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The access controller schematic diagram works in two modes. One is the inspection mode, and the other is the recognition mode. In the inspection mode, the controller continuously sends query codes to the card reader and receives reply commands from the card reader. This mode will be maintained until the card reader senses the card. When the card reader senses the card, the card reader generates different responses to the controller’s inspection command. In this response command, the card reader transmits the read sensor card internal code data to the access control controller to make the access control The controller enters the recognition mode.
In the recognition mode of the access controller, the access controller analyzes the internal code of the proximity card, compares it with the card data stored in the device, and implements subsequent actions. After the access control controller completes the action of receiving data, it will send a command to reply to the card reader, so that the card reader will restore the state, and at the same time, the access controller will return to the inspection mode.
Through the above work flow of the access controller and card reader, it can be seen that in order to open the door, the following steps need to be passed:
Among them, step 1 is completed inside the card reader, and steps 3 and 4 are completed in the access controller. They have been solidified into the device and cannot be changed. The second step is completed by connecting the RS485 communication line of the two devices, which creates conditions for us to fundamentally prevent the “backdoor card”.
We design a device called a data filter, which is serially installed on the data communication channel. All the internal codes of the card swiping are compared with the device first, and the card internal code data is sent to the access control for the approved data. The controller performs follow-up operations; directly discards the data that is not recognized; this makes the data of the “backdoor card” unable to be sent to the access control controller at all, thus fundamentally cutting off the channel of the “backdoor card” information.
The data filter is the same as the access controller. Generally, the schematic diagram of the access controller works in the inspection mode. It continuously sends inspection data to the proximity card reader and waits to obtain the internal code data of the proximity card. In this process, the proximity card reader has been completely separated from the access controller, and the access controller’s inspection commands to it are completely completed by the data filter. Only after the data filter obtains the card information and passes its own verification, the data is sent to the access control controller. Establish the connection between the proximity card reader and the access controller. The data source for the data filter to verify itself is the card internal code data obtained through reliable channels. The internal code of the “backdoor card” cannot be passed to the data filter, thereby preventing the “backdoor card” attack.
According to the above ideas, a single-chip microcomputer can be used to realize the hardware circuit design. A serial port of the single-chip microcomputer, which communicates with the access controller and the card reader. This serial port uses a switching circuit to ensure that it can only communicate with one of the two devices at a time. All commands sent to the access controller are The legal command confirmed by the MCU program can filter and isolate the data in this way. At the same time, the single-chip microcomputer also monitors the communication between the access controller and the control computer through another serial port, obtains the legal internal code data of the proximity card by analyzing the communication content, and stores the data in a large-capacity E PROM, as The basis for data comparison.
The serial port is the communication port that connects the access controller and the proximity card reader. In the inspection mode, the data filter simulates the access controller through the serial port. Send a query command to the proximity card reader; the proximity card reader is not swiped, and send a reply command that there is no proximity card; the data filter performs the next round of query.
When the proximity card reader has swiped the card, the card data will be transmitted to the data filter. The data filter enters the recognition mode and compares the card data with the standard data stored locally, if the data does not exist. Then discard the data, and reply that the proximity reader data has been received. The data filter returns to the inspection mode and starts the next round of query.
If the data is found in the memory, indicating that the card is a legal card, the data should be sent to the access controller. At this time, the device first switches the serial port to enable the single-chip microcomputer to communicate with the access controller. The data received from the proximity card reader is sent to the access controller as it is. And wait for the reply from the access controller; after receiving the reply. Switch the serial port back to communicate with the proximity card reader again, and forward the reply command from the access controller; after the data transmission is completed, the data filter returns to the inspection state for the next round of inquiry.
In the schematic diagram of the access controller, the data filter obtains the legal internal code data of the proximity card by monitoring the communication between the access controller and the control computer in real time, and stores it in the E PROM of the data filter as future data Basis for comparison. The workflow is as follows: The data filter monitors all commands sent from the computer to the access controller, and obtains all internal operation commands for adding, deleting, and modifying the card through analysis. According to the commands, the sensor card stored in the E2pROM is stored accordingly. The code data is added, deleted, and modified to ensure that the data stored in the data filter is consistent with the legal data of the access control controller.
In reality, the security requirements for the schematic diagram of the access control controller should be different. Only a deep understanding of the schematic diagram of the access control controller can ensure the safety and reliability of the access control system. Apply to life.
When the controller outputs an alarm, this relay will act. Its principle is the same as that of an electric lock. Other electric locks or other equipment can also be connected. Such as broadcasting, switches, lights, etc.
The connection method is the same as that of an electric lock! Please refer to the wiring method of the electric lock.
Its function is to protect data from being lost after power off, and the controller can continue to work after power on.
1 － 2 jumper wire break protection is valid; 2 － 3 jumper wire cut off protection is invalid
If you need to clear the data, please skip to 2-3, and disconnect the power supply and communication interface at the same time. The data can be cleared after 1 minute, and the indicator light of the controller will no longer flash after the power is turned on again.
There are 3 lights on the controller, 2 of which are powered separately, and 1 represents the status of the controller.
The flashing frequency of 1 second indicates that the controller is working but not communicating with the computer.
Fast flashing indicates communication with the computer.
Off or long on indicates that the controller is faulty or data has been cleared.
The power supply of the controller uses a 12V DC power supply, which generally shares the same power supply with the electric lock, because the electric lock needs a relatively large current when it operates, and must reach a capacity of 12V3A. The access terminal is on a separate side of the control board.
The communication protocol used by the controller is 485, which is an industrial protocol for serial communication. It has good installation performance and anti-interference performance.
The access terminal for communication is on the corner of the control board, and there is a difference between positive and negative.
Multiple controllers can be connected at the same time, but they must be connected as a bus. The distance between a single controller and the bus is recommended not to be greater than 5 meters. Connect one end to the computer.
When multiple controllers are connected according to the bus type, if the communication quality is not good, terminal resistors can be used. The method is to adjust the jumper on the control board farthest from the computer to pin 1-2, the default is pin 2-3, be careful not to jump the terminal resistance of other controllers.
After communication, the status light of the controller will flash quickly.
The single-door controller can be connected to two Wiegand format card readers, and can also be connected to other input devices in Wiegand format. The input and output on the control panel are Reader A and Reader B, which are connected to two card readers respectively. They respectively represent the entrance and exit of the door.
Reader A is the access terminal of the card reader at the door; Reader B is the access terminal of the card reader at the door.
Each card reader has 6 input pins, which are:
The positive pole of the power supply of the DC12V card reader;
GND The ground of the card reader power supply;
Data0 data 0;
Data1 data 1;
The light of the LED card reader;
Buzzer of BUZ card reader;
Among them, LED and BUZ can be disconnected, but their function is to prompt the status of the card and whether it is a valid card.
The buzzer of the card reader will sound 3 times, the invalid time will sound 2 times, and the valid card sound will sound 1 sound.
The controller can also use a card reader device with buttons, but it is not compatible with the keyboard input of all keyboard readers. If you don’t know whether it is compatible, you can contact the supplier to modify the product to obtain compatibility.
The WG interface of the card reader has 4 wires +12V GNG Data0 Data1, among which Data0 and Data1 are the data wires that must be connected; generally there are 2 wires, the functions are LED and BUZ respectively, which can be used to control the sound of the card reader And lights.
According to the card reader, the direction of entry and exit can be judged. Reader A means entering the door, and Reader B means exiting; this function can be set by the software to display all the doors as valid. The entry and exit direction of the door is only valid when the authentication method is single-card identification, and other authentication methods are displayed as the corresponding door opening.
Each door corresponds to an exit button. When the exit button is pressed, the two terminals of the button input are short-circuited, and the controller can open the electric lock and add a record of “Exit button open”.
The function of the door sensor is to detect the state of the door switch. When the door sensor input point is short-circuited, it means the door is closed, and disconnected means the door is open. The signal of the door sensor is also displayed on the software, and you can see the switch status of the door on the software. The connection method of the door sensor is shown in the figure:
When the electric lock is kept closed, if the door is magnetically opened, an alarm record will be generated: “Door alarm”, which means that the door is opened illegally, and the alarm output will be activated and the output will be maintained for 10 seconds.
When the electric lock is turned off, the door sensor still does not detect the door closing after a period of time, and an alarm record will be generated: “The door has been opened for too long”, and the alarm output will be activated at the same time, and the output will be maintained for 10 seconds. This function can be enabled by software settings.
The alarm input is the input terminal of other equipment signals to control the alarm output. The single-door controller defines the alarm input as “fire alarm”. When there is an alarm input, an alarm “fire alarm” is generated, and the door is opened at the same time, so that the sound and light of the card reader will beep and flicker continuously until a valid card is swiped.
Electric lock and alarm belong to the output terminal and their wiring terminals are together, as shown in the figure:
This is a relay control point, which can control the switches of other circuits to achieve the purpose of controller output. It is mainly to control the electric lock to achieve the purpose of controlling the opening and closing of the door. This output point has 3 terminals, only 2 of them are used. One of them is the public terminal, so that you can control two different locks: power-off unlocking and power-on unlocking. Their wiring diagram is as follows:
Power off and unlock: When the power is turned off, the lock opens.
Power-on unlock: When there is current, the lock opens.
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