With the popularity of automobiles in China, car theft has become an important issue for car safety. Using GPS anti-theft, high operating costs, so only for some high-end cars. So how to achieve effective anti-theft of some economical cars, the simplest way is to add GSM module or CDMA module in the simple simple one-way alarm system, you can achieve two-way alarm.
Let's clarify a few concepts:
One-way alarm: refers to the alarm sound generated by the car itself during the alarm period, warning people who steal the car, remind people around the car. This form is the most common, sensing methods are vibration sensing or ultrasonic sensors. (In the spring thunder season We often hear car alarms screaming. This method is used when the owner is not far from the parking alarm.
Two-way alarm: refers to when the car sensor (oscillation sensor or ultrasonic sensor) detects an abnormal condition, the car's own alarm call, warning the thief, and then immediately through an effective way (GSM or CDMA network) rule the owner.
Jump Code / Fixed Code Door Lock: There are two kinds of mechanical door locks: mechanical lock and remote lock. The remote lock code of the remote lock can be divided into two types:
One is fixed, and every time the code is transmitted, the system detects the code and can release the system alarm or start the alarm or open the door or lock the door. This has the disadvantage that for high-tech thieves, it can be decrypted by a receiving device. Change the code and then develop a remote control of the same code, you can open the door or remove the alarm.
The other type is code jumping, which means that each time the remote control launches a different code, so that even if the thief receives the previous remote control code, the remote control that can copy the same code cannot open the door.
Wireless embedded system: Use the current mature CDMA or GSM network to detect or control the devices and systems in the network through SMS. Since the two-way alarm system currently uses CDMA or GSM networks for notification and control of automobiles, it will increase wireless operating systems with low operating costs. He can save monthly monthly rents and expensive terminal costs of GPS, and drivers can know the Status, so it is very popular with consumers.
working principle:
The car can identify the remote control code through remote control decoding. When the code is the anti-theft code, the car sensor starts. When the car is in the anti-theft state, it detects the car car body abnormal situation, starts the car's own alarm device, alarms the alarm to the thieves, and passes CDMA. Or the GSM module sends a text message or calls the driver to inform the driver. The driver can send a text message to inquire about the starting status of the car. At the same time, the driver can cut off the oil circuit or the power supply system of the car to make the car unable to start normally and win the return time. At the same time, if the car is There is a car-jacking on the road. The driver can automatically cut off the circuit or oil circuit of the system as long as he presses the distress signal easily. At the same time, he informs himself of the position so that the reinforcements can arrive at the accident site in time.
The main function of the EEPROM in the system is the memory CDMA control message, and the storage of remote control code function, due to the CDMA data stream is large and fast and EEPROM write wait and other reasons, the system must be mcu must have a larger RAM, with For buffering CDMA data streams, power monitoring can maintain proper system operation.
Since the bidirectional alarm system is basically an improved one-way alarm system, the function of the one-way alarm is relatively simple. The system adopts a low-configuration, low-cost but high-reliability mcu, so the mcu will have less RAM, and it is necessary to store CDMA. SMS data must be replaced with high-value MCUs. This will increase the mcu cost due to space in the RAM. There is a FRAM solution below, which can eliminate the need to replace mcu due to RAM space, and improve the reliability of the system; FRAM data Storage plan.
Shenyang Zhongda Huanxin Refrigeration Technology Co., Ltd.
