/**********************    Thermal PT1 System on Arduino       ***********************************/
float gridtime = 20;                // grid time in ms:  in WOKWI >= 5,  in Arduino >= 5
unsigned long oldMillis = 0;        // counter for grid-generation 
int ctr;                            // counter to slow down outputs
int ctrMax = int(40/20);      // underlayed counter for slower output (1...10=every 10th value)
                                    // e.g. 200/ gridtime gives a 200 ms output grid
float T_Mass;                       // temperature of thermal mass (state variable)
float T_MassOld;                    // previous temp. of mass     

float dT;                           // delta temp C=>Amb
float hfToAmb;                      // heatFlow to Ambient

//**********************    Define here the Parameter       **************************************// 
float T_Amb = 20;                   // ambient temperature [°C]
float hfToCircuit = 50;            // heat flow to circuit [W]
float hceC = 50;                    // heat capacity [J/K]
float hresC = 0.4;                  // heat resistance [K/W]
//************************************************************************************************// 

void setup() {
  // put your setup code here, to run once: Calculate C and L
  Serial.begin(115200);             // initialize the serial output to the PC at 38400 Baud 

  T_Mass = T_Amb;                   // initialize temperatures
  T_MassOld = T_Amb;                // initialize temperatures

}

void loop() {
  // put your main code here, to run repeatedly:

  if (millis()-oldMillis >20) { 
     if (oldMillis > 2000) {
      T_Mass = 1/hceC*(hfToCircuit+T_Amb/hresC)*hceC*hresC*exp(-1/(hceC*hresC));
     } 
     if (ctr == ctrMax+1) {
       Serial.print(50); Serial.print(" "); 
       Serial.print(0); Serial.print(" ");
       Serial.print(T_Mass,4); Serial.print(" "); 
       Serial.println(hfToAmb,4); 
       ctr = 0;
       }  
     ctr = ctr+1; //  
  oldMillis = oldMillis + 20;  // Update "oldMillis" to new value   
  }

}