Integrated Wiring in access control systems

The Integrated Wiring System belongs to the physical layer of any smart system. In the initial definition, the word "integrated" is defined as: it can replace various weak current systems (that is, intelligent systems ).

However, because of the price and consciousness, the Integrated Wiring System has been widely used in telephone and computer network systems for a long time. With the increasing popularity of Integrated Wiring System technology, many smart systems gradually begin to use integrated cabling systems as their transmission lines.

This article will introduce the Integrated Wiring application in the access control system.

1. Access Control System Overview

An access control system is a sub-system of the entrance management system. It usually uses technologies such as card swiping and biometric feature identification to manage the entrance and exit under the control of management software, allow free access to eligible people and interfere with those who do not have access.

Because the access control system can quickly identify people, it has quickly stepped out of the movie for more than a decade and entered the office of office buildings and large multinational corporations, it also guards the door of the garage, subway, residential buildings, and even before the desktop computer is used, you can use it to confirm the identity of the user. It can be said that the access control system is installed almost everywhere where identity verification is required.

The principle of access control system is as follows:

Door-based access control is equipped with various access control devices inside and outside the door and above the door:

When the cardholder intends to enter the door, he will use the sensor card to swipe the card on the card reader and enter the password on the password keyboard, you may also use the fingerprint reader, the palm print reader, and the retina reader to check your identity. When the cardholder swipes the card, the information is transmitted north to the Controller near the door, identified by the computer in the controller, after confirming that the cardholder is eligible to enter, the control signal is sent to the top of the door (or the door side) to open the door to allow the cardholder to access.

After the cardholder enters the door, the door will be automatically closed (using ground spring, closed door device and other devices ). A sensor (Lock State sensor) is often installed in the electric lock. Once the door or the electric lock is in the Enabled state, it will return a signal to the Controller. when the door is opened for too long, the controller or bell will make a sound, notifying the door opener to close the door quickly (this phenomenon is often seen at the door of the hotel room ).

When the controller opens the door, the cardholder's information is sent to the access control management computer in the data room. After receiving the information, the computer will store the information and display it on the screen. At the same time, the information will be transmitted to the relevant software (such as attendance software.

When the cardholder wants to go out after the event, he can press the button on the inside of the door (one-way Card swipe. If it is a two-way swipe card, you also need to swipe the card inside the door), the door automatically opens. If the cardholder's information is not registered, the Controller will not open the door. The controller will open the door only when the card information is entered into the management software and downloaded to the Controller memory.

When the access control system loses power, the system automatically places the electric lock in the Enabled state, allowing free access. To avoid escape in case of fire. The principle of the access control system is similar to that of the industrial control system (Automatic Control System) and building automation system (BA). Its operation can be divided into three steps: sensing, management, and execution, it is compact and simple.

Sensing:

Card readers, cryptographic keyboards, various biometric identifiers, outgoing buttons, and lock status sensors all belong to sensors. Their tasks are to receive commands, upload signals or upload after checking (biometric identifiers ).

Management:

Controllers and management software are responsible for the management function of the access control system. After receiving the information sent from the sensor, they determine whether to open the door based on the time, card number, and other information, then, issue the door opening command to the electric lock. When the lock status sensor is received, the timer starts and an alarm is triggered when the sensor times out.

Run:

When an electrical lock receives a command to open or close the door (power supply or power-off), it "executes" the command to adjust the working status to be consistent with the command. The lock status sensor in the electric lock plays the role of feedback and supervision. Some controllers can use relays (or other contact switches, commonly known as hard contacts) to output control signals to control associated cameras and lights.

2. Access Control System Transmission Lines

According to the above working principle, there are several transmission lines in the access control system:

Power cord

The power supply of the access control system is mostly from the UPS of the data center, so as to avoid opening the door by mistake during sudden power failure on site. The power cord is usually in a v ac transmission mode to reduce the pressure drop on the power cord.

The Controller is equipped with a regulated power supply. The ac v power supply is converted into a DC 12 V power supply, which supply the controller and the electric lock respectively.

The vast majority of the locks used in the access control system belong to the 12 v dc power supply mode. In the moment when the electric lock is broken, due to the role of the electric lock midline package (electromagnet coil), it will generate a strong current on the power cord, it is easy to cause power fluctuations, this power supply fluctuation is extremely unfavorable to the stability of the Controller;

Therefore, in access control systems with high reliability requirements, controllers and locks use different power modules, that is, when v ac power is supplied to the Controller, two 12 v dc power supply modules are used to supply the locks and controllers respectively after their respective Rectification/regulation.

The selection of various power cords is basically based on the electrical manual, the selection of standard power cords.

Controller signal line

The Controller has three signal lines connected to the card reader (4 ~ 9-core), lock status sensor (2-core) and push button (2-core) in the electric lock ). These three signal lines can be replaced by twisted pair wires in integrated cabling.

To avoid electromagnetic interference in space, the signal line of the card reader should be shielded. The other two signal lines can be shielded or non-shielded.

Remote signal line

There is a signal line between the Controller and the management computer. Most of its transmission protocols are RS485, which may be RS232 (to reduce one RS232/RS485 converter) when the distance is near ), when the transmission rate is fast, the TCP/IP protocol is used for transmission over Ethernet.

These three protocols can use twisted pair wires, but during RS485 or RS232 transmission, the shielded wires are basically required in the product manuals of the Access Controller. To avoid electromagnetic interference, this signal line should be shielded twisted pair wires.

When the controller needs to use an output hard contact to directly control the hard video recorder (Synchronous Video Recording when the card is swiped to open the door), this control line (2 cores) should be shielded, this prevents false triggering caused by electromagnetic interference when the input signal amplitude of the DVR is small. However, if you use a hard contact to directly transmit the power of the lighting, you should use a power cord. According to the above analysis, we can see that the power cord should be used for transmission power supply (Power Supply for Power locks, controllers and lighting), and its cross-sectional area can be calculated based on the voltage drop and heating caused by current, you can also find the electrician manual.

When transmitting sensor signals and control signals, select a screen or non-screen line according to the installation manual of the card reader and controller.

3. Integrated Wiring in access control systems

As the number of door locks in the access control system increases, the transmission speed of the system becomes increasingly high (response time is shortened ), in addition, the construction unit often engaged in the access control system will also carry out the construction of the integrated wiring system. Therefore, the use of twisted pair wires as the transmission line of the access control system has become one of the cable choices of the access control system.

According to the analysis of various access control cables, twisted pair wires can be used for signal lines and control lines between card readers, controllers, and management computers.

In smart buildings with access control systems and integrated wiring at the same time, twisted pair wires shorter than 20 meters often lose the value of use in Integrated Wiring projects and become engineering waste lines. For distributed-installed controllers (single-door dual-open or dual-door single-open controllers), the outgoing button signal line, card reader signal line, and lock status signal line mostly use these waste lines.

For the remote signal line using TCP/IP protocol, it must be transmitted using twisted pair wires. It can use the standard star structure of the Integrated Wiring System to achieve remote signal transmission. The RS485 and RS232 cables can also use twisted pair wires. According to the installation manual of the Access Controller, these cameras should use shielded twisted pair wires to avoid misoperation caused by electromagnetic interference.

Iv. considerations when applying the Integrated Wiring System in the access control system

When using the Integrated Wiring System as the access control line, pay attention to the following factors:

The wiring method should be in full accordance with the wiring rules of various access control equipment, and keep the Detailed wiring diagram to avoid the pain of judging the line during maintenance. The shielding layer of shielded twisted pair wires should be grounded according to the Installation manuals of card readers and controllers.

If you use shielded twisted pair wires to transmit TCP/IP, you can use the shielding layer connection rules of the Integrated Wiring System. When using the TCP/IP protocol, it is best not to share a network switch with other smart systems (including office automation systems and other software systems), that is, the access control system is separately equipped with a network switch, to avoid transmission exceptions due to Protocol conflicts.

When using the TCP/IP protocol, you can consider the access control system management computer as a server in the access control network and connect it to the distribution frame using twisted pair wires or optical cables. The Integrated Wiring System can be used for access control systems. This has been confirmed by the access control system vendors and installers, but the cost, construction and performance should be fully evaluated in the project to achieve the best effect.