Making a Self-Watering Plant System with Micro:bit

Our plant takes care of itself — with a little help from technology!

What is a Self-Watering Plant?

• A self-watering system helps a plant get water even when nobody is around to do it!

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• Sensors and micro:bit work together to “know” when the plant is thirsty.

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• When the soil gets dry… the system gives the plant a drink automatically.

How Does it Work?

1. Sensor checks how wet or dry the soil is.
2. micro:bit decides when the plant needs water.
3. Water pump and servo motor turns on and waters the plant from a case full of water
4. Everything is powered by batteries or USB for automatic care!

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What You'll Need

Sensor:bit

Soil moisture sensor

A BBC micro:bit V2

A USB cable to connect it to a computer

A battery pack 

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A plant that needs

a high-tech friend!

Relay

2 jumper wires

1 single jumper wire

Screwdriver

What You'll Need

Sensor:bit

Soil moisture sensor

A BBC micro:bit V2

A USB cable to connect it to a computer

A battery pack 

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A plant that needs

a high-tech friend!

Relay

2 jumper wires

1 single jumper wire

Screwdriver

Connect the Soil Sensor

• Connect the jumper wire to the soil moisture

Soil moisture sensor

Jumper wire

Connect the Relay

• Connect the jumper wire to the relay

Jumper wire

Relay

Connect the sensor bit to the micro:bit

Connect the soil moisture to the sensor bit

• Connect the soil moisture sensor to the P1 of sensor:bit.
• The colors of the wires should match the ones of the sensor bit.

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Connect the relay to the sensor bit 1/2

• Connect the relay using the jumper wire to the P2 of sensor:bit (near P1, where moisture sensor connection).
• Use the screwdriver for the screws of the relay.
• The colors of the wires should again match the ones of the sensor bit.

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Connect the relay to the sensor bit 2/2

• Connect a single wire (take color red) from the jumper and connect the middle terminal of the relay to the V pin of P16 on the sensor:bit.

We need to connect the pump to the sensor bit

• Connect the black wire (ground) of the submersible pump to the G pin at the P16 of sensor bit.

We need to connect the pump to the relay

• Connect the red cable (VCC) from the pump to the NO (normal open) input of the relay.

Connect the micro:bit to the micro B cable

Coding the Self-Watering System

• How does the code work?
• It checks the soil moisture every few minutes.
• If the soil is dry (sensor value is low), micro:bit turns on the pump/relay for a short time.
• Then it waits and checks again.
• Block code example:
• Read moisture value from P0.
• If value < 30 (dry), turn on P1 pin for 10 seconds (activates pump).
• Wait for next cycle.

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Connect the USB to the computer and...�Let’s Get Coding!

• Time to tell the micro:bit what to do.
• Open your web browser and go to: makecode.microbit.org
• Click on New Project and give it a name like “Water Plant".

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Coding the Soil Moisture

• Let's check if the plant is thirsty.

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• Access Extensions and search for smarthome.

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• From Basic, get show number block.
• From Smarthome select value of soil moisture (0~100) at pin P1 and place it in the show number block.
• Put the show number block in the forever loop block.

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• Test the code and put the moisture sensor in the water, then dry it.

Coding the Soil Moisture�Let’s add avatars!

• We'll show a happy face 😊 for wet soil and a sad face 😟 for dry soil.

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• From Logic, drag an if <true> then... else block and place it inside a forever loop.
• From Logic again, get a 0 < 0 comparison block.
• In the first slot add value of soil moisture (0~100) at pin P1 and in the second one put a number, like 30.
• This is our "dry" threshold (you can experiment with this number!).

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Coding the Soil Moisture (cont)�Let’s add avatars!

• In the then section, use a show icon block to show a sad face (for when the reading is low, meaning dry).
• In the else section, use show icon to show a happy face (for when the reading is high, meaning wet).
• Again, wet, then dry the moisture sensor!

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Bring the water to the plant!

• Access Advanced -> Pins, then select digital write pin P2 to 1 (this switches your relay and the pump ON)
• Put it in the case where the plant is thirsty (if moisture is below 30).
• Also add a pause (ms) 2000, meaning 2 seconds
• or 5000 for 5 seconds, we can experiment with it.
• In the else case, include digital write pin P2 to 2.
• Add a pause (ms) 30000 (30 seconds)
• This is for experimenting only, in practice, we should

put it for 600 000 ms (10 minutes) of even 1 hour.

Water the plant and save the battery!

• Let’s figure out what the program does!

Plant monitoring & Avatar

Plant monitoring

• When we had the trip to the Danube, the sensors collected data for a plant.

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Plant monitoring

• When we had the trip to the Danube, the sensors collected data for a plant.

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Plant monitoring

• When we had the trip to the Danube, the sensors collected data for a plant.

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Using the data for a plant avatar

https://scratch.mit.edu/projects/1228205114