What are the common mistakes of Xi'an access control system ? How to analyze and deal with such errors? The editor of the Xi'an branch of Shaanxi Sixiang Industrial Co., Ltd. tells you:
Although the access control system is very simple, we must pay special attention to some issues during construction to prevent system instability. Today, we will focus on the construction error of the access control system .
Common mistakes in access control construction: 1. Use a network cable to electrically lock the cable to the controller.
The line from the electric lock to the controller in the access control construction looks very ordinary. If it is not standardized, it will easily cause a failure phenomenon that is difficult to find the cause. This must be paid attention to! It is very wrong to replace the dedicated electric lock control line with a general network cable. Because the electric lock has a relatively large working current (compared to other devices in the access control system, such as a controller card reader), the electric lock has a certain distance from the controller, and the voltage drop on the line will be relatively large. If the pressure drop is too large, the electric lock can sometimes be moved, sometimes it cannot be moved. Magnetic locks sometimes have insufficient suction. It appears that the door switch is abnormal. It will even snatch current resources with the controller, making the controller lack of power, restarting or even crashing.
Some engineering staffs are convenient for wiring for a while, or convenient to purchase. It is easy to cause failures by using network cables to distribute the electric locks to the controller. Although it seems that there is no problem when debugging, after a period of time, problems will often occur. .
For the cable from the electric lock to the controller, if the cable length is less than 50 meters, a two-core power cable with a cross-sectional area of 1.0 square millimeter is required, and no shielding is required. If it exceeds 50 meters, double the additional two-core power cable and supply power in parallel. If the cable is longer than 100 meters, it is recommended to move the controller closer to the door electric lock to shorten the wiring distance. The cross-sectional area of the network cable is 0.2 square millimeters, which is 5 times smaller than our standard cable, so it is absolutely impossible, even if the distance from the controller to the electric lock is very close. The magnetic signal line for electric door lock can use network cable. Some people combine the four strands of the network cable to power the electric lock. Although it is theoretically close to the norm, it is not recommended. Doing so will cause other hidden dangers such as unstable terminals.
Common mistakes in access control construction II: Excessive power load
The power load is too heavy! The main manifestation is too much electric lock! The standard power supply is a 12V / 5A linear power supply. It can meet (with the wiring specifications and a large cross-section area) the power supply of more than four doors (4 electric mortise locks or 3 magnetic locks). A double door magnetic lock is converted into the power of two single door magnetic locks. If the system exceeds this configuration, for example: more than 4 electric mortise locks or more than 3 magnetic locks, you need to add a power supply and the original power distribution power supply. Note: If some electric locks have too much power, the load capacity of the power supply will be weaker.
If the power is not enough, it may not show up when debugging, unless it is not enough. It is manifested that sometimes the door can be locked, sometimes it can't be locked, and it will even grab current with the controller, causing the controller to restart or even crash.
Because the effective power of the linear power supply is not high and it generates heat, the effective power generally ranges from 40 to 70%. The nominal 5A power supply has an effective current of about 3A. However, the linear power supply runs stably with less interference and is suitable for long-term stable running equipment. It is a type of power supply commonly used in access control equipment at home and abroad. Some engineering companies ask whether it is possible to use a switching power supply. The switching power supply has high power and high effective power. We do not recommend using a switching power supply. The switching power supply generally has a high frequency ripple, which will affect the stability of the host operation.
Common mistakes in access control construction III: 485 control line does not use twisted pair
485 lines do not use twisted pairs or use low-grade passive converters. The 485 communication line cannot be connected in a star connection, and must follow the standardized bus mode. If the 485 cable is not standardized or exceeds the communication range, there will be communication failure or sometimes communication failure. 485 transmission is a differential mode transmission mode. Only 485+ and 485- are twisted to each other, so that the 485 transmission mode can receive less interference, longer transmission, and better transmission quality. Some engineers do n’t use twisted pair cables, which will cause a lot of interference. Some engineers mistakenly think that the thicker wires will have better transmission quality. The twisted pair cables are combined into one strand, and the other twisted pair cable is also combined into a twist. Instead, the communication quality has been greatly reduced.
There is a compact converter on the market without a power supply, which is cheap. However, the anti-interference performance is not good, and it is generally used for indoor short-distance communication of a single machine, such as an attendance machine. Not suitable for access control systems. Although it claims to be able to carry 32 sets of equipment with a transmission distance of 1,000 meters, in fact, it is often far from reaching the target in practical applications. It is recommended that you do not use this passive converter. Unless it is indoors, the communication distance is less than 100 meters, and the number of loads is less than two. From a cost perspective, it can be considered for adoption. Otherwise, it is strongly recommended that you use an active 485 converter, which is not expensive and much more stable. There are also many load controllers. Anti-interference, anti-lightning, anti-surge effect is also very good.