Design of Automobile Anti-theft Alarm System Based on GSM Network

The GSM (G10bal System for Mobile Communication) network is a system based on time division multiple access technology and frequency division multiple access technology, and belongs to the second generation of communication technology (2G). The technology is mature and covers a wide range. GSM short message service (sholt Message Service), as a basic service, has attracted more and more system operators and system developers’ attention.

The GSM (G10bal System for Mobile Communication) network is a system based on time division multiple access technology and frequency division multiple access technology, and belongs to the second generation of communication technology (2G). The technology is mature and covers a wide range. As a basic service of GSM short message service, more and more system operators and system developers pay attention.

Traditionally, there are many problems, such as short operating distance, environmental pollution caused by alarm noise, and false alarms often occur. These problems have brought great troubles to residents’ lives, and some residential areas even prohibit the installation of alarms.

The car alarm system designed using GSM network, with the addition of software intelligent design control, can easily solve the above-mentioned problems.

1 System structure and principle

The system structure is shown in Figure 1. After the car alarm detects the signal, it transmits the alarm signal to the user’s mobile phone through the software processing system and the GSM network. Long-distance transmission of alarm signals is realized.

Design of Automobile Anti-theft Alarm System Based on GSM Network

The main hardware structure of the system is shown in Figure 2. The detection signal is input through P0. 0 and P0.1, and the interrupt mode is not used to prevent false alarms. The control signal is output through P0.7. Connect to the serial port of TC35 through the level conversion chip MAX202. Because it is asynchronous serial communication, no-flow control mode can be used, just connect 2, 3, and 5 of interface J1.

Design of Automobile Anti-theft Alarm System Based on GSM Network

2.1 Introduction to TC35 module

TC35 is a high-performance GSM module developed by Siemens, which is easy to integrate in the application system. Its characteristics are: (1) the frequency band is dual-frequency GSMg00MHz and GSMl800MHz (phase2/2+); (2) supports data, voice, short message and fax; (3) wide range; (4) RS and voice interface.

2.2

Pyroelectric sensors or vibration sensors can be used. The pyroelectric infrared sensor outputs electrical signals by detecting infrared rays emitted by humans or animals, with an acting angle of 110°. BISS001 infrared finished components can be used, and the working distance is adjusted by the Fresnel lens. The vibration sensor can use the ND-l type highly sensitive vibration displacement sensor. It is an all-in-one solid-state control device integrating vibration and vibration. It has high detection sensitivity to vibration, suppresses the sound signal of the surrounding environment, and has a strong anti-interference ability. Its sensitivity is adjustable through.

2.3 Control

When the user receives the alarm message, if he needs to take measures, he can dial the TC35 module. After receiving the signal, send an ATH command to hang up the dialing, and then send a control signal to the P1.7 port. After the control signal is amplified by the operational amplifier, the ignition wire is cut off to ensure the safety of the car. To recover, dial TC35 again. The internal resistance of the relay is very small and must be driven by an OC gate. The driving circuit is shown in Figure 3.

Design of Automobile Anti-theft Alarm System Based on GSM Network

3 software design

3.1 AT commands related to SMS

The command interface provided by the GSM engine module complies with GSM07.05 and GSM07.07 specifications. The AT Command interface defined in GSM07.07 provides a general interface between the mobile platform and data terminal equipment; GSM07.05 has detailed provisions for short messages, and the short message from the network is received in the short message module At this time, the instruction message can be sent through the serial port, and the data terminal device can send various commands to the GSM module. The GSM AT commands related to SMS are shown in Table 1.

Design of Automobile Anti-theft Alarm System Based on GSM Network

The AT commands used in this system are as follows:

Send: AT+CMGF=0 //Set the format of short message sending

Answer: OK

Send: AT+CMGS=24 //The length of the short message, please note that it is decimal.

Answer:>

Send: 0001030D91683108480646F932080A67094EBA-52A88F66FF01 //PDU data packet

Answer: +CMGS:[,]

3.2 Introduction to PDU format

Currently, text and PDU (Prutoeol Data Unit) modes are commonly used to send short messages. The code for sending and receiving short messages in Text mode is simple and easy to implement, but the biggest disadvantage is that it cannot send and receive Chinese short messages; and PDU mode not only supports Chinese short messages, but also can send English short messages. Three kinds of codes can be used for sending and receiving short messages in PDU mode: 7-bit, 8-bit and UCS2 codes. 7-bit encoding is used to send ordinary ASCII characters, 8-bit encoding is usually used to send data messages, UCS2 encoding is used to send Unicode characters, and the encoding type is specified in the PDU data packet.

The following examples illustrate the composition of the PDU format. For example, if you want to send the five words “Someone moving a car!” to 13808460649, the PDU data is:

0001030D91683108480646F932080A67094EBA52A88F-66FF01

(1) 00 means omitting the SMS center number;
(2) 01 represents the file header byte;
(3) 03 represents the information type (TP-Message-Reference);
(4) 0D represents the length of the called number;
(5) 91 indicates the type of called number;
(6) 683108480646F9 represents the called number, which has undergone displacement processing;
(7) 32 represents the protocol identification TP-PID;
(8) 08 represents the data coding scheme TP-DCS, because the U-NICODE inner code is to be sent, USC2 (16bit) coding is used;
(9) 0A represents the user data length TP-UDL (in 8-bit code as the unit (octet));
(10)67094EBA52A88F66FF01 represents user data.

3.3 Chinese character encoding

As in the GSM standard, the Chinese encoding uses Unicode instead of the currently commonly used GB-2312 encoding in China, so just convert the decimal Unicode encoding to hexadecimal, or it can be obtained from the GB-2312 encoding through conversion. . For example, the decimal Unicode codes of the two characters “Hello” are 24744 and 22909 respectively, which are converted into hexadecimals as 60A8 and 597D.

3.4 Alarm strategy

In order to distinguish the urgency of the situation, two short messages can be set. If a signal is detected by a single detector, SMS 1 will be sent; if both signals are detected, SMS 2 will be sent. After sending the short message, the user can cut off the ignition wire only by dialing. If there is a problem with the network, dial the user’s mobile phone.

3.5 Software process

In the main program, 89C51 uses clever algorithms to sample infrared signals and vibration signals, which is equivalent to integrating the signals. If 80% of the signal is valid within 4 seconds (adjustable according to the actual situation), it means that there is an intrusion of illegal personnel. After the alarm signal is generated, it is controlled by the program to ensure that the second alarm signal will not be generated within 15 minutes.

The main loop of the program is shown in Figure 4.

Design of Automobile Anti-theft Alarm System Based on GSM Network

Experiments have verified that the use of a GSM short message-based communication method to control the car alarm system can not only improve the communication reliability of the alarm system, but also the communication distance is basically unlimited, thus realizing long-distance real-time monitoring of the car by users. In addition, the system can also distinguish the urgency of intrusion, which is convenient for users to take measures according to the situation and meets the requirements of car users. The cost of this system is not high and it is easy to promote. Through practical applications in a variety of vehicles, the system works well.

The GSM (G10bal System for Mobile Communication) network is a system based on time division multiple access technology and frequency division multiple access technology, and belongs to the second generation of communication technology (2G). The technology is mature and covers a wide range. GSM short message service (sholt Message Service), as a basic service, has attracted more and more system operators and system developers’ attention.

The GSM (G10bal System for Mobile Communication) network is a system based on time division multiple access technology and frequency division multiple access technology, and belongs to the second generation of communication technology (2G). The technology is mature and covers a wide range. As a basic service of GSM short message service, more and more system operators and system developers pay attention.

Traditionally, there are many problems, such as short operating distance, environmental pollution caused by alarm noise, and false alarms often occur. These problems have brought great troubles to residents’ lives, and some residential areas even prohibit the installation of alarms.

The car alarm system designed using GSM network, with the addition of software intelligent design control, can easily solve the above-mentioned problems.

1 System structure and principle

The system structure is shown in Figure 1. After the car alarm detects the signal, it transmits the alarm signal to the user’s mobile phone through the software processing system and the GSM network. Long-distance transmission of alarm signals is realized.

Design of Automobile Anti-theft Alarm System Based on GSM Network

The main hardware structure of the system is shown in Figure 2. The detection signal is input through P0. 0 and P0.1, and the interrupt mode is not used to prevent false alarms. The control signal is output through P0.7. Connect to the serial port of TC35 through the level conversion chip MAX202. Because it is asynchronous serial communication, no-flow control mode can be used, just connect 2, 3, and 5 of interface J1.

Design of Automobile Anti-theft Alarm System Based on GSM Network

2.1 Introduction to TC35 module

TC35 is a high-performance GSM module developed by Siemens, which is easy to integrate in the application system. Its characteristics are: (1) the frequency band is dual-frequency GSMg00MHz and GSMl800MHz (phase2/2+); (2) supports data, voice, short message and fax; (3) wide range; (4) RS and voice interface.

2.2

Pyroelectric sensors or vibration sensors can be used. The pyroelectric infrared sensor outputs electrical signals by detecting infrared rays emitted by humans or animals, with an acting angle of 110°. BISS001 infrared finished components can be used, and the working distance is adjusted by the Fresnel lens. The vibration sensor can use the ND-l type highly sensitive vibration displacement sensor. It is an all-in-one solid-state control device integrating vibration and vibration. It has high detection sensitivity to vibration, suppresses the sound signal of the surrounding environment, and has a strong anti-interference ability. Its sensitivity is adjustable through.

2.3 Control

When the user receives the alarm message, if he needs to take measures, he can dial the TC35 module. After receiving the signal, send an ATH command to hang up the dialing, and then send a control signal to the P1.7 port. After the control signal is amplified by the operational amplifier, the ignition wire is cut off to ensure the safety of the car. To recover, dial TC35 again. The internal resistance of the relay is very small and must be driven by an OC gate. The driving circuit is shown in Figure 3.

Design of Automobile Anti-theft Alarm System Based on GSM Network

3 software design

3.1 AT commands related to SMS

The command interface provided by the GSM engine module complies with GSM07.05 and GSM07.07 specifications. The AT Command interface defined in GSM07.07 provides a general interface between the mobile platform and data terminal equipment; GSM07.05 has detailed provisions for short messages, and the short message from the network is received in the short message module At this time, the instruction message can be sent through the serial port, and the data terminal device can send various commands to the GSM module. The GSM AT commands related to SMS are shown in Table 1.

Design of Automobile Anti-theft Alarm System Based on GSM Network

The AT commands used in this system are as follows:

Send: AT+CMGF=0 //Set the format of short message sending

Answer: OK

Send: AT+CMGS=24 //The length of the short message, please note that it is decimal.

Answer:>

Send: 0001030D91683108480646F932080A67094EBA-52A88F66FF01 //PDU data packet

Answer: +CMGS:[,]

3.2 Introduction to PDU format

Currently, text and PDU (Prutoeol Data Unit) modes are commonly used to send short messages. The code for sending and receiving short messages in Text mode is simple and easy to implement, but the biggest disadvantage is that it cannot send and receive Chinese short messages; and PDU mode not only supports Chinese short messages, but also can send English short messages. Three kinds of codes can be used for sending and receiving short messages in PDU mode: 7-bit, 8-bit and UCS2 codes. 7-bit encoding is used to send ordinary ASCII characters, 8-bit encoding is usually used to send data messages, UCS2 encoding is used to send Unicode characters, and the encoding type is specified in the PDU data packet.

The following examples illustrate the composition of the PDU format. For example, if you want to send the five words “Someone moving a car!” to 13808460649, the PDU data is:

0001030D91683108480646F932080A67094EBA52A88F-66FF01

(1) 00 means omitting the SMS center number;
(2) 01 represents the file header byte;
(3) 03 represents the information type (TP-Message-Reference);
(4) 0D represents the length of the called number;
(5) 91 indicates the type of called number;
(6) 683108480646F9 represents the called number, which has undergone displacement processing;
(7) 32 represents the protocol identification TP-PID;
(8) 08 represents the data coding scheme TP-DCS, because the U-NICODE inner code is to be sent, USC2 (16bit) coding is used;
(9) 0A represents the user data length TP-UDL (in 8-bit code as the unit (octet));
(10)67094EBA52A88F66FF01 represents user data.

3.3 Chinese character encoding

As in the GSM standard, the Chinese encoding uses Unicode instead of the currently commonly used GB-2312 encoding in China, so just convert the decimal Unicode encoding to hexadecimal, or it can be obtained from the GB-2312 encoding through conversion. . For example, the decimal Unicode codes of the two characters “Hello” are 24744 and 22909 respectively, which are converted into hexadecimals as 60A8 and 597D.

3.4 Alarm strategy

In order to distinguish the urgency of the situation, two short messages can be set. If a signal is detected by a single detector, SMS 1 will be sent; if both signals are detected, SMS 2 will be sent. After sending the short message, the user can cut off the ignition wire only by dialing. If there is a problem with the network, dial the user’s mobile phone.

3.5 Software process

In the main program, 89C51 uses clever algorithms to sample infrared signals and vibration signals, which is equivalent to integrating the signals. If 80% of the signal is valid within 4 seconds (adjustable according to the actual situation), it means that there is an intrusion of illegal personnel. After the alarm signal is generated, it is controlled by the program to ensure that the second alarm signal will not be generated within 15 minutes.

The main loop of the program is shown in Figure 4.

Design of Automobile Anti-theft Alarm System Based on GSM Network

Experiments have verified that the use of a GSM short message-based communication method to control the car alarm system can not only improve the communication reliability of the alarm system, but also the communication distance is basically unlimited, thus realizing long-distance real-time monitoring of the car by users. In addition, the system can also distinguish the urgency of intrusion, which is convenient for users to take measures according to the situation and meets the requirements of car users. The cost of this system is not high and it is easy to promote. Through practical applications in a variety of vehicles, the system works well.

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Author: Yoyokuo