Design of non-contact smart card motorcycle sprocket lock
Author: SUN Xiu-fang, COLLAGEN, Liu Junsheng, Sun Jiangong
introduction
Contactless Smart Card (CLSC), also known as RF card, has the advantages of no mechanical wear, easy maintenance, and convenient use. It is widely used in identification, credit service, automatic control, security and other fields, such as China's second-generation ID card, access control system (Door Access System), highway non-stop charging system, water, electricity, gas meter charging system, parking lot, subway, taxi toll system, banking service "one card" and so on. Especially in the field of security, non-contact IC cards and locks have a combination of machines, can form a variety of smart locks. On the basis of systematic research on non-contact smart card technology, the author discusses its application in motorcycle sprocket locks.
First, the working principle and characteristics of non-contact smart card
The IC smart (RF) card is manufactured using an advanced chip manufacturing process with built-in high-speed CM0S EEPROM, MCU. The card has no other components except the IC microchip and a high efficiency antenna. There is no power supply on the card (no battery is required). When working, the antenna of the card reading and writing system sends electromagnetic waves to the antenna on the card to generate magnetic and electrical energy conversion. When the voltage reaches 2 V or above, the IC starts working, no additional power supply is required. You can complete the transfer of related data.
The contactless smart card has many advantages: it can transmit data under the condition of no contact, thus avoiding the fault caused by contacting and reading data; the operation is convenient, the data can be transmitted in the range of 5~2O0 cm, safe and reliable; There are read-only mode cards and read-write mode cards to meet different needs; confidentiality is strong, and the chip solidifies one set of password information in the special key digital group in production, which represents the cardholder's identification and is unique. Unbreakable translation, high confidentiality; long life, high reliability, up to 100,000 readings and writes, and data can be maintained for more than 10 years; antistatic protection capacity of more than 2 kV; no power, long-term use The trouble of replacing the battery is avoided; the chip of the card is small, only 4 mm×8 mm×1 mm, and can be made into various styles according to requirements, such as a business card type, a key card type, a decorative type or other hidden styles, not only Decorative, easy to carry, and also has good confidentiality and concealment. The contactless smart card and the host's read/write recognition system are transmitted by radio waves during data transmission, and are completed by a high-frequency wireless receiving/transmitting circuit, which includes oscillation, frequency division, power amplifier, demodulation, filtering, amplification, etc. The operating frequency is divided into low frequency band (125 ~ 134kHz), high frequency band (13.56 MHz), ultra high frequency band (868 915 MHz) and microwave segment (2.45 GHz) multiple frequency bands. In the application, this part of the circuit is generally solidified, called the "reading module", which makes the whole system simple in application. According to different performance and requirements, the card reading module is divided into several types, for example, the pointing can be divided into non-directional type, wide-point type, narrow-point type; according to the sensing distance, it is divided into close-range type, medium-distance type and long-distance type. According to the frequency, it is divided into low frequency band, high frequency band, ultra high frequency band and microwave segment; it is divided into read-only card, read-write card and so on according to data access mode. The card reading module can transfer data in both directions and transmit data to the contactless smart card. The received contactless smart card data can be sent to the control system of the single chip microcomputer or the related system of the computer for subsequent processing through the data output terminal.
Because contactless smart cards have many advantages, they are quickly widely used, but they also have the following problems:
(1) The system price is relatively high. In the field that is not sensitive to price, it is relatively more applicable. There is still a lot of room for price reduction from the price required for popularization, and it must be reduced to a widely accepted price. In fact, with the continuous improvement of technology, the direct cost of a single-machine system has been relatively low. To carry out large-scale promotion, as long as the "high added value" part is lowered, the price can be greatly reduced.
(2) There is still much room for improvement in application technology. The development cost in the application process is high, and the application software development and hardware design have repeated development and repeated design parts, which is time-consuming, laborious, and costly. Standardizing and modularizing software and hardware such as system software and functional components, as well as productization and industrialization, can greatly reduce development costs, reduce initial investment and development time, reduce development costs, and lower the threshold for technical use, which is beneficial to application personnel. And promote the use of large areas.
(3) Application awareness should be further improved. The fields and products that can be applied are far more than the above. It is very important to popularize the knowledge of contactless smart cards, improve the technical application ability of professional technicians in various industries and enhance the application awareness of non-professionals.
Second, the principle of radio frequency identification
Radio Frequency Identification (RFID) is an automatic identification technology that emerged in the 1990s. It uses wireless radio frequency for contactless two-way communication to achieve identification and exchange data. A typical RFID system consists of an electronic tag (Tag), a reader/writer (Read/write Device), and a data exchange and management system. The electrical label is also called the RF card, which has the ability of intelligent reading and writing and encrypted communication. The reader is composed of a wireless transceiver module, a large line, a control module and an interface circuit. Radio frequency identification is a passive system, that is, the electronic tag does not contain a battery, and the energy of the electronic tag is provided by the radio frequency pulse emitted by the reader. The receiver receives the RF pulse, rectifies and charges the capacitor. The capacitor voltage is regulated and used as the operating voltage. The data demodulation section demodulates the data from the received RF pulse and sends it to the control logic. Control logic accepts instructions to complete storage, send data, or other operations. EEpROM is used to store the user ID number of the electronic tag and other user data.
Radio frequency identification technology in contactless smart cards has been widely used in the field of identity recognition, and has matured.
Third, non-contact smart card motorcycle sprocket lock
The author introduces the non-contact smart card motorcycle sprocket lock, which is an application of the non-contact smart card identification technology in the security lock of the security field. The actual production is convenient and the cost is low. The direct material cost does not exceed RMB 5 yuan. A variety of people like the shape, good quality and low price, high use value and broad market prospects.
The motorcycle sprocket lock currently used adopts a common mechanical lock unlocking technology with a key, and a high-strength lock cylinder is stuck on the sprocket to cause the sprocket to be stuck, thereby locking the rear wheel of the motorcycle to be unable to rotate, thereby preventing The purpose of illegal movement and theft. The overall shape and structure of the original lock is complete and difficult to break. The principle of the lock cylinder sprocket has proved to be feasible in practical use, but the stolen motorcycles still occur frequently, and the problem lies in the mechanical lock. Although people often say "a key to open a lock", in fact, the key's re-encoding rate is too high, even if the "cross-shaped" key, its confidentiality is very limited. The method of using the mechanical lock with key has the common problem of the key lock, which is easy to be opened, the safety performance of the lock itself is too poor, the anti-theft effect is very low, and the desired purpose cannot be achieved at all, and the requirements of the customers cannot be met.
The author uses a smart card with a passive encrypted memory read-only mode. It mainly combines the characteristics of "contact identification" of non-contact smart card with the traditional motorcycle sprocket lock to form a smart recognition function of "lock". Each user's ID and other information are stored in the electronic tag, and the user's verification is effective to drive the opening and closing of the lock, overcome the disadvantages of the high key rate of the ordinary key, improve the safety performance of the lock itself, enhance the anti-theft capability, and achieve economical reliability. the goal of. Figure 1 is a schematic view of the structure of the lock body.
In Figure 1, the lock cylinder is in the "locked" position, the extension of the lock cylinder is stuck to the motorcycle sprocket, and the card stop is welded to the lock cylinder as a whole. The outer casing is formed by welding more than 2 mm steel plate, and the rear cover is made of steel plate larger than 2 mm. The fastener is connected with the outer casing to protect the internal structure and various parts of the circuit from being damaged. The rear part of the motorcycle is connected and fixed. The receiving coil is enclosed in an engineering plastic housing and is fixed on the outside of the housing. Figure 2 is a key chain decorated non-contact smart card.
The non-contact smart card has a small card core and can be packaged in a card or in various small decorative parts. It has good concealment and is carried along with the key chain.
Very convenient and beautiful. In order to prevent moisture, dust and damage, the control system is packaged as a whole with special glue for packaging. Only the wires left are connected to the receiving coil, electromagnet and motorcycle power supply. The appearance of the card reading module is shown in Figure 3.
The circuit diagram of the contactless smart card control system is shown in Figure 4. Locking process: When locking the car, press the end of the lock core close to the outer end by hand, and when the card retaining piece slides below the iron core with the lock core, the iron core is pressed against the lock core by the iron core return spring. When the hand releases the lock cylinder, the lock cylinder returns under the elastic force of the lock core return spring, but because the iron core block control circuit holds the card stop piece, the lock core is prevented from returning, and the lock core extension portion is stuck in the motorcycle chain. On the gap of the wheel, the rear wheel of the motorcycle is locked and the lock process is completed.
Unlocking process: When the motorcycle power switch lock is turned on, the non-contact smart card control system gets the power supply to start working. When the non-contact smart card is close to the receiving coil 1O0 ITIITI, the receiving coil receives the data information in the card and sends it to the receiving module, and the receiving module Output card information data to IC3, identify the password information related to the card, and when the recognition is not a legal card, do not perform the unlocking process; when it is recognized as a legitimate card, the 9-pin output of IC3 sends a high-level unlock signal. TR2 is turned on, J1 pulls on the power supply of the electromagnet, and the electromagnet generates an electromagnetic field force to pull the iron core into the coil. When the "locked" state is blocked, the card retainer is released, and the spring is reset. Next, the lock cylinder is reset, release the stuck motorcycle sprocket, and complete the unlocking process.
Fourth, the conclusion
The contactless smart card is unlocked under the condition of no contact. The internal chip of the smart card contains a unique serial password, which cannot be deciphered and represents the identity of the cardholder. Only when the identification is correct, the unlock signal can be issued. Since the traditional key is not used, the lock is not touched when the lock is unlocked, and the safety measures are fully taken into consideration in the design of the mechanical execution part. The lock is completely closed and the lock core is concealed, so that the safety and reliability are high, and the overall anti-destructive performance of the lock is achieved. Greatly improve. It can be applied to the safety precautions of various parts of various vehicles when the circuit is not changed much.
references
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