Automation of humidity in the greenhouses for plant cultivation

. Greenhouse is a building formed to protect and care for plants from various kinds of weather and pests on plants. In addition, greenhouses also function to manipulate and control environmental conditions so that the conditions needed for plant growth are met. Air humidity is one of the environmental conditions that affect plant growth and can be controlled by automatic fogging so that plants can grow optimally. This research aims to produce an atomization system and maintain air humidity in the greenhouse automatically. The use of this research is as an information material for farming communities to control air humidity automatically in greenhouses through the use of technology. This research was carried out by designing automatic fogging to keep the air humidity value constant. The sensor test results show that the air humidity (RH) value when plants photosynthesize optimally, namely morning to evening within a 12 hour period, is around 84.17% with setting points of 80% and 90%. And the test results show that the system can maintain the air humidity value constant according to the given setting point.


Introduction
Greenhouse is a building formed to protect and care for plants from various kinds of weather and minimize pests on the plants inside.In the cultivation process, the use of greenhouses serves to manipulate and control environmental conditions so that the conditions needed for plant growth are met [1].However, the use of greenhouses also often has problems related to the environmental conditions in it, one of which is air humidity.For example, during the dry season, the intensity of radiation from the sun is very strong, which results in less air humidity compared to the rainy season.This makes it difficult for some plants to grow optimally.
Plant production in greenhouses can be optimized by applying good cultivation techniques, one of which is by optimizing the photosynthesis process so that the energy obtained for plant growth is maximum.One way to optimize the photosynthesis process is by providing air humidity of 80% -90%, RH needs of Kale plants [2].
Air humidity affects the photosynthesis process in plants.To produce air humidity this research uses a fogging system, air humidity that is too high can inhibit plant growth by slowing down the photosynthesis process so that plants wither and also cause mold and disease.Conversely, if the air humidity is low, it can increase the transpiration rate and the use of water and mineral substances also increases, which will automatically increase the availability of nutrients for plants.This is in accordance with the opinion of [3], which states that air humidity will affect the rate of evaporation or transpiration of plants.If the humidity is low, the transpiration rate increases so that the absorption of water and mineral substances also increases.
Therefore, microclimate control, especially air humidity, needs to be applied in the greenhouse so that the needs of plants can be met [4,5].Cultivators will be overwhelmed if they manually adjust the air humidity every day.Therefore, this research uses an automatic system so that farmers or plant cultivators in the greenhouse no longer control the air humidity manually.The purpose of this study is to control air humidity in the greenhouse so as to optimize plant growth.

Materials and methods
The tools used in this research are a laptop with Arduino IDE software, cutter, saw, meter, Avometer, 12V adapter, 12V DC water pump, nozzle, 5V adapter, ESP32-WROOM-32, SD card module, DHT22 sensor, 0.96 "Serial I2C LCD, Exhaust fan, RTC DS3231, laptop and smartphone camera.The materials used in this research are PCB board, duct tape, bamboo, tis rope, DC jack connector, water reservoir, 6 mm and 11 mm polyethylene hose, water hose filter, nozzle, T connector, jumper cable, head cable, 5V 1 channel relay, Solid State Relay 40-DA, plug.The system model that will be applied is a closed-loop system, where the control center of the system is the ESP32-WROOM32 microcontroller which will read the output value of the DHT22 sensor.The DHT22 sensor has a limited range of data readings, as for the measurement range from 0%-100% RH with an absolute accuracy of 2%-5% [6].In this system, the ESP32 will be connected to the internet and also the platform as an access to see real-time RH conditions through a smartphone as a monitoring tool for the existing system.In this system, ESP32 also acts as a control center for the 5V relay and SSR from the reading of the DHT22 sensor output value.Then if the DHT22 RH sensor reading is below 80% then the relay is ordered to ON so that the pump can turn on and if the RH is above 80% then the relay is ordered to OFF.If the RH condition is above 90% then the SSR is ordered to ON then the exhaust fan can turn on and if the RH is below 90% then the SSR is ordered to OFF.The sensor reading results will be displayed on the LCD, this ESP32-WROOM-32 microcontroller system uses C programming with Arduino IDE application software (Figure 1).

Fig. 2. Sketch of the greenhouse room view
The design of the greenhouse is depicted in sketch form, as can be seen in Figure 2, where the height of the nozzle is 200 cm, the height of the sensor is 95 cm, the height of the fan which has a size of 40 cm² is 70 cm and the height of the fan which has a size of 34.3 cm² is 35 cm.The greenhouse roof height is 265 cm, the back height is 220 cm and the front height is 255 cm, the greenhouse width is 164 cm and the length is 205 cm.Therefore, the greenhouse has a volume of 8.25 m³.

Results and discussion
The results of the design of the data acquisition system that has been made, can be seen in Figure 3, where the DHT22 sensor is a temperature and humidity sensor which in this study is used to measure air humidity in the greenhouse, the DHT22 sensor can work well because the average air humidity measurement results obtained are still in the range of the needs of kailan plants, namely 80%-90%.ESP32-WROOM-32 is the control center of the control system that can provide data input signals.RTC or Real Time Clock is a component that can count time from seconds to years.Solid state relay (SSR) is an electrical switch that is used as a controlling device for the exhaust fan and 5V relay is also an electrical switch that is used as a controlling device for the DC pump.0.96 "oled LCD is a display media to display the results of DHT22 sensor readings.microSD card is a component that functions to store data, and in this study the data stored is from DHT22 and RTC sensors in real time.The test results of the control system based on the given RH, work well on the amount of air humidity from the initial RH of 64% to the given setting point limit of 80% in the room controlled in the program through the DHT22 sensor reading.This test was carried out during the day at 14:20, it can be seen in Figure 5 showing the results of testing the air humidity control function using the DHT22 sensor which functioned to read the air humidity value, so as to maintain stability and maintain air humidity.This is shown with an overshoot value of 1.8% and RH settling time of less than 5 minutes.According to [7], the DHT22 sensor has an element made of polymer capacitors, the sensor performance is stable for a long time and has an air humidity measurement range from 0%-100%.So that the measurement data obtained is relatively more stable and accurate.Data retrieval of the air humidity control function can be seen in Figure 4, it can be seen that at second 90 the system has reached the setting point of 80% RH, thus the application of this control system is declared successful.This shows that the requirements for the application of the control system have been met, namely the RH settling time to reach the settling time is short, which is less than 5 minutes.This test is carried out with the aim of monitoring and ensuring that the air humidity in the room remains at a stable RH, and meets the moisture needs of plants.In this test, air humidity data was collected for 6 hours, starting from 00 until 06 in the morning (Figure 5a).The maximum value is 95%, the minimum value is 89.9% and the average value is 92.32%.Where the first 33 minutes of RH stabilized at 90% and then rose to the highest figure of 95.9% at 01:52:48, it shows the inability of the exhaust fan to remove air humidity in the early morning.In addition, the average humidity in Makassar city in the month the data was taken (June, 2023) was 96.66% according to the Potere Maritime Meteorological Station.Then the RH dropped back to 92% at 00:00 and remained relatively stable until 06:00:00 with an average value of 92.59%.a).RH hours 00 to 06 b).RH hours 06.00 to 18.00 c).RH hours 18.00 to 00.00

Fig. 5. Air humidity inside the greenhouse
In this test, air humidity data was collected for 12 hours, starting from 06:00-18:00 (Figure 5b).At 06:24:24 the RH started to drop at 90% and continued to drop to 80% RH at 08:03:54 and continued to stabilize until 14:35:06 and had an average of 81.46%, then the RH rose again to 90% at 17:15:18.The RH value obtained for 12 hours is the maximum value of 92.6%, the minimum value is 77.6% and the average value is 84.17%.This is in accordance with the opinion [6], the difference in the humidity value designation on the DHT22 sensor is in accordance with the DHT22 sensor data sheet, namely the measured humidity must be no more than 5%.This shows that the air humidity in the room from morning to evening can be controlled properly.
In this test, data on air humidity was collected for 6 hours, starting from 18:00 pm to 00:00 pm (Figure 5c), the maximum value is 93.3%, the minimum value is 88.7% and the average value is 90.52%.At 18:00:00 until 22:03:54, the RH was relatively stable with an average value of 89.73%, then the RH rose to 93.3% at 22:27:24 and stabilized until 23:29:18 with an average of 92.53%, then fell back to 90% at 23:45:24 until 00:00:00 with an average of 90.88% average of 90.88%.
Outdoor RH monitoring is carried out with the aim of seeing changes in air humidity outside the greenhouse without RH control and as a comparison to the RH of the controlled greenhouse room.In Figure 6, shows the test results of the RH value obtained far from the minimum plant needs of 80% (minimum RH of kailan plants), in this test the lowest RH was  The difference between the minimum air humidity needed by plants and the RH obtained is 24.3%, the low air humidity during the day cannot meet the needs of plants, according to [8], which states that if the air humidity is low, the transpiration rate increases and the absorption of water substances will increase, it will increase the availability of nutrients for plants.This is also agrees with [9], plant growth is also influenced by air humidity.If the RH is outside the limit, the growth of the plant will be disturbed.Each group requires different air humidity for optimal growth.

Conclusion
Based on the results of the research that has been carried out regarding the automation and monitoring of air humidity in the greenhouse, it can be concluded that the system is able to monitor changes in RH values inside and outside the greenhouse in real-time through the platform.The system is able to meet the RH needs of Kailan plants from morning to night, while in the early morning until morning the system has not been able to reduce RH.

Fig. 3 .
Fig. 3. Design of data acquisition system components