加拿大28精准大小算法

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6 questions let you understand POE power supply

source: Shanghai Biaojun Electronic Technology Co., Ltd. time: 2018-08-29

加拿大28精准大小算法   In recent years, with the rapid development of network monitoring, the technical threshold is getting higher and higher, and the technical support provided by manufacturers is becoming more and more comprehensive and systematic. One of the most confused problems in engineering communication is the POE power supply. What are the difficulties in POE power supply? Which issues are worthy of attention from the engineering company? Six questions let the engineering company understand the POE power supply!

  Question 1: What is PoE technology?

  PoE (PowerOverEthernet) refers to some IP-based terminals (such as IP phones, WLAN access points APs, network cameras, etc.) without any changes to the existing Ethernet Cat.5 cabling infrastructure. While transmitting data, it also provides DC power supply technology for such devices. PoE technology can ensure the normal operation of existing networks while minimizing costs while ensuring the security of existing structured cabling.

加拿大28精准大小算法   A complete PoE system includes two parts: a power supply device (PSE, PowerSourcing Equipment) and a power receiving device (PD, PoweredDevice).

加拿大28精准大小算法   Power Supply Equipment (PSE): An Ethernet switch, router, hub, or other network switching device that supports POE.

加拿大28精准大小算法   Receiving device (PD): In the monitoring system, it is mainly the network camera (IPC).

  Question 2: Is the PoE power supply stable?

加拿大28精准大小算法   From a technical point of view, PoE technology has been developed for many years and is now in a very mature stage. However, due to the cost pressure of the current monitoring market, the quality of the selected PoE switch or wire is too inferior, or the design of the solution itself is unreasonable, resulting in a particularly large workload for the maintenance of the project using PoE power supply. Therefore, the PoE power supply is generally not available to the engineering company. A stable view.

  The network monitoring project is different from ordinary network integrated wiring. The data transmission volume is very large, the power is high, and it requires all-weather uninterrupted work. The use of quality-guaranteed PoE equipment and wires is the guarantee of the stability of the whole system.

  Question 3: What are the advantages of the PoE power supply solution?

加拿大28精准大小算法   1. Simplify wiring and save labor costs

  A network cable transmits data and power simultaneously. PoE saves time and money by eliminating the need for expensive power and the time it takes to install the power supply.

加拿大28精准大小算法   2, safe and convenient

加拿大28精准大小算法   The PoE power supply device only supplies power to the devices that need to be powered. Only when the device that needs to be powered is connected, the Ethernet cable will have voltage, thus eliminating the risk of leakage on the line. Users can safely mix legacy devices and PoE devices on the network, which can coexist with existing Ethernet cables.

  3, easy to remote management

  Like data transmission, PoE can monitor and control the device by using Simple Network Management Protocol (SNMP). This feature provides features such as night shutdown and remote reboot.

  Question 4: What are the risks or disadvantages of PoE power supply technology in engineering applications?

加拿大28精准大小算法   1. Insufficient power, the power receiving terminal does not move: 802.3af standard (PoE) output power is less than 15.4W, which is enough for general IPC, but for high-power front-end equipment such as ball machines, the output power is not up to To the request.

  2. The risk is too concentrated: Generally speaking, one PoE switch will supply power to multiple front-end IPCs at the same time. Any failure of the POE power supply module of the switch will cause all cameras to fail to work, and the risk is too concentrated.

加拿大28精准大小算法   3, equipment, maintenance costs are high: Compared with other power supply methods, PoE power supply technology will increase the after-sales maintenance workload, from the perspective of security and stability, the stability and security of the individual power supply is the best.

  Question 5: How to choose a PoE switch?

加拿大28精准大小算法   1. It is necessary to supply power to devices with large power consumption: PoE switches use different standards and different output powers. For example, IEEE802.3af does not exceed 15.4W at maximum. Due to the loss of transmission wires, the maximum power consumption can be no more than 12.95W. The device is powered. A PoE switch that complies with the IEEE802.3at standard can supply power to devices with a maximum power consumption of less than 25W.

加拿大28精准大小算法   2. How many devices can be powered at most: An important indicator of a PoE switch is the total power of the PoE. 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 is The power supply is calculated at 30W, and at the same time, only 12 ports can be powered (370/30=12).

加拿大28精准大小算法   3. The number of interfaces required, whether with fiber ports, with no network management, and speed (10/100/1000M).

  Question 6: The safe transmission distance of PoE power supply? What are the suggestions for the selection of network cable?

  The safe transmission distance of POE power supply is 100 meters. It is recommended to use super five types of copper cables.

  The POE power supply network requires that this problem is only a problem in countries where fake goods such as China are rampant, and it is not a problem in many developed countries. The POEIEEE802.3af standard requires that the output power of the PSE output port be 15.4W or 15.5W. The PD device receiving power after transmission of 100 meters must be no less than 12.95W. According to the 802.3af typical current value of 350ma, the resistance of the 100m network cable must be (15.4-12.95W) / 350ma = 7 ohms or (15.5-12.95) / 350ma = 7.29 ohms.

  The standard network cable is natural to meet this requirement. The IEEE802.3afpoe power supply standard itself is measured by standard network cable. However, only the POE power supply network cable is required to solve this problem because many network cables on the market are non-standard network cables, and are not strictly manufactured according to the requirements of standard network cables. The non-standard network cable materials in the market mainly include copper clad steel, copper clad aluminum, copper clad iron, etc. These cables have large resistance values and are not suitable for POE power supply. The POE power supply must use a network cable made of oxygen-free copper, that is, a standard network cable.

加拿大28精准大小算法   The PoE power supply technology has high requirements on the wire. It is recommended that in the monitoring project, do not save costs on the wire, and it is not worth the candle.

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