Simple soil moisture alarm circuit diagram using 1.5V battery

Why withered trees. It is dying. Oh, the soil is too dry. How can we use electronics to help trees?

Build Simple soil moisture alarm circuit.

The tree is very necessary for humans. Because can clean waste air, as a food, housing, medicine, etc., We should tree planting as well.

Water is necessary for the trees. But the trees should be watered properly. If too much water rotten the trees, but less water to the trees wither, maybe dead.

soil moisture

As an electronic projects creator. This project would help solve this problem. It will alarm us to watering the plants when the soil is dry. or lack of water for a long time. and can be customized to detect soil moisture levels as well.

How soil moisture alarm works

See various transistors in the circuit as show Figure 1 then do not go away due to thinking so really difficult. They do not have anything look at! below…

When we connect a battery to provide circuit. The C6 is a first components that received before. To filter voltage to smooth and regularity of voltage before to others section.

Simple soil moisture alarm circuit diagram using 1.5V battery
Simple soil moisture alarm circuit.

Then, both transistors Q1 and Q2 are connected into the astable multivibrator circuit to produce a triangle wave that has frequency about 4 kHz.

This frequency is set from R2 x C2 or R3 x C3 (R2 = R3 and C2 = C3 must the same size) By have R1 and R4 are current limiter through a collector of the transistor.

The frequency will pass into R5, R6, and C3 before to base of Q3 and Q4 that connected as a complementary signal amplifier. Next, a signal is amplified then out of to collector of both Q3 and Q4.

Now, we have signal in 2 ways are (1) pass to C5 then come to measure point. and (2) Come to a piezo speaker. Which will pass to any way depends on moisture stage now be wet or dry.

In the first event of still a moisture or wet so compare with low resistance. signal so pass to this way to as bias voltage to Q5, by has a VR1 is adjusting sensitivity in checking the soil moisture.

Then when Q5 is biased to base of Q5.

So has conducting voltage from power supply through to R8 to collector. Next, out to emitter of Q5 to ground. so the piezo speaker does not loud sound.

After that, when soil dry at sensor point has higher resistance. or compare that not connect together. The signal at the collector of Q3 and Q4 so come to the piezo-speaker (BZ1) passes to collector of Q6. Which now, the base of Q6 receive the bias voltage passes from R8.

Therefore, the signal passed to collector, so flow to ground and can flow through the emitter to a piezo speaker. so emit sound we hear. When coming to this point as the end working is enough.

How it builds

This project has a small size. You may assemble them on universal PCB.  All components layout Important: Do not put the wrong position or switch legs.

Otherwise, this project will not work. and the checking point should use cord reinvigorate to be plugged deep and not rocking too easy.

How to use its

We test easily this project, by connects the 1.5V battery to the battery holder, then separate the checking point apart. we will hear shrill tone out to the piezo speaker.

But when we caught the two tangent wires, so this sound stop once. Show that this project is working properly.

And then, how to apply them just simply plug the checking point in the flower pot. The moderately deep root of the tree. Then adjust VR1 to suit the soil conditions.

This is just used it. If you think that weak sound. can raise the voltage of power supply But under 9 volts.

The list of all components

Resistors ¼ W + 5%
R1, R4: 22K
R2, R3: 220K
R5, R6, R8: 100K
R7: 47K
R3: 10M
VR1: Trimmer POT, 100K potentiometer
The capacitors
C1: 10uF 16V, Electrolytic capacitors
C2, C3: 820pF 50V___Polyester capacitors
C4: 470pF 50V___Polyester capacitors
C5: 1uF 16V, Electrolytic capacitors
C6: 0.1uF(104)50V___Polyester capacitors
The semiconductor
D1: 1N4148, 0.75A 200V Diode
Q1-Q3, Q5-Q6: BC550, 45V 100mA NPN Transistor
Q4: BC560, 50V 100mA PNP Transistor
Others parts
BZ1: Piezo speaker
Battery 1.5V with battery holder AA 1.5Vx2
Solid wire.

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4 thoughts on “Simple soil moisture alarm circuit diagram using 1.5V battery”

  1. Sir,
    WONDERFUL CIRCUITS we always enjoy them BUT PLEASE, just give us the size of ALL THE PC BOARDS that way we can reduce ourselves to the size we want when we print out the pcb board so please, just simply provide the size of the PCB many thanks

  2. Hi, Thanks for the circuit, I just made it, but the sensitivity of the circuit is very high and the siren is alight with the smallest connection to the soil, even if it is dry, the potentiometer does not change the sensitivity of the circuit, thanks if you are guided.


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