🌱 Soil Humidity Sensor

📌 Description

The soil humidity sensor detects whether the soil is dry or moist. It works by measuring conductivity: wet soil conducts electricity better than dry soil. The sensor sends a digital signal (HIGH or LOW) to the microcontroller.

🎯 Use

In our projects, the soil humidity sensor is used to:

• Monitor plant watering needs.
• Trigger irrigation systems automatically.
• Help robots interact with natural environments.

👉 Think of the soil humidity sensor as the robot’s gardener tool — it tells the robot if plants need water.

Module parameters

Pin name	Description
G	GND (Power Input Negative)
V	VCC (Power Input Cathode)
S	Digital signal pins
A	Analog signal pins

• Supply voltage: 3.3V/5V
• Connection: 2.54mm pin header
• Installation method: double screw fixing

---

🖥️ Code Explanation

import machine

pin26 = machine.Pin(26, machine.Pin.IN)    # Sensor input
pin17 = machine.Pin(17, machine.Pin.OUT)   # LED output

while True:
    if pin26.value() == 1:                 # If soil is dry
        pin17.value(0)                     # LED OFF
        print('dry soil')
    else:                                  # If soil is moist
        pin17.value(1)                     # LED ON
        print('Moist soil')

Step by Step

1. pin26 = machine.Pin(26, machine.Pin.IN) → Reads the soil sensor’s digital signal.
2. pin17 = machine.Pin(17, machine.Pin.OUT) → Controls the LED (output).
3. while True: → Loop that repeats forever.
4. if pin26.value() == 1: → Checks if soil is dry.
5. pin17.value(0) → LED stays off when soil is dry.
6. print('dry soil') → Displays message “dry soil”.
7. else: → If soil is moist…
8. pin17.value(1) → LED turns on.
9. print('Moist soil') → Displays message “Moist soil”.

👉 Together, this program makes the LED indicate soil condition and prints the status.

---

✅ Conclusion of the Test

• If the LED stays off and the console prints “dry soil” when the soil is dry, and turns on with “Moist soil” when the soil is wet, the program is working correctly.
• This test shows how the robot can sense soil moisture and react with an output (LED + message).
• Later, the sensor could be connected to a pump or irrigation system to automatically water plants when the soil is dry.