Many weak friends mentioned the problem of monitoring power supply configuration. If the power supply configuration is not well understood, it will often cause troubles in work. Today we will come together to understand the importance and design of the power supply in the security system.
First, how to properly configure the camera power supply of the entire monitoring system?
A: This problem often makes many weak friends feel embarrassed. I feel that many programs have found that the power supply capacity of the original design was not enough, and additional equipment was needed, which caused a problem with the party. In fact, because the camera starts at a moment, the starting current is very large, and the loss of long-distance transmission in engineering, the power required by the surveillance camera is not simply added to the rated power of all cameras. The correct way is to add the power of the camera of the entire monitoring system and multiply by 1.3 times. This is the actual power required by the camera, and then add about 30% of the loss. Finally, add 30% of the margin. Expansion will be used in the future.
Here we remind everyone, we do not recommend 12V centralized power supply, in places where conditions, we recommend 220V centralized power supply, or use 12V independent power supply, 220V socket installed next to the camera.
for example:
If there is a fixed gun camera in a commercial building, and the rated power of each surveillance camera is 4W, how do we configure the camera power supply?
According to the above calculation method, we calculated that the rated power of the camera is 4W*100 units=400W, and the actual power used by the camera is 400W*1.3 times=520W. After considering the loss, the power required by the camera is 520W*1.3 times=676W. With the power supply margin, the power supply that the camera finally needs to be configured is 676W*1.3 times = 878W
Summarized as follows: the power required to be configured by the camera = the rated power of the camera *1.3*1.3*1.3
(Note: If the monitoring distance is extremely long, it is necessary to increase the power supply appropriately and increase the power supply voltage)
Second, the configuration of the surveillance camera power supply, what is the most taboo?
A: The most taboo is that the entire monitoring system shares a power supply. The reasons are as follows:
1. When the system is being repaired, it is often necessary to turn the power on and off. All the cameras are started at the same time when the power is turned on, and the starting current is particularly large, and the impact on the power supply is great, and the power supply is severely burned.
2. All surveillance cameras share one power supply. When the power supply fails, the entire closed-circuit monitoring system is paralyzed. In particular, some important entrance and exit images cannot be monitored, which may cause unnecessary trouble.
So what should be the right approach? As in the above example, a commercial building has 100 fixed cameras, which require a total of about 800W of power. The correct configuration should be 4, each 200W power supply. In this way, when a power supply fails, the camera of the important entrance and exit can be connected to other good power supplies without affecting the operation of the entire system.
Third, the choice of surveillance camera power supply also need to pay attention to what problems?
First: When connecting the camera to the power supply in the centralized power supply scheme, do not connect the camera with a far distance to the surveillance camera with a close distance to the same power supply. If connected to the same power supply, the power supply voltage is high, the camera will be burnt at a close distance, the power supply voltage is low, and the camera with a long distance has no image. Nowadays, the camera of Kaiwei series basically adopts wide power supply design, can work stably for a long time in the range of DC input voltage 12V-36V, completely eradicate the damage caused by unstable input voltage (such as surge) to the camera. It can be well solved. this problem. It is the ideal solution for centralized power supply to the camera.
Second: If the monitoring distance is too far, you need to configure a higher voltage power supply, such as 30V, 36V, etc., or even directly for 220V AC, and then transform to the front end.
Fourth, explore video monitoring several power supply methods
There are three common types of power supply for video surveillance, namely point-to-point power supply, centralized power supply, and PoE power supply. Let's take a look at their respective advantages and disadvantages.
1, point-to-point power supply
Point-to-point power supply means that 220V AC is directly taken from the monitoring room, and DC12V or AC24 power is connected to the camera.
Advantages: 220V AC has low voltage loss and strong anti-interference ability during transmission.
Disadvantages: Each point must be installed with a power supply, which is more troublesome to construct.
2, centralized power supply
The centralized power supply mode refers to the centralized power supply to the front-end load by using a 12V switching power supply in the monitoring room or at an intermediate point.
Advantages: Convenient construction, easy maintenance, saving power costs
Disadvantages: DC low-voltage power supply transmission distance is too high, high voltage loss, poor anti-interference ability during transmission, easy to cause front-end camera voltage instability, less than 12V and so on.
3, PoE power supply
PoE power supply refers to the technology of providing DC power to other devices without any changes to the existing Ethernet cabling infrastructure. This method is mainly applied to high-definition network digital monitoring systems or wireless AP networks.
Advantages: Reduce cost, flexible deployment, single port maximum power up to 30W.
Disadvantages: The quality of the network cable is high and the transmission distance is limited.
Precautions:
When using an infrared camera, centralized power supply is not recommended. Because the current is large when the infrared is turned on, it is difficult to ensure that the infrared effect of all cameras is optimal. Point-to-point power supply is sometimes cumbersome to find, and you need to find a suitable power point. The PoE power supply mode is now used more often, and is often powered by a PoE switch or a power supply, which can save labor costs.
V. Application of POE power supply in video surveillance
Many people who are new to PoE switches do not know how many surveillance cameras a PoE switch can connect to. It is necessary to understand how many cameras the PoE switch can connect at the same time. See three aspects: PoE switch power supply standard, PoE switch total power supply, camera code. flow.
1. PoE switch power supply standard
There are two standards for popular PoE switches in the market. IEEE802.3af and IEEE802.3 at define the power supply of 15.4W and 30W respectively, but the actual power supply is 12.95W and 25W due to the loss during transmission.
When using a PoE switch that supports the IEEE802.3af standard, the power of the powered device cannot exceed 12.95W. When the PoE switch of the IEEE802.3at standard is used in the same way, the power of the powered device cannot exceed 25W.
Generally, a PoE switch that supports the IEEE802.3af/at standard at the same time, the power supply is adaptive. For example, it is connected to a 5W device, which provides 5W of power; if it is connected to a 20W device, it provides 20W of power.
2, the total power supply of the PoE switch
This can be judged from the total power of the PoE switch. Under the IEEE802.3af standard, if the total power of a PoE power supply of a 24-port PoE switch reaches 370W, then it can supply 24 ports (370/15.4=24), but if it is a single port according to the IEEE802.3at standard. The maximum power supply is 30W, and at most 12 ports can be powered (370/30=12).
For example, an 8-port PoE switch supports the IEEE802.3af/at standard. The power of a single camera is 11W. Then the switch can connect 8 such cameras. If the power of a single camera is 20W, reserve one or two ports. Ideally, it is recommended to connect 5-6 cameras.
3, the camera's code stream
If the power supply from the PoE switch is inaccurate, because the network monitoring requires high definition and smoothness, it depends on the code stream of the camera. After all, the PoE switch not only supplies power but also transmits video data.
The code stream of common cameras: 720P (1 million pixels) code stream is 4.5M, 960P (1.3 million pixels) code stream is 6M, 1080P (2 million pixels) code stream is 8M, 3 million pixel code stream is 10M, 500 The megapixel code stream is 13-15M.
When transmitting video data, the actual bandwidth utilization of the PoE switch is only about 60%. For example, an 8-port PoE switch, the port transmission rate is 100 megabytes, the camera is 720P, how many such cameras can be connected?
The camera stream of the 720P is 4.5M. The available bandwidth of this PoE switch is about 60Mbps, and about 60/4.5 is about 13. Since the PoE switch has only 8 PoE power ports, it can be fully loaded.
Similarly, if the 8-port 100-megabit PoE switch is connected to a 1080P camera, then at most seven such cameras can be connected.
When actually using a PoE switch, it is necessary to consider both the power supply and the camera code stream, and the two must be satisfied before they can be used safely and smoothly.
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