Thermocouples are temperature sensors that are commonly used in various applications, ranging from industrial processes to DIY projects. They work based on the principle of the Seebeck effect, where a voltage is generated across two different metals when they are exposed to a temperature gradient. One popular thermocouple is the MAX6675, which is compatible with Arduino boards and provides accurate temperature measurements. In this tutorial, we will walk you through the steps to set up and use the MAX6675 thermocouple with an Arduino board.
Materials Needed:
- Arduino board (e.g., Arduino Uno)
- MAX6675 thermocouple module
- Type K thermocouple probe
- Breadboard
- Jumper wires
- Computer with Arduino IDE installed
- Understanding the MAX6675 Thermocouple Module
The MAX6675 IC chip is a thermocouple-to-digital converter. It converts the analog voltage output from the thermocouple into a digital value that can be read by the Arduino board. The MAX6675 has 7 pins: T-, T+, SO, CS, SCK, VCC and GND. T- and T+ are for connecting the thermocouple IC to the thermocouple probe. The SO, CS and SCK are used for SPI connection to microcontroller MCU or microcontroller board like Arduino. The VCC and GND are used to power the IC.
- Connecting the MAX6675 Thermocouple IC to Arduino
To connect the MAX6675 module to the Arduino board, follow these steps:
- Connect the VCC pin on the MAX6675 module to the 3.3V pin on the Arduino board.
- Connect the GND pin on the MAX6675 module to the GND pin on the Arduino board.
- Connect the SCK pin on the MAX6675 module to any digital pin on the Arduino board (e.g., D13).
- Connect the DO pin on the MAX6675 module to any digital pin on the Arduino board (e.g., D12).
- Connect the CS pin on the MAX6675 module to any digital pin on the Arduino board (e.g., D11).
Following is circuit diagram that shows how to interface with a MAX6675 thermocouple IC and display temperature
readings on a 16x2 LCD using the LiquidCrystal library.
- Connecting the Type K Thermocouple Probe
The MAX6675 thermocouple IC is designed to work with Type K thermocouples, so you will need a Type K thermocouple probe to measure temperature. To connect the thermocouple probe to the MAX6675 module, follow these steps:
- Connect the positive (red) wire of the thermocouple probe to the T+ pin on the MAX6675 IC.
- Connect the negative (blue) wire of the thermocouple probe to the T- pin on the MAX6675 IC.
- Arduino Code MAX6675 thermocouple
The following is Arduino code that reads the data from MAX6675 thermocouple and display the temperature in Celcius and Farenheit format.
#include <max6675.h>
#include <LiquidCrystal.h>
#include <Wire.h>
int DOpin = 11;
int CSpin = 12;
int CLKpin = 13;
MAX6675 thermocouple(CLKpin, CSpin, DOpin);
LiquidCrystal lcd(7, 6, 5, 4, 3, 2);
void setup() {
Serial.begin(9600);
lcd.begin(16, 2);
// wait for MAX chip to stabilize
delay(500);
}
void loop() {
//print the current temp
lcd.clear();
lcd.setCursor(0, 0);
lcd.print(thermocouple.readCelsius());
lcd.write(0xdf); // to display °
lcd.print("C");
// go to line #1
lcd.setCursor(0, 1);
lcd.print(thermocouple.readFahrenheit());
lcd.write(0xdf); // to display °
lcd.print("F");
delay(500);
}
Let's go through the code step by step:
Libraries:
The code includes three libraries: max6675.h, LiquidCrystal.h, and Wire.h. These are standard Arduino libraries used for interfacing with the MAX6675 module, LCD, and I2C communication respectively. One can install the MAX6675 library from the library manager in Arduino IDE as shown below.
Pin Definitions:
The code defines three pin numbers: DOpin, CSpin, and CLKpin, which are connected to the DO (Data Out), CS (Chip Select), and CLK (Clock) pins of the MAX6675 module respectively. It also defines the pin numbers for the LCD interface, which are connected to RS, EN, D4, D5, D6, and D7 pins of the LCD module respectively.
Object Instantiation:
An instance of the MAX6675 class is created with the name "thermocouple" and is passed the pin numbers for CLKpin, CSpin, and DOpin as parameters. Similarly, an instance of the LiquidCrystal class is created with the name "lcd" and is passed the pin numbers for RS, EN, D4, D5, D6, and D7 pins of the LCD module as parameters.
Setup():
The setup() function is a standard Arduino function that is called once at the beginning of the program. In this code, it initializes the serial communication with a baud rate of 9600 for debugging purposes using Serial.begin(9600). It also initializes the LCD module with 16 columns and 2 rows using lcd.begin(16, 2), and adds a delay of 500 milliseconds for the MAX6675 chip to stabilize.
Loop():
The loop() function is another standard Arduino function that runs in a continuous loop after the setup() function. In this code, it reads the temperature in Celsius and Fahrenheit from the MAX6675 module using the thermocouple.readCelsius() and thermocouple.readFahrenheit() methods respectively. It then displays the temperature readings on the LCD module in Celsius and Fahrenheit units, with the respective unit symbols (°C and °F) using lcd.print() and lcd.write() methods. The delay() of 500 milliseconds provides a small delay between each reading to avoid flickering on the LCD display.
Overall, this code allows you to read temperature values from a MAX6675 thermocouple module and display them on an LCD module using an Arduino, providing a simple way to monitor temperature in your projects.
- Uploading the Code to Arduino
Now that the hardware is set up, you can upload the code to the Arduino board. Here is an example code that reads temperature values from the MAX6675 module and displays them on the serial monitor:
- Testing the MAX6675 Thermocouple with Arduino
Once you have uploaded the code to the Arduino board, you can open the serial monitor in the Arduino IDE to see the temperature readings from the MAX6675 module. Make sure the baud rate in the serial monitor matches the baud rate specified in the code (in this case, 9600 baud). You should see the temperature values displayed in Celsius with a 1-second delay between each reading.
You can also customize the code to suit your specific needs. For example, you can display the temperature in Fahrenheit or implement additional functionalities such as triggering alarms based on temperature thresholds.
Conclusion
In this tutorial, we have shown you how to get started with the MAX6675 thermocouple IC and Arduino. By following the steps outlined above, you should now be able to read accurate temperature values from a Type K thermocouple probe using the MAX6675 module and display them on the serial monitor. With this knowledge, you can now incorporate thermocouples into your Arduino projects to measure and monitor temperature in various applications. Happy experimenting!
References and Further Readings
[1] Arduino PID Controller - Temperature PID Controller
[2] Arduino AD8495 Thermocouple Amplifier
[3] Arduino MAX31855 thermocouple
[4] LM35 Temperature Sensor with Arduino and LCD
[5] Display Temperature on Web with NodeMCU, LM35 and Node-Red
