Introduction

The MAX6675 is a cold-junction compensated thermocouple-to-digital converter that provides accurate temperature readings from 0°C to +1024°C using a K-type thermocouple. This SPI-compatible module is ideal for high-temperature applications like 3D printer hotends, kilns, and industrial processes.

Key Features

Technical Specifications

Pin Configuration

Pin	Label	Description	Arduino Connection
1	VCC	Power (3.3V-5V)	5V
2	GND	Ground	GND
3	SCK	SPI Clock	D13 (SCK)
4	CS	Chip Select	D10 (or any digital pin)
5	SO	SPI Data Out	D12 (MISO)
6-7	T+/T-	Thermocouple Input	K-type thermocouple

Wiring Diagram (Arduino Uno)

// MAX6675 Connections:
// VCC → 5V
// GND → GND
// SCK → D13 (SCK)
// CS  → D10 (or any digital pin)
// SO  → D12 (MISO)

// Thermocouple:
// T+ → Red wire (positive)
// T- → Yellow wire (negative)

Basic Temperature Reading

#include "max6675.h"

// Define SPI pins
int thermoDO = 12;  // SO
int thermoCS = 10;  // CS
int thermoCLK = 13; // SCK

MAX6675 thermocouple(thermoCLK, thermoCS, thermoDO);

void setup() {
  Serial.begin(9600);
  delay(500); // Wait for MAX6675 stabilization
}

void loop() {
  Serial.print("Temperature: ");
  Serial.print(thermocouple.readCelsius());
  Serial.println("°C");
  
  // For Fahrenheit:
  // Serial.print(thermocouple.readFahrenheit());
  // Serial.println("°F");
  
  delay(1000);
}

Advanced Features

// Multiple MAX6675 with separate CS pins
MAX6675 thermocouple1(13, 10, 12); // CS=10
MAX6675 thermocouple2(13, 9, 12);  // CS=9

void loop() {
  float temp1 = thermocouple1.readCelsius();
  float temp2 = thermocouple2.readCelsius();
}

// Check thermocouple connection
if(thermocouple.readCelsius() == NAN) {
  Serial.println("Thermocouple error!");
  // Check connections and thermocouple
}

// Moving average filter
#define READINGS 5
float tempHistory[READINGS];
int index = 0;

float getAvgTemp() {
  tempHistory[index] = thermocouple.readCelsius();
  index = (index + 1) % READINGS;
  
  float sum = 0;
  for(int i=0; i

// Basic PID control example
#include 

double Setpoint, Input, Output;
PID myPID(&Input, &Output, &Setpoint, 2,5,1, DIRECT);

void setup() {
  Setpoint = 200; // Target 200°C
  myPID.SetMode(AUTOMATIC);
}

void loop() {
  Input = thermocouple.readCelsius();
  myPID.Compute();
  analogWrite(heaterPin, Output);
}