# A Novel Intelligent IoT System for Improving the Safety and Planning of Air Cargo Operations
## 2 System Description
### Hardware
It features a powerful 16-bit RISC CPU, 16-bit registers, and constant generators that contribute to maximum code efficiency [38]. Wireless module: The communication between the HMI and the mainboard is achieved by a dedicated microcontroller, the Espressif ESP32 [39], supporting communication in 2.4 GHz, 802.11 b/g/n, Wi-Fi and Bluetooth. The communication protocol selected is MQTT [40]. It was chosen due to its lightweight, low power, small bandwidth, easy-to-use characteristics, and extended use in IoT applications. CAN bus module: The CAN protocol allows microcontrollers and devices to communicate with applications without a host computer. In the INTELLICONT system, the CAN bus module is used to achieve communication between the microcontroller and the smoke detector. The CAN controller used is MCP2515. It is a second-generation stand-alone CAN controller, and it includes features like faster throughput, data byte filtering, and support for time-triggered protocols [41]. Power management unit: The power management unit comprises two separate units: the power supply unit and the power switching and monitoring unit. The power supply unit is designed to provide diverse levels of voltage needed for the operation of the microcontroller and every sensor interface of the mainboard out of a single 24 VDC input. However, it is also capable of supplying the required voltage for an input voltage as low as \begin{table}
\begin{tabular}{c c c} \hline \hline
**Type of Sensors** & **Output/Characteristics** & **Value** \\ \hline Piezoelectric sensors & Output voltage & \begin{tabular}{c} 100 mV to 100 V depending \\ on force or circuit impedance \\ \end{tabular} \\ \hline Smoke detector & \begin{tabular}{c} Temperature and humidity \\ measurements \\ \end{tabular} & \({}^{\circ}\)C/\%RH \\ \hline Contact switches & Operating frequency & \begin{tabular}{c} 30 operations/min (max) \\ 4 V to 10 V DC \\ \end{tabular} \\ \cline{2-3} Position sensors & Output voltage & \
\begin{tabular}{c} 1.75 V to 2.25 V \\ \end{tabular} \\ \cline{2-3}  & Typical sensitivity &
\begin{tabular}{c} 0.90 mV/Gauss \\ \end{tabular} \\ \cline{2-3}  & Operating temperature & \(-40\)\({}^{\circ}\)C to \(100\)\({}^{\circ}\)C \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Sensors—technical specifications. Figure 3: The RMC Mainboard. 10 V. It can also provide an adequate amount of current for each device's operation within its electrical specifications. The unit provides five separate DC voltages: +24 V, +12 V, \(-\)12 V, +5 V and +33 V.  
The power supply unit incorporates several safety features that make it eligible for installation on an aircraft, according to the CS-25 certification requirements for aircraft [36]: it provides power isolation of 1500 VDC for protection of sensitive and expensive equipment such as the smoke detector; it features choke inductors for current limitation, proper fuses for overcurrent protection of all the main board's devices and sensor interfaces, as well as reverse polarity protection circuitry. Moreover, it is designed to isolate its input reference voltage from its output reference voltage to eliminate input noise propagation and ground loop problems. The power switching and monitoring unit consists of two battery packs that provide a constant voltage between 12 VDC and 17 VDC and three submodules. The first submodule constantly monitors the voltage of the two battery packs powering the device. In case the voltage of the battery pack drops below a certain level, it instantly switches to the second battery pack, provided that it is charged, to supply the device. The switching between the two battery packs is instant so that the functionality of the device is not affected and there is no downtime for the system. Each of the other two submodules monitors each battery pack's charge level so that it can be presented to the aircraft's crew via the HMI.