Design of infrared intrusion detection system based on ZigBee protocol

Based on the study of wireless sensor networks (WSN) and ZigBee protocol, a design scheme of infrared intrusion detection system based on ZigBee technology is proposed. This scheme takes advantage of the advantages of ZigBee technology in short-range wireless communication, uses Microchip's RF chip MFR24J40, and adopts active infrared intrusion detection device to realize real-time detection and alarm of intrusion objects.

In recent years, with the development of science and technology and the improvement of people's awareness of safety precautions, intrusion detection and alarm technology based on infrared technology has begun to be applied to anti-theft systems [1]. Existing infrared intrusion detection systems mostly use wired technology for networking. The disadvantages of this type of solution are poor scalability, cumbersome wiring, and high false alarm rate when the line is aged or worn. Wireless intrusion detection networks built using wireless transmission methods can avoid these problems. Relatively speaking, wireless methods are more flexible and can adapt to the needs of mobility or changes. However, the application of wireless communication technology in the security field is relatively rare.

Wireless sensor networks (WSNs) are a revolution in information perception and collection technology. Due to their flexible deployment and simple maintenance, they have broad application prospects in many aspects such as environment, events, monitoring, and deep water.

ZigBee technology is a short-range, low-complexity, low-power, low-data-rate, low-cost two-way wireless communication technology [2] that can be embedded in a variety of devices and supports geolocation. Compared with various existing wireless communication technologies, ZigBee technology has the characteristics of ultra-low power consumption and cost, and is suitable for carrying services with small data traffic. Therefore, ZigBee technology is very suitable for use in wireless sensor network-related applications.

Based on the study of ZigBee protocol, this paper proposes a design scheme of active infrared intrusion detection system based on ZigBee protocol, which has good scalability and low false alarm rate.

1 System Design

As shown in Figure 1, there are 8 monitoring points (rooms) on a flat floor of a building. In view of this situation, the system can adopt a star-shaped network. The entire system consists of wireless infrared intrusion detection nodes, regulator nodes, monitoring hosts and PCs. Among them, a wireless infrared intrusion detection node is installed in each room as a terminal node to monitor the room for security and send a security status signal to the regulator node at regular intervals. As the central node of the entire network, the regulator node is responsible for establishing the network, receiving terminal devices (infrared intrusion detection nodes) to join the network, and transmitting and forwarding data. The measurement and control host is also a terminal device, but unlike the wireless infrared intrusion node, it is responsible for receiving the monitoring status sent by the regulator and sending it to the PC through the serial port. The security status of each monitoring point can be viewed in real time on the PC. When an object invades, the alarm device is immediately activated and the number of the invaded room is displayed on the PC, so that security personnel can respond quickly.

If you want to monitor a multi-story building or a residential area, you can use a tree topology to build a network. Each floor or each building has a coordinator that is responsible for collecting data, exchanging data with the central coordinator, and forwarding the data to the monitoring host.

2 Hardware Node Design

[page]

The design of hardware nodes[3] is a key. Among them, the terminal device (wireless infrared intrusion detection node) is similar to the coordinator structure, but has an additional intrusion detection unit. As shown in Figure 2, the infrared detection node consists of four parts: the intrusion detection unit is responsible for sensing the security status of the monitoring point and sending it to the microcontroller through the AD converter; the microprocessor component is responsible for coordinating the work of various parts of the node and performing necessary processing and storage; the wireless communication unit uses a dedicated ZigBee radio frequency chip MRF24J40 to exchange data with other nodes; the energy supply module provides the energy necessary for the work of other functional units.

2.1 Intrusion Detection Unit

As shown in Figure 3, the intrusion detection unit uses an active infrared sensor circuit, which is characterized by a low false alarm rate. The unit includes an infrared transmitting part and an infrared receiving part. The transmitting part is excited by AC, and a pulse generating circuit is formed by NE555, and a pair of lenses are added to enhance the transmission distance. The receiving part uses a PIN photodiode to receive infrared light and U2 amplifies the received weak signal by 20,000 times. U3 is a voltage comparator, and the reference voltage is 0.8V. When there is no intrusion, the infrared light is normally received, amplified, and rectified by the photodiode, and a voltage higher than the reference value of 0.8V is generated at the positive input pin of U3. At this time, Vout output is high level. When an object invades, it will partially or completely block the emitted infrared light. At this time, the signal received by the photodiode is greatly weakened or disappears, so the voltage generated by the positive input pin of U3 will be less than the reference voltage, and Vout output is low level, and an alarm signal will be generated.

2.2 Wireless Transmission Part

Microchip's RF chip MRF24J40 is a 2.4GHz IEEE 802.15.4 transceiver for ZigBee protocol and proprietary wireless protocol, suitable for RF applications that require low power consumption and excellent RF performance. The PIC 8-bit microcontroller has a unique RISC structure and a Harvard bus structure with separate data bus and instruction bus, which makes the instruction have a single word length and allows the instruction code to have more than 8 bits. Compared with the traditional 8-bit microcontroller with CISC structure, this can achieve 2:1 code compression and increase the speed by 4 times. Based on the above characteristics, the PIC 8-bit microcontroller and MRF24J40 are used to form the wireless transmission part of the node.

[page]

As shown in Figure 4, the PIC microcontroller is connected to the MRF24J40 via the SPI bus and some discrete control signals. The controller acts as the SPI master and the MRF24J40 acts as the slave. The controller implements the IEEE 802.15.4 MAC layer and the ZigBee protocol layer. It also contains application-specific logic. It uses the SPI bus to interact with the MRF24J40 transceiver. Wireless communication is achieved with fewer wires.

3. Software Design

The focus of the software design [4] is the porting and application of the ZigBee protocol. Microchip provides a ZigBee-based protocol stack. The protocol stack has the following features: support for simplified functional devices and coordinators; non-volatile storage of adjacency tables and binding tables in the coordinator node; support for non-time-slot star networks; and portability between most PIC18 series microcontrollers. Based on the above features, this system uses the protocol stack to build a star network. The regulator node is the central node of the entire network, responsible for forming the network and receiving terminal devices to join the network. As shown in Figure 5, the coordinator starts networking by sending the NLME-NETWORK-FORMATION. request primitive, and then sends the MLME-SCAN. request primitive to start channel detection. When a suitable channel is found, the MAC layer will send the MLME-SCAN. confirm primitive to the network layer. After receiving the primitive, the network layer entity (NLME) will select the best channel to establish a new network, select a PAN ID and logical address for the network, and send the NLME-NETWORK-FORMATION. confirm primitive back to the application layer. After such a process, a new network is established.

[page]

Figure 6 is the main program flow chart of the coordinator node. When the coordinator establishes a new network, the terminal device (wireless infrared intrusion detection node) requests to join the network. When the device successfully joins the network, the coordinator collects the detection data of each detection node at a regular interval. When an intrusion is detected, the coordinator transmits the information of the invaded monitoring point (room number) to the monitoring host, and the security personnel can view the security situation of the monitoring point in real time and respond.

Sensor network is one of the important technologies that will affect human life in the future. It combines multiple new technologies such as sensors, microcontrollers, radio frequency communications, and networks, providing people with a new way to obtain and process information.

This paper proposes a design of an infrared intrusion detection system based on wireless sensor networks and ZigBee protocol. This design can reduce the false alarm rate of infrared alarms, reduce the complexity of construction, and has good scalability, and can provide reliable data for security monitoring.

References

[1] Tian Liang, He Peixiang, Li Qingdong, et al. Design of a new intelligent infrared anti-theft system[J]. Laser & Infrared, 2006, 36(7):580-581.

[2] Wang Kai, Peng Yu, Zheng Liguo, et al. Research and design of automatic meter reading system based on ZigBee wireless water meter [J]. Automation Instrumentation, 2006, 27:166-169.

[3] Wu Jian, Yuan Shenfang. Design and implementation of wireless sensor network nodes[J]. Chinese Journal of Scientific Instrument, 2006, 27(9):1120-1123.

[4] ZigBee Alliance． ZigBee Specification[S]． ZigBee Alliance, 2004, 221.

[5] Zhan Haomin, Sun Changsong, Wu Shan, et al. Application of ZigBee technology in underground coal mine rescue system [J]. Computer Engineering and Applications, 2006, 42(24):181-183.

[6] Qiu Huimin, Shi Xinru, Yang Yixian, et al. A secure wireless sensor node structure design scheme[J]. Computer Engineering and Applications, 2006, 42(11):116-118.

[7] Zhu Xiangqing, Wang Jianming. Research and implementation of ZigBee protocol network layer[J]. Electronic Technology Application, 2006, 32(1):129-132.

[8] Chen Shuai, Zhong Xianxin, Liu Jixue, et al. New progress and applications of wireless sensor networks[J]. Piezoelectrics & Acoustooptics, 2006, 28(3):297-299.