RF identification technology is mainly a non-contact automatic identification technology. In the process of its application, it is necessary to utilize RF signals to obtain information for information on the target object based on the electromagnetic principle. Due to its extensive application, it can be implemented. Applications in different regions are therefore extensive applications in various environments. Among the radio frequency identification system, the output data of the RF reader needs to strictly abide by the provisions of the Wieggand format, that is, two data lines are 0 and 1, respectively.
Access control systems based on single-chip microcomputer and RF identification techniques are based on SMS STC89C52 and IC RF card design, RF identification lock systems, which can be used in laboratory, computer room, office building, archives, financial room, etc..
1, system design
This access control system consists of two parts: the authorized end of the client on the door and the authorized end of the new card. The client consists of a power module, a microcontroller minimum system, a serial communication module, a swipe module, a buzzer module, and an electromagnetic lock module, as shown in Figure 1. At the client, when the user needs to open the door, you need to put the IC RF card in the induction area of the card reader to read the interior information. When the read information is successfully verified, the buzzer "嘀" At the same time, the door lock is open, and the lock is retracted after a second; if the information verification fails, the buzzer will send four consecutive and short-proof. The authorization is used to authorize information about each IC card. The entire system can work with a single credit card machine and easy to operate.
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Figure 1 Hardware system module block diagram
2, system hardware design
2.1, power module circuit design
The function of the power module is power supply throughout the system. In the system, the swipe module uses a power supply voltage of 3.3V. The electromagnetic lock module needs to use 12V voltage, and the minimum system portion of the single-chip microcomputer needs to use 5V voltage. Therefore, the power supply module needs to be provided with 12V, 5V and 3.3V three. The module achieves conversion of 12V to 5V and 5V to 3.3V voltage via two chips of the LM7805 and AMS1117, respectively. Figure 2 is a system power module circuit design.
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Figure 2 Power Module Circuit
2.2, credit card module circuit design
RF read-write chip MFRC522 is a low power, small, highly integrated non-contact (13.56MHz) read and write card chip introduced by NXP, which is fully integrated in 13.56MHz using the principles of modulation and demodulation. All types of passive non-contact communication methods and protocols. Multi-layer applications for ISO14443A are supported. Its internal transmitter part can drive communication with the ISO14443A / Mifare card and the ISO14443A / Mifare card, without other circuits. The receiver portion provides a rugged and efficient demodulation and decoding circuit for processing the ISO 14443A compatible transponder signal. Digital Circuit Section Process ISO14443A Frames and Error Detection (Patent & CRC). In addition, it supports fast Crypto1 encryption algorithms for verifying the Mifare series. MFRC522 supports MIFARE series's higher speed non-contact communication, with bidirectional data transmission rates up to 424kbit / s. It uses communication between the main units with less serial communication, and can choose one of the SPI, I2C or Serial UART (similar to RS232) mode according to the different needs of the user, which is advantageous for reducing circuit connection, reduced the volume of the board. ,reduce manufacturing cost. The application circuit of the MFRC522 in the swipe module is shown in Figure 3.
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Figure 3 Credit card module circuit
2.3, buzzer module circuit design
When the user switches, if the information verification is successful, the P2.0 pin of the single chip microcomputer is given a low level (software setting), the triode Q2 (PNP type) is turned on, and the buzzer emits a buzzer. When the information is verified, the buzzer issues four consecutive tweezers. The module circuit is designed as shown in Figure 4.
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Reprinted from -Wiku Electronic Market Network
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