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MAX6675 Module + K Type Thermocouple Sensor Measure 1024°C Temperature
MAX6675 Thermocouple Temperature Sensor Module
High-Temperature Measurement up to 1024°C with K-Type Thermocouple
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
High Range
0°C to +1024°C measurement
12-bit Resolution
0.25°C temperature resolution
SPI Interface
Simple 3-wire communication
Cold Junction Comp.
Built-in ambient temperature compensation
Technical Specifications
| Temperature Range | 0°C to +1024°C |
|---|---|
| Resolution | 0.25°C (12-bit) |
| Accuracy | ±2°C (0-700°C), ±3°C (700-1024°C) |
| Supply Voltage | 3.0V to 5.5V |
| Interface | SPI-compatible (3-wire) |
| Response Time | 100-200ms (typical) |
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 |
Important: Never reverse thermocouple polarity (T+/T-)
Wiring Diagram (Arduino Uno)
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// 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
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#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); } |
Library Required: Install “MAX6675 library” by Adafruit or equivalent
Advanced Features
Multiple Sensors
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// 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(); } |
Error Handling
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// Check thermocouple connection if(thermocouple.readCelsius() == NAN) { Serial.println("Thermocouple error!"); // Check connections and thermocouple } |
Temperature Averaging
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// 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<READINGS; i++) { sum += tempHistory[i]; } return sum / READINGS; } |
PID Temperature Control
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// Basic PID control example #include <PID_v1.h> 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); } |
Troubleshooting
No Temperature Reading
- Verify thermocouple connection (T+/T- polarity)
- Check SPI wiring (SCK, CS, SO)
- Ensure proper power supply (3.3V-5V)
Incorrect Readings
- Check for thermocouple damage (kinks or breaks)
- Ensure cold junction area is at stable temperature
- Verify thermocouple type is K-type
Erratic Values
- Add 0.1μF capacitor between VCC and GND
- Keep wires away from EMI sources
- Implement software averaging
