Soil Moisture Monitoring System Applied to the Internet of Things (IoT) Based Automatic Watering Equipment in Papaya Fields

In this research, the design of an automatic plant watering device and a real-time soil moisture monitoring system was realized in an internet of things (IoT) based papaya farm. The design of this automatic plant watering device aims to create an automatic plant watering system using the FC-28 sensor and a monitoring system using the Blynk application on papaya fields. In the system, the microcontroller used is an Arduino UNO with outputs, namely a dc pump, 16X2 LCD, and Blynk application. Based on the android interface app, the Blynk app can monitor the soil moisture value in real-time every 1 second. Data collection was done by measuring the moisture value in 3 papaya farms with different crop ages, and the tool will water when the soil moisture value read by the sensor is> 350 or <65%. Based on the study results, the device can run well, as shown by the pump can water when the soil moisture value is> 350 or <65 %, and the pump will stop when the soil moisture value is <350 or > 65%.


Introduction
Papaya is a plant that comes from Southern Mexico. Papaya plants are easy to cultivate, so they are widely found in various countries such as Central and South America, North Africa, Hawaii, India, Indonesia, Malaysia, Thailand, and Sri Lanka (Sujiprihati & Suketi, 2019). Papaya plants consist of several types including Bangkok papaya, F1 solo papaya, Calina papaya (California), mountain papaya, and ornamental papaya (Sofiana, 2016) . The manufacture of papaya requires superior varieties and quality seeds, such as the Calina IPB 9 papaya or California papaya (Ardiansyah, 2020). Papaya plants can grow in the tropics, lowlands, and highlands, namely at an altitude of 1000 m above sea level and have a temperature of 24°C to 25°C, with a soil pH of 6.0 for dry soil irradiated by direct sunlight. (Sugito and Edy, 2017). Adetia et al., 2022/ J. Energy Mater. Instrum. Technol. Vol. 3 No. 2, 2022 With where to grow papaya plants, it is necessary to know the characteristics of the soil to improve the quality of papaya plants. The high level of soil fertility is indicated by the quality of the soil and the availability of sufficient water so that an increase in plant productivity can be realized. In addition to supporting plant growth, good soil quality can also regulate and distribute water flow equality and protect the environment (Juarti, 2016). Soil moisture is vital in the plant growth process, with a soil moisture range of 300% -700% (Fahrurrozi & Nuraharjo, 2020). Soil moisture below this value causes plants to wither and even die from drought (Yahwe et al., 2016).
One of the factors that affect soil moisture is the water content in the soil. The watering process can meet these factors. Watering is one of the treatment processes for plants to maintain water content in the soil as a source of food for plants. Manually watering plants is less efficient for farmers in terms of time and energy for large-scale agriculture, so this study seeks to minimize it by monitoring soil moisture as an indicator for automatic watering. This system is equipped with Internet of Things ( IoT ) technology to monitor soil moisture conditions as the basis for activating the watering pump. The process of watering plants is carried out automatically based on information from the input voltage that has been converted to the value of soil moisture. This research will create an automatic plant watering device and a soil moisture monitoring system based on the explanation above. The input section consists of an FC-28 sensor that detects soil moisture value. The input from the sensor will then be processed by Arduino Uno to be communicated serially with the ESP8266 Wifi module so that it produces output in the form of a visual display on a 16X2 LCD, relay, and pump. Then Arduino will send data via the internet or Wifi to the Blynk application.

Research methods
The tools and materials used in this research are a laptop, Arduino uno, 12V 5A adapter, ESP8266, 16X2 LCD, soil moisture sensor FC-28, relay, water pump, USB type B standard cable, jumper, bucket, PVC, Arduino IDE, Blynk, fritzing and Android.

Overall Tool Design
The tool's design consists of 3 parts, namely input, process, and output. The input section contains an FC-28 soil moisture sensor that detects soil moisture. The process section, Arduino UNO, works as an input data processor and produces output data directed to a relay to drive the pump, a 16x2 LCD for data display in the toolbox, and an ESP8266 Wifi module to send data to the Blynk application. System planning block diagram in Figure 1.

Figure 1. System planning block diagram
The working principle of the tool is based on information on the detection of soil moisture sensor FC-28 which is plugged into the soil around the papaya plant. The sensor detection data is then sent to Arduino via cable media to be read and processed for conversion and displayed on the Arduino IDE serial monitor. This data process is divided into two categories. First, when the FC-28 soil moisture sensor value is >350 or <65% or the soil is dry, the relay will drive the pump, and watering occurs. Second, the pump will stop watering when the sensor value is <350 or >65% or the soil is moist. In addition to driving the relay, the output of this sensor also displays the humidity value on the 16x2 LCD. It displays the sensor value data that is read to the Blynk application in real-time via the internet/Wifi. The Blynk application monitors the soil moisture value system on papaya land through Android. The complete series of watering tools can be seen in Figure 2, which was made using the fritzing device application.  Based on the circuit in Figure 2, the Arduino microcontroller uses nine digital pins, one analog pin, 2 VCC, and 2 GND. The FC-28 sensor is connected to pins A0, VCC, and GND. The ESP8266 wifi module is connected to VCC, GND, TX (D6), RX (D7), and pins 5 and 7 on the ESP8266 are connected. Then the relay is connected to pin D(8), VCC, and GND, then NO is connected to the negative of the pump, and COM is connected to the negative of the adapter. The positive part of the pump is connected to the positive of the adapter, and the negative of the pump is connected to the NO relay. Then connect the 16-pin LCD with Arduino and potentiometer, pin rs with D(12), pin en with D(11), pin d4 with D(5), pin d5 with D(4), pin d6 with D(3), pin d7 to D(2). GND, E, and cathode are connected to Arduino GND, then VCC and anode are connected to Arduino VCC, and VEE is connected to pin 2 of the potentiometer. The design of the automatic plant watering device is shown in Figure 3.  Figure 3, the box used is 19 cm x 13.5 cm x 13.5 cm and made of acrylic. At the top of the box, there is a 16X2 LCD that functions to display the soil moisture value. Inside the box are an Arduino UNO and an ESP8266 Wifi module that functions as a processor. Then the relay functions as a switch to turn on the pump. Furthermore, the soil moisture sensor functions to read the soil moisture value.

System Design Implementation
The instrumentation system for watering plants and a monitoring system for soil moisture in papaya fields have been realized with the results shown in Figure 4. The components contained in this tool include Arduino UNO, ESP8266 Wifi module, FC-28 soil moisture sensor, 16X2 LCD, and potentiometer. The box used in this tool has 19 cm x 13.5 cm x 13.5 cm and is acrylic. Before this tool is realized, first, the characterization of the FC-28 sensor is carried out. This characterization is carried out to ensure the sensor works well in terms of linearization, accuracy, and precision.  In this study, the principle of a closed-loop control system is applied with the output signal affecting the control process (Andrizal & Yendri, 2017). The closed-loop control system consists of input, controller, plant, feedback, and output parts. Figure 5 shows the block diagram of a closed-loop control system. . Figure 5. Block diagram of a closed-loop control system (Erinofiardi et al., 2012).
In this closed-loop system, there is an input of soil moisture value, Arduino UNO as controller, pump as plant, with feedback, namely FC-28 sensor, and produces soil moisture value output. The soil moisture output value is used to determine the input to the pump or plant.

FC-28. Soil Moisture Sensor Testing
The FC-28 sensor has an analog output, so it needs to be converted by Arduino Uno. The characterization of the FC-28 sensor was carried out using a calibrated soil moisture meter (HTC-2). The testing process was carried out in papaya fields by comparing the value read by the FC-28 sensor with the value of the soil moisture meter, as shown in Figure 6.  Energy, Material, and Instrumentation Technology Vol. 3 No. 2, 2022 The mechanism for testing the FC-28 sensor is by plugging the sensor into the soil, and there is already a comparison measuring instrument (HTC-2) used to measure the value of soil moisture. The test was carried out on five different papaya tree fields. This measurement was repeated five times so that the results of the FC-28 sensor soil moisture measurement on the measuring instrument were shown in Table 1. Based on the data obtained, a graph of the results of the FC-28 sensor characterization was made on the soil moisture measuring instrument, which is shown in Figure 7. The results of soil moisture measurement using the FC-28 sensor on the soil moisture measuring instrument shown in Figure 7 show a very linear value with R2 of 0.9953 and a gradient value close to one. These values indicate a strong relationship between the FC-28 and the HTC-2 gauge. Based on the data obtained from the test results, calculate the percentage value of error (error), accuracy, and precision using Equation 1, Equation 2, and Equation 3 where Y = reference parameter value, n X = nth measured parameter value, n X = average parameter value measured nth.
Based on the calculations, the average accuracy value for the soil moisture sensor (FC-28) is 99.21%, the average precision value is 100%, and the average error value is 0.78%. This shows that the soil moisture sensor (FC-28) has a high accuracy level, so it can be applied to calculate soil moisture value in papaya fields.

Android Interface Application Testing
The android interface application used is the Blynk application. Blynk monitors sensor readings or soil moisture values of papaya land. The Blynk application can be downloaded via the play store. The Blynk application can run

FC-28
if there is an internet connection (mobile hotspot) or Wifi. In programming, enter the auth token sent by Blynk via email, then enter the Wifi name and password. When Arduino UNO is connected to Wifi, Arduino UNO can directly send data to the Blynk application. The monitoring system created can be accessed using other androids by scanning the barcode on the Blynk application. Testing the Blynk application is carried out to determine whether the Internet of Things (IoT) system that has been created can run well and receive data in real-time. Testing the data transmission rate to the Blynk application is also carried out by comparing the time indicated on the super-chart in the Blynk application with the time in the Digital Clock application, as shown in Figure 8.

Figure 8. Display of Blynk application and application Digital Clock
In the display of the blynk application using the Widget Gauge and superchart, which can be purchased on the Widget Box menu. Figure 8 shows the blynk application and the Digital Clock application display. Based on Figure  8, the time shown by the superchart on the blynk application is 16.52.30, and the time displayed by the digital clock application is 16.52.30. So that the data obtained for five repetitions is shown in Table 1. Based on the data obtained, a graph of the results of testing the Blynk application against the Digital clock application is made, shown in Figure 9.   Energy, Material, and Instrumentation Technology Vol. 3 No. 2, 2022 Based on the graph, it can be seen that the time listed on the Blynk application corresponds to the time stated on the Digital Clock application so the Blynk application can be used for a monitoring system for soil moisture values in papaya fields in real-time.

Data Collection and Analysis
Data collection for implementing the tool is carried out in papaya fields by placing the hardware system in the specified place. In general, the data collection is shown in Figure 10.

Figure 10. System implementation on papaya land
The soil moisture needed for papaya plants is 66% (Muktiani, 2011), and the lack of moisture in the soil makes the plants wilt and even die (Yahwe et al., 2016). This humidity value becomes the basis for setting the sensor and relay performance limits to activate the pump. When the sensor reads the soil moisture value >350 or <65%, the relay automatically turns on the pump, and when the soil moisture value is <350 or >65%, the relay automatically turns off the pump. Figure 10 also shows an automatic plant watering system, and watering is carried out using a 12V 3A dc pump connected to a 12V 3A adapter as a voltage source. The water used is in a bucket and will be channeled through a PVC with a length of 190 cm and 130 cm, which has been perforated in 4 equal parts with a distance to the sensor of 60 cm for trees one and tree 2 and 50 cm for tree 3. measuring the soil moisture of papaya land on three trees with different growth periods, namely, newly planted trees, trees leading to fruiting and trees that are already fruiting. The papaya land used has an area of 200 x 200 cm.
The sensor will send data in the form of a 16X2 LCD for the monitoring system and send data to the interface application, namely the Blynk application, in real-time. The following is a program used to display data to a 16X2 LCD.
The above program is used to initialize the 16X2 LCD to be able to receive sensor data. The programming explains that the 16X2 LCD pins are connected to the Arduino UNO pins, namely const int rs = 12, en = 11, d4 = 5, d5 = 4, d6 = 3, d7 = 2; then display the value on the 16X2 LCD with the command lcd.print("KLB : "); with a repetition interval of 1000 ms. Based on the program that has been made, the results of soil moisture measurements on a 16X2 LCD are displayed, as shown in Figure 11. #include <LiquidCrystal.h> const int rs = 12, en = 11, d4 = 5, d5 = 4, d6 = 3, d7 = 2; LiquidCrystal lcd(rs, en, d4, d5, d6, d7); lcd.setCursor(0, 0); lcd.print("KLB : "); lcd.print(klbtanah); lcd.print(" % "); delay (1000); Figure 11. Display of soil moisture value on LCD Based on the value seen on the LCD, the soil moisture value is 62%. The data sent to the LCD will be updated with an interval of 1 second during the data retrieval process. It can also see the program used to send data to the Blynk application.  Fields, Journal of Energy, Material, and Instrumentation Technology Vol. 3 No. 2, 2022 The above program initializes the Blynk application as an interface to receive data based on random values. In programming, enter the auth token sent by Blynk via email, then enter the wifi name and password. The RX TX pins are connected to pins D(7) and D(6) and use a baud rate of 115200. The process of sending data to the Blynk application with a repetition interval of 1000ms. The results of monitoring soil moisture values in the Blynk application can be seen in Figure 12.  The display on the Blynk application contains Gauge and Super-chart with a value range of 1-100. The data retrieval process shows that the Blynk application can receive data every 1 second, and on the graph, it is displayed every 8 seconds. Based on the monitoring results, the data obtained from monitoring soil moisture are shown in Table 3. The data in Table 3 results from monitoring the soil moisture value of tree one on September 27, 2021. The data collection process was carried out in Air Kubang Village, Airnaningan District, Tanggamus Regency, for 30 days from September 27, 2021, to October 26, 2021, and was carried out every afternoon with an interval of 1 second until the watering was process stops. Data collection was carried out by measuring the soil moisture of papaya land on three trees with different growth periods: newly planted trees, trees leading to fruiting, and trees that were already fruiting. Based on the data obtained, a graph of the soil moisture value against time is made, as shown in Figure 13, Figure  14, and Figure 15. Adetia et al., 2022/ J. Energy Mater. Instrum. Technol. Vol. 3 No. 2, 2022  In Figure 13, Figure 14, and Figure 15, the soil moisture value of papaya land can is seen against time. In Figure 13, or tree soil moisture, the value of soil moisture at the initial watering condition for one month ranges from 25%-58% with the pump OFF condition. Soil moisture with the driest initial conditions is on October 25, 2021,