Published April 7, 2022 © GPL3+

Solar weather station

This kit get charged from solat battery and provides information about temperature, light level, CO2 level and moisture level of the soil.

BeginnerFull instructions provided1 hour2,554

Things used in this project

Hardware components

BBC micro:bit board

Seeed Studio Grove - Temperature Sensor

Seeed Studio Grove - Air quality sensor v1.3

DFRobot Gravity: Analog Soil Moisture Sensor For Arduino

Seeed Studio Grove - Light Sensor

grove shield micro:bit

Software apps and online services

Microsoft MakeCode

Story

As warm time of the year approaches, people spend more time outside and there's a need for measuring outside parameters devices.

I connected the sensors and a solar battery to micro:bit device to measure different parameters. This is a very convenient and easy to use a weather station that can run independently without batteries or USB connection to the computer. It contains four sensors - a temperature sensor to get air temperature, a CO2 sensor to receive information about a pollution level, a light level sensor and a moisture sensor to detect the state of the soil for a possible pique-nique on the grass or for sport games.

Each sensor provides specific information:

A grove temperature sensor gives information about air temperature in C°. It uses a thermistor to detect the ambient temperature. The resistance of a thermistor will increase when the ambient temperature decreases. In general, the most comfortable air temperature for a human is considered to be between 18C° and 24C°.
A grove light sensor has an integrated photo-resistor to detect the intensity of light and it's resistance decreases when the intensity of light increases. It's considered to be a dark time if the value of the sensor decreases to less than 50 Lux.
A grove gas sensor (SGP30) is an air quality detection sensor. Output range for CO2 detection is from 400 ppm to 60000 ppm. Normal outdoor level: 350 - 450 ppm.
A grove soil moisture sensor gives values based on soil resistivity meansurement. The value higher than 300 indicates a humid soil.

.So I connected the sensors to the grove shield for micro:bit:

CO2 sensor → I2C port
light sensor → P0 port
temperature sensor → P1 port
moisture sensor → P2 port

Then I wrote a code in MicroPython to get values from the sensors (the code is located in the part Attachments). I used Polysilicon solqr pannel and it provides 6V to the micro:bit, but the board authomatically changes it to needed 3, 3V.

But I also added notifications in the sode: micro:bit will display warnings if a sensor value goes out of the range of comfortable and safe parameters. For example, if outside temperature goes below 18 degrees then micro:bit will display "! COLD !" and if the temperature goes higher than 24 degrees then micro:bit will display "! HOT !". The same happens if a light level drops to less than 50 Lux - micro:bit will show a warning "! DARK !". If a solar weather station is located in a polluted place and the value gets higher than 700ppm - micro:bit will display "! POLLUTED !". To check amoisture level you should place a moisture sensor inside the soil and if the value goes higher than 300 - the warning "! HUMID !" will be shown. I added 1 second pause between the appearance on the display of the values of each sensor to avoid information overlap.

I hope that my project Solar weather station will be valuable for everybody!

Code

Code for micro:bit board

from microbit import *
import time
import math
from sgp30 import SGP30

# Temperature Sensor on pin1
# Light Sensor on pin0
sgp30 = SGP30()
# Moisture Sensor on pin2

def getGroveTemperature(pin, unit='celsius'):
  R = 1023.0/(pin.read_analog()+1e-3) - 1
  t = 1/(math.log(R)/4250+1/298.15) - 273.15 # celsius
  if unit == 'fahrenheit':
    t = t * 9/5 + 32
  elif unit == 'kelvin':
    t += 273.15
  return t

while True:
  led_image = Image('99999:00900:00909:00900:00909')
  display.show(led_image)
  time.sleep(1)
  display.show(getGroveTemperature(pin1))
  time.sleep(1)
  if getGroveTemperature(pin1) > 24:
    display.show('! HOT !')
  if getGroveTemperature(pin1) < 18:
    display.show('! COLD !')
  time.sleep(1)
  led_image = Image('90000:90000:90009:90000:99909')
  display.show(led_image)
  time.sleep(1)
  display.show(pin0.read_analog())
  time.sleep(1)
  if pin0.read_analog() < 50:
    display.show('! DARK !')
  time.sleep(1)
  led_image = Image('99900:90000:90009:90000:99909')
  display.show(led_image)
  time.sleep(1)
  display.show(sgp30.eCO2())
  time.sleep(1)
  if sgp30.eCO2() > 700:
    display.show('! POLLUTED !')
  time.sleep(1)
  led_image = Image('90009:99099:90909:90909:90909')
  display.show(led_image)
  time.sleep(1)
  display.show(pin2.read_analog())
  time.sleep(1)
  if pin2.read_analog() > 300:
    display.show('! HUMID !')
  time.sleep(1)