Simple Soil Dryness Detector Circuit

Like humans, plants also need water to stay strong and healthy! however, sometimes it is a little hard to know when plants need water.

In this article, we show how to make a Simple Soil Dryness Detector Circuit, so it can sense soil moisture.

When the soil becomes dry and plants need water, this device gives an alert, also this article provides an easy formula to help build the circuit.

What is a Soil Dryness Detector Circuit:

This Simple Soil Dryness Detector Circuit checks soil moisture to show whether the soil is wet or dry.

Also, people mostly use this type of circuit in gardens and farming to monitor water systems and ensure plants get enough water.

Circuit Overview:

This smart soil dryness detector circuit uses two NPN transistors which work like switch and one buzzer, also it really show when there is no water in the soil.

Also, other things like metal or nails can work well for checking moisture, in this circuit we use copper wire without plastic cover for sensing.

Circuit Working:

Parts List:

Components	Values	Quantity
Resistors	1k 1/4 W	2
	Preset 100k	1
Semiconductors	Transistors BC547	2
	Red 20mA 5mm	1
	Green 20mA 5mm	1
	Aluminum Probes	2
	Power Source 9V Battery PP3	1
	Audio Device Buzzer	1

First, a 9V battery powers the circuit and connects to all its parts, we can then place two bare copper wires (or other sensors) into the soil.

Hence, these wires check if soil have water or not and if soil is dry and sensor does not find water then Q1 stays OFF.

Then current connects from Q1 collector to base of Q2 and this make Q2 turn ON and when Q2 is ON then buzzer makes beep sound.

This beep means the soil is dry and needs water, therefore we have added LED lights for a fast signal.

If soil have good water then green LED turn ON and if soil is dry then red LED blinks.

Sensor wires or other material help to check water in soil and when soil is wet, Q1 turns ON, so it stops current going to Q2 and buzzer stays OFF.

But when soil is dry Q1 stays OFF and sends current to Q2 which make buzzer beep and red LED blink to show no water.

Formulas with Calculations:

Here is the formula for Simple Soil Dryness Detector Circuit:

We can calculate sensitivity of S by using this formula:

S = R2 / (R1 + Preset)

where:

• S is sensitivity
• R2 is sensor resistance
• R1 the fixed resistor with 100k variable resistor preset

Steps to calculate:

Put values in formula:

S = (1kΩ) / (1kΩ + 100kΩ)

Now solve:

S = 1 / 101

So S = 0.0099

This mean sensor change 0.0099 when resistance change 1 ohm.

Sometimes, S writes as voltage per ohm (V/Ω) or current per ohm (A/Ω) and this means sensor gives small voltage or current change for each ohm in resistance.

But for real sensors this does not always stay same but sometimes it changes, so this value only is good for basic idea.

Important Note:

We think sensor resistance R2 and output signal change the same way, but in some cases it does not always happen because which this can make small problem in calculation.

How to Build:

To build a Simple Soil Dryness Detector Circuit follow the below connection steps:

• First, put two copper wires without cover or other sensor in soil where we want to check for water.
• Next, be sure they are not too close, so no wrong signal happen by touching.
• Also, give 9V battery power to both transistor switch and moisture sensor circuit.
• Connect one wire from sensor to base of Q1 transistor.
• Use 100k preset to set how sensitive the sensor is and if soil have water then Q1 will turn ON and let positive current go.
• If soil is dry then Q1 will stay OFF and then bias connects through Q1 collector and turn ON Q2.
• Also, when Q2 turns ON, buzzer starts beep sound to show soil is dry and when soil is wet then green LED turns ON but if soil is dry then red LED blinks.

Conclusion:

Overall, this Simple Soil Dryness Detector Circuit is very helpful for taking care of plants and saving water, which gives actual time signal about how much water is in soil so people know when to give water.

Thus, this will stop giving too much or too little water.