Several doubts about the choice of access control power supply

First, video access control alarm system

The video access control project is accompanied by the progress of social management innovation, which plays an irreplaceable role in the management of the population, especially the floating population. At present, the construction of video access control in all parts of the country is in full swing, and a new type has been formed in the security industry. Market power. In order to meet the needs of the market, suppliers of access control systems and suppliers of video systems, including supporting optical transceivers, power supplies, etc., are optimizing their product solutions according to the specific needs of the video access control market. Can be more competitive in the market competition.

This article is mainly for the characteristics of video access control applications, combined with their own actual video access control engineering experience, to share in the actual project selection, several issues should be noted for the selection of video access control power.

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Second, the importance of video access control power supply selection

There is no doubt that the power supply is the basis for ensuring the stable operation of the entire video access control system. The choice of power supply can directly determine whether the engineer can earn as much profit as possible when implementing the project, and at the same time choose from the power supply. The above can also reflect the ability of the engineering firm to control the quality of the project.

Unfortunately, when I investigated the macro market of video access control, I found that more than 90 system failures were caused by improper selection of power supplies, and some failures may have affected the smooth promotion of the project. In summary, the faults caused by the power supply are mainly manifested in the following aspects:

1 After a period of use, there is a problem of insufficient power supply.

2 After a thunderstorm, a large-scale power failure occurred.

3 There is a power failure in hot and cold weather.

4 The battery is often broken and does not have the ability to power down to maintain normal operation of the system.

5 Short circuit caused the power to be burnt out.

6 During the peak period of power consumption, there is a problem of insufficient power supply.

Third, the application and selection of power supply in video access control alarm system

1. Measure the actual output power of the power supply

The video access control alarm system involves a lot of equipment to be powered. To ensure that all devices can operate normally and stably, the power supply needs to have enough power to supply power to each device. When purchasing the power supply, pay special attention to the nominal value of the power supply, and it is best to test the actual parameters in the field, because there are some low-cost access control power supplies on the market that often fail to reach the nominal value in practical applications, which seriously affects the video. The normal operation of the access control alarm system. It is recommended to select the power supply manufacturer with the technical parameters up to standard, reliable quality, good reputation and suitable for video access control alarm system when purchasing power supply. At present, some video access control manufacturers, the power supply is sold with the controller. Generally, these manufacturers consider the actual application of the project for the power supply selection, and also have better guarantees for the overall quality of the system, such as Shenzhen. SHOONIS brand, Mais brand and so on.

An easy way to test the output power of the power supply: add the load corresponding to the power output of the power supply (such as cement resistance), run for more than 48 hours, measure the actual output voltage and current of the power supply with a multimeter, and compare it with the nominal value to Is the voltage output after the load is detected stable? Is the calorie normal? It is best to be able to install the test run in the field.

2. Effective lightning protection

Due to the particularity of the video access control alarm system project, the installation environment is bad (farmers' houses, rented houses, Laowu Village, Chengzhong Village), the outdoor lines are intertwined, and it is easy to attract lightning, and the lines connected by the power supply are inevitably appearing outdoors. Therefore, the power supply is required to have strong and effective protection measures against lightning protection.

Whether the product has lightning protection judgment:

1 Visually check if there is a protection circuit design on the power supply. (This method is suitable for researchers on circuit hardware).

2 Understand whether the manufacturer has accumulated technology in lightning protection technology, such as the actual demonstration of product reliability. Lightning detection reports for related products, etc.

I have learned that a manufacturer can simulate the lightning strike to simulate the reliability of the product in order to prove the reliability of the product. This method is worth promoting. For details, please refer to ***.

3. Wide temperature adaptation range

At present, the installation of video access control, the southernmost Shenzhen is known for its hot weather, and the northernmost Urumqi is known for its coldness. If the product does not have a wide range of adaptation to high and low temperatures, the reliability of the system is not guaranteed, especially the power supply part, so the product should be selected according to the installation environment.

In general, the temperature adaptation range is -40 degrees - 85 degrees, you can meet the requirements.

The specific test method can be required by the manufacturer to provide, or the warranty can be clearly defined in the contract terms to guarantee their legal rights.

4. Intelligent charge and discharge management of backup battery

Due to the special environment of the rental house or community, the power outage occurs during the power outage, and the video access control, especially the middle access control, is directly related to the lives of the people. It is required to operate normally at any time, so the video access control is generally established everywhere. In the specification, the battery life of the backup battery will be specified. Generally, it can maintain the normal operation of the system for 4-6 hours after the power is cut off. The power supply has a charge and discharge management function.

The charging and discharging management function of the power supply mainly prevents the battery from being overcharged and damages the battery, and does not recharge after over-discharging. The charging current is too large to lower the current supply of other devices, resulting in unstable system.

Supplement: Compared with the access control, the power consumption of the video system is relatively large, and it does not affect the direct opening and closing of the door. Therefore, in the actual construction, for the power supply after the power failure, many engineers choose to give priority to the access control after power off. power supply. At present, some power supply products already have the power-off detection function of the mains. After the power is cut off, the power supply of the video system is cut off, so as to ensure that the battery life of the access control system is longer with the smallest possible battery, and the actual saving project The investment in construction of the backup battery.

5, fault isolation, to avoid damage to individual equipment and affect the overall stability of the system

Due to the variety of hardware devices of the video access control alarm system, it is bound to involve a power supply to provide unified power supply to multiple devices. At this time, it is necessary to pay attention to the optional power supply with multiple output terminals for independent power supply output, and the power supply can be intelligently judged. Output current, this can solve the power supply centralized power supply or when the output of one power supply fails, it will not affect the power supply output of other roads. Even if one power supply output is directly short-circuited, it will not affect the output of other ports. Of course, the power supply will not be burnt out due to a short circuit on one port.

6. Wide voltage adaptation range, stable power supply output

Mains voltage fluctuations often occur, either high or low. Therefore, the power supply must have a wide range of mains voltage fluctuations, and the output voltage can be stabilized at 12V output, avoiding unstable power supply caused by fluctuations in the mains voltage, and affecting the normal and stable operation of the video access control alarm system.

The author has tested many power supply brands for video access control projects. One of them has a particularly impressive impression. The city's electric power adaptability range can reach AC85-265V. For specific parameters, please refer to ****

7, on the choice of switching power supply and linear power supply

In the actual project application, whether to choose switching power supply or linear power supply, many engineering business friends have no way to start, in fact, just grasp two points:

1 In a hot area in the south, if a linear power supply is selected, it is not recommended to place the linear power supply and other equipment in the same equipment box because the linear power supply is expensive and the heat itself is very high, and other equipment is in one equipment box. If the heat is not delivered in time, it is likely to cause unstable operation of other devices. And if the linear power supply is equipped with a dedicated cabinet, it will bring some cost increase.

2 Low-cost linear power supplies generally do not have battery charge and discharge management functions, which can easily cause damage to the battery.

Summary summary

In summary, the choice of power supply for video access control projects is purely personal experience. I hope that all engineering companies can provide reference for product selection. At the same time, we welcome friends from engineering companies to enlighten me and add more methods and The skills come in, so that I can improve this article and contribute to the overall progress of the security industry.