Research on GSM Family Car Anti-theft Alarm System

Abstract: Nowadays, people are constantly pursuing material life, and cars have gradually entered the family and become a popular means of transportation. However, due to the development of science and technology, car theft technology is getting higher and higher, which makes people hard to guard against. Car burglar has extremely important research value for both automobile manufacturers and social insurance industry. It is aimed at the popular burglar alarms on the market. Most of the products have shortcomings such as single anti-theft function, low reliability, lack of tracking and monitoring functions. The paper designs a car anti-theft system based on GSM communication platform and GPS satellite positioning. Through the design of embedded system, wireless using GSM short message. The communication protocol builds an interactive platform for communication between the owner, the monitoring center and the car, and realizes the combination of car navigation and anti-theft functions.
Keywords: GSM (Global System for Mobile Communications); car anti-theft system; embedded system; communication protocol

In response to the current upward trend of car theft in the world, various automobile manufacturers are constantly improving the anti-theft technology, especially with the advancement of microelectronic technology, car anti-theft technology has been developing towards automation and intelligence. Car alarms are roughly classified into four categories according to their structure and function: mechanical, electronic, chip and network. Among them, the mechanical lock is the most traditional anti-theft device, generally not used alone; the electronic anti-theft system is currently the most widely used device; and the chip-type digital anti-theft device and the network anti-theft system is the development direction of the car anti-theft system. According to the basic principle of car anti-theft system and the GSM short message protocol used in system data information processing, this paper introduces the hardware structure of the system in detail, including system power circuit, microcontroller MSP430F149, GSM wireless module, TC35, GPS receiver module and Peripheral detection control circuit. The advantage of this system relative to other types of anti-theft alarm systems on the market is that some ordinary electronic anti-theft devices that have been installed on the owner's car can be converted into a network-type car anti-theft system, thereby greatly reducing the user's cost investment and improving the cost performance of the product.

1 The working principle of the anti-theft system The car anti-theft system is a platform that comprehensively uses embedded technology, GPs technology (4), GSM wireless communication technology. The system uses a mobile phone network as a communication medium. The GPs positioning technology, electronic technology, computer technology and other means are used to monitor and track the monitored vehicles in an all-round way, and the corresponding data information is transmitted to the monitoring center through the GSM network. The vehicle terminal detects the state of the vehicle. If an abnormality is found in the vehicle, an alarm message is sent to the monitoring center and the user. It also receives commands from the monitoring center and the user, and parses the commands to perform the corresponding operations. The anti-theft system is mainly composed of an in-vehicle terminal, a wireless communication network and a monitoring center. The composition principle of the system is shown in Figure 1.

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2 System hardware design The GSM-based car anti-theft system mainly consists of: vehicle terminal (microcontroller, GPs module, GSM module, sensing circuit), transmission network (GSM network), monitoring center, user mobile phone. Based on the analysis of the communication platform, positioning technology, function and performance requirements of the system, the overall design scheme of the system is proposed. Figure 2 shows a block diagram of the hardware structure of the system.

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The main technical indicators of the hardware include:
1) Two UART serial ports are required.
2) Due to the complexity of the program, online simulation needs to be supported.
3) GPS positioning requires positioning accuracy within 10 m.
4) The processing speed of the MCU is required to be high.
5) Since the entire system draws power from the car battery, the system power consumption is required to be low.
6) Using the signal light to reflect the system status, the power indicator light, the GSM search network indicator and the GPS positioning indicator are required.
2.1 MSP430 MCU Introduction The control core selected in the design is MSP430F149 MCU is one of TI's MSP430 series MCUs. This series of MCUs has a 16-bit RISC structure, which can achieve high code efficiency. MSP430 series MCU also has the following remarkable features:
1) Low voltage, low power consumption, stable operation between 1.8 and 3.6 V, and the current consumption can be reduced to less than 400 μA when the system clock frequency is low.
2) Strong processing power. The MSP430 family of microcontrollers has a 16-bit RISC architecture and a compact core instruction system with an instruction cycle of 125 μs when operating at an 8 MHz system clock.
3) Stable working performance. In the MSP430 microcontroller, the built-in watchdog, while the system can switch between multiple clock sources to ensure the normal operation of the system.
4) Rich on-chip resources. The MSP430 series has built-in rich on-chip resource modules, including watchdog (WDT), timer A (Timer A), timer B (Timer B), comparator, serial port 0, serial port 1, hardware multiplier, and mode. Digital conversion (ADC), basic I/O port, basic timer, etc.
5) Industrial grade products. MSP430 series MCUs are industrial grade products with an operating temperature range of -40 degrees to +85 degrees and strong anti-interference ability. The internal structure of MSP430F149 microcontroller is shown in Figure 3.

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2.2 GSM module TC35
TC35 is a new generation wireless communication GSM module launched by Siemens. It can quickly and safely realize data, voice transmission, short message service (Short Messa ge Service) and fax in system solution. TC35 module is mainly composed of GSM baseband processor and GSM. The RF module, power supply module (ASIC), flash memory, ZIF connector, and antenna interface are composed of six parts, as shown in Figure 4.

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2.3 GPS receiver The GPS receiver, which is the main component of the GPS user, is used to receive and process satellite position information sent by GPS satellites. The receiver is composed of a host antenna, an arithmetic unit, an output channel, and the like. The core of the host is composed of a low noise amplifier, a channel circuit, a central processing unit, a memory, and the like. Under the operation of the software, the receiver receives, acquires, amplifies, identifies, stores, processes, and outputs useful positioning information, speed information, and time information. In the secondary development of the GPS receiver, the TARMIN GPS25-LVC receiver was used. Figure 5 shows the schematic diagram of the receiver.

3 module circuit design
3.1 System Power Supply High quality power supplies are the basis for stable hardware performance. Stable output voltage, large output current, small temperature drift and heat generation are the standards for measuring power quality. How to design a reliable and stable power system is the focus of the entire hardware design. Since this system needs to be powered by car battery, the input voltage is about 12 V, and there are three kinds of output voltage: TC35 needs power supply voltage 3.3~5.5 V, here we choose 3.5 V; MSP430F149 needs power supply voltage 3. 3 V; 5 V supply voltage required by other devices; main current consumption of each module: GPS25LP-LVC input current is 140 mA typical, input current is small when TC35 is idle, but peak current can reach 2 when data transmission A; other circuits consume less power, about tens of milliamps. Figure 6 shows the power supply circuit of the system.

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3.2 TC35 module interface circuit design The TC35 module is mainly connected to the serial port of the MCU through two wires (TXD, RXD), thus realizing the control of the TC35 module by the MCU. Figure 7 below shows the interface design of the TC35 module.

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3.3 GPS25LP-LVC circuit GPS25LP-LVC only needs to be connected to the system through a 12-pin pin. TXD1 and RXD1 are GPS25LP-LVC communication ports, which are 5 V logic level and can be directly connected to the serial port of MSP430F149. Connected; pin 10 is the power supply of GPS25LP-LVC. In order to ensure the stability of its operation, a 10MF holding capacitor can be added between pin 10 and pin 8. As shown in Figure 8.

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3.4 Single-chip processing circuit The single-chip circuit is the core control part of the whole system, mainly to complete communication with TC35 and GPS25LP-LVC modules. The serial port 1 is used for communication between the MSP430F149 and the TC35, and the serial port 0 is used for communication with the GPS25LP-LVC. Since they are all CMOS/TTL levels, no level shifting is required. The specific circuit is shown in Figure 9.

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3.5 Car burglar alarm circuit The ignition lock and manual lock installed on the car can not effectively prevent the car from being stolen. Therefore, many modern cars have installed electronic burglar alarms. When a theft occurs, the alarm horn will continue to sound for a period of time while the car is powered off. However, if the user is far away from the car, when someone tries to enter the car or other East two collision cars, the user can not hear the alarm sound of the speaker, causing some unclear loss, so only the speaker can not achieve the purpose of theft prevention. The anti-theft system can turn the alarm signal of the alarm into a short message "Your car is moved, go and see" and send it to the user to remind the attention, fully realize the purpose of remote monitoring of the car. The state of detecting the alarm speaker line is used to determine whether there is a theft situation, as shown in FIG.

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3.6 Other functional circuits 1) Liquid crystal display module The human-machine interface module is a bridge between the user and the controller, and is mainly composed of a keyboard and a display. The keyboard implements the modification of the controller parameters, and the display is used to display various parameters of the system and the operating state of the system. This controller uses a CGM-12232 dot matrix LCD with two SED1520FOA driver chips. The current operating status of the system can be visually displayed through the LCD screen.
2) Keyboard interface In the system design, the keyboard interface adopts 4X4 determinant matrix keyboard interface, which uses the query scanning method to work. The row and column lines respectively use 4 data lines. The keyboard has 16 keys, among which there are 0-9 total 10 numeric keys; a function switching key can be used to input the user's mobile phone number and detect the left front and rear doors of the car, the front and rear doors and the front cover box and the back cover box are opened abnormally; ENTER OK button, one CANCEL cancel button, three reserved buttons, as shown in Figure 11.

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4 Conclusion The embedded car anti-theft system based on GSM/GPS is an extension of the traditional anti-theft device field by using mobile communication technology and satellite positioning technology. The system proposed in this paper adopts new technologies such as GSM and GPS. By designing a communication platform with remote monitoring function, it provides a comprehensive solution for vehicle anti-theft and monitoring, and provides a technical basis for the development of wireless network of car anti-theft system. The installation of the GPS module on the original vehicle anti-theft system will enable the system to retain the original connection with the car navigation system, and can be independently put into the market independently of the car navigation system, greatly increasing the practicality of the system. , has a broad application prospects.

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