Discover the latest advancements and insights in the field of biomedical engineering and electronics at the BioElectronix Hub. Our blog provides in-depth analysis, expert opinions and hands-on tutorials on the cutting-edge technologies revolutionizing the medical industry. Join us as we explore the intersection of electronics and healthcare, and stay ahead of the curve in this exciting and rapidly evolving field
Showing posts with label PID Temperature controller. Show all posts
Showing posts with label PID Temperature controller. Show all posts
Calibrating a temperature sensor using an Arduino code involves the following steps:
Connect your temperature sensor to your Arduino board.
Write the Arduino code to read the temperature from the sensor. You can use the built-in libraries in Arduino IDE to read the temperature from various sensors, such as the DS18B20, LM35, or DHT11 sensors.
Once you have the temperature reading, you can compare it to a known temperature reading to calibrate your sensor. For example, you can place your temperature sensor in a container of ice water and measure the temperature. The temperature of ice water should be around 0 degrees Celsius or 32 degrees Fahrenheit. If your sensor is not reading the correct temperature, you can adjust the code to compensate for the difference.
Another way to calibrate your sensor is to place it in boiling water and measure the temperature. The temperature of boiling water should be around 100 degrees Celsius or 212 degrees Fahrenheit. Again, if your sensor is not reading the correct temperature, you can adjust the code to compensate for the difference.
Once you have calibrated your temperature sensor, you can use it to measure the temperature in other environments. Make sure to take into account any calibration adjustments you made to the code when using the sensor in other settings.
One Point Calibration
One point calibration is the simplest type of calibration. If the
sensor output is already scaled to useful measurement units, a one point
calibration can be used to correct for sensor offset errors in the
following cases:
Only one measurement point is needed. If you have an
application that only requires accurate measurement of a single level,
there is no need to worry about the rest of the measurement range. An
example might be a temperature control system that needs to maintain the
same temperature continuously.
The sensor is known to be linear and have the correct slope over the desired measurement range.
In this case, it is only necessary to calibrate one point in the
measurement range and adjust the offset if necessary. Many temperature
sensors are good candidates for one-point calibration.
A one point calibration can also be used as a "drift check" to detect
changes in response and/or deterioration in sensor performance.
For example, thermocouples used at very high temperatures exhibit an
'aging' effect. This can be detected by performing periodic one point
calibrations, and comparing the resulting offset with the previous
calibration.
How to do it:
To perform a one point calibration:
Take a measurement with your sensor.
Compare that measurement with your reference standard.
Subtract the sensor reading from the reference reading to get the offet.
In your code, add the offset to every sensor reading to obtain the calibrated value
ESP32 PID Temperature Controller using MAX6675 K-Thermocouple to Digital Converter IC
PID based Temperature Controller
This is a PID Controller based Heater that
can be used to control the temperature of the Ceramic Heater.
What is a Temperature PID Controller ?
As the name suggests a temperature PID controller deals
with temperature, PID temperature control is a closed-loop control
algorithm that improves the accuracy of the process. The PID temperature
control works using a mathematical formula to calculate the difference
between the current temperature and set point. And then it tries to
deliver the required power to ensure the target temperature remains constant,
this not only reduces environmental impact but it also reduces
overshoots that can be found in the traditional on-off control
mechanism.
How does a Temperature PID Controller work?
As in any PID control first, we need to be aware
of the output or what we want the controller to do, for this project we
want to maintain a certain temperature of the heating element (we will
set that temperature with the help of the rotary encoder) so to maintain
the temperature we need to read out of the temperature, for that we are
using a K-type thermocouple, in conjunction with MAX6675 Cold-Junction-Compensated K-Thermocouple to Digital Converter IC that
can measure hundreds of degree Celsius without any issues. And the
temperature readout from the thermocouple acts as feedback. Now as we
have set the temperature we want to achieve and we have a real-time
readout of the temperature value the controller can calculate the error
value and with the help of proportional integral and derivative control
the system can achieve its target, for this project we will control a
PWM signal with the calculated output value. That is how a Temperature Based PID controller works.
MAX6675 K-Thermocouple IC Working
Components Required to build a PID Enabled Temperature Controller
The components required to build the MAX6675 based PID Controlled Heater are listed below
ESP32 - 1
128 X 64 OLED Display - 1
Generic Rotary Encoder - 1
MAX6675 Module - 1
K-type Thermocouple - 1
PID Enabled Temperature Controller Circuit Diagram
Download EAGLE CAD file from GIT Hub
In this project, we use the MAX6675 K-type Thermocouple sensor to
read the temperature data from the thermocouple, and in this section,
we will explain all the details with the help of the schematic. Let me
give you a brief overview of what is happening with this circuit. The
MAX6675 is a Cold-Junction-Compensated K- Thermocouple to Digital Converter module
and it connects to Arduino according to the schematic. The power is
provided to the circuit with the help of a +5V supply of the ESP32 .
Also to set the temperature and change the modes we are using a generic
Rotary encoder.
Next, we have the 128X64 OLED display the display shows the temperature
data and it also shows the set temperature. By pressing the button on the rotary encoder,
we can switch in between two modes one is to set the temperature and
another one to monitor the trout from the thermocouple. Other than that,
the circuit stays pretty simple.
MAX6675 based PID Enabled Temperature Controller ESP32 Code
The complete code used in this project can be
found at the bottom of this page. After adding the required header files
and source files, you should be able to directly compile the Arduino
code without any errors. You can download the PID controller library, MAX6675 Library, AAdafruit_SSD1306 Library from the link given below, or else you can use the board manager method to install the library.
A simple explanation of the code is given as
comments, and in this section, we will go a little more in-depth about
it. First, we start by including all the required libraries, after that,
we define all the necessary pins that are required to read the encoder,
drive the OLED and MAX6675 Thermocouple temperature sensor. Once that
is done, we define all the values for the Kp, Ki, and Kd, and include
all the required variables.
Next, we have defined the __Kp, __Ki, and __Kd values
for our code. These three constants are responsible for setting up the
output response for our code. Please do note that for this project, I
have used the trial-and-error method to set the constants, but you can
calculate the values if that is something necessary for your project.
/*In this section we have defined the gain values for the
* proportional, integral, and derivative controller I have set
* the gain values with the help of trial and error methods.
*/
#define __Kp 30 // Proportional constant
#define __Ki 0.7 // Integral Constant
#define __Kd 200 // Derivative Constant
Next,
we declare all the required variables and we create three instances one
for PID one for the OLED, and the final one for the thermocouple.
Variable clockPin and clockPinState, debounce, and encoder_btn_count all four used to read data from the encoder the temperature_value_c holds the temperature readout from the thermocouple, finally the encoder_btn_count holds how many times the button of the encode is pressed.
PID Enabled Temperature Controller Testing
To test the circuit the following setup is used,
as you can see, I have connected Multimeter to display the
duty cycle of the output PWM signal.
And as a heater, I have used a ceramic heating element, controlled by SSR
Now, to set the temperature you need to press the
button of the rotary encoder, which set the setpoint or the target
temperature of the PID algorithm once set press the button another time
to make the changes permanent and the heater block starts heating and
you can see the duty cycle also increases.
Once the desired temperature is reached the PWM
duty cycle is reduced and you can observe a certain spike in the duty
cycle when the controller wants to compensate for the error and increase
the temperature.
This marks the end of the tutorial. I hope you
liked the article and learned something new. If you have any questions
regarding the article, you can leave them in the comment section below
or you can use our Electronics Forum. You can also check out the video at the bottom.
ESP32 Code and Eagle CAD file can download here,
there are two files, one for OTA update, use any one at your preference,
==========================Update on 20-02-2023======================
I have successfully designed and fabricated a printed circuit board (PCB), which involved the assembly of various electronic components through soldering. Moving forward, I plan to integrate a calibration mechanism for the sensor and implement a closed-loop system to reduce any errors in temperature regulation when controlling the heater.
To achieve this, I will need to establish a set of procedures to determine the sensitivity and accuracy of the sensor, and calibrate it accordingly. This process may involve adjusting gain, offset, and linearity of the sensor output to match the expected response. Once the sensor is properly calibrated, I will proceed to implement a feedback loop system that utilizes the sensor data to regulate the temperature of the heater.
My GitHub repository boasts a treasure trove of electronic design assets, including the Eagle CAD file that is available for your perusal.If you have a keen eye for detail and an unquenchable thirst for electronic design, then you will undoubtedly appreciate the intricate layout and intricate component placement within this file. It is a testament to the power of technology and human ingenuity, and it stands as a shining example of what can be achieved through tireless effort and unwavering dedication.
So, why wait? Visit my GitHub repository today and explore the myriad of design assets that are available for you to download and use in your own projects. With the Eagle CAD file at your fingertips, you too can experience the thrill of creating your own electronic masterpiece and pushing the boundaries of what is possible in the world of electronic design.
