Arduino K-Type Thermocouple with MAX6675 Amplifier and SSD1306 Oled Display- K-Type Thermocouples are widely used temperature sensors in industrial and laboratory settings due to their high accuracy, wide temperature range, and fast response time. The MAX6675 Amplifier is an integrated circuit that amplifies and digitally converts the small voltage generated by a K-Type Thermocouple into a digital output, making it much easier to interface with microcontrollers and other digital devices. Together, the K-Type Thermocouple and the MAX6675 Amplifier offer a convenient and accurate solution for temperature measurement and control in a variety of applications. In this article, we will take a closer look at how to use a k-type thermocouple with Max6675 Amplifier and display temperature sensor data on SSD1306 Oled Display.
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What is K-Type Thermocouple?
A type K thermocouple is a temperature sensor made of two different metal wires, usually nickel-chromium and nickel-aluminum, that are joined at one end. When the junction between the two wires is heated or cooled, a small electrical voltage is generated that can be measured and used to determine the temperature at the point of measurement. Type K thermocouples are widely used in industrial and laboratory settings because they are relatively inexpensive, accurate, and can measure a wide range of temperatures.
Working principle of the thermocouple
The working principle of the thermocouple is that there is a temperature difference at the two ends of the thermocouple wire which makes the electrons in the wire move from an area with a high temperature to an area with a low temperature. So that at the end of the wire connected to the flame, the voltage can be read.
In a thermocouple, there are two different wires connected. This is because if the materials of the two wires are the same then there will be no electronic differences that can be detected as voltages. It’s the same as how the battery works where we can find out the battery voltage by installing a multimeter on the two poles, namely the positive and negative poles.
Now, because there is a difference, the voltage from the battery can be detected/read. However, if we connect it only to one of the poles of the battery, the voltage from the battery will not be read.
Types of Thermocouples
There are many types of thermocouples where each type or type that distinguishes one from another is the material of the wire or conductor which causes the temperature range that can be detected or read by the thermocouple also varies. In addition, the sensitivity of the thermocouple also varies due to differences in the material of the conductor.
Type B thermocouple
The conductor materials for type B are platinum and rhodium which can reach temperatures of 1370 °C to 1700 °C. This type of thermocouple can measure high temperatures but cannot measure low temperatures because this type becomes insensitive when used at low temperatures.
Type E thermocouple
This type of thermocouple is used in the temperature range between 0 to 870 °C. The material used in this thermocouple is Nickel Chromium / Constantan. Type E thermocouple is more stable than type K, so it is often used as the choice of use.
Type J thermocouple
This thermocouple should be used at temperatures below 750 °C because it degrades rapidly at temperatures above 550 °C. Type J thermocouples are generally also not used below ambient temperature because condensation will occur on the wires which cause rust.
Type K thermocouple
Type K thermocouple is the most common type of thermocouple used in various industries, for example the oil and gas industry because of its wide reading range and relatively affordable price. These thermocouples are sometimes called chromel–alumel thermocouples.
Type N thermocouple
This type of thermocouple can be used to perform higher temperature measurements compared to the use of type K thermocouples and has better repeatability in the temperature range of 300 °C to 500 °C. This type provides many advantages over the R&S Type at almost a tenth of the cost, making it a popular alternative to thermocouple options.
Type R thermocouple
Type R thermocouple has the same application as type S thermocouple but has better stability compared to type S so this type of thermocouple tends to be used as a reference for type S.
S Type Thermocouple
Type S thermocouple has the advantage that it can be used at a temperature of 1450 °C.
Type T thermocouple
This type of thermocouple is rarely used for industrial applications and tends to be used in laboratories.
What is MAX6675 Amplifier?
The MAX6675 Amplifier is an integrated circuit that amplifies and digitally converts the small voltage generated by a thermocouple into a digital output. It is specifically designed to work with K-Type thermocouples, which are widely used temperature sensors in industrial and laboratory settings. The MAX6675 Amplifier provides a convenient digital output that can be easily read by microcontrollers, making it ideal for use in temperature control and monitoring applications.
One of the main advantages of the MAX6675 is its high accuracy and wide temperature range, which can measure temperatures from -200 to +700 degrees Celsius with a resolution of 0.25 degrees Celsius. It also has a built-in 12-bit analog-to-digital converter, and it communicates with a microcontroller via the SPI bus. It needs a power supply voltage of 3.0V to 5.5V DC.
The MAX6675 Amplifier also has a thermocouple cold-junction-compensation feature which allows it to measure the accurate temperature without the need of a separate sensor. This feature makes the MAX6675 a very compact and low-cost solution for temperature measurement.
The MAX6675 Amplifier is widely used in a wide range of applications such as in industrial process control, temperature measurement in scientific experiments, medical equipment, and even in food processing. It is also a popular choice for hobbyists and DIY enthusiasts due to its low cost and easy-to-use nature.
Overall, the MAX6675 Amplifier is a powerful, accurate and convenient solution for temperature measurement and control, it can be easily interfaced with microcontrollers and other digital devices, and it’s widely used in a wide range of applications, making it a great choice for a variety of projects and applications.
K-Type Thermocouple with Max6675 Specification:
The technical specifications of a K-Type Thermocouple with MAX6675 Amplifier include:
- Temperature Range: The K-Type Thermocouple can measure temperatures ranging from -270°C to +1372°C, while the MAX6675 Amplifier can measure temperatures ranging from -200 to +700 degrees Celsius with a resolution of 0.25 degrees Celsius.
- Accuracy: The K-Type Thermocouple is known for its high accuracy, typically within ±2.2°C or ±0.75% of the reading, whichever is greater. The MAX6675 Amplifier has a 12-bit analog-to-digital converter, which provides a high level of accuracy.
- Response Time: The K-Type Thermocouple has a fast response time, typically within a few milliseconds.
- Communication: The MAX6675 Amplifier communicates with a microcontroller via the SPI bus.
- Power supply: The MAX6675 Amplifier needs a power supply voltage of 3.0V to 5.5V DC.
- Physical dimension: The MAX6675 Amplifier board is typically small in size, usually around 20mm x 14mm.
- Thermocouple cold-junction-compensation: The MAX6675 Amplifier has a thermocouple cold-junction-compensation feature which allows it to measure the accurate temperature without the need of a separate sensor.
- Cost: Both K-Type Thermocouple and MAX6675 Amplifier are relatively inexpensive and durable, making them a popular choice for a wide range of applications.
- Compatibility: The project code will work on both Arduino Uno and Arduino Nano boards.
LM75 Vs MAX6675 K-Type thermocouple
The LM75 and a MAX6675 K-Type thermocouple are both temperature sensors, but they operate in different ways and have different characteristics.
The LM75 is an integrated circuit that uses a small amount of power to measure temperature using a built-in thermistor, which is a resistor that changes resistance with temperature. The LM75 is a digital sensor, meaning it outputs a digital signal that can be read by a microcontroller or other digital device.
A MAX6675 K-Type thermocouple, on the other hand, is an analog sensor that generates a small electrical voltage at its measurement junction that changes with temperature. This voltage is then measured by a device called a thermocouple reader, which converts the voltage into a temperature reading.
The main difference between these sensors is that the LM75 is a digital sensor, while the t MAX6675 K-Type thermocouple is an analog sensor. The LM75 is also less expensive, more compact and requires less power compared to the thermocouple. However, the thermocouple can measure a wider range of temperatures(from -200°C to 1250°C) compared to the LM75(-55°C to 150°C).
SSD1306 Oled Display:
The SSD1306 OLED display is a small, low-power display that uses organic light-emitting diodes (OLEDs) to display text, images, and other information. The display is controlled by a driver IC (integrated circuit) called the SSD1306, which communicates with the host device (such as a microcontroller or computer) over an interface such as I2C or SPI.
The OLED display has several advantages over other types of displays, such as:
- High contrast ratio: OLEDs emit their own light, so the display does not require a backlight, resulting in a high contrast ratio.
- Wide viewing angle: OLEDs emit light from each individual pixel, so the image can be viewed from a wide angle.
- Low power consumption: OLEDs use very little power, making them ideal for battery-powered devices.
The SSD1306 OLED display is commonly used in small projects like wearable devices, portable devices, and other devices that require a small, low-power display.
Required Libraries Installation:
The SSD1306 OLED display is a small and low-power device that can be used to display text, graphics, and other information on a small screen. It is typically controlled by a microcontroller, such as an Arduino, and can be connected to the microcontroller through a variety of interfaces, such as I2C or SPI. There are libraries available for various programming languages that make it easy to control the display and display information on it.
The MAX6676 K-type thermocouple library is a library that provides an interface for reading temperature measurements from a MAX6676 thermocouple amplifier. The library provides functions for initializing and configuring the thermocouple, as well as functions for reading temperature measurements. The library can be installed through the Arduino Library Manager or by manually downloading and installing the library files.
To install the SSD1306 OLED library and MAX6676 K-type thermocouple library, you can typically use the library manager built into the development environment you are using. For example, in the Arduino IDE, you can go to Sketch > Include Library > Manage Libraries, and search for the libraries by name. Once you find the libraries, you can install them by clicking the “Install” button.
So let’s install the required libraries manually
First open your Arduino Ide and click on the sketch, in the sketch dropdown menu click on include library then click on manage libraries
In the library Manager window, search for your required libraries by name, so for this project, I am installing the SSD1306 OLED display and max6675 libraries.
So first search for SSD1306 OLED display as you can see in the below image
Select the required library and click on the install button. But in my case, I already installed it so it shows me the update button instead of install.
Repeat the same steps for the max6675 amplifier library
So, that’s all about the libraries installation.
Interfacing Arduino K-Type thermocouple with Max6675:
Let’s start with the SSD1306 Oled display module, as you can see the VCC and GND pins of the Oled display module are connected with the Arduino Nano3.3V and GND pins. Whereas the SDA and SCL pins of the SSD1306 Oled display module are connected with the Arduino Nano A4 and A5 pins. In Arduino Nano SDA and SCL pins are A4 and A5 respectively. So, it doesn’t matter if you use Arduino Nano or Arduino Uno.
The Red and Blue color sleeve wires of the K-type thermocouple are connected with the Max6675 + and – contacts. The SCK, CS, and SO pins of the Max6675 amplifier board are connected with the Arduino Nano pins D6, D5, and D3 respectively.
On the Left side, you can see a 5V regulated power supply based on the most popular linear voltage regulator 7805. This power supply is optional, because you can also use your laptop or computer to power up your Arduino board. But its good to have this 5V power supply. So, that’s all about the circuit diagram.
Arduino K-Type Thermocouple with Max6675 Amplifier Code:
#include <Wire.h> // you don’t need to download and install this library
int thermoDO = 3;
int thermoCS = 5;
int thermoCLK = 6;
MAX6675 thermocouple(thermoCLK, thermoCS, thermoDO);
float temp; //Stores temperature value
#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels
// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
#define OLED_RESET -1 // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
temp = thermocouple.readCelsius();
K-type thermocouple with max6675 practical testing:
As you can see I connected all the components as per the circuit diagram.
You can see our project is successfully run and displaying k-type thermocouple temperature sensor data on SSD1306 oled display
I applied some temperature on the k-type thermocouple sensor
So you can see the temperature is changed from 45.00°C to 57.50°C.
So, that’s all about the Arduino K-type thermocouple with Max6675 Amplifier and SSD1306 Oled display. If you want to learn more about k-type thermocouple with max6675 Amplifier Temperature sensor read my other articles the links are given in the related article section.