Automated plant watering system in Raspberry Pi - Step-by-Step Execution

Concept Flow - Automated plant watering system

Start System

↓

Read Soil Moisture Sensor

↓

Is moisture < threshold?

No→Wait and Read Again

Yes↓

Activate Water Pump

↓

Water for set time

↓

Deactivate Water Pump

↓

Wait before next check

↩Back to Read Soil Moisture Sensor

The system reads soil moisture, checks if watering is needed, waters if dry, then waits before checking again.

Execution Sample

Raspberry Pi

import time
from gpiozero import MCP3008, OutputDevice

sensor = MCP3008(channel=0)
pump = OutputDevice(17)

while True:
    moisture = sensor.value
    if moisture < 0.3:
        pump.on()
        time.sleep(5)
        pump.off()
    time.sleep(10)

This code reads soil moisture and waters the plant for 5 seconds if moisture is below 0.3, then waits 10 seconds before repeating.

Execution Table

Step	Action	Moisture Value	Condition (moisture < 0.3)	Pump State	Wait Time (seconds)
1	Read sensor	0.25	True	Off	0
2	Check condition	0.25	True	Off	0
3	Pump ON	0.25	True	On	5
4	Pump OFF	0.25	True	Off	0
5	Wait before next check	0.25	True	Off	10
6	Read sensor	0.35	False	Off	0
7	Check condition	0.35	False	Off	0
8	Pump remains OFF	0.35	False	Off	0
9	Wait before next check	0.35	False	Off	10
10	Read sensor	0.20	True	Off	0
11	Check condition	0.20	True	Off	0
12	Pump ON	0.20	True	On	5
13	Pump OFF	0.20	True	Off	0
14	Wait before next check	0.20	True	Off	10

💡 Loop continues indefinitely; this trace shows two watering cycles and one skip.

Variable Tracker

Variable	Start	After Step 1	After Step 6	After Step 10	Final
moisture	N/A	0.25	0.35	0.20	0.20
pump state	Off	Off	Off	Off	Off

Key Moments - 3 Insights

Why does the pump turn on only when moisture is below 0.3?

Because the condition in the execution_table at steps 2, 7, and 11 checks if moisture < 0.3; only when True does the pump activate.

What happens if the moisture is above 0.3?

At step 7 and 8, the condition is False, so the pump stays off and the system waits before checking again.

Why is there a wait time after watering or skipping watering?

The wait time (steps 5, 9, 14) prevents the system from checking too frequently, giving time for soil moisture to change.

Visual Quiz - 3 Questions

Look at the execution_table, what is the pump state at step 8?

A Off

B On

C Turning On

D Unknown

💡 Hint

Check the 'Pump State' column at step 8 in the execution_table.

At which step does the system decide not to water the plant?

A Step 2

B Step 7

C Step 11

D Step 3

💡 Hint

Look at the 'Condition' column in the execution_table where it is False.

If the moisture threshold changed to 0.4, how would the pump behavior change at step 6?

A Pump would remain OFF

B Pump would turn ON only after waiting

C Pump would turn ON

D No change

💡 Hint

Compare moisture value at step 6 with new threshold 0.4 in the execution_table.

Concept Snapshot

Automated Plant Watering System:
- Read soil moisture sensor value
- If moisture < threshold (e.g., 0.3), turn pump ON
- Water for fixed time (e.g., 5 seconds)
- Turn pump OFF
- Wait before next sensor reading
- Repeat indefinitely

Full Transcript

This automated plant watering system uses a soil moisture sensor connected to a Raspberry Pi. The program continuously reads the moisture level. If the moisture is below a set threshold (0.3), it activates a water pump for 5 seconds to water the plant. After watering, the pump turns off and the system waits 10 seconds before checking again. If the moisture is above the threshold, the pump stays off and the system waits before the next check. This cycle repeats indefinitely to keep the plant properly watered without overwatering.