Research on boat fire safety monitoring system based on ZigBee

0 Introduction

my country is a large maritime country, with an ocean area accounting for one-third of its land area. Various types of ships and boats play a very important role in national defense, national economy and marine development. The basic part of a ship is the hull, which contains various cabins such as work cabins, living cabins, storage cabins, and equipment cabins. Since most of the cabins of ships and boats are small and semi-enclosed spaces, fire safety monitoring in the cabin is particularly important.

Traditional fire safety monitoring systems for boat cabins generally use wired monitoring, and fire detectors are directly connected to the controller through hard wires. Wired monitoring systems are expensive, have complex wiring, poor scalability, and are difficult to maintain later. At present, wireless sensor networks have been widely used in monitoring systems for various environmental conditions. The monitoring system for boat cabins uses wireless sensor networks, which will not cause the inconveniences caused by traditional wiring methods. Since fire safety requires long-term continuous monitoring, the use of ZigBee, a short-range wireless communication technology that is easy to install and consumes little energy, is very suitable. This paper proposes a design scheme for a boat fire safety monitoring system based on ZigBee technology, which realizes fire safety monitoring inside each cabin of the boat under the premise of low cost and easy implementation.

1. ZigBee Wireless Sensor Network

1.1 Introduction to ZigBee Technology

ZigBee is a new short-distance two-way wireless communication technology with low complexity, low cost, low power consumption and low rate. It is a standard based on the reliable physical layer (PHY) and media access layer (MAC) defined by IEEE 802.15.4. IEEE 802.15.4 defines two types of devices: reduced function devices (RFI) and full function devices (FFD). In the ZigBee system, these two types of devices refer to physical device types. In a ZigBee network, a node can have three roles: ZigBee coordinator, ZigBee router and ZigBee terminal device. There are three network topologies that can be realized by ZigBee technology: star, tree and mesh, as shown in Figure 1.

1.2 ZigBee Technical Features

Compared with traditional wireless communication methods such as radio, microwave, Bluetooth, and radio frequency , ZigBee technology is the technology with the lowest power consumption and lowest cost. ZigBee technology has the following main features:

(1) Low power consumption. In low power mode, two ordinary AA batteries can be used for 6 to 24 months.

(2) The equipment cost is low, the protocol is simple, the protocol is free of patent fees, the cost of building the platform is low, and it is suitable for widespread use.

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(3) The network has a large capacity and can accommodate up to 65,000 devices.

(4) The network has strong self-organization and self-healing capabilities, and communications are reliable.

2. Boat cabin fire safety monitoring system

2.1 System design

The principle of fire detection by the ship fire safety monitoring system is to detect the changes in the three physical parameters of smoke density, temperature and light before and after the fire occurs, and to collect these environmental parameters using sensor nodes distributed in the test area of ​​the cabin.

The design of the ship fire safety monitoring system consists of two parts: hardware circuit design and system software design. ZigBee technology is used to build a wireless communication network through a controller and several sensor nodes. Multiple sensor nodes are placed in each cabin of the ship. The sensors collect smoke concentration, humidity, and light intensity data, and send the collected results to the router node through wireless communication. The router node then sends the data to the coordinator node through wireless communication. The coordinator node analyzes and processes the collected data and displays it on the LCD display. At the same time, the collected information can be transmitted to the PC through the serial port. The main structure of the system design is shown in Figure 2.

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2.2 Functional module design

The ZigBee device selected by the system is the JN5139 ZigBee solution based on Jennic, which provides a complete ZigBee protocol stack, software editing, compiling/linking, debugging, downloading and other tools. The JN5139 chip is a series of high-performance, low-power wireless chips launched by Jennic, a British company. The antennas of this series of chips have high sensitivity, low power consumption and long communication distance, providing a good solution for ZigBee technology. The system node block diagram is shown in Figure 3.

The onboard UART interface of the ZigBee network coordinator module device is used to connect to the embedded motherboard or PC for data transmission and software download or debugging. As a network coordinator, it is responsible for managing the establishment and maintenance of the entire ZigBee network. The sensor node/routing module device is powered by 2 No. 5 batteries and provides analog sensor and digital sensor expansion interfaces for connecting smoke concentration, temperature, and light intensity sensors. As a routing node or terminal node, it can collect data by itself and forward data packets from other nodes.

2.3 System software design

The software platform also uses Jennic CodeBlocks, a code editing and compiling environment provided by Jennic. CodeBlocks is an open source C/C++ development tool, based on which Jennic has expanded to form its own development platform. Jennic Flash Programmer is used to download the compiled code in CodeBlocks to the controller board or sensor board.

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The software design of the system includes the design of the network coordinator node and the sensor node. The network coordinator node finds a suitable channel during the initialization process, establishes a network, and cyclically detects the binding request of the sensor node. When the sensor node joins the network, data can be transmitted. The software flow chart of the sensor node is shown in Figure 4. The main function of the program is to join the sensor node to the wireless network established by the network coordinator node, read the environmental parameter data measured by the sensor in real time, and periodically send this data to the network coordinator node.

3 Conclusion

A design and implementation method of a boat fire safety monitoring system based on ZigBee with JN5139 module as the core is proposed. Applying ZigBee, a low-power, high-reliability, and highly scalable wireless network, to fire safety monitoring avoids various on-site wiring, enhances the flexibility and reliability of the system, improves the ability of boat fire safety monitoring, and better avoids the occurrence of boat fires.