Soil Moisture Content Based Cost-Effective Smart Irrigation System for Poly Tunnels
by Viraj Dhanushka, Ashan Serasinghe, Hans Thisanke, Sumudu Lakmali, and Akitha Madusanga.
Abstract: People who are enthusiastic about gardening always try to build a small polytunnel in their gardens. But in polytunnels, the environment is not like a natural environment. Since the crops are in an artificial environment the owner has to pay extra attention to crops. Watering the crops at the correct time is one of the most critical tasks in polytunnels. Fertilizing and pest control are also important. But people are not able to do these things at the correct time with their busy schedules. One of the solutions is automating the irrigation system with IoT.
Keywords: ESP8266, Flutter, IoT, MQTT, NRF, Polytunnel
1. Introduction
These days IoT based solutions are very common in the industry. But those solutions are usually expensive. It is not a big problem for robust industrial applications. But, if we introduce an IoT base automation system to the small polytunnels mentioned above, the system should be affordable for an average person. And also it should be more user-friendly. Using ESP modules both goals can be achieved. Since the polytunnel is closer to the home, the home Wi-Fi connectivity is available in the polytunnel as well. So it is easy to connect the system to the internet. The system can be made more user-friendly by introducing a mobile app, available on both Android and iOS, to control the system.
Existing systems use manual valves like shown in Figure 1.2 to control the water supply. And there is a water pump before this valve. This IoT solution aims to replace this manual valve with an automated unit and control the water pump using the same unit. The automation process is taken palace based on the decision taken by the sensor units installed in the polytunnel. But the user has full control of the system through the mobile app. Sensor units and main control unit are wirelessly connected using NRF modules
2. Methodology
The system is consisting of 2 units. But they do 3 separate tasks. One unit controls the water pump and the electric valve. Another one monitors sensor data and takes decisions. And also it sent its decisions to the main controlling unit. The main controlling unit notifies the user via mobile app using push notifications. If the user was unable to take the action according to the notification, within a certain pre-defined period, the system automatically starts the watering process. After soil moisture content reaches the required level the water supply is automatically turn off. The user is notified via the mobile app
Pipelining diagram with the automated unit can be shown as in Figure 2.2
2.1 Main controlling unit
The main controlling unit responsible for turning on and turning off the irrigation valve and power on and off the water pump, and also receiving the information sent by the sensor units installed in the polytunnel. The main controller is connected to the home Wi-Fi system. It can be remotely controlled by a mobile app with the help of the EMQX cloud-based MQTT broker. Here the main controlling unit and the mobile app act as MQTT clients that are subscribed to the same topic. So mobile app receives messages through the MQTT broker. The main unit is powered by the 240V main supply. The water pump is powered through the main controlling unit. The triggering signal of the electric valve is also supplied by the main controller. If the system has any issue or the user wants to turn off the automation, it can be done by the switch on the main unit. Switching off that switch, the system becomes a manual system.
2.2 Sensor unit
The sensor unit consists of a soil moisture sensor, NRF module, and a microcontroller (Arduino Nano). The unit analysis the moisture content and inform the main controlling unit if the moisture content is not within pre-defined limits. The moisture content depends on the type of crops. The type of crops can be set via the main controller. The mobile app can upload the type of crops to the main controlling unit. The sensor unit is powered by a rechargeable battery and there is a solar-powered battery charging unit. If the tunnel is big, instead of one sensor unit few units can be installed. The main system considers the majority response.
2.3 Mobile app
A mobile app is developed using the flutter framework so the app is available on both Android and iOS. Using the mobile app, the user can turn off and on the valve and the pump at any time. The system gives push notifications via the mobile app when the moisture content is below the cutoff. Then the user can turn on the valve and pump. If the user was unable to turn on the water supply within the given period, the system automatically starts watering. But the user can go against the suggestion of the system and stop watering via mobile app.
3. Safety
Before the pump is turn on the valve should be open. Otherwise, the pipes and the pump would be damaged. So the system makes sure that the valve is open before turn on the pump. When the pump is turn on the moisture content should be increased with time, if not there should be a problem with the water supply. So for the safety of the pump, it will turn off automatically and the user will notify via mobile app.
Results and discussion
This system is designed for polytunnels. But the system can make such that it fits outside farming by replacing the ESP8266 with a suitable device that fit a robust environment
Reference
T. Thevananthan and V. Joy Vahini “Smart, easy end-user installation and reliable node-coordinator system and protocol solution for IoT applications using cost-effective embedded systems” Transaction 2018 (IESL)
