The power supply is the basis for the stable operation of the access control system, and the quality of the power supply is self-evident to the importance of the entire access control system. According to the survey, more than 90% of access control system failures are caused by the improper selection of power supply. On the whole, the failure caused by the power supply is mainly manifested in the following aspects:

① After using it for a period of time, the failure phenomenon of insufficient power supply occurs.

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

③ Power failure occurs in hot and cold weather.

④ The battery is often broken, and it does not have the ability to maintain the normal operation of the system when the power is cut off.

⑤ The short circuit of the line causes the power supply to be burned out.

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

The above are some reasons for the power failure of the access control system. Let's talk about the application and selection points of the power supply in the access control system.

1. Measure the actual output power of the power supply

There are many devices involved in the power supply in the video access control alarm system. In order to ensure the normal and stable operation of each device, the power supply needs to have enough power to supply power to each device. When purchasing a power supply, pay special attention to the nominal value of the power supply, and it is best to test the actual parameters on the spot because some cheap access control power supplies on the market often fail to reach the nominal value in practical applications, which seriously affects the video quality. The normal and stable operation of the access control alarm system. When purchasing a power supply, it is recommended to choose a power supply manufacturer with up-to-standard technical parameters, reliable quality, a good reputation, and suitable for video access control and alarm systems. At present, some video access control manufacturers sell the power supply together with the controller. Generally speaking, such manufacturers consider the actual application of the project when selecting the power supply, and have a better guarantee for the overall quality of the system. 

A simple method to test the output power of the power supply: add a load (such as cement resistance) 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 to obtain Check whether the output voltage is stable after adding the load? Is the heat generation normal?

2. Effective lightning protection

Due to the particularity of the video access control and alarm system project, the installation environment is harsh (farmer houses, rental houses, old villages, urban villages), and the outdoor lines are intertwined, which very easy to causes lightning, and the lines connected to the power supply will inevitably appear outdoors. , so it is required that the power supply should have extremely strong and effective protection measures for lightning protection.

Judgment on whether the product has lightning protection:

① Visually inspect whether there is a protection circuit design on the power supply. (This method is suitable for those who have researched circuit hardware).

② Find out whether the manufacturer has technical accumulation in lightning protection technology, such as the actual demonstration of product reliability. Lightning protection test reports of related products, etc.

In order to prove the reliability of the product, a manufacturer can simulate lightning strikes on the spot to intuitively show the reliability of the product. This method is worth promoting.

3. Wide temperature range

At present, with the installation of video access control, the southernmost Shenzhen is known for its hotness, 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, there is no way to guarantee the reliability of the system, especially the power supply, so when choosing a product, you should choose according to your own installation environment.

Generally speaking, the temperature adaptation range is between -40 degrees to 85 degrees, which can meet the requirements.

Specific test methods can be provided by the manufacturer or can be specified in the terms of the contract in terms of quality assurance to ensure their legitimate rights and interests.

4. Intelligent charging and discharging management of the backup battery

Due to the special environment of rental houses or residential areas, power outages occur from time to time, and video access control, especially the middle access control, is directly related to the lives of ordinary people and requires normal operation at all times, so video access control is generally built in various places. In the specification, there will be specific requirements for the battery life of the backup battery. Generally, it is required to maintain the normal operation of the system for more than 4-6 hours after a power failure, and the power supply has charge and discharge management functions.

The charge and discharge management function of the power supply is mainly to avoid damage to the battery due to overcharging of the battery, and it will not cause the system to be unstable due to excessive charging current and pull down the current supply of other devices due to recharging after overcharging.

Supplement: Compared with 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 actual construction, for the power supply after a power failure, many engineering companies choose to give priority to ensuring access control after power failure. power supply. At present, some power supply products already have the detection function of mains power failure. After the power failure, the power supply of the video system will be cut off in conjunction, so as to ensure that the smallest battery possible can be used to ensure a longer power supply life for the access control system, which can actually save projects. The construction investment of the manufacturer in the backup battery.

Usually, it is best to install and test run on-site if conditions permit.

5. Fault isolation, avoiding the damage of individual equipment and affecting the overall stability of the system

Due to the diversity of video access control and alarm system hardware devices, it is bound to involve one power supply to provide a unified power supply to multiple devices. At this time, it should be noted that the purchased power supply should have multiple output terminals for independent power supply output, and the power supply should be intelligently judged Output current, which can solve the problem of centralized power supply of one power supply or when one power supply output 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 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 the fluctuation of the mains voltage in a wide range, and the output voltage can be stably output at 12V, so as to avoid the unstable power supply caused by the fluctuation of the mains voltage and affect the normal and stable operation of the video access control alarm system.

7. About the choice of switching power supply and linear power supply

In the actual project application, whether to choose a switching power supply or a linear power supply, many engineering friends have no way to start. In fact, as long as you grasp two points:

① For projects in hot southern regions, if you choose a linear power supply, it is recommended not to put the linear power supply and other equipment in the same equipment box, because the linear power supply has a large loss and heats up very badly, and other equipment in the same equipment box, if Untimely heat dissipation is likely to cause unstable operation of other devices. And if the linear power supply is equipped with a dedicated box, 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 battery damage.

Author: Written by Anna Zhang He from S4A INDUSTRIAL CO.,LIMITED