Design of RFID lock system based on STC89C52 and IC RFID card

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Design of RFID lock system based on STC89C52 and IC RFID card [Copy link]

Radio frequency identification technology is mainly a non-contact automatic identification technology. In its application process, it is necessary to use radio frequency signals based on electromagnetic principles to obtain information about the target object. Due to its wide application, it can be applied in different areas, so it is widely used in operations in various environments. In the radio frequency identification system, the output data of the radio frequency reader must strictly comply with the regulations made in the Wieggand format, that is, it is transmitted using two data lines that transmit 0 and 1 respectively.

The access control system based on single-chip microcomputer and radio frequency identification technology is a radio frequency identification lock system designed based on single-chip microcomputer STC89C52 and IC radio frequency card. It can be used in laboratories, computer rooms, office buildings, archives rooms, financial rooms and other places with high security requirements.

1. System design

This access control system consists of two parts: a client installed on the door and an authorization end for authorizing the writing of new cards. The client consists of a power module, a single-chip minimum system, a serial communication module, a card swiping 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, he needs to put the IC RFID card in the sensing area of the card reader to read the information in the card. When the read information is successfully verified, the door lock opens at the same time as the buzzer "beeps", and then relocks after a delay of one second; if the information verification fails, the buzzer will emit four consecutive short beeps. The authorization end is used to write authorization information to each IC card. The entire system can work with a single card reader, which is easy to operate.

Figure 1 Hardware system module block diagram

2. System hardware design

2.1. Power module circuit design

The power module is used to power the entire system. In the system, the card swiping module needs a 3.3V supply voltage, the electromagnetic lock module needs a 12V voltage, and the single-chip minimum system needs a 5V voltage. Therefore, the power module needs to provide three types of power: 12V, 5V, and 3.3V. The module uses the LM7805 and AMS1117 chips to realize the conversion of 12V to 5V and 5V to 3.3V voltage respectively. Figure 2 shows the circuit design of the system power module.

Figure 2 Power module circuit

2.2 Card swiping module circuit design

The RF reader/writer chip MRC522 is a low-power, small-package, highly integrated contactless (13.56MHz) reader/writer chip launched by NXP. It fully integrates all types of passive contactless communication methods and protocols at 13.56MHz using the principles of modulation and demodulation. It supports multi-layer applications of ISO14443A. Its internal transmitter part can drive the reader/writer antenna to communicate with ISO14443A/MIFAＲE cards and transponders without the need for other circuits. The receiver part provides a robust and effective demodulation and decoding circuit for processing ISO14443A compatible transponder signals. The digital circuit part processes ISO14443A frames and error detection (parity & CRRC). In addition, it also supports the fast CRYPTO1 encryption algorithm for authenticating MIFARE series products. MRC522 supports higher-speed contactless communication of the MIFARE series, with a two-way data transmission rate of up to 424kbit/s. It uses serial communication with fewer connections to communicate with the host, and can select one of the SPI, I2C or serial UART (similar to RS232) modes according to different user needs, which is conducive to reducing circuit connections, reducing the size of the circuit board, and reducing production costs. The application circuit of MFRC522 in the card swiping module is shown in Figure 3.

Figure 3 Card swiping module circuit

2.3 Buzzer module circuit design

When the user swipes the card, if the information verification is successful, the P2.0 pin of the microcontroller is given a low level (software setting), the transistor Q2 (PNP type) is turned on, and the buzzer emits a beep. When the information verification is unsuccessful, the buzzer emits four consecutive short beeps. The circuit design of this module is shown in Figure 4.

Figure 4 Buzzer module circuit