Main Idea
Students get acquainted with the concept of “soil moisture”. With the help of
micro: bit conduct research.
| Creator | Sokol Iryna, OU Miksike |
| Subject | Biology, Computer Science |
| Length | 60 minutes |
| Pedagogical Approach | Real-life learning, Tactile |
| Competences | creative skills, logical thinking, computational thinking, cognitive development, self-Directed, engaged Learning |
| Grades | 6th grade |
| Technologies | Computers |
Learning Activities
Activity 1:
Soil – The unconsolidated mineral or organic material on the immediate surface
of the Earth that serves as a natural medium for the growth of land plants.
Soil moisture capacity (water capacity, water retention force, soil capillarity) –
the property of the soil to receive and retain in its porous cavities a certain
amount of drip water, not allowing the latter to drain.
Watch the video: htps://youtu.be/hgsIFyITvJE. Why is Measuring Soil Moisture
Important?
Αctivity 2: We are conducting research (Example:
https://youtu.be/S8NppVT_paw)
You will code your moisture meter using a pot of dry dirt and wet dirt. This is so
you can set the micro:bit to know what both dry and wet conditions are.
Step 1: Measuring moisture
The soil itself has some electrical resistance which depends on the amount of
water and nutrients in it. It acts like a variable resistor in an electronic circuit.
The water is not conductive but the nutrient content is. The combination of water
and soil nutrients makes the soil have some conductivity. So, the more water
there is, combined with the nutrients, the less the soil will have electrical
resistance.
To measure this, we read the voltage on pin P0 using which
returns a value between 0 (no current) and 1023 (maximum current). The value is
graph on the screen using .
Experiment!
• Insert the nails in the dry dirt, press A and note the value. You should see
a value close to around 250for dry dirt.
• Insert the nails in the wet dirt, press A and note the value. You should see
a value somewhere near 1000 for wet dirt.
Step 3: Don’t waste energy!
We want our soil probes to work for a long time and to save our battery power,
so we need to tweak our code so our moisture sensor doesn’t use too much
energy.
• Our circuit connects directly to the 3V pin so it is always using electricity.
Instead, we will connect it to P1 and turn that pin high only while the
measurement is taken. This saves electricity and also avoids corrosion of
the probes.
• We will also lower the brightness of the screen to lower the energy
consumption from the LEDs.
• Soil moisture changes very slowly so we don’t need to measure it all the
time. Let’s add a sleep of 5 seconds in the loop as well.
Experiment!
• Using the dry soil and wet soil pots, test that your circuit still works.
Remember you’ll have to wait up to 10 seconds to see a change!