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Atmospheric Sensor

On this page we will learn

  • how to connect the Atmospheric Sensor
  • how to read temperature, air pressure and humidity
  • how to estimate altitude from air pressure

Terminology

  • air pressure – the weight of the air pushing down on us, which drops as we go higher.
  • humidity – the amount of water vapour in the air, measured as a percentage.
  • altitude – the height above sea level, which the Atmospheric Sensor works out from air pressure.
  • pascal – the unit for measuring pressure (Pa); 100 pascals make 1 hectopascal (hPa).

The PiicoDev Atmospheric Sensor (BME280) measures temperature, air pressure and humidity.

Possible uses:

  • weather stations
  • indoor climate monitors
  • measuring changes in height (altitude)
  • science experiments

Connect it

  1. Connect the sensor to the PiicoDev adapter with a PiicoDev cable. See Using PiicoDev.
  2. Upload these files to the micro:bit with main.py:
    • PiicoDev_Unified.py
    • PiicoDev_BME280.py

Set it up

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from microbit import *
from PiicoDev_BME280 import PiicoDev_BME280

sensor = PiicoDev_BME280()

Methods

Method Parameters Returns Description
sensor.values() none tuple (temp, pressure, humidity) Temperature (°C), air pressure (Pa) and relative humidity (%)
sensor.altitude(pressure_sea_level=1013.25) pressure_sea_level: today's sea-level pressure in hPa float (m) Height above sea level, calculated from air pressure

values()

Returns the temperature (°C), air pressure (Pa) and humidity (%) together as a tuple.

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from microbit import *
from PiicoDev_BME280 import PiicoDev_BME280

# Setup
sensor = PiicoDev_BME280()

# Main loop
while True:
    print(sensor.values())
    sleep(1000)

PRIMM

  1. Predict what you think will happen. Be specific.
  2. Run the program.
  3. Time to investigate the code. What does each line do?
Code explanation
  • line 1 → imports all the commands from the microbit library.
  • line 2 → imports the Atmospheric Sensor driver.
  • line 5 → creates the sensor and calls it sensor.
  • line 8 → starts an endless loop.
  • line 9 → prints the temperature (°C), air pressure (Pa) and humidity (%) in the Shell.
  • line 10 → waits 1 second before the loop repeats.

altitude()

Returns the height above sea level in metres, calculated from the air pressure.

Air pressure drops as you go higher, so the sensor can work out changes in height. For an accurate height above sea level, enter today's sea-level pressure from the Bureau of Meteorology.

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from microbit import *
from PiicoDev_BME280 import PiicoDev_BME280

# Setup
sensor = PiicoDev_BME280()

# Main loop
while True:
    print(sensor.altitude())
    sleep(1000)

PRIMM

  1. Predict what you think will happen. Be specific.
  2. Run the program.
  3. Time to investigate the code. What does each line do?
Code explanation
  • line 1 → imports all the commands from the microbit library.
  • line 2 → imports the Atmospheric Sensor driver.
  • line 5 → creates the sensor and calls it sensor.
  • line 8 → starts an endless loop.
  • line 9 → prints the altitude in metres in the Shell.
  • line 10 → waits 1 second before the loop repeats.

Documentation

Documentation is the official guide written by the people who made the code library, and we can use it to look up every method and its parameters, including ones that aren't covered on this page.

Exercises

PRIMM

Time to modify the code and see what happens.

Starter files are in the atmospheric folder of your tutorial files. Solutions are on the Exercise Solutions page.

Exercise 1

Starter: atmospheric/ex1_buttons

Can you make the micro:bit show the temperature, rounded to a whole number, when button A is pressed, and the humidity when button B is pressed?

Exercise 2

Starter: atmospheric/ex2_height_change

Can you make the micro:bit show how much the altitude has changed since the last time button A was pressed?