# Smart Hydroponic Cultivation System for Lettuce
## 1 Introduction
The physical layer consists of various sensors capable of measuring variables such as air temperature, water level, pH and total dissolved solids (TDS) in the water. It also includes control mechanisms such as pumps for water, nutrients and saline solutions to maintain the stability of the nutrient solution. An ESP32 microcontroller (Espressif Systems, Shanghai, China) is used for data collection, decision-making and sending information to the cloud. The service layer is implemented using the Blynk platform. The user experience layer is applied through a mobile application for user data visualization. In [25], a vertical indoor aeroponic system architecture is proposed. The physical layer consists of various sensors for monitoring variables such as pH, EC, water tank level, air temperature, RH and photosynthetically active radiation. The system uses a Raspberry Pi as the central control unit for decision-making, managing the activation of three peristaltic pumps for precise nutrient management using feedback control and two LED lamps to provide adequate lighting. The collected data is sent to an MQTT broker. The service layer generates alerts about the system status, which are displayed to the operator through the user experience layer. In [26], an IoT hydroponic system was developed with the dimensions of \(150\) cm \(\times\)\(150\) cm \(\times\)\(235\) cm. For the physical layer, sensors were integrated for the measurement of environmental variables such as air temperature and RH, as well as nutrient solution variables such as pH, water temperature and EC. They include various control mechanisms such as fans, full-spectrum LED lamps, a heating system and pumps for water and nutrient circulation. A NIDO ONE central controller [27] is used for data collection, decision-making and communication with the database. The collected information is processed and displayed to the user via the NIDO PRO platform. In [28], a hydroponic system with a nano bubble generator is proposed. The system's physical layer includes sensors capable of measuring variables in nutrient solutions such as Dissolved Oxygen (DO), TDS and pH; similarly, air temperature and RH are monitored. The only control mechanism in the system is the nano bubble generator. Multiple microcontrollers (Arduino UNO, NodeMCU, ESP32-E) are used to gather sensor data. A Raspberry Pi is employed as a local server and for decision-making processes. In the service layer, the data is sent to the Antares platform. The user experience layer is supported through both a web application for real-time monitoring and a local monitor serving the same purpose. In [29], an automated IoT-based hydroponic system for indoor cultivation was developed. The system's physical layer was implemented using a series of sensors to measure environmental variables such as air temperature and RH, as well as nutrient solution variables such as pH and TDS. For automation, pumps were integrated for nutrient control, along with white LED lights. An Arduino UNO microcontroller is responsible for collecting the data, which is transmitted via a Raspberry Pi to a platform built-in Node-RED [30]. In the service layer, the data are stored in a MongoDB database and visualized through the user experience layer via a web application accessible from a computer or a mobile device connected to the same network. In [31], a Deep Water Culture (DWC) IoT hydroponic monitoring system is presented. The physical layer includes sensors for measuring variables such as pH and water temperature. A NodeMCU microcontroller [32] is used to collect data, perform decision-making tasks and transmit information to the cloud. In the service layer, the Firebase platform [33] is used to store the data. The analysis layer is implemented through a Mamdani fuzzy logic algorithm [34] to determine whether the system conditions are within normal limits or out of range. In the user experience layer, the users receive alerts generated by the fuzzy logic algorithm via WhatsApp and view the information through a web application.