Which soil moisture sensor used in automatic irrigation system?

What is an automatic irrigation system?

An automatic irrigation system is a system that utilizes advanced control technology and sensors to manage and distribute water in a way that allows for automatic irrigation without human intervention. This type of system is commonly used in agriculture, landscaping, golf courses, stadiums, and other situations that require regular irrigation. Below are the main components and features of an automatic irrigation system:

 Main components of an automatic irrigation system

1. Sensor:

- Soil Moisture Sensor: used to monitor the moisture content in the soil.

- Rainfall Sensor: Used to monitor the amount of rainfall.

- Temperature Sensor: For monitoring the air temperature.

- Wind speed and direction sensor: for monitoring wind speed and direction.

- Light sensor: for monitoring light intensity.

- EC conductivity sensor: for monitoring the conductivity of the soil solution, reflecting the soil salt content.

- Liquid level transmitters: for monitoring the level of a pool or tank.

- Pressure sensor: to monitor the water pressure in the irrigation system.

- Soil pH sensor: sensor to measure soil acidity and alkalinity

Automatic irrigation system sensors

Anemometer Wind Speed sensor	Wind direction sensor	Tipping bucket rain gauge sensor	Evaporation sensor	Sunshine Duration Sensor
Atmospheric Temperature Humidity air pressure Sensor	ultrasonic wind speed and direction sensor	5 in1 Ultrasonic Weather Station Sensor	7 in1 Ultrasonic Weather Station Sensor	Water level sensor
Carbon dioxide sensor(CO2 sensor)	Soil pH sensor	3-in-1 Soil Temperature Humidity EC Sensor	illumination sensor	Soil Moisture Temperature sensor

2. control unit:

   - Is the “brain” of the system, responsible for receiving sensor data, according to the preset program and logic to control the irrigation operation.

   - Usually includes a central processor, memory and input/output interfaces. 

3. Execution mechanism:

   - Valve: used to control the switch of water flow.

   - Water pump: used to transport water.

   - Sprinkler: for spraying water.

   - Drip irrigation pipe: used for drip irrigation.

4. communication network:

   - Connecting sensors, control units and actuators, which can be wired or wireless.

   - Common wireless technologies include 4G, 5G, Zigbee, LoRa, Wi-Fi, etc.

5. software/user interface:

   - Allows users to set up irrigation schedules, view system status, adjust parameters, etc.

   - This can be a local touch screen interface or a remote cell phone application.

 Features of Automatic Irrigation System

1. Automation: The system can automatically start or stop irrigation according to soil and environmental conditions. 

2. Accuracy: Precise monitoring by sensors ensures that crops receive the right amount of water and avoids over- or under-irrigation.

3. Resource Conservation: Reduces water waste and improves water use efficiency.

4. Flexibility: Different irrigation schedules can be set up for different crops and soil types.

5. Convenience: Users can manage irrigation through remote control or preset programs, reducing manual labor.

6. Scalability: the system can usually be easily expanded to accommodate irrigation needs for larger areas.

 Working Principle of Automatic Irrigation System

1. Monitoring phase:

   - The sensor continuously monitors environmental factors such as soil moisture, rainfall, air temperature, wind speed, and light.

   - When the soil moisture falls below the set threshold, the sensor sends the information to the control unit.

2. Decision-making phase:

   - The control unit analyzes the sensor data and combines it with other factors (e.g., weather forecast, crop water requirement, etc.) to make a decision on whether to irrigate or not.

   - If irrigation is required, the system calculates the amount of irrigation needed.

3. Execution phase:

   - The control unit sends a start signal to the irrigation equipment.

   - Irrigation equipment (e.g., sprinkler heads, drip irrigation pipes, pumps, etc.) starts working and irrigates according to the preset irrigation schedule. 

4. Feedback adjustment phase:

   - During the irrigation process, the sensor continues to monitor the soil moisture and feeds the data back to the control unit in real time.

   - The control unit adjusts the working status of the irrigation equipment according to the feedback to ensure that the irrigation is uniform and not excessive. 

5. Record and optimization phase:

   - After the completion of irrigation, the system records the relevant data of this irrigation.

   - By analyzing these data, the irrigation strategy can be optimized to achieve more efficient and save water.

 Commonly used soil moisture sensors in automatic irrigation systems

1. Capacitive soil moisture sensor:

   - Principle: Soil moisture is determined by measuring the change in the dielectric constant of the soil. The dielectric constant of water is much larger than that of dry soil, so the capacitance value of the sensor increases as the water in the soil increases.

   - Characteristics: high sensitivity, fast response speed, wide measuring range and strong adaptability.

   - Scenario: Widely used in a variety of automatic irrigation systems, especially suitable for the need for cost-effective occasions.

2. Resistive soil moisture sensor:

   - Principle: Utilizes the change in conductivity of the soil to measure the moisture content. When the moisture in the soil increases, the resistance value of the soil decreases.

   - Characteristics: Simple structure, low price, easy to maintain, but more sensitive to soil type and salt content.

   - Scenario: Suitable for small gardening projects with limited budget.

3. Time Domain Reflection (TDR) soil moisture sensor:

   - Principle: Moisture content is determined by measuring the propagation time of electromagnetic waves through the soil. The propagation speed of the electromagnetic wave is affected by the soil moisture.

   - Characteristics: High measurement accuracy, insensitive to soil texture and type, but more expensive and requires specialized calibration and maintenance.

   - Applicable scenarios: suitable for agricultural production scenarios with strict requirements on measurement accuracy or high adaptability to soil texture and type.

4. frequency domain reflection (FDR) soil moisture sensor:

   - Principle: Utilizes the frequency response of electromagnetic waves in the soil to measure the dielectric constant and thus calculate the soil moisture content.

   - Characteristics: Relatively low cost, fast measurement speed, flexible probe shape, suitable for simultaneous measurement at multiple depths.

   - Scenarios: Suitable for most automatic irrigation systems, especially for applications requiring fast measurements and multi-depth monitoring.

 Considerations for selecting sensors for automatic irrigation systems

1. accuracy: different sensors have different measurement accuracy, the selection should be based on specific needs.

2. Stability and durability: agricultural production environment is complex and changing, the sensor needs to have good stability and durability.

3. maintenance costs: some sensors may require periodic calibration or replacement parts, which can increase operating costs. 4. system integration: the choice of sensor should be based on specific needs.

4. System integration: When choosing a sensor, you also need to consider its compatibility with other irrigation system components and how easy it is to integrate.

5. Budget: Prices vary greatly from sensor to sensor and the overall budget of the system should be taken into account when selecting a sensor.

 Application Example of Automatic Irrigation System

Assume that in a modern agricultural park, an automatic irrigation system needs to be installed to manage the irrigation needs of multiple greenhouses and fields. The specific steps are as follows:

1. Install sensors:

   - Select representative locations in each greenhouse and field to install capacitive soil moisture sensors and temperature sensors.

   - Rainfall sensors and weather sensors were installed at the park entrances.

2. Data Acquisition:

   - Sensors transmit data to the central control unit via wireless network (e.g. 4G/5G).

3. data processing:

   - The central control unit processes the received data and sets soil moisture thresholds (e.g., irrigation starts when soil moisture is below 30%).

4. decision making:

   - The control unit combines sensor data and weather forecasts to decide whether irrigation is needed and how much.

5. irrigation initiation:

   - When the soil moisture is below the set threshold, the control unit sends a start signal to the irrigation equipment to open the valve and start the pump.

6. irrigation control:

   - The system adjusts the irrigation time and flow rate based on real-time feedback from the sensors to ensure that the right amount of water is applied to the soil.

7. End of irrigation:

   - Once the soil moisture reaches the preset upper threshold or the irrigation time reaches the preset value, the system will automatically turn off the irrigation equipment.

8. Data logging and feedback:

   - The system records the date, time, duration and water consumption of each irrigation.

   - By analyzing these data, the irrigation strategy can be optimized to achieve more efficient and save water.

 Summary

By integrating multiple sensors and advanced control technologies, an automated irrigation system can realize precise monitoring and automatic control of the irrigation process. Such systems not only improve irrigation efficiency and reduce water waste, but also enhance crop yield and quality. Efficient and intelligent irrigation management can be realized by choosing the right sensors and system components and combining them with specific agricultural production needs.

Soil moisture sensor datasheet:

1.NBL-S-THR Soil Temperature Moisture Sensor datasheet

NBL-S-THR-Soil-temperature-and-moisture-sensors-Instruction-Manual-V4.0.pdf

2. NBL-S-TMC Soil Temperature Moisture EC Sensor datasheet

NBL-S-TMC-Soil-temperature-and-moisture-conductivity-sensor.pdf

3. NBL-S-TM Soil Temperature Moisture Sensor datasheet

NBL-S-TM-Soil-temperature-and-moisture-sensor-Instruction-Manual-4.0.pdf

4. NBL-S-TMCS Soil Temperature, Moisture, Conductivity and Salinity Integrated Sensor

NBL-S-TMCS-Soil-Temperature-Humidity-Conductivity-and-Salinity-Sensor.pdf