simple pid controlled fan with encoder

fan temperature control.ino

/* Sammy Oina Kerata
 *  ENM221-0089/2017
 *  fan speed control with temprature with encoder
 */
float revCounts=0; //revolutions counted
float motorSpeed=0; //current motor speed
unsigned long prevTime = 0;  //previous time used to calculate
float speedFreq=0;            //motor speed in HZ
float kp = 3.4;             //proportional gain of the motor control
float kd = 34;              //derivative gain
float previousError = 0;    //previous error of motor speed
int targetSpeed = 0;      //target motor speed

void setup () {
   pinMode(A0,INPUT);
   pinMode(6,OUTPUT);
   attachInterrupt(1,stepsCounter, RISING); //count pulses using interrupts from the motor
   digitalWrite(6,HIGH);                    //start motor on high speed
   Serial.begin(115200);
   delay(3000);                             //allow motor to get high speed
   revCounts = 0;
   prevTime = millis();
}

void loop() {
   float temp = ((analogRead(A0)/1024.0)*5000)/10;  //get temperature from lm35
   Serial.print("Temp: ");
   Serial.print(temp);
   Serial.print(" ");
      if (temp >= 26){                //vary target motor speed with select temperature
   targetSpeed = 150;
      }else if (temp >= 23){
   targetSpeed = 120;
      }else if (temp >= 20){
   targetSpeed = 90;
      }else{
   targetSpeed = 0;
      }
      if (targetSpeed != 0){
   targetSpeed += 44;
      }
    float error = targetSpeed - motorSpeed; //get error on speed
    float proportionalVal = error * kp;     //get PID values
    float derivativeVal = (error - previousError) * kd;
    previousError = error;
    float KD = proportionalVal + derivativeVal;
    float motorVal = constrain(KD, 0, 255); //write motor speed
    analogWrite(6, motorVal);
    if (revCounts >= 24){                   //calculate motor speed
      unsigned long currentTime= millis();
      int timeDiff = currentTime - prevTime;
      speedFreq = (revCounts *1000) / (24 * (timeDiff));
      prevTime = currentTime;
      revCounts = 0;
      motorSpeed = speedFreq * 60;
    }
    Serial.print("Motor Speed: ");
    Serial.println(motorSpeed);
    //delay(500);
}

void stepsCounter(){  //count motor steps
   int x = digitalRead(5);
   if (x == 1){
      revCounts++;
   }else{
      revCounts--;
   }
}

speed.ino

float revCounts=0; //revolutions counted
float motorSpeed=0; //current motor speed
unsigned long prevTime = 0;  //previous time used to calculate
float speedFreq=0;            //motor speed in HZ
void setup() {
  // put your setup code here, to run once:
  attachInterrupt(1,stepsCounter, RISING); //count pulses using interrupts from the motor
  Serial.begin(115200);
  revCounts = 0;
   prevTime = millis();
  
}

void loop() {
  // put your main code here, to run repeatedly:
  if (revCounts >= 24){                   //calculate motor speed
      unsigned long currentTime= millis();
      int timeDiff = currentTime - prevTime;
      speedFreq = (revCounts *1000) / (24 * (timeDiff));
      prevTime = currentTime;
      revCounts = 0;
      motorSpeed = speedFreq * 60;
    }
    Serial.print("Motor Speed: ");
    Serial.println(motorSpeed);
}
void stepsCounter(){  //count motor steps
   revCounts++;
}