Design of smart home security system based on WSN

People's pursuit of quality of life is getting higher and higher, and they are more eager for a safe, smart and healthy home environment. The traditional smart home security system has a single function, low efficiency, high false positive rate, high maintenance cost, and can not be well integrated with the rapidly developing Internet technology. It has been difficult to meet the requirements of the market and the public for home security systems. The development of modern wireless sensor network technology (WSN) and Internet of Things technology makes the networked smart home security system have the characteristics of security, intelligence, convenience and environmental protection, while ensuring the system's real-time performance, high reliability, low false alarm rate, Low power consumption and low cost maintenance. To this end, this paper proposes WSN and smart phone Android platform based on features such as low power consumption, self-organizing network, low-rate, low-cost and two-way communication characteristics. It can use the home gateway to construct video data collection, transmission and network background storage. The smart home security system, while the system can use the Internet network for remote monitoring.

1. The WSN part of the system design system adopts the ZigBee protocol, which consists of multiple terminal nodes and a coordinator. Each terminal node can self-organize the network, and the data is finally aggregated to the coordinator node, and then accesses the Internet through the home gateway. The user can remotely monitor the smart home through the Internet on the PC, the set-top box, and the mobile client. The sensor information in the home is collected by the GPIO port on the terminal node and sent to the coordinator via the WSN network. The coordinator completes the data communication with the home gateway through the USB-TTL module, and the home gateway reports the data to the server. In order to reduce the false alarm rate of the security system and ensure its high reliability, the sensor responsible for collecting the concentration of combustible gas in the wireless sensor network deliberately selects the high-sensitivity combustible gas sensor, and combines the anti-false alarm algorithm integrated in the terminal node protocol stack. To ensure the accuracy and reliability of the information.
The communication between the WSN network coordinator and the home gateway needs to be completed under the conversion of the USB-TTL module. The USB-TTL module driver development is based on the Linux system. In order to realize the intelligentization of the smart home security system, the device of the module is designed according to the redundant design requirements. The descriptor will recognize the USB interface changes and read and write to the device descriptors that may be transformed. The overall design of the system is shown in Figure 1.

2, hardware circuit design 2.1 home gateway hardware overall design The main controller of the smart home security system based on WSN is composed of the set-top box of the home gateway and the ZigBee coordinator. Each terminal node of the WSN wirelessly transmits the collected data to the coordinator for aggregation, and completes the data communication with the set top box through the serial port to the USB communication module, and the smart home security application system on the set top box uploads the data according to the standard TCP/IP protocol. Go to the server so that users can view current and historical data via network access. At the same time, the home security video data collection terminal pushes the monitoring screen to the user through the Internet network, and the user can monitor the indoor situation in real time through the PC, the mobile phone client, and the upper computer on the set top box. The overall hardware structure is shown in Figure 2.

2.2 Coordinator and MT8389 interface circuit use the main control chip for the MT8389 home gateway set-top box. The WSN node collects sensor data and sends it to the ZigBee coordinator, and then completes its data communication with the set-top box through the USB-TTL module. The interface circuit of the ZigBee coordinator and the USB-TTL module is shown in FIG.

Figure 3 Coordinator and USB-TTL module interface circuit

2.3 MT8389 and Internet Interface Design MT8389 is the main control chip of the set-top box motherboard. It collects and comprehensively processes the data from the wireless sensor network, video capture terminal and Internet terminal, and then collects the data through the DM9000 single-chip Fast Ethernet MAC controller module. Upload to the server. MT8389 and network interface circuit design shown in Figure 5.

3, system software design 3.1 WSN protocol stack and coordinator and terminal node communication program design The system's wireless sensor network protocol stack uses TI's Z-StackTM protocol stack, the protocol stack is complete, open source, good stability, can guarantee data Real-time transmission. The entire Z-Stack protocol stack architecture is shown in Figure 6. The Z-Stack protocol stack is executed from main, performs initialization of the system hardware platform, and then initializes the operating system. This part is completed by the osal_init_system function, and the operating system entity is executed by osal_start_system() to start querying the event table. If there is no scheduling, The polling type judgment is always performed. When an event occurs, the corresponding task layer calls the idx corresponding to the event in the task processing function tasksEvents[idx], and the scheduling function is sequentially changed from high to low according to the event task priority. arrangement. The coordinator and terminal node serial communication program design is developed under Linux, mainly through the read and write operations on the USB device to assist in the completion. The USB device read/write program under Linux has been integrated into the set-top box operating system. Through the program coordinator and the MT8389 main controller, the two-way communication between the two can be completed by means of the USB-TTL module. The specific process is as shown in Fig. 7. Show.

3.2 Server and mobile client program design process The interaction between the server and the mobile phone client and the set-top box is completed through the Internet network. The communication method is socket communication with low data loss rate, simple use and easy portability. The socket communication first establishes two-way connection and connection. After the establishment is completed, the data transmission is started, and the operation of actively pushing the information can be completed in the connection state, and it is not necessary for the client to send a request to the server every time. The socket provides a port for communication with the outside world within the program, providing a channel for data transfer between the two parties. The programming process is shown in Figure 8.

3.3 PC software design Mobile client and set-top box applications use Android platform, using Java programming, the host computer programming interface shown in Figure 9. The user can display the current temperature and humidity, light intensity, flammable gas concentration and other data in real time, and can view the trend of each data in the past time through the alarm item in the navigation bar. When an abnormal situation occurs, the abnormal information is pushed to the display interface. The user can click the abnormal icon to view the abnormal type. At the same time, the user can click the video view icon under the abnormal situation icon to remotely access the indoor situation through the 3G network or the Internet network. Monitoring.

Conclusion <br> This smart home security system features high stability, low false alarm rate, safe and convenient operation, and simple operation. It allows users to view indoor combustible gas concentration, temperature and humidity, and light intensity in any place that can be connected to the network. Waiting for the situation. Abnormal situation push and background automatic processing can help users to grasp the indoor situation in real time and further provide security measures. Users can remotely call video data to view the cause of abnormality in real time, and provide more reliable basis for protecting family members' life and property safety. . It has important reference value in the design of modern smart home security system.

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