In this article we connect a MAX6675 to a Micro:bit
The MAX6675 performs cold-junction compensation and digitizes the signal from a type-K thermocouple. The data is output in a 12-bit resolution, SPI™-compatible, read-only format.
This converter resolves temperatures to 0.25°C, allows readings as high as +1024°C, and exhibits thermocouple accuracy of 8 LSBs for temperatures ranging from 0°C to +700°C.
The MAX6675 is available in a small, 8-pin SO package.
Key Features
- Cold-Junction Compensation
- Simple SPI-Compatible Serial Interface
- 12-Bit, 0.25°C Resolution
- Open Thermocouple Detection
Parts List
| Name | Link |
| Microbit | Micro:bit Development Board, |
| Extension Board for BBC micro:bit | Edge Breakout I/O Expansion Extension Board for BBC micro:bit |
| Connecting cable | Free shipping Dupont line 120pcs 20cm male to male + male to female and female to female jumper wire |
| Max6675 module | MAX6675 Module + K Type Thermocouple Thermocouple Senso Temperature Degrees Module |
Schematic
The part is not an exact match but the connection is the same, I also had a thermocouple with the MAX6675 which is not shown in this layout
microbit and max6675
Code
I used the following library as it worked with th emicro:bit and the ARduino IDE, you can import it via the library manager or download from https://github.com/YuriiSalimov/MAX6675_Thermocouple
[codesyntax lang=”cpp”]
#include <MAX6675_Thermocouple.h>
#define SCK_PIN 2
#define CS_PIN 1
#define SO_PIN 0
MAX6675_Thermocouple* thermocouple = NULL;
// the setup function runs once when you press reset or power the board
void setup() {
Serial.begin(9600);
thermocouple = new MAX6675_Thermocouple(SCK_PIN, CS_PIN, SO_PIN);
}
// the loop function runs over and over again forever
void loop() {
const double celsius = thermocouple->readCelsius();
const double kelvin = thermocouple->readKelvin();
const double fahrenheit = thermocouple->readFahrenheit();
Serial.print("Temperature: ");
Serial.print(String(celsius) + " C, ");
Serial.print(String(kelvin) + " K, ");
Serial.println(String(fahrenheit) + " F");
delay(500);
}
[/codesyntax]
Output
Open the serial monitor and you will see something like this
Temperature: 26.50 C, 299.65 K, 79.70 F
Temperature: 26.75 C, 299.90 K, 80.15 F
Temperature: 26.50 C, 299.65 K, 79.70 F
Temperature: 26.50 C, 299.65 K, 79.70 F
Temperature: 27.00 C, 300.15 K, 80.60 F
Temperature: 27.75 C, 300.90 K, 81.95 F
Temperature: 27.25 C, 300.40 K, 81.05 F
Temperature: 27.50 C, 300.65 K, 81.50 F
Temperature: 28.00 C, 301.15 K, 82.40 F
Temperature: 28.00 C, 301.15 K, 82.40 F
Temperature: 28.25 C, 301.40 K, 82.85 F
Links
https://datasheets.maximintegrated.com/en/ds/MAX6675.pdf