Design of access control security management system based on single chip microcomputer

This system organically combines ID card technology, computer control technology and electronic door locks, uses ID cards to replace keys, and cooperates with computers to achieve intelligent access control and management, effectively solving the shortcomings of traditional door locks such as cumbersome use and inability to record information. The use of data collected by the data controller to achieve digital management can bring unexpected results for the effective management of internal human resources.

Electronic key: The authorized ID card can be used as an electronic key. When the electronic key is waved in front of the sensor, the controller will authenticate the card. Once the card is verified to be legitimate, the electronic door lock will be automatically opened.

Door opening authority: The effective door opening area (controller number) can be set according to the cardholder's identity authority. The system can have a highest authority card, which can open all electronic door locks within the system's jurisdiction.

Automatic alarm: In abnormal situations such as illegal use of cards or forced opening of door locks, the system will automatically send out an alarm signal. The system will automatically record detailed information such as the time, door number, status, etc. of the abnormal situation to ensure the safety of the door lock and subsequent verification.

This system is composed of 51 series single chip microcomputer AT89S52, buttons, buzzer, T7122M-I card reader and other modules. It realizes the function of storing one management card and multiple user cards; at the same time, the management personnel can also change the management card, add user cards, delete user cards, clear all user cards, etc. by pressing buttons.

Because the access control card swiping distance changes with the change of compensation capacitor (compensation capacitor is about 300PF), the maximum card swiping distance is about 5-12CM; for non-management cards or user cards, this access control controller does not respond; each button controller has a corresponding prompt sound to prompt the operation.

During normal use, the user holds the card close to the card reader antenna, the access controller reads the card number and compares it with the card number stored internally. If the card numbers are the same, it means the card is legal and the access controller sounds a long tone to indicate success. If the card reading fails, there will be no response.

01 Main control circuit design

02 Keyboard circuit design

7SLS164 is a serial-to-parallel conversion chip, which converts the serial data on SDA (P27) into 8-bit parallel data. S1/S2/S3/S4/S5/S6/S7/S8 are used as keyboard scan lines, and P26 is the keyboard data return line.

When the keyboard is scanned, S1~S7 outputs a low level at a time, and then detects P26 (loopback line). If P26 (loopback line) is high, it means that no key is closed. If P26 (loopback line) is equal to 0, the data on S1~S7 is simply processed to obtain the corresponding key value.

KEY1: Add user card; KEY2: Delete user card

KEY3: Delete management card; KEY4: Clear all user cards

03 Buzzer circuit design

The microcontroller controls the operation and shutdown of the buzzer through P37. When P3.7=1, the PNP transistor is turned off and the buzzer stops working; when P3.7=0, the PNP transistor is turned on and the buzzer starts working; thus, the microcontroller only needs P3.7 to output 0 or 1 to control the buzzer.

(1) The buzzer sounds once, indicating that the user card has been read.

(2) The buzzer sounds twice, indicating that the management card has been read.

(3) A corresponding prompt sound is given when the corresponding key is pressed.

(4) If the buzzer does not respond, it means that the card is not read.

04 Card reader circuit design

Data output format: 

A total of 48 bits are output, i.e. 6 bytes. The first byte is the ID card identification code, the second to fifth bytes are the card number, and the last byte is the checksum of the first five bytes. The checksum operation variable type is BYTE type, and the carry is discarded during the operation.

When synchronous serial output mode is selected, the high bit of each byte is output first; when asynchronous serial output mode is selected, the low bit of each byte is output first. The output baud rate is 9600 Bits/S.

Data output waveform:

(1) The ID card number is read through the card reader antenna when the card is swiped.

(2) The card number is transmitted to the microcontroller pin through SO.

(3) A low level is transmitted through CP, indicating that a card has been swiped.

05 Software Programming

The main work in the program loop is to determine whether a card is swiped. If so, it determines what card it is and then performs corresponding processing. The overall process of the access control system is shown below.

The management card function subroutine flow chart is shown below.

The access control security management system is a new modern security management system, which integrates microcomputer automatic identification technology and modern security management measures. It involves many new technologies such as electronics, machinery, optics, computer technology, communication technology, biotechnology, etc. It is an effective measure to solve the security management of the entrances and exits of important departments. It is suitable for various confidential departments, such as banks, hotels, parking lot management, computer rooms, armories, confidential rooms, offices, intelligent communities, factories, etc.