Project Hub /Basic Analog & Power Electronics/Power Supplies & Voltage Regulators/Decorative Automatic Garden Watering System Circuit and Code

Beginner

ANALOG / DISCRETE

₹500 – ₹1,500

3 – 6 Hours

Partial Kit

Decorative Automatic Garden Watering System Circuit and Code

An automated decorative garden watering system that monitors real-time soil moisture levels to ensure optimal water delivery and plant growth.

Originally published on ElectronicsForU

View original tutorial

Parts You'll Need

This project is sourced from another site, not written by us — this list is our best match of their components against what we stock, not a verified bill of materials. Always check the original blog (linked above) for the actual parts list before buying.

LM2596 Step Down DC-DC Buck Converter Rs. 99.00
Soil Moisture Sensor Rs. 75.00
Jumper Wire 10 Pin Male To Male 20cm Rs. 45.00
5V 1 Channel Relay Module Rs. 45.00
10pcs 5mm RED Diffused Light Emitting Diodes - LEDs Set Rs. 39.00
400 Points Mini Solderless Prototype PCB Breadboard High Quality Rs. 89.00
MB102 Adjustable Breadboard Power Supply Module (3.3V & 5V) for Arduino & Raspberry Pi Rs. 139.00
Jumper Wire 10 Pin Male To Female 20cm Rs. 45.00

Selected: Rs. 0.00

We don't carry yet: Passive Components (generic)
Voltage Regulator IC (7805 / LM317 / 1117)
Transistors (BC547 / 2N2222 / TIP / MOSFET)

Browse all components

How It Works

The Decorative Automatic Garden Watering System operates by transforming high-voltage AC mains power down to safer, usable direct current levels to drive both sensing logic and actuation hardware. A step-down transformer (X1) lowers the AC mains voltage, which is then regulated into two distinct DC rails: a 12V supply via an LM7812 voltage regulator (IC1) and a 5V supply via an LM7805 voltage regulator (IC2). The system's core intelligence relies on a soil sensor module equipped with a sensor probe and jumper wires to continuously monitor real-time moisture conditions in the earth. When soil moisture drops below a designated threshold, the sensor's output state shifts, controlling a discrete semiconductor switching stage. Specifically, a PNP transistor (BC558, T1) and an NPN transistor (BD139, T2) work in tandem to amplify the weak sensor signals, providing sufficient current drive to actuate a 5V SPDT relay. The relay acts as an electromechanical switch to control the watering mechanism or pump. Additionally, a colorful array of eight different colored LEDs (LED1 through LED8) provides visual feedback, illuminating dynamically to indicate different operational states, power delivery, or moisture levels across the garden setup.

Why Build This

Design and implement practical analog power supply stages utilizing step-down transformers alongside linear voltage regulators (LM7812 and LM7805) to generate dual-rail DC power.

Apply discrete transistor configurations (BC558 PNP and BD139 NPN) for signal amplification and inductive relay driving in real-world control systems.

Construct a completely autonomous, closed-loop environmental monitoring system combining moisture sensing, switching logic, and visual status indication.

Real-World Application

Automated home gardening, indoor plant care, and small-scale agricultural irrigation conservation.

Skills You'll Learn

Linear voltage regulation

AC-to-DC power supply design

transistor biasing and switching

relay interfacing

discrete semiconductor circuit design

sensor integration

Safety Precautions

Exercise caution when working with mains voltage connected to the step-down transformer.

Technology Tags

SOIL MOISTURE SENSOR

LM7812

LM7805

BC558

BD139

RELAY

LEDS

AUTOMATION

GARDENING

Frequently Asked Questions

Why does the circuit use two different voltage regulators, the LM7812 and LM7805?

Different components in the circuit require different operating voltages. The LM7812 provides a stable 12V rail suitable for driving components like the relay and certain indicators, while the LM7805 steps that down further to 5V to power the logic and sensor circuitry safely.

Can I build and test this project without connecting it to AC mains power?

While the step-down transformer requires mains input to function as intended, you can initially test the low-voltage DC section (the regulators, transistors, relay, and LEDs) using a pre-regulated dual DC bench power supply to ensure your breadboard connections are correct before working near mains voltage.

What is the purpose of using both a PNP (BC558) and an NPN (BD139) transistor?

Pairing PNP and NPN transistors creates an effective complementary switching and amplification stage. The weak output signal from the soil sensor is stepped up by this transistor combination to supply the higher base or control current needed to securely trigger the 5V SPDT relay.

This page is part of Kitkraft's Project Hub — a curated collection of electronics & robotics projects gathered from the maker community to help students and hobbyists discover and learn to build. Kitkraft does not claim authorship of the original project, and makes no representation as to the accuracy, completeness or safety of third-party source material. The summary and "How It Works" explanation above are AI-generated, rewritten with reference to the original tutorial — not a reproduction of it. Full credit and a direct link to the original source are provided above. If you're the original creator and have a concern about how your work is represented here, please contact us and we'll address it promptly.

Kitkraft Project Hub — curated from the maker community, credited at the source.

PRJ-01127