PID_Peltier_LM35DZ.ino

#include <math.h>

//目標の温度
double targetTemperature = 40.0;

//リレーを制御するピン
int enablePin = 2; 

double currentTemperture; //温度センサの温度

int count = 0;
double input = 255.0;
double preinput = 255.0;
double deltainput = 0;
double e = 0;
double e1 = 0;
double e2 = 0;

double kp = 2.0; //比例ゲイン
double ki = 1.0; //積分ゲイン
double kd = 0.5; // 微分ゲイン

void setup() {
  Serial.begin(9600); 
  pinMode(A0, INPUT); //A0番ピンを入力用に設定する
  pinMode(enablePin, OUTPUT);
  digitalWrite(enablePin, HIGH);
}

void loop() {

  currentTemperture = getTemperature();

  Serial.print(targetTemperature);
  Serial.print(", ");
  Serial.println(currentTemperture);


  if (targetTemperature <= 24.0) {
    e = currentTemperture - targetTemperature;
  } else {
    e = targetTemperature - currentTemperture;
  }

  controlRelay();

  if (count == 0) {
    e1 = e;
    preinput = input;
  } else {
    e1 = e;
    e2 = e1;
    preinput = input;
  }

  count++;
  delay(1000);
}


double getTemperature() {
  double result = 0;
  for (int i = 0; i < 10; i++) {
    result += analogRead(0) * (5.0 / 1023.0) * 100;
  }
  result /= 10;
  return result;
}

void controlRelay() {
  if (count >= 2) {
    if (pid() > 125) {
      digitalWrite(enablePin, HIGH);
    } else {
      digitalWrite(enablePin, LOW);
    }
  }
}

//PID制御
int pid() {
  deltainput = kp * (e - e1) + ki * e + kd * ((e - e1) - (e1 - e2));
  input = preinput + deltainput;
  input = constrain(input, 0, 255);
  return input;
}