Reading Pulse Signal From 10 PC Fans

Projects General Guidance
4

Hi Mark,

So I have 10 fans providing ventilation across 30+ vivariums. These are not easily monitored visually so all have their hall effect sensor output wired up to a central point. I have an Arduino Mega controlling lighting and water misting via a touch screen so thought it would be useful to also log\display the fan RPM's.

The data is logged to an SD card and also Blynk - in addition to the (on demand) LCD with dynamic images for each fans status:

This allows me to check the fan status from the screen or via Blynk when travelling.
Acuraccy is not a priority, responsiveness to serial commands from the LCD are which is why I thought the below external interrupt method (from zitrons playground example) would be ideal.

Do you have any examples of polling that wouldn't introduce any delay\blocking? Most examples I've found seem to use external interrupts for fan RPM reading.

unsigned long lastmillis = 0;

volatile int rpmcounter1 = 0;
volatile int rpmcounter2 = 0;
volatile int rpmcounter3 = 0;
volatile int rpmcounter4 = 0;
volatile int rpmcounter5 = 0;
volatile int rpmcounter6 = 0;

int rpm1 = 0;
int rpm2 = 0;
int rpm3 = 0;
int rpm4 = 0;
int rpm5 = 0;
int rpm6 = 0;

void hallSensor1() {
  rpmcounter1++;
}

void hallSensor2() {
  rpmcounter2++;
}

void hallSensor3() {
  rpmcounter3++;
}

void hallSensor4() {
  rpmcounter4++;
}

void hallSensor5() {
  rpmcounter5++;
}

void hallSensor6() {
  rpmcounter6++;
}

void setup() {

  Serial.begin(115200);

  attachInterrupt(0, hallSensor1, FALLING);//interrupt 0 is on pin 2
  attachInterrupt(1, hallSensor2, FALLING);//interrupt 1 is on pin 3
  attachInterrupt(2, hallSensor3, FALLING);//interrupt 2 is on pin 21
  attachInterrupt(3, hallSensor4, FALLING);//interrupt 3 is on pin 20
  attachInterrupt(4, hallSensor5, FALLING);//interrupt 4 is on pin 19
  attachInterrupt(5, hallSensor6, FALLING);//interrupt 5 is on pin 18
}

void loop() {

  if (millis() - lastmillis == 1000) {
    noInterrupts();
    rpm1 = rpmcounter1 * 30;
    rpm2 = rpmcounter2 * 30;
    rpm3 = rpmcounter3 * 30;
    rpm4 = rpmcounter4 * 30;
    rpm5 = rpmcounter5 * 30;
    rpm6 = rpmcounter6 * 30;
    interrupts();

    rpmcounter1 = rpmcounter2 = rpmcounter3 =  rpmcounter4 =  rpmcounter5 =  rpmcounter6 = 0;

    lastmillis = millis();

    Serial.print("fan1: ");
    Serial.print(rpm1);
    Serial.print("\t");
    Serial.print("fan2: ");
    Serial.print(rpm2);
    Serial.print("\t");
    Serial.print("fan3: ");
    Serial.print(rpm3);
    Serial.print("\t");
    Serial.print("fan4: ");
    Serial.print(rpm4);
    Serial.print("\t");
    Serial.print("fan5: ");
    Serial.print(rpm5);
    Serial.print("\t");
    Serial.print("fan6: ");
    Serial.println(rpm6);
  }

}