Simple Soil Dryness Detector Circuit

Like humans plants to require water to be strong and healthy!

Knowing when to water the plants might be little challenging.

The construction of a soil moisture sensor is explained in this article.

When the soil becomes dry and need watering this device will give an alert.

To assist in construction the circuit the post even provides some simple formulas.

What is a Soil Dryness Detector Circuit:

The main purpose of this Simple Soil Dryness Detector Circuit is to check whether the soil is wet or dry by monitoring the level of moisture present in the soil.

These circuits are mostly used in the gardening and agricultural sectors to keep an eye on irrigation systems to be sure the plants are getting the right quantity of water.

Circuit Overview:

Two NPN transistors that operate as switches and a buzzer element are the foundation of this innovative soil dryness detector circuit which truly indicates when there is no water in the soil.

Although other materials like conducting substances or nails can also work well as moisture detecting sensors, and also the sensing technique uses insulation stripped copper wires as detectors.

Circuit Working:

Parts List:

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.

Here 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 is a warning sign that the soil needs to be watered since it is dry.

LED indicators have been built into the circuit to provide immediate feedback.

When the soil has enough moisture the green LED glows and when the soil is dry the red LED flashes.

The soil moisture sensor copper wires or other materials supply the moisture sensing system.

The circuit makes sure that Q1 is turned on when the soil is wet avoiding bias from flowing to Q2 and keeping the buzzer OFF

However when the soil is dry Q1 remains OFF sending bias to Q2 which turns on the buzzer and flashes the red LED to provide an indication of moisture.

Formulas:

Below are the formulas for Simple Soil Dryness Detector Circuit:

We can now do the calculation for sensitivity S by giving 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 for preset which is 100k variable resistor.

Steps:

Substitute the values: the formula substitute the correct 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 undefined 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.

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

The sensors sensitivity S is 101 if S is not specified ratio.

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

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

The voltage or current change that the sensor produces for a specific resistance change must be explained further in order to understand the sensitivity value (101 V/Ω or 101 A/Ω).

Remember:

The output signal and sensor resistance R2 are assumed to have an equal relationship in the calculation above.

In certain sensor applications the relationship might not be perfectly constant.

This might affect some aspects of the formulas sensitivity estimations for especially high R2 levels.

How to Build:

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.
• To prevent accidental touch, make sure they are not positioned too close to one another.
• 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.
• Q1 stays OFF if the soil is dry turning on Q2 by passing bias through the Q1 collector.
• In order to signal soil dryness Q2 activation sets off the buzzer which makes a unique beep sound.
• When there is enough moisture a green LED illuminates when there is not a red LED indicates dryness..

Conclusion:

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

By providing real time feedback on soil moisture levels it offers users to increase 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