Control systems are integral to modern automation and robotics, enabling devices to maintain desired outputs despite changing inputs or environmental conditions. Arduino, an open-source electronics platform, is well-suited for developing simple to moderately complex control systems due to its flexibility and ease of use. This article will guide you through the process of creating a basic control system using Arduino, specifically focusing on a PID (Proportional-Integral-Derivative) controller, which is a common type of control system.

Examples:

1. Understanding PID Control: A PID controller continuously calculates an error value as the difference between a desired setpoint and a measured process variable. It applies a correction based on proportional, integral, and derivative terms, hence the name.

2. Components Required:

   • Arduino Uno or any compatible board
   • Temperature sensor (e.g., LM35)
   • Actuator (e.g., a fan or heater)
   • Breadboard and jumper wires
   • Power supply

3. Setting Up the Hardware: Connect the temperature sensor to the Arduino. For an LM35, connect the Vout pin to an analog input on the Arduino, the Vcc to 5V, and the ground to GND. Connect the actuator (e.g., a fan) to a digital output pin via a transistor to control it.

4. Arduino Code for PID Control:

   // Include the PID library
   #include <PID_v1.h>
   
   // Define the pins
   const int tempSensorPin = A0;
   const int actuatorPin = 9;
   
   // Define variables for PID
   double setpoint = 25.0; // Desired temperature in Celsius
   double input, output;
   double Kp = 2.0, Ki = 5.0, Kd = 1.0; // PID coefficients
   
   // Create PID instance
   PID myPID(&input, &output, &setpoint, Kp, Ki, Kd, DIRECT);
   
   void setup() {
    // Initialize the actuator pin
    pinMode(actuatorPin, OUTPUT);
   
    // Initialize the PID controller
    myPID.SetMode(AUTOMATIC);
   }
   
   void loop() {
    // Read the temperature from the sensor
    int sensorValue = analogRead(tempSensorPin);
    input = (sensorValue / 1024.0) * 500.0; // Convert to Celsius
   
    // Compute the PID output
    myPID.Compute();
   
    // Control the actuator based on PID output
    analogWrite(actuatorPin, output);
   
    // Add a delay for stability
    delay(1000);
   }

5. Explanation:

   • The PID library is used to simplify the control logic.
   • The setpoint is the desired temperature.
   • The input is the current temperature read from the sensor.
   • The output determines the actuator's behavior (e.g., fan speed).
   • The PID controller adjusts the output to minimize the error between the setpoint and the input.

6. Tuning the PID Controller: Adjust the Kp, Ki, and Kd values to achieve the desired response. This process, known as PID tuning, can be done manually or using software tools.