Common mistakes in access control construction

First, the common mistakes in the construction of access control phenomenon: the use of a network cable to lock the line to the controller! Access control from the electric lock to the controller in a section of the line, looks very ordinary, if not standardized, it is easy to cause The phenomenon of failure, this must pay attention! Because the operating current of the electric lock is relatively large (as opposed to other devices of the access control system such as the 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 held in motion, sometimes with no movement. Magnetic locks are sometimes not enough suction. The performance of the door switch is not normal. Even with the controller to grab current resources, making the controller power supply is insufficient, restart or even crashes. Some engineering personnel have convenient wiring or convenient purchasing. It is very easy to cause faults by using the network cable to electrically lock the wires of the controller. Although it seems that there is no problem during debugging, after a while, problems will often arise. . From the electric lock to the controller, if the line length is less than 50 meters, a two-core power cable with a cross-sectional area of ​​1.0 mm2 is required, and no shielding is required. If the cable length exceeds 50 meters, double a multi-core power cord and parallel the power supply. If the line length is greater than 100 meters, it is recommended to move the controller closer to the door 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 wire, so it is absolutely impossible, even if the controller is close to the electric lock. Electric magnetic signal cable, you can use network cable. Some people will connect the four strands of the network cable and provide power to the electric lock. Although it is theoretically close to the norm, it is not recommended to do so. Doing so will make the terminals unstable and other hidden dangers.

Second, common mistakes in the construction of access control II:

Excessive power load load! The main performance of the belt with too much power! Access control system power configuration recommendations, fortunately the United States to provide the standard configuration power supply is 12V, 5A linear power supply. He can meet (wired specification, line cross-sectional area is thick enough) up to four doors (4 electric locks or 3 magnetic locks) power supply. A double door magnetic lock translates to the power of two single door magnetic locks. If the system exceeds this configuration, for example: more than 4 electrical plugs or more than 3 magnetic locks will need to add a power supply and the original power distribution. Note: If some of the electric lock power is too large, the power supply will have a weaker load capacity. If electricity is not enough, it will not necessarily show up when debugging, unless it is not enough. The performance is sometimes that the door is locked, sometimes it is not locked, and even the controller may snatch the current, causing the controller to restart or even crash. Since the linear power source has low effective power and heat, it usually has an effective power of 40-70%, a nominal 5A power supply, and an effective current of about 3A. However, the linear power supply operates stably with less interference and is suitable for long-term stable operation of equipment. It is the type of power source commonly used at home and abroad access control equipment. Some projects ask whether switching power supply can be used. The switching power supply has large power and high effective power. We do not recommend the use of switching power supplies. Switching power supplies generally have high-frequency ripple and affect the stability of the host.

III. Common Mistakes in Access Control Construction III:

Lines do not use twisted pair, or use low-end passive converters! 485 communication lines can not go star connection, you must go to the standard hand-in-hand bus mode. If the 485 wiring is not standardized or exceeds the communication range, there will be a phenomenon that the communication is not on or sometimes the communication may not be able to communicate. Transmission is a differential mode transmission mode. Only the 485+ and 485- are mutually twisted, which can make the 485 transmission mode suffer the least interference, the longest transmission, and the best transmission quality. Some manufacturers do not use twisted pair cables, which may cause great interference. Some engineering companies mistakenly believe that some of the transmission quality of the lines will be better. One twisted pair is synthesized, and the other twisted pair is also integrated. This is counterproductive. Instead, the quality of communications has been greatly reduced. There is a compact converter without a power supply on the market, which is inexpensive. However, the anti-interference performance is not good, and it is generally used for stand-alone indoor short-distance communication, such as attendance. Not suitable for access control systems. Although it claims to be able to bring 32 devices with a transmission distance of 1,000 meters, it is often far from reaching the targets in practical applications. Therefore, it is recommended that you do not use this passive converter. Unless in the room, the communication distance is less than 100 meters and the number of loads is less than 2, which can be considered from the perspective of cost. Otherwise, it is highly recommended that you use an active 485 converter, which is also inexpensive and stable. There are many load controllers. Anti-interference, anti-lightning, anti-surge effect is also very good. 485 cabling is forbidden for star connection, ie it is not possible to pull cables from the converter to each controller separately, and then connect them in parallel on the converter. This connection makes the communication quality poor. Be sure to get out of the converter, go to a controller first, and then connect to the next control. One will continue to go down like a string of grasshoppers. Non-standard 485 wiring will not help even if it is later improved with a shielded ground termination resistor.

Fourth, access control construction wiring common errors:

Other notes:

1. Without consulting and understanding, arbitrarily connect some devices (such as automatic doors or elevators) of non-access control systems; each external device, even different manufacturers of the same device, have different electrical characteristics if these characteristics are If you are not familiar with it, it is very easy to cause instability in the access control system and generate a lot of interference. Therefore, before connecting external devices, please contact the technical personnel of the access control factory to obtain relevant experience and gain some experience. At the same time, you must also strengthen the electrical performance of the external devices. Familiarity with, and the improvement and precipitation of the engineer's own technical experience.

2. When the customer sometimes refers to replacing this product with other products, the wiring has been laid out. When the line cannot meet the specification requirements, the line must be re-arranged, and the standard cannot be used until it is reduced. At this moment, saving time or getting lucky will inevitably put a heavy price and effort on future work.