With the development of wireless technology, the development momentum of wireless transmission technology is getting stronger and stronger. Among them, POE power supply technology has become a scene of wireless coverage, wireless monitoring and smart grid with its simplification, energy saving and security advantages. New favorite. Then, regarding the POE power supply technology in the wireless monitoring system, many users still have many questions and misunderstandings. Let's take a look at the six common problems of POE power supply.
1. How to choose PoE switch for wireless monitoring and wireless coverage
There are many types of PoE switches, ranging from 100 Mbps to Gigabit to full Gigabit. There are also differences between non-network management and network management. The difference in the number of different ports. To choose the right switch, comprehensive and comprehensive considerations are needed. . Take the project that requires high-definition monitoring as an example.
Step 1: Select a standard PoE switch (see Reason 2 for reasons)
Step 2: Choose a 100M or Gigabit switch
In the actual solution, it is necessary to integrate the number of cameras, camera resolution, code rate, frame number and other parameters. Major monitoring equipment vendors such as Haikang and Dahua provide professional bandwidth computing tools. Users can use tools to calculate the required bandwidth to select the appropriate PoE switch.
Step 3: Select af or at standard PoE switch
According to the wireless monitoring device power selection. For example, using a well-known brand of camera, power 12W max, this situation requires the use of af standard switch. A high-definition dome machine has a power of 30W max. In this case, an at-standard switch is required.
Step 4: Select the number of ports on the switch
The PoE switch can be divided into four ports, eight ports, sixteen ports, and four ports according to the number of ports. It can comprehensively monitor the power, quantity, and location of the device, and the power and price of the switch.
2. Why do you have to use standard PoE switches to supply power?
First, you need to distinguish between standard PoE switches and non-standard PoE switches. The standard PoE power supply switch has a PoE control chip inside. It has a function of detecting before power supply. When the device is connected, the PoE power supply sends a signal to the network to detect whether the terminal in the network is a PD device that supports PoE power supply.
The non-standard PoE product is a strong supply type network power supply device. It is powered when powered on. There is no detection step. No matter whether the terminal is powered by PoE powered devices, it is easy to burn the access device.
Take the NetEase MS series standard PoE switch as an example. After power-on, the switch will automatically detect the powered device. If the non-PoE powered device is detected, it will automatically stop the power supply and protect the powered device from burning. The situation of the equipment occurs, making the power supply process more secure. The testing process is as follows. Therefore, you must use a standard PoE switch to supply power.
3. How to distinguish between standard PoE and non-standard PoE is very simple, just use a multimeter to measure. Methods as below:
Start the device, adjust the multimeter to the voltage measurement position, and touch the power supply pin of the PSE device with the two meter pens (usually 1/2, 3/6 or 4/5, 7/8 of the RJ45 port). ), if a device with a stable output of 48V or other voltage values â€‹â€‹(12V, 24V, etc.) is detected, it is a non-standard product. Because in this process, the PSE does not test the powered device (here, the multimeter) and directly supplies power with 48V or other voltage values.
Conversely, if the voltage is not measured and the multimeter's hands are beating between 2 and 10V, it is a standard POE. Because at this stage, the PSE detects the PD side (here a multimeter), and the multimeter is not a legitimate PD, the PSE does not supply power, and no stable voltage is generated.
4. Is PoE power supply stable?
In actual construction and application, there will still be cases where the PoE switch cannot supply power or the power supply is unstable. Is the PoE power supply really stable?
In fact, PoE technology has been developed for many years and is now in a very mature stage. The standard PoE power supply is stable and safe enough. Most of the conditions are due to the selection of non-standard PoE switches or the quality of the wires is too inferior, or the design itself is unreasonable, the power supply distance is not arranged or the connection of too many high-power devices has insufficient power supply (especially the night monitoring device turns on the heating mode). Time). Therefore, in the actual deployment, it is found that the external power supply is unstable.
5. Is the power of the PoE power supply switch as high as possible?
Due to the emergence of high-power devices such as high-definition domes and real-time video cables, network equipment vendors are eager to develop PoE switches with higher total power. However, many products only pursue the improvement of total power, ignoring the relationship between power and port number. At the same time of high power, the overall cost of the device will be increased. As a result, the PoE switch selected by the user is not practical and has low cost performance.
Therefore, in actual deployment, determine the power and quantity of the PD device according to the steps of Problem 1, and select a suitable PoE switch.
6, PoE power supply distance can only be 100 meters?
Transmission of DC power over a standard Ethernet cable can be transmitted very far, so why is the transmission distance limited to 100 meters?
The fact is that the maximum transmission distance of a PoE switch mainly depends on the data transmission distance. When the transmission distance exceeds 100 meters, data delay and packet loss may occur. Therefore, the transmission distance should not exceed 100 meters in the actual construction process. However, some PoE switches have a transmission distance of 250 meters. The MS-based standard PoE switches use the L-PoE function to extend the PoE transmission distance to 250 meters to meet long-distance power supply. It is also believed that with the development of PoE power supply technology, the transmission distance will be extended to a long time.
Followed by the network cable, the network cable also determines the power supply distance, the national standard super 5, 6 network cable is ok, especially the super 6 national standard network cable is certainly possible. Some customers use some cheap, poor quality network cables to use them, and they can't reach the distance requirements of power supply. On the contrary, we have problems with our Runda PoE switches or PoE splitters, and when we sent technical engineers in the past, we discovered that There is no problem with our PoE switch, and the problem is solved after replacing the network cable.
The network cable is not a regular network cable, there are many people can not distinguish, the network cable on the market is too fake. I will give you a few ways to decide whether the network cable is true or not, for reference only:
a, the regular national standard network cable, the resistance value of the distance of 10 meters - 100 meters is less than 10 ohms, this has a multimeter can be directly measured, when greater than 10 ohms, such as the resistance value reached 30 ohms, then the network cable must be false;
b. The official national standard network cable, a box of about 305 meters, the market price of 450-500 yuan (the price of imports will be higher), familiar friends 430 yuan may also buy, but if it is lower than this price, basically Fake goods.
c. The regular national standard network cable is pure copper, or oxygen-free copper. What other materials are copper-clad iron, copper-clad aluminum, etc. are fakes.
The above is a brief introduction to the common problems of POE. More relevant knowledge can be paid to Tengyuan Zhituo. If you have any needs and help in this area, please consult our customer service staff, we will provide you with detailed answers.
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