makers-n-creators

Storm Distance Calculator

Challenge

During a thunderstorm, measuring the time between a lightning flash and the sound of thunder tells you roughly how far away the storm is. Here we will write a program to wait for lightning, then wait for thunder and then calculate an approximate distance to the storm.

Notes

functions - the def keyword at the top of the file starts a function definition, a way of packing a piece of code that can be re-used in several places.
buttons - the microbit has two buttons, a and b, was_pressed can be used to ask if a button has been pressed since the microbit started or the last time you asked.
image - Images are strings of text, separated by colons to split them into rows, and represent the brightness of each LED in the 5x5 matrix. 0 is off, 9 is fully on.

Extensions

We calculate the distance in metres. Can we make the display better if it’s more than 1km away?

Example Solution

from microbit import *

# Wait for a button push and return the time
def wait_for_any_button():
    time = 0

    while True:
        if button_a.was_pressed() or button_b.was_pressed():
            time = running_time()
            break

        sleep(100)

    return time

def calculate_distance(speed, time):
    return speed * time

speedOfSoundMetresPerSecond = 340

lightning = Image("00990:09900:99999:00990:09000")
ear       = Image("09999:90000:90009:90000:09999")

while True:
    flashTime = 0
    thunderTime = 0

    # we're waiting for lightning
    display.show(lightning)
    flashTime = wait_for_any_button()
    # now wait for thunder
    display.show(ear)
    thunderTime = wait_for_any_button()

    timeDifference = thunderTime - flashTime
    timeDifferenceInSeconds = timeDifference / 1000

    distanceInMeters = calculate_distance(
		speedOfSoundMetresPerSecond,
		timeDifferenceInSeconds)

    display.scroll(str(distanceInMeters) + " m")