Automatic Plant Watering System Circuit Diagram

In this electronics project, we aim to create an automatic plant watering system that automatically shuts off when the soil reaches the desired water level. We have already published a project on an automatic irrigation system using a PIC microcontroller. In this circuit, we utilize a basic concept: dry soil has high resistance, while wet soil has very low resistance. When the water level drops below a certain threshold, the water pump will start supplying water to the plant until the water content in the soil reaches a certain threshold value. At that point, we will switch off the water pump. To achieve this, we insert two probes into the soil. When the soil is wet, the probes connect through the soil, triggering the pump to start pumping water. Conversely, when the soil is dry, both probes disconnect, causing the pump to start supplying water.

Components of Automatic Plant Watering System

The following components were used:

  • NE555 Timer
  • LM 324 Comparator
  • 6V Relay
  • Two pieces of copper used as probes
  • 12V pump
  • Hex Invertor (not used in final project)

Block Diagram of Automatic Plant Watering System

block diagram automatic plant watering system
  • Proteus simulation of circuit
  • PCB design and testing
  • Final testing using pump and soil

Circuit Diagram of Automatic Plant Watering System

Project Modules and Design Overview is given below: Following is the Proteus ISIS simulation:

Circuit diagram automatic plant watering system

PCB Design of Automatic Plant Watering System

Following is the PCB design:

PCB design of automatic plant watering system
  • We insert two probes in the soil in such a way that they will conduct when the soil is wet and they will not conduct when the soil is dry. So, when the probes do not conduct, the system will automatically detect this condition with the help of a comparator which will become high when the input is lower than the reference voltage of 0 Volts.
  • The comparator will trigger the NE555 Timer which will switch on the electric valve and allow water to flow to the plant.
  • When the soil is wet, the probes will conduct again and make the output of the comparator low, which will also make the NE555 output low and switch off the relay, thereby turning off the pump.


The automatic plant watering system has various applications in different areas. Some of the applications include:

  1. People who have home gardens and want to ensure their plants are watered consistently find the system ideal. The system takes away the hassle of manually watering the plants and ensures that it delivers the appropriate amount of water based on the moisture levels of the plants.
  2. Greenhouse owners commonly use automated plant watering systems to water large quantities of plants efficiently. The system can monitor and control the water levels of multiple plants simultaneously, saving time and effort.
  3. The agricultural sector utilizes automatic plant watering systems in crop fields to ensure that plants receive adequate water. The system helps conserve water resources by delivering water only when the soil moisture level requires it.
  4. Individuals participating in urban farming benefit from the automatic plant watering system, as it offers an effective solution for maintaining plants in small urban gardens or vertical farming setups. It eliminates the need for constant manual watering.
  5. Botanical gardens customize the automatic plant watering system to suit the specific moisture requirements of different plant species, ensuring their optimal growth and health. The system helps keep the plants in botanical gardens healthy and vibrant.
  6. Landscapers and garden designers benefit from the automatic plant watering system when creating and maintaining ornamental gardens. The system helps to keep the plants healthy and vibrant, ensuring that they remain visually appealing.

Overall, the automatic plant watering system finds its applications in diverse settings, from small home gardens to large-scale agricultural operations. It simplifies plant care, improves water efficiency, and ensures plants receive the necessary hydration for optimal growth and development.

Technical Issues of Automatic Plant Watering System

The main technical issue faced was the detection of voltage from probes. First, we used iron nails which caused a great drop in voltage. Then we used copper strips, which conduct voltage without drop. The second issue was the usage of the battery. We connected the battery to the circuit, but it had a very high current rating which the circuit could not endure. The battery gave a 1.8A current output while the NE555 timer used could only function up to 200mA. We tried to lower the current using a 7809 IC and a 7812 IC, but it lowered the current so much that the pump did not turn on, so we had to use a direct power supply.


In conclusion, this project describes an efficient and reliable automatic plant watering system that maintains optimal soil moisture levels. The system effectively triggers the water pump to provide water to the plant when the soil is dry and shuts off automatically when it reaches the desired water level by utilizing the concept of resistance in soil. The circuit design ensures precise control and functionality by integrating components such as the NE555 Timer, LM 324 Comparator, and the 6V Relay. Accurate soil moisture detection is achieved through the inclusion of copper probes, which prove to be a crucial factor. Despite encountering technical challenges with voltage detection and power supply, we successfully addressed these issues by implementing appropriate modifications. Overall, this automatic plant watering system offers gardening enthusiasts a practical and automated approach to nurturing plants, making it a valuable tool.

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