『Abstract〠This article first briefly introduces the working principle and design process of the GSM car anti-theft alarm system developed by the company. Next, it will introduce in detail the working principle of the new acceleration sensor introduced by Freescale Semiconductor, and the practical application of the combination with the car anti-theft GSM alarm. Finally, the design uses the acceleration sensor, the existing problems, and the design improvement ideas.
1 Introduction
With the vigorous development of China's economy, people's living standards are increasing, the application of automobiles is developing rapidly, and the ownership of various types of automobiles is constantly increasing. The popular application of cars has brought convenience to people's lives, but at the same time, the use of cars has also raised a big problem for people - car anti-theft. Car anti-theft has become a hot topic in the lives of car owners, and is also a hot spot for car manufacturers. At present, various car anti-theft methods and products are emerging one after another. However, the car anti-theft problem is still not completely solved, it can be said that the road is one foot high and the devil is one foot high. Car theft cases still occur from time to time, causing great losses to people's lives and property. Existing methods are based on physical measures, such as anti-theft doors, anti-theft windows; there are also electronic means, such as electronic door locks, electronic alarms and so on.
With the development of technology, cars are becoming more and more secure, but the means of stealing car thieves is becoming more and more sophisticated. The anti-theft window can still be broken, and the electronic lock can be opened, that is, the physical path of car theft cannot be completely cut off. We can imagine such a car theft scene: the car was first towed to a remote corner (abnormal movement), then the window or door was opened (abnormal vibration and vibration), and the car was stolen. So we want to automatically and quickly detect these abnormal situations, and at the same time, fast and effective alarms?
This design is to solve the shortcomings and shortcomings of the traditional car anti-theft method and develop a new integrated anti-theft GSM alarm system with three functional modules of sensing, control and alarm. By installing the alarm in the car, when the sensor receives When the vehicle vibrates and moves signals, the GSM network is used as the channel, and the alarm information is notified to the user by SMS/telephone, thereby realizing an accurate and real-time alarm effect.
2 car anti-theft GSM alarm features
The current popular car alarms can be easily classified into three categories, namely: mechanical anti-theft devices, electronic anti-theft devices and network anti-theft devices. From the difficulty of cracking the car thief, the higher the technological content of the above three types of anti-theft devices However, the price is basically proportional to the scientific and technological content.
(1) Mechanical anti-theft device
The mechanical anti-theft device is the simplest and cheapest anti-theft device on the market. The principle is very simple, that is, locking the steering wheel, control pedal or handle.
Advantages: cheap, easy to install, a few hundred dollars or even tens of dollars can be fixed.
Disadvantages: The anti-theft is not complete, it is troublesome to disassemble each time, and you have to find a place to place when not in use.
(2) Electronic alarm
Electronic anti-theft device electronic anti-theft is to add the electronic identification code to the car lock, unlocking or keying all need to enter more than a dozen passwords. The biggest selling point of electronic anti-theft is password unlocking and voice alarm.
The main functions of the electronic anti-theft device are as follows: voice alarm function, safety reminder function, remote car search function, central door lock remote control function.
(3) Network alarm
The network anti-theft device utilizes modern electronic information technology, aerospace technology and network technology to realize real-time information feedback of cars and car owners, and is represented by the Global Positioning System (GPS). It uses the receiving satellite transmitting signal to form a global positioning system with the ground monitoring equipment and the GPS signal receiver. The satellite constellation continuously sends the dynamic target--the three-dimensional position, speed and time information of the car, and receives the feedback information to know the car at that time. The location. The current GPS system has various functions such as vehicle positioning, anti-robbery alarm, network anti-theft, remote control flameout, in-vehicle monitoring, anchor rescue, road condition information, manual navigation, vehicle inquiry and the like.
The defects of GPS anti-theft: First, the GPS in the area where the satellite positioning ground monitoring center is not established cannot work; secondly, due to the limited number of satellites, there is a certain “blind zone†in the information scanning coverage, so that the monitoring is often in a discontinuous “lost†state; The price is generally more than several thousand yuan. It costs about six or seven thousand yuan to install a GPS without a display screen, and it is necessary to pay a service fee of nearly one thousand yuan to the service provider every year. The high cost has discouraged many car owners.
The car anti-theft GSM alarm system developed by the company is a high-tech product integrating the traditional vehicle-mounted anti-theft alarm unit and GSM global mobile communication network control. The product does not need to have an operation center, relying on the GSM public network with high coverage, using GSM wireless communication service and short message value-added service, adopting the interactive anti-theft mode of the vehicle and the vehicle to remotely monitor and locate the vehicle; Remote control call voice alarm function, send and remote control off alarm short message function, robbed alarm button, vibration alarm and other functions, so that the owner can get rid of the passive burglary situation that can not be seen or heard; no need to set up an operation center, solve the GPS The high cost of access to the network and the small monitoring range of ordinary vehicle burglar alarms, and the troublesome sound and noise, can make your car at your fingertips anytime, anywhere.
3 The working principle and design process of this design
The working principle of the system is: when the car is stolen, because the abnormal motion of the vehicle body is detected by the acceleration sensor, the system CPU passes the analysis, processing and classification algorithm set by the system according to the three-way acceleration information of the two acceleration sensors. , generate several types of alarm information; at the same time, the system CPU controls the GSM module to send a short message alarm.
The realization of the car anti-theft GSM alarm system of this design: Firstly, the acceleration sensor is used to detect whether the car has abnormal movement, abnormal vibration, abnormal vibration, abnormal lifting and abnormal body inclination. Next, the control unit analyzes and confirms the occurrence of the abnormality according to the algorithm model. Finally, the GSM module receives the confirmed abnormal situation signal information, and sends an alarm message to the preset user, such as the public security department, the user, and the second-level user. After receiving the alarm information, the user can call back the monitor to realize the interaction. An application diagram is shown below (see Figure 1):
This article refers to the address: http://
Figure 1 Schematic diagram of the application of the system
The working principle and design process of this design are described in detail below based on the system block diagram and software flow chart.
Figure 2 System function block diagram
As shown in Figure 2, the system is mainly composed of three parts; the sensing module, the control module and the alarm module.
The sensing module consists of two accelerometers: MMA1260D and MMA6260Q. MMA1260D is a 1.5g z-axis acceleration sensor; MMA6260Q is a 1.5g xy biaxial acceleration sensor. The two acceleration sensors can be combined and combined to obtain the acceleration information in three directions of xyz. Get information such as speed and displacement.
The control module is a 56F8323, a 16-bit CPU with excellent DSP-capable, rich MCU peripherals integrated by Freescale Semiconductor. It can be used to sample analog signals input from sensors and integrate it. The SCI controller controls the operation of the GSM module.
The GSM module, which sends alarm messages to complete the system's alarm work.
Figure 3 is a flow chart of the main program of the design system, which mainly realizes the signal acquisition, analysis and extraction, judgment and classification of the acceleration sensor. In addition, it is responsible for controlling the reception and transmission of the corresponding alarm information of the GSM module.
Figure 3 main program flow chart
4 Acceleration sensor principle and application
The performance analysis and application research of Freescale's new accelerometer are a key and difficult point of this design. At the same time, some basic rules have been summarized in the research project of this design, and preliminary attempts have been made for its various application methods. The following briefly introduces the basic characteristics of the acceleration sensor, and then discusses the way and method of its application.
(1) Characteristics of the acceleration sensor
Sensor chip selection: In the X and Y axes, the new product of Freescale Semiconductor, 2004, MMA6260Q chip, which is a biaxial low G MEMS accelerometer, is used in the Z axis. This is a MMA 1260D chip. Z axially sensitive MEMS accelerometer. Microelectromechanical devices are a class of semiconductor devices with many advantages. Accelerometers made with MEMS also have new features not found in conventional sensors. At the heart of the traditional accelerometer is a gyroscope, which is a sophisticated but expensive instrument. Freescale Semiconductor's accelerometer is a surface MEMS process integrated circuit sensor consisting of a surface MEMS process capacitive sensing cell and a signal conditioning ASIC. See Figure 4, It is a simplified functional block diagram of the acceleration sensor:
Figure 4 simplified acceleration sensor function block diagram
(2) Application methods and methods
The research work of this design mainly focuses on the algorithm research of acceleration sensor, and has achieved phased results. Based on the establishment of algorithms and experimental verification, the application of acceleration sensors can be divided into two categories, which correspond to two types of algorithms.
Two types of applications for accelerometers are the application of dynamic acceleration and the application of static acceleration. Among them, the application of dynamic acceleration can be vibration, vibration, movement, detection and control of positioning information; the application of static acceleration can be detection and control of target tilt and rotation information. The application of this design is mainly the application of static acceleration.
Corresponding to two different applications, the acceleration sensor algorithm can be summarized into two categories, namely static acceleration compensation algorithm and dynamic acceleration compensation algorithm. The former is for dynamic acceleration applications, the purpose of which is to exclude static acceleration, that is, the influence of acceleration caused by gravity on the detection result; the latter is for the application of static acceleration, the purpose is to exclude the influence of dynamic acceleration. The implementation of the static acceleration compensation algorithm mainly relies on the method of self-correction of the acceleration balance point; and the dynamic acceleration compensation needs to rely on the method of high-frequency filtering, and the analog low-pass filter or the digital low-pass filter can be used to filter out the voltage corresponding to the acceleration. Because of motion (including translation, vibration, etc.) in the signal.
5 Application and improvement ideas
As mentioned above, this design is primarily an application of an acceleration sensor. Now summarize its application in this design and propose some improvements.
In this design, the basic application of the acceleration sensor is realized, and the high sensitivity of the low-g acceleration sensor is also reflected. However, there are many deficiencies in the application and still need to be improved. Why are these problems occurring? First of all, the acceleration sensor has a certain inductive bandwidth and its changing frequency. The pure software in the design, that is, the pure digital design method is in the defect. The speed of digital-to-analog conversion is limited, so that the fast-changing acceleration signal cannot be well collected and utilized. Secondly, the precision-limited digital-to-analog conversion for continuously varying voltage analogs must sacrifice the accuracy of the analog quantity, and the error of the digital-to-analog conversion itself must be considered to make the calibration of the acceleration difficult.
We will improve in the follow-up research work. Change the original pure software implementation method, change the software and hardware method, and change the original pure software integral, that is, the digital quantity accumulation into the analog integrator method, and use the self-correction of the simulation method. Add an analog low pass filter.
6 Summary
This design focuses on the research of digital signal processing (including differentiation, judgment, noise filtering, morphological analysis, etc.) of the prevention information such as vibration, vibration, tilt, lifting, movement and glass breakage of the acceleration sensor, and combines with the company. The mature technology - GSM SMS sending and alarm technology, constitutes a new application - car anti-theft GSM alarm system, is expected to be promoted to the community during the year.
APM satisfies High Voltage Dc Power Supply application demands, allowing the SP series to cover a voltage range from 0V to 800V. It delivers advanced features. The compact 2U high 19inch wide Adjustable Dc Power Supply were designed to meet the needs of both system integrator and bench top users.
Some features of the Switch Mode Power Supply as below:
- Ultrafast respond time and high efficiency
- Accurate voltage and current measurement capability
- Constant Power and wide range of voltage and current output
- Equips with LIST waveform editing function
- Compliant with SCPI communication protocol
- Support RS232/RS485/LAN/USB (standard) ,GPIB (optional)
- Built-in standard automobile electrical testing curves
- Full protection: OVP/OCP/OPP/OTP/SCP
- Voltage drop compensation by remote sense line.
- Have obtained CE,UL,CSA,FCC.ROHS
800V Dc Power Supply,Smps Power Supply,Variable Voltage Power Supply,Dc Adapter Power Supply
APM Technologies (Dongguan) Co., Ltd , https://www.apmpowersupply.com