Access controller purchase
Recommendation 1: Choose an access controller with anti-crash and self-test circuit design If the access controller crashes, it will make the user unable to open the door or close the door, which will bring great inconvenience to the customer, and also increase the maintenance and maintenance cost of the engineer. The access controller must be equipped with a reset chip or a CPU with a reset function. Generally, the CPU of the 51 series does not have a reset function, and a reset chip needs to be added. At the same time, it must have a self-test function. If the circuit crashes due to interference or abnormal conditions, the system can self-test and self-start in an instant. Recommendation 2: Access controller with three-level lightning protection circuit design Since the communication line of the access controller is distributed and vulnerable to inductive lightning, the access controller must be designed for lightning protection. We recommend a three-level lightning protection design, first discharge the high current and high voltage generated by the lightning strike through the discharge tube, clamp the current and voltage into the circuit through the inductor and the resistance circuit, and then pass the residual current through the TVS high-speed discharge tube. And the voltage is released at high speed before it damages the circuit. The lightning protection index requires 4000V induction lightning for 50 consecutive times without damage to the equipment. The lightning protection index is high, and the anti-surge and anti-static ability of the equipment will be correspondingly high. Some products advertise that they also have 1500V lightning protection capability. In fact, this indicator is available on all chips, and does not have the ability to prevent lightning strikes and surges. Recommendation 3: The storage capacity of the registration card should be large, and the storage capacity of the offline recording should be large enough. The storage chip needs to use a non-volatile memory chip. It is recommended that the registration card permission should reach 20,000, and the offline storage record should reach 100,000, which is suitable for most customers' storage capacity requirements, and is convenient for attendance statistics. Be sure to use non-volatile memory chips such as Flash. Power loss or shock information will not be lost. If the RAM+ battery mode is used, if the battery is dead or loose, or if the current impact information is lost, the system may fail. Recommendation 4: The design of the communication circuit should have a self-test function, which is suitable for the needs of large system networking. The networking of access controllers is usually networked using the 485 industrial bus structure. Usually, many manufacturers choose max 485 487 or 1487 chips for cost savings. These chips have weak load capacity, usually the maximum load capacity is 32 devices, and if there is any bus A communication chip damage can affect the communication of the entire communication line, and it is impossible to find out which controller chip is damaged. We recommend using a high-end communication chip and integrated circuit similar to max3080. This circuit has a self-test function. If the chip is damaged, the system will automatically disconnect its connection, so that the control devices on other buses can communicate normally.
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