Some doubts about the choice of access control power supply

First, the importance of video access power selection

There is no doubt that 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 project company can earn as much profit as possible when implementing this project. The above can also reflect the engineering company's ability to control project quality.

Unfortunately, when the author investigated the macroscopic market of video access control, he discovered that more than 90 system failures were caused by improper selection of power supply, and some failures may have affected the smooth promotion of the project. From a comprehensive point of view, the faults caused by power supply mainly manifest in the following aspects:

1After using for a period of time, there is a phenomenon of insufficient power supply.

2 After a thunderstorm, there was a scale power failure.

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

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

5 Circuit short circuit causes the power supply to be burned out.

6 During the peak period of power consumption, the problem of insufficient power supply has arisen.

Second, the power in the video access control alarm system application and selection

1. Measure the actual output power of the power supply

The video access control alarm system involves a great deal of equipment to supply power. In order to ensure that each equipment can operate normally and stably, the power supply needs enough power to supply power to each equipment. When purchasing the power supply, pay special attention to the nominal value of the power supply, and test the actual parameters in the field. Because there are some low-cost access control power supplies in the market, they often do not reach the nominal value in practical applications, seriously affecting the video. The normal and stable operation of the access control alarm system. It is recommended to select power supply manufacturers that meet the technical parameters, quality, reliability, and good reputation for the video access control alarm system when purchasing power. At present, some manufacturers of video access control, the power supply is sold together with the controller, usually these types of manufacturers for the power supply is to consider the actual application of the project, the overall quality of the system also has better protection, such as Shenzhen's SHOONIS brand, Mais brand and so on.

An easy way to test the output power of the power supply: add the load (such as cement resistor) corresponding to the output power of the power supply to the power supply, run it 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. Check whether the output voltage is stable after the load is loaded and whether the heat is normal. It is better to install the test run on site.

2. Effective lightning protection

Due to the particularity of the video access control alarm system project, the installation environment is harsh (peasant room, rental room, old house village, and village in the city), outdoor lines are intertwined, and it is easy to ignite lightning, and the lines connected by the power supply are inevitable to appear outdoors. Therefore, it is required that the power supply should have extremely effective protection measures for lightning protection.

Does the product have lightning protection?

1 Visually inspect the power supply for protection circuit design. (This method is suitable for researchers on circuit hardware).

2 Understand whether manufacturers have accumulated technology in lightning protection technologies, such as actual demonstration of product reliability. Lightning detection reports of related products, etc.

The author has learned that in order to prove the reliability of a product, a factory can simulate the lightning strike on the spot to intuitively demonstrate the reliability of the product. This method is worth promoting.

3. Wide temperature adaptation range

At present, the installation of video access control, the southernmost city in Shenzhen is known as hot, and the northernmost Urumqi is known for its cold. If the product does not have a wide range of adaptability to high and low temperatures, the reliability of the system cannot be guaranteed, especially the power supply. Therefore, when choosing a product, you should choose according to your own installation environment.

In general, the temperature adaptation range of -40 degrees - 85 degrees, it can meet the requirements.

The specific test method can require the manufacturer to cooperate with the provision, or in the warranty can be clearly defined in the terms of the contract to ensure their own legitimate rights and interests.

4. Intelligent charge and discharge management for back-up battery

Due to the special environment of rented houses or communities, there are frequent outages in the city power supply, and video access control, especially the middle access control, is directly linked to the people’s lives and requires normal operation at all times. Therefore, video access control is generally established in various places. Specifications for the battery life of the battery will provide specific requirements, generally require power to maintain normal operation of the system after 4 - 6 hours or more, the power supply with charge and discharge management.

The charge and discharge management function of the power supply is mainly to prevent the battery from being overcharged to damage the battery, and not to recharge after over-discharging, and the current supply of other devices is pulled down because the charging current is too large, resulting in unstable system.

Added: Compared to access control, the video system's power consumption is relatively large, and does not affect the direct opening and closing of the door, so in the actual construction time for the power supply after the power outage, many engineering companies choose to give priority to ensure the access control after power failure power supply. At present, some power products already have a utility power outage detection function. After the power is cut off, the power supply of the video system is cut off in a linkage, so as to ensure the use of the smallest possible battery to ensure a longer power supply life of the access control system. Real savings are achieved. Business investment in the construction of backup batteries.

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

Due to the diversity of video access control alarm system hardware devices, it is bound to involve a power supply to multiple devices for unified power supply. At this time, it is necessary to pay attention to the optional power supply should have multiple output power supply independent power supply output, and requires the power supply can intelligently determine Output current, this can solve the problem of centralized power supply or when one output of the power supply fails, it will not affect the output of other roads. Even if the output of one power supply is directly short-circuited, it will not affect the output of other ports. Of course, the power supply will not be burned out because of a short circuit in one port.

6. Wide voltage range, stable power output

Mains voltage fluctuations often occur, either high or low. Therefore, the power supply must be able to adapt to a wide range of mains voltage fluctuations, and the output voltage can be stable at 12V output, to avoid the instability of power supply voltage fluctuations, affecting the normal operation of the video access control alarm system.

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

In the actual application of the project in the end is the choice of switching power supply or the choice of linear power supply, many engineering business friends can not start, in fact, as long as you grasp two points:

1 In a project in the hot southern area, if linear power source is selected, it is recommended not to put the linear power source and other equipment in the same equipment box, because the linear power source has a large loss and the heat is very severe, and other equipment is in a equipment box. Unsatisfactory heat dissipation may cause unstable operation of other devices. If the linear power supply is equipped with a dedicated box, it will bring about some increase in cost.

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

Third, summary

In summary, the choice of power supply for video access control projects is purely personal experience accumulation. It is hoped that they can provide reference to various engineering companies when selecting products. At the same time, it also welcomes the vast number of engineering contractors and friends who can not hesitate to enlighten us and add more methods. Skills come in to allow me to improve this article and make contributions to the overall progress of the security industry.