As the security subsystem in the weak current system, access control is often encountered, and almost all large projects will have this system, because the access control system will be configured for personnel management. There is a very important device in the access control system, that is, access control Power supply, what exactly does it do? How to choose?

Although the access control controller is the core part of the access control system, the power supply is also a link that cannot be ignored to ensure the stability of the entire system. 

Is it better to choose a linear power supply or a switching power supply? 

The advantages of linear power supply: stable performance, no interference such as high frequency ripple. 

Disadvantages of linear power supply: heat generation, low energy utilization. There is no choice of super powerful power supply. 

Advantages of switching power supply: It is convenient to use high-power power supply for centralized power supply, and it shows better cost performance when the price of raw materials continues to rise. Small size and light weight.

Disadvantages of switching power supply: If the quality of the power supply is not good, the high-frequency ripple is not easy to control. For some access controllers with poor anti-interference ability, it is easy to cause the access controller to crash, resulting in the situation that the door cannot be opened.

How much power is suitable for choosing a power supply? 

Most of the access control systems use 12V DC power supply, so the power of the power supply can be evaluated through the rated current parameters of the power supply. Considering impact resistance and long-term stable operation, the following suggestions are made:

If you choose a linear power supply, a controller with 4 electric plug locks is calculated, and it is recommended to choose a 5-7A linear power supply. One controller is calculated with one electric plug lock, it is recommended to choose a linear power supply above 3A. the

If you choose a switching power supply, a controller with 4 electric plug locks is calculated, and it is recommended to choose a 4-5A switching power supply. One controller is calculated with one electric mortise lock, and it is recommended to choose a switching power supply above 3A. One controller is equipped with 8 electric plug locks or 6 magnetic locks, it is recommended to choose a switching power supply above 10A.

Precautions

For power supply selection, the larger the power and rated current, the better, and there will be no major side effects. If it is lower, it will not work.

The power supply is the basis for ensuring the stable operation of the entire access control system. The selection of the power supply can directly determine whether the engineering company can earn as much profit as possible when implementing the project. At the same time, the selection of the power supply can also reflect the project The supplier's own ability to control the quality of the project.

When we investigated the macro market of access control, we found that more than 90% of system failures were caused by improper selection of power supply, and some failures may have affected the smooth promotion of the project. On the whole, the failure caused by the power supply is mainly manifested in the following aspects:

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

② After a thunderstorm, a large-scale power failure occurs;

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;

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

Application and Selection of Power Supply in Access Control Alarm System

1. Measure the actual output power of the power supply

2. Effective lightning protection

3. Wide temperature range

4. Intelligent charging and discharging management of the backup battery

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

6. Wide voltage range, stable power output

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

1. Measure the actual output power of the power supply

There are many devices involved in power supply in the 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 access control system. The normal and stable operation of the alarm system. When purchasing a power supply, it is recommended to choose a power supply manufacturer with up-to-standard technical parameters, reliable quality, good reputation, and suitable for access control and alarm systems. At present, in some access control manufacturers, the power supply is sold together with the controller. Generally speaking, such manufacturers consider the actual application of the project in the selection of 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 corresponding to the output power of the power supply (such as cement resistance) 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 load? Is the heat generation normal? If possible, it is best to install and test run on site.

2. Effective lightning protection

Judgment on whether the product has lightning protection:

① Visually check 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.

3. Wide temperature range

The temperature adaptation range is within -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

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.

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

Due to the diversity of access control and alarm system hardware devices, it is bound to involve one power supply to provide 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 able to intelligently judge the output Current, this can solve the problem of centralized power supply of one power supply or when a certain power output fails, it will not affect the power supply output of other roads, even if one power 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 access control 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.

②The low-cost linear power supply generally does not have the battery charge and discharge management function, which can easily cause damage to the battery.

The connection terminals of the special power supply for access control generally include the following: power output +12V, power output GND, switch control signal input push, electrical signal control input control+ and control-, normally closed electric lock control output NC, Normally open electric lock control output terminal NO, where the power output terminal +12V and power output terminal GND are connected to the +12V and GND of the access controller or all-in-one machine;

The power supply output terminal GND and the switch control signal input terminal push are connected to the door open button and the door open switch signal output by the access control. Note that this interface can only be connected to a pure switch signal. If the signal has power, it will be troublesome. The control part of the power supply may be blocked. burn. Sometimes several devices are required to control the electric lock at the same time, as long as the pure switch signal can be directly connected in parallel to achieve common control; the electric signal control input terminals control+ and control- are connected to the electric signal for controlling unlocking output by the access control or building intercom, if the device If the control output is an electrical signal, use these two ports, and the voltage must be between 5-12V;

The control output terminal NC of the normally closed electric lock (such as magnetic lock, conventional electric mortise lock, power-on lock type cathode lock, etc.) of the special power supply for access control is connected to the positive pole (red line) of the normally closed electric lock, and the negative pole (black line) of the electric lock ) is connected to the GND of the special power supply for access control; the control output terminal NO of the normally open electric lock (such as electric control lock, power-on unlocking type cathode lock, etc.) is connected to the positive pole (red line) of the normally open electric lock, and the electric lock The negative pole (black wire) of the access control is connected to the GND of the special power supply for access control.

What needs to be specially explained is the control of the electric control lock. There is no positive or negative distinction between the two wires. As long as one is connected to the NO terminal and the other is connected to the GND, it is enough. When connecting the electric control lock, special attention must be paid First of all, the special power supply for access control and the door opening delay of the simple access control all-in-one machine should be adjusted to the minimum, otherwise the high current of the electric control lock up to 3A is like a flash flood, and the connected equipment will be burned.

Author:Written by Ms.Rebecca Fu from S4A INDUSTRIAL CO.,LIMITED