2. Compass Directions

2.1. Compass Readings

Use compass.heading() to get an angle from True North where North is 0.

from microbit import *

compass.calibrate()

while True:
    display.scroll(compass.heading(), delay=80)
    sleep(500)

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Exercises

1. Use the code above and turn the microbit till it reads a number close to 0.

2. Turn about 90 degrees clockwise to the East and get the reading.

3. Turn another 90 degrees clockwise to the South and get the reading.

4. Turn another 90 degrees clockwise to the West and get the reading.

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2.2. Compass Pointer

The compass has readings from 0 to 359 degrees. (360 degrees is 0 degrees.)

This can be divided up into 12 directions like the hours on a clock.

The code below is to test the formula used.

For readings from 346 to 15, the clock position should be at 12 or 0 o’clock.

For readings from 16 to 45, the clock position should be at 11 o’clock.

For readings from 46 to 75, the clock position should be at 10 o’clock.

For readings from 316 to 345, the clock position should be at 1 o’clock.

For readings from 286 to 315, the clock position should be at 2 o’clock.

So the clock hand points towards north, while the reading is the direction the top (where the USB connection is) of the microbit is pointing towards.

from microbit import *

# compass.calibrate()  # should be OK without recalibrating

while True:
    display.scroll(compass.heading(), delay=60)
    needle = ((-compass.heading() + 15) // 30) % 12
    display.show(Image.ALL_CLOCKS[needle])
    sleep(500)

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Tasks

1. What are the readings for 1 o’clock? Write code to test three values at either end of the range.

2. What are the readings for 2 o’clock? Write code to test three values at either end of the range.

3. What are the readings for 11 o’clock? Write code to test three values at either end of the range.

4. What are the readings for 10 o’clock? Write code to test three values at either end of the range.

Q1

What are the readings for 1 o’clock? Write code to test three values at either end of the range.

About 345 to 316

from microbit import *

compass_heading_list = [346, 345, 344, 316, 315, 314]
while True:
    for compass_heading in compass_heading_list:
        display.scroll(compass_heading, delay=60)
        needle = ((-compass_heading + 15) // 30) % 12
        display.show(Image.ALL_CLOCKS[needle])
        sleep(500)

Q2

What are the readings for 2 o’clock? Write code to test three values at either end of the range.

About 315 to 286

from microbit import *

compass_heading_list = [316, 315, 314, 286, 285, 284]
while True:
    for compass_heading in compass_heading_list:
        display.scroll(compass_heading, delay=60)
        needle = ((-compass_heading + 15) // 30) % 12
        display.show(Image.ALL_CLOCKS[needle])
        sleep(500)

Q3

What are the readings for 11 o’clock? Write code to test three values at either end of the range.

About 16 to 45

from microbit import *

compass_heading_list = [14, 15, 16, 44, 45, 46]
while True:
    for compass_heading in compass_heading_list:
        display.scroll(compass_heading, delay=60)
        needle = ((-compass_heading + 15) // 30) % 12
        display.show(Image.ALL_CLOCKS[needle])
        sleep(500)

Q4

What are the readings for 10 o’clock? Write code to test three values at either end of the range.

About 46 to 75

from microbit import *

compass_heading_list = [44, 45, 46, 74, 75, 76]
while True:
    for compass_heading in compass_heading_list:
        display.scroll(compass_heading, delay=60)
        needle = ((-compass_heading + 15) // 30) % 12
        display.show(Image.ALL_CLOCKS[needle])
        sleep(500)

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Exercises

1. Place a small piece of paper on the ground. Turn so the clock hand points to 0 o’clock and walk 5 paces. Turn so the clock hand points to 4 o’clock and walk 5 paces. Turn so the clock hand points to 8 o’clock and walk 5 paces. Did you end up at your starting point?

2. Place a small piece of paper on the ground. Turn so the clock hand points to 0 o’clock and walk 5 paces. Turn so the clock hand points to 3 o’clock and walk 5 paces. Turn so the clock hand points to 6 o’clock and walk 5 paces. Turn so the clock hand points to 9 o’clock and walk 5 paces. Did you end up at your starting point?