https://github.com/skiselev/MLX90615

#include <Wire.h>
#include <mlx90615.h>
 
MLX90615 mlx = MLX90615();
 
void setup() 
{
  Serial.begin(9600);
  Serial.println("Melexis MLX90615 infra-red temperature sensor test");
  mlx.begin();
  Serial.print("Sensor ID number = ");
  Serial.println(mlx.get_id(), HEX);
}
 
void loop() 
{
  Serial.print("Ambient = ");
  Serial.print(mlx.get_ambient_temp());
  Serial.print(" *C\tObject = ");
  Serial.print(mlx.get_object_temp());
  Serial.println(" *C");
  delay(500);
}

 

 

Test Output

In the serial monitor and you should see something like this. The warmer object reading was when I placed my finger near the sensor

Ambient = 24.31 *C Object = 33.23 *C
Ambient = 24.23 *C Object = 31.63 *C
Ambient = 24.19 *C Object = 32.25 *C
Ambient = 24.23 *C Object = 37.57 *C
Ambient = 24.27 *C Object = 38.31 *C
Ambient = 24.37 *C Object = 37.11 *C
Ambient = 24.41 *C Object = 36.87 *C
Ambient = 24.45 *C Object = 35.99 *C
Ambient = 24.49 *C Object = 35.47 *C
Ambient = 24.49 *C Object = 33.81 *C

 

Web page Example

There are 3 lines that will/may need changed for your Wifi details

#define WIFI_AP "wifi ssid here"
#define WIFI_PASSWORD "password here"
#define WIFI_AUTH LWIFI_WPA

The last one you can select from from LWIFI_OPEN, LWIFI_WPA, or LWIFI_WEP according to your WiFi AP configuration

 

Now for the complete code example

#include <LTask.h>
#include <LWiFi.h>
#include <LWiFiServer.h>
#include <LWiFiClient.h>
#include <mlx90615.h>
 
#define WIFI_AP "iainhendry"
#define WIFI_PASSWORD "iain061271"
#define WIFI_AUTH LWIFI_WPA
 
MLX90615 mlx = MLX90615();
LWiFiServer server(80);
 
 
void setup()
{
    LTask.begin();
    LWiFi.begin();
    Serial.begin(9600);
    //output MLX90615 info via serial
    Serial.println("Melexis MLX90615 infra-red temperature sensor test");
    mlx.begin();
    Serial.print("Sensor ID number = ");
    Serial.println(mlx.get_id(), HEX);
    // keep retrying until connected to AP
    Serial.println("Connecting to AP");
    while (0 == LWiFi.connect(WIFI_AP, LWiFiLoginInfo(WIFI_AUTH, WIFI_PASSWORD)))
    {
        delay(1000);
    }
    //connect and display IP address
    printWifiStatus();
    Serial.println("Start Server");
    server.begin();
    Serial.println("Server Started");
}
 
int loopCount = 0;
 
void loop()
{
    // put your main code here, to run repeatedly:
    delay(500);
    loopCount++;
    LWiFiClient client = server.available();
 
 
    if (client)
    {
        Serial.println("new client");
        // an http request ends with a blank line
        boolean currentLineIsBlank = true;
 
        unsigned long timer_out = millis();
 
        while (client.connected())
        {
 
            if(millis()-timer_out > 5000)break;
 
            if (client.available())
            {
                // we basically ignores client request, but wait for HTTP request end
                int c = client.read();
                Serial.print((char)c);
 
                if (c == '\n' && currentLineIsBlank)
                {
                    Serial.println("send response");
                    // send a standard http response header
                    client.println("HTTP/1.1 200 OK");
                    client.println("Content-Type: text/html");
                    client.println("Connection: close");  // the connection will be closed after completion of the response
                    client.println("Refresh: 5");  // refresh the page automatically every 5 sec
                    client.println();
                    client.println("<!DOCTYPE HTML>");
                    client.println("<html>");
                    // output the value of each analog input pin
 
                    client.print("Ambient = ");
                    client.print(mlx.get_ambient_temp());
                    client.print(" *C\tObject = ");
                    client.print(mlx.get_object_temp());
                    client.println(" *C");
                    break;
                }
                if (c == '\n')
                {
                    // you're starting a new line
                    currentLineIsBlank = true;
                }
                else if (c != '\r')
                {
                    // you've gotten a character on the current line
                    currentLineIsBlank = false;
                }
            }
        }
        // give the web browser time to receive the data
        delay(500);
 
        // close the connection:
        Serial.println("close connection");
        client.stop();
        Serial.println("client disconnected");
    }
}
 
void printWifiStatus()
{
    // print the SSID of the network you're attached to:
    Serial.print("SSID: ");
    Serial.println(LWiFi.SSID());
 
    // print your WiFi shield's IP address:
    IPAddress ip = LWiFi.localIP();
    Serial.println("Please open your browser, and input the following address:");
    Serial.println(ip);
 
    Serial.print("\r\nsubnet mask: ");
    Serial.println(LWiFi.subnetMask());
 
    Serial.print("gateway IP: ");
    Serial.println(LWiFi.gatewayIP());
 
    // print the received signal strength:
    long rssi = LWiFi.RSSI();
    Serial.print("signal strength (RSSI):");
    Serial.print(rssi);
    Serial.println(" dBm");
}

This example has test code to help you out – the printWifiStatus function, open up the USB Modem Port – not the programming port. You should see a message like this

Connecting to AP
SSID: your ssid here
Please open your browser, and input the following address:
192.168.1.15

Web page Output

Open up your favourite web browser and you should see a line that updates every 5 seconds

Ambient = 23.09 *C Object = 24.23 *C

 

Links

https://www.melexis.com/-/media/files/documents/datasheets/mlx90615-datasheet-melexis.pdf

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