from gpiozero import Button
import time

import math

wind_count = 0 # counts how many half-rotations

radius_cm = 9.0 # radius in cm of the anemometer

wind_interval = 5 # how often (secs) to report speed

ADJUSTMENT = 1.18 # adjustment of the anemometer given by the manufacturer



# every half-rotation, add 1 count

def spin():
 
    global wind_count

    wind_count = wind_count + 1

    # print("spin" + str(wind_count))



# calculate the wind speed

def calculate_speed(time_sec):

        global wind_count

        circumference_cm = (2 * math.pi) * radius_cm

        rotations = wind_count / 2.0

        dist_km = (circumference_cm * rotations) / 100000.0 # divided by cm in a km

        km_per_sec = dist_km / time_sec

        km_per_hour = km_per_sec * 3600 # multiplied by secs in an hour

        return km_per_hour * ADJUSTMENT



def reset_wind():

    global wind_count

    wind_count = 0

    # recommended function to reset the wind_count to zero when assembling the weather station


wind_speed_sensor = Button(5)

wind_speed_sensor.when_pressed = spin



# loop to measure wind speed and report at 5 secs interval
while True:

        wind_count = 0

        time.sleep(wind_interval)

        print( calculate_speed(wind_interval), "km/h")