Simple Soil Dryness Detector Circuit

Plants need water to grow healthy and strong, just like people do!

It can be tricky to know when to water your plants, though.

This article shows you how to build a soil moisture sensor.

This device will tell you when your soil is dry and needs watering.

The guide even includes some easy to understand formulas to help you build it.

What is a Soil Dryness Detector Circuit:

A Soil Dryness Detector Circuit is an electronic circuit designed to measure the moisture level in soil and indicate whether the soil is dry or wet.

Such a circuit is commonly used in agriculture or gardening applications to automate the irrigation system and ensure that plants receive the appropriate amount of water.

Circuit Overview:

Our innovative soil dryness detector circuit is built around two NPN transistors functioning as switches coupled with a buzzer element to audibly signal the absence of water in the soil.

The sensing mechanism employs insulation stripped copper wires as detectors although alternative materials like conducting substances or nails may also serve as effective moisture detecting sensors.

Circuit Description

Parts List:

Below mentioned are the circuit descriptions details:

The circuit is powered by a 9V battery.

This regulated power is distributed to the various components of the circuit.

Two insulation stripped copper wires or alternative detectors are inserted into the soil.

These sensors serve as the indicators of soil moisture levels.

If the soil is dry and the sensor does not detect moisture Q1 remains in the OFF position.

In this case, the bias flows through Q1 collector to the base terminal of Q2.

This action turns Q2 ON.

The activation of Q2 triggers the buzzer element producing an audible beep sound.

This sound serves as an alert indicating that the soil is dry and in need of watering.

The circuit includes LED indicators for visual feedback.

The Green LED lights up when there is sufficient moisture in the soil, while the red LED illuminates when the soil is dry.

The moisture sensing mechanism is facilitated by the soil moisture sensor copper wires or alternative materials.

When the soil is moist the circuit ensures that Q1 is ON preventing bias flow to Q2 and keeping the buzzer silent.

In contrast, when the soil is dry Q1 stays OFF directing bias to Q2 activating the buzzer and providing a visual indication through the red LED.

Formulas:

We can now perform the calculation for sensitivity S given the following information and steps:

S = R2 / R1 + P_reset

where,

• S is sensitivity.
• R2 is the resistance of the sensor
• R1 is the fixed resistance, and preset is the 100k variable resistor.

Steps:

Substitute the values: In the formula, substitute the appropriate values for R1, R2 and Preset:

S = (1kΩ) / (1kΩ) + (100kΩ)

Simplify the expression:

S = 1 + 100
S = 101

The sensors sensitivity S is 101 if S is a dimensionless ratio.

This suggests that the total resistance seen by the circuit will change by 101 ohms for every 1 ohm change in the sensor resistance R2.

Should S be expressed in voltage per ohm (V/Ω) or current per ohm (A/Ω) units:

To understand the sensitivity value (101 V/Ω or 101 A/Ω), we must further details on the voltage or current change the sensor generates for a certain resistance change.

Remember:

The above formula makes the assumption that the output signal and sensor resistance R2 have a linear relationship.

It is possible that the connection is not exactly linear in some sensor applications.

This may have an impact on the formulas sensitivity calculations accuracy, particularly for high R2 levels.

Construction details

To construct this circuit follow the below connection steps:

• Insert two insulation stripped copper wires or alternative detectors into the soil at the desired detection range.
• Ensure they are not placed too closely to avoid unintended contact.
• A 9V battery power is then directed to both transistor switches and the soil moisture detector setup.
• Connect one terminal from the sensor to the base of the Q1 transistor.
• Adjust sensitivity levels using 100k preset.
• Q1 turns ON when moisture is present allowing positive supply flow.
• If the soil is dry Q1 remains OFF directing bias through Q1 collector to turn ON Q2.
• Q2 activation triggers the buzzer producing a distinctive beep sound to indicate soil dryness.
• A Green LED illuminates when there is sufficient moisture, while a red LED signals dryness.

Conclusion:

This Soil Dryness Detector Circuit serves as a vital tool in plant care and water resource management.

By offering real time feedback on soil moisture levels, it empowers users to optimize watering schedule preventing both overwatering and underwatering.

References

DESIGN AND DEVELOPMENT OF SOIL MOISTURE SENSOR AND RESPONSE MONITORING SYSTEM

Design and Implementation of a Soil Moisture Detection system