Temperature-controlled fan on an Arduino Uno

// Thermostat fan: a TMP36 on A0 and an L9110 fan module on pins 5 and 4.
//
//   A0       the TMP36's VOUT (VS to 5V, GND to GND)
//   pin 5    the fan module's INA, a PWM pin
//   pin 4    the fan module's INB, held low
//   VCC/GND  the fan module's supply, 5 V
//
// The TMP36 gives 10 mV a degree with 500 mV at 0 C, so on a 5 V board a
// reading of n is n x 5000 / 1023 mV and (mV - 500) / 10 degrees. Under 24 C
// the fan is off; from 24 C it starts at 40% (slower and a small motor may not
// turn the propeller at all) and rises to full at 32 C.
//
// The L9110 on the module brakes when both inputs are low, so PWM on INA with
// INB low is drive and brake in turn, and the duty sets the speed.

const int SENSOR = A0;
const int INA = 5;
const int INB = 4;

const int START_C10 = 240;  // tenths of a degree
const int FULL_C10 = 320;
const int START_DUTY = 102; // 40% of 255

void setup() {
  Serial.begin(115200);
  Serial.println("Mokxi Arduino Uno: thermostat fan");
  pinMode(INA, OUTPUT);
  pinMode(INB, OUTPUT);
  digitalWrite(INB, LOW);
}

void loop() {
  long mv = (long)analogRead(SENSOR) * 5000 / 1023;
  int tenths = (int)(mv - 500);
  int duty;
  if (tenths < START_C10) {
    duty = 0;
  } else if (tenths >= FULL_C10) {
    duty = 255;
  } else {
    duty = START_DUTY + (int)((long)(255 - START_DUTY) * (tenths - START_C10) / (FULL_C10 - START_C10));
  }
  analogWrite(INA, duty);

  Serial.print(tenths / 10);
  Serial.print('.');
  Serial.print(tenths % 10);
  Serial.print(" C  fan ");
  Serial.print((long)duty * 100 / 255);
  Serial.println("%");
  delay(500);
}