micro:bit and MLX90614 infrared thermometer example

The MLX90614 is a non-contact infrared thermometer with a measurement range from -70 to +380 degree Celsius. Just connect the four leads to your Wemos and you will have a accurate thermometer with a resolution of 0.01 and a accuracy of 0.5 degrees, or for that matter you can use any microcontroller that can communicate with it through it’s I2C interface.

Being an I2C device you simply need to connect to the SDA, SCL and choose a suitable GND and Vin. I used 3.3v to be safe, although the breakout states 3 to 5v.

This version I chose comes with a breakout board with all of the components needed for operation. Here is a picture of that breakout board

 

Features:
Small size, low cost
Mounted on a breakout board with two types of pins
10k Pull up resistors for the I2C interface with optional solder jumpers
Factory calibrated in wide temperature range:
-40 … + 125 ° C for sensor temperature and
-70 … + 380 ° C for object temperature.
High accuracy of 0.5 ° C over wide temperaturerange (0 … + 50 ° C for both Ta and To) High (medical) accuracy calibration
Measurement resolution of 0.02 ° C
Single and dual zone versions
SMBus compatible digital interface
Customizable PWM output for continuous reading
Sleep mode for reduced power consumption

 

Connection

VIN -> Micro:bit 3.3v
GND -> Micro:bit GND
SCL -> Micro:bit 19
SDA -> Micro:bit 20

 

Code

There is a library from Adafruit and rather than reinvent the wheel, here is the basic code example. In practice you connect to an LCD, warning LED or perhaps a buzzer to warn if a certain maximum temperature was reached

The sketch below is fairly straightforward, most of the work is done in the Adafruit MLX96014 library which outputs the result via the serial monitor

#include <Wire.h>
#include <Adafruit_MLX90614.h>
 
Adafruit_MLX90614 mlx = Adafruit_MLX90614();
 
void setup() 
{
  Serial.begin(9600);
  mlx.begin();  
}
 
void loop() 
{
  Serial.print("Ambient = "); 
  Serial.print(mlx.readAmbientTempC()); 
  Serial.print("*C\tObject = "); 
  Serial.print(mlx.readObjectTempC()); 
  Serial.println("*C");
  Serial.print("Ambient = "); 
  Serial.print(mlx.readAmbientTempF()); 
  Serial.print("*F\tObject = "); 
  Serial.print(mlx.readObjectTempF()); 
  Serial.println("*F");
 
  Serial.println();
  delay(1000);
}

 

Output

Open up that Serial monitor window and you should see something like the following, the interesting one is the object temperature and how it varied when I placed an object in front of the sensor, the ambient reading stayed the same

Ambient = 22.89*C Object = 19.09*C
Ambient = 73.20*F Object = 66.36*F

Ambient = 22.85*C Object = 19.07*C
Ambient = 73.13*F Object = 66.33*F

Ambient = 22.83*C Object = 19.07*C
Ambient = 73.09*F Object = 66.33*F

Ambient = 22.79*C Object = 19.17*C
Ambient = 73.02*F Object = 66.51*F

 

Links

Here is a link to the datasheet and also the breakout I purchased, come in at about $6 a piece.

MLX90614 datasheet
GY-906 MLX90614ESF New MLX90614 Contactless Temperature Sensor Module For arduino Compatible