First. Communication mode of access control:

The common communication modes of the access controller are RS485 and TCP/IP

(1) RS485 communication mode:

Multiple controllers, through the RS485 communication bus (must use twisted pair, or one of the network cable), the controller through the hand in series, a bus connected to the RS485 converter (hub), and then connected to the computer serial port, to achieve a computer (software) to multiple controller management and communication.

1. Communication distance:

The theoretical distance between the farthest controller and the computer is 1200 meters, it is recommended that customers control within 800 meters, and the best effect can be controlled within 300 meters. If the distance is too long, you can buy 485 repeater (extender) (please buy from a professional converter production company, the position of the repeater is in the middle of the bus or the beginning, please refer to the relevant manufacturer's instructions.) Optional Repeaters can theoretically be extended up to 3,000 meters.

2. Load quantity:

That is, a 485 bus can take how many controllers, this depends on the controller of the communication chip and 485 converter of the communication chip selection, there are generally 32, 64, 128, 256 several choices, this is the theoretical number, practical application, according to the field environment, communication distance and other factors, the number of loads can not reach the index number. Blue Base controllers and converters are designed according to 256 units, and customers are actually advised to control each bus within 80 units. If there are hundreds or thousands of controllers, use multiple serial ports or 485HUB. For details, see "How to Network the System If there are hundreds or thousands of Controllers?". Resolutely prohibit the use of passive 485 converter, passive 485 converter cost only ten dollars, although the nominal load number is 32, the actual application of 5 can not take, communication bus can not exceed 100 meters, there is no lightning strike, surge prevention design, please refer to "why prohibit the use of passive 485 converter?"

RS485 communication mode, must hand in hand through the twisted pair series connection, do not fork or star connection, please refer to the "RS485 communication principle and construction wiring precautions".

(2) TCP/IP communication mode:

TCP/IP communication protocol is the current computer network common standard protocol, with the advantages of fast transmission speed, international standards, good compatibility and so on. The access mode of the controller is the same as that of the HUB of the LAN and the computer network card.

1. Communication distance:

In a small local area network, the communication distance can be extended through the cascade of the HUB, and the communication distance of each level is up to 100 meters, which can be cascaded to multiple levels. Moreover, large local area networks can be extended to far away or even many kilometers through various ways such as fiber optic wireless, even across cities, and thousands of kilometers of networking through the Internet can be.

2. Load quantity:

In theory, there is no limit, the HUB can be cascaded, thousands of controller networking is no problem.

3. Communication speed:

The communication speed is fast, taking the nabon's product as an example, the communication speed of TCP/IP products is ten times or even tens of times that of RS485 RS232 controller. More than 100 or even hundreds of upload permissions or download records per second.

(3) Other communication networking methods:

In addition to RS485 TCP/IP mainstream communication methods, a very small number of companies also use LAN LONGWORK and other bus networking, these methods are rarely used, there are advantages and disadvantages, the compatibility between the products is not good, the technology is not popular, here is not introduced.

Second, the advantages and disadvantages of RS485 controller and TCP controller:

1, the advantages of RS485 controller:

The cost is relatively low, separate networking, will not be interfered by the shared network of other devices.

2. Disadvantages of RS485 controller:

The number of networks is limited, generally within 1000, the more devices the more complex the network, the greater the interference. The network range is limited, generally only within a few hundred meters. The communication speed is relatively slow, for more than 10,000 people, hundreds of doors of the system, upload permissions, download records and other operation speed is relatively slow.

3, the advantages of TCP/IP controller:

The use of international standards of popular communication protocols, advanced and performance are better, will not be eliminated. The number of networks is unlimited, and the network range is wide, and can be cross-regional or even cross-border. The communication speed is fast, suitable for more than 10,000 people, more than 100 doors of the access control system. The communication quality is stable and not susceptible to external interference. If the user already has a LAN and other networks, you can use the existing network networking without relaying the network.

4. Disadvantages of TCP/IP controller:

The cost will be slightly higher than the RS485 controller.

High-end and high-end users tend to use TCP controllers, and the trend is that more and more users of TCP controllers are expected to reverse in a few years. The networking method of wireless access control is not mature and stable, there are many policy and interference problems, and the application proportion is still small. For details, please refer to "Status and problems of wireless access control"

Some manufacturers on the market will 485 controller RS485 +TCP/IP converter to do network access controller, in fact, is a false TCP controller mode, please refer to "why 485 access controller +TCP/IP converter access control system is false TCP/IP access control system?" .