# Remote Water Quality Monitoring System for Use in Fairway Applications
## 2 Materials and Methods  
### Remote Water Quality Monitoring System Architecture  
Thanks to the use of modern technologies, such as hydrological sensors, it is possible to continuously and precisely collect data on the physical and chemical parameters of water for the management of water resources and environmental protection. Technologies consistent with the concept of the Internet of Things (IoT) were effectively used to monitor water quality in the river by implementing an intelligent system that automatically collects, analyzes, and transmits data using a series of sensors, control electronics, and GSM telecommunications technologies. Figure 1 shows a diagram of the remote water quality monitoring system. The system consists of a central unit located in an autonomous buoy and a main server connected to a computer or mobile device with a monitoring and analytical application installed. This creates an integrated environment that allows for the collection, processing, and analysis of data in real time or at a specified interval. * Central unit The main components of the central unit are the integrated water quality sensor system (IWQSS), the signal processing unit (SPU), and the GSM module for data transmission. The autonomy of the central unit is ensured by battery power supply. The central unit has a modular character; i.e., each element of the system (IWQSS, SPU + GSM, battery) is connected by quick connectors and is located in hermetic enclosures. * SPU + GSM module The choice of an Arduino-based or compatible SPU was due to its properties:
* Programming simplicity;* Modularity;
* Low price;
* Support and documentation (a large number of ready-made libraries, which simplify the implementation of various functions);
* Versatility and possibilities for rapid prototyping (can be easily adapted to various applications);
* Expandability with ready-made modules or shields. As a result of research and analysis, consisting of tests of various models and microcontroller development kits, in order to determine the optimal one in terms of energy consumption while maintaining the correct data transmission, the DFR0355 board manufactured by DFRobot was selected (Table 1). This system is compatible with the Leonardo module of the Arduino platform, with an integrated GSM/GPRS/GPS SIM808 module enabling the creation of IoT projects. The DFR0355 board is based on the ATmega32u4 microcontroller (DFRobot, 63-640 Brain, Poland. ), which provides 20 digital inputs/outputs, 7 PWM channels, 12 analog inputs (4 of them are used to measure water quality), and popular communication interfaces. The battery life \(B_{L}\) was determined from a simple relationship:  
\[B_{L}[\text{days}]=\frac{B_{C}[\text{mAh}]}{24\cdot L_{C}[\text{mA}]}, \tag{1}\] \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**SPU** & **GSM** & \begin{tabular}{c} **Load** \\ **Current** \\ **(Standby Mode)** \\ \end{tabular} & \begin{tabular}{c} **Battery Life** \\ **(Estimated)** \\ \end{tabular} & \begin{tabular}{c} **Load Current** \\ **Maximal** \\ **(Data Transfer)** \\ \end{tabular} & \
\begin{tabular}{c} **Data** \\ **Transfer** \\ **Quality** \\ \end{tabular} \\ \hline Arduino Uno Rev3 & Quectel MC60 & 120 mA & 6.94 days & 240 mA & Correct \\ Arduino Uno Rev3 & GPS SIM/7000E & 110 mA & 7.57 days & 230 mA & Correct \\ Arduino Uno Rev4 & Quectel MC60 & 70 mA & 11.9 days & 140 mA &
\begin{tabular}{c} Connection \\ breaking \\ Connection \\ breaking \\ Connection \\ breaking \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Analysis of different Arduino + GSM system topologies. Figure 1: Schematic diagram of the remote water quality monitoring system. where  
\(B_{\rm C}\)--Battery Capacity;  
\(L_{\rm C}\)--Load Current. In the chosen development kit, the GSM module communicates with the microcontroller module via the UART serial interface (RX, TX) by AT commands. This set allows for the implementation of advanced projects, such as location tracking, SMS communication, voice calls, and data transfer over the Internet.