//*****************Arduino anemometer sketch******************************
const byte interruptPin = 3; //anemomter input to digital pin
volatile unsigned long sTime = 0; //stores start time for wind speed calculation
unsigned long dataTimer = 0; //used to track how often to communicate data
volatile float pulseTime = 0; //stores time between one anemomter relay closing and the next
volatile float culPulseTime = 0; //stores cumulative pulsetimes for averaging
volatile bool start = true; //tracks when a new anemometer measurement starts
volatile unsigned int avgWindCount = 0; //stores anemometer relay counts for doing average wind speed
float aSetting = 60.0; //wind speed setting to signal alarm
void setup() {
pinMode(13, OUTPUT); //setup LED pin to signal high wind alarm condition
pinMode(interruptPin, INPUT_PULLUP); //set interrupt pin to input pullup
attachInterrupt(interruptPin, anemometerISR, RISING); //setup interrupt on anemometer input pin, interrupt will occur whenever falling edge is detected
dataTimer = millis(); //reset loop timer
}
void loop() {
unsigned long rTime = millis();
if((rTime - sTime) > 2500) pulseTime = 0; //if the wind speed has dropped below 1MPH than set it to zero
if((rTime - dataTimer) > 1800){ //See if it is time to transmit
detachInterrupt(interruptPin); //shut off wind speed measurement interrupt until done communication
float aWSpeed = getAvgWindSpeed(culPulseTime,avgWindCount); //calculate average wind speed
if(aWSpeed >= aSetting) digitalWrite(13, HIGH); // high speed wind detected so turn the LED on
else digitalWrite(13, LOW); //no alarm so ensure LED is off
culPulseTime = 0; //reset cumulative pulse counter
avgWindCount = 0; //reset average wind count
float aFreq = 0; //set to zero initially
if(pulseTime > 0.0) aFreq = getAnemometerFreq(pulseTime); //calculate frequency in Hz of anemometer, only if pulsetime is non-zero
float wSpeedMPH = getWindMPH(aFreq); //calculate wind speed in MPH, note that the 2.5 comes from anemometer data sheet
Serial.begin(57600); //start serial monitor to communicate wind data
Serial.println();
Serial.println("...................................");
Serial.print("Anemometer speed in Hz ");
Serial.println(aFreq);
Serial.print("Current wind speed is ");
Serial.println(wSpeedMPH);
Serial.print("Current average wind speed is ");
Serial.println(aWSpeed);
Serial.end(); //serial uses interrupts so we want to turn it off before we turn the wind measurement interrupts back on
start = true; //reset start variable in case we missed wind data while communicating current data out
attachInterrupt(digitalPinToInterrupt(interruptPin), anemometerISR, RISING); //turn interrupt back on
dataTimer = millis(); //reset loop timer
}
}
//using time between anemometer pulses calculate frequency of anemometer
float getAnemometerFreq(float pTime) { return (1/pTime); }
//Use anemometer frequency to calculate wind speed in MPH, note 2.5 comes from anemometer data sheet
float getWindMPH(float freq) { return (freq*2.5); }
//uses wind MPH value to calculate KPH
float getWindKPH(float wMPH) { return (wMPH*1.61); }
//Calculates average wind speed over given time period
float getAvgWindSpeed(float cPulse,int per) {
if(per) return getWindMPH(getAnemometerFreq((float)(cPulse/per)));
else return 0; //average wind speed is zero and we can't divide by zero
}
//This is the interrupt service routine (ISR) for the anemometer input pin
//it is called whenever a falling edge is detected
void anemometerISR() {
unsigned long cTime = millis(); //get current time
if(!start) { //This is not the first pulse and we are not at 0 MPH so calculate time between pulses
// test = cTime - sTime;
pulseTime = (float)(cTime - sTime)/1000;
culPulseTime += pulseTime; //add up pulse time measurements for averaging
avgWindCount++; //anemomter went around so record for calculating average wind speed
}
sTime = cTime; //store current time for next pulse time calculation
start = false; //we have our starting point for a wind speed measurement
}
