The standard poe power supply voltage is set at 48V, and the power supply voltage fluctuates between 44-57V. Poe refers to Power over Ethernet, which is a technology that can transmit power and data to devices through twisted pairs in an Ethernet network. If the voltage at the power supply end is not enough, or the voltage is 40V, the transmission distance of the data signal will be greatly reduced, maybe only 30 meters or 40 meters; and since using POE power supply is definitely for convenience and hopes to transmit a longer distance, so the power supply The voltage cannot be too low.
The operating environment of this tutorial: Windows 7 system, Dell G3 computer.
What is poe
Power over Ethernet (PoE for short) is also called PoE power supply. The technology of stranding wires to transmit power and data to devices.
The starting point of Ethernet power supply technology is to allow small network devices such as IP phones, WLAN access points, and network cameras to obtain power directly from Ethernet cables (the idle 2 pairs of the 4 pairs of twisted pairs for transmission) , no need to lay separate power lines to simplify system wiring and reduce network infrastructure construction costs.
The typical PoE networking is as shown in the figure:
A typical Ethernet power supply system. Keep the Ethernet switch equipment in the wiring cabinet, and use a power supply hub (Midspan HUB) to provide power to the twisted pair of the LAN. At the end of the twisted pair, this power is used to power phones, wireless access points, cameras, and other devices. To avoid power outages, use a UPS.
How much V does poe supply?
The standard poe power supply voltage is set at 48V, and the power supply voltage fluctuates between 44-57V. If the voltage at the power supply end is not enough, or the voltage is 40V, the transmission distance of the data signal will be greatly reduced, maybe only 30 meters or 40 meters. Since the use of POE power supply is definitely for convenience and hopes to transmit longer distances, the power supply voltage cannot be too low.
The higher the voltage, the farther the power transmission will definitely be. But don’t forget about the network cable and how much it can withstand. After the network cable is powered, there will be current. The greater the current, the greater the strength of the network cable. If it exceeds 2A, problems or dangers will occur. Just like the wires we use in our homes, if the wire itself is very thin but connected to a high-power electrical appliance, there is a possibility of burning the wire. Returning to POE power supply, the voltage naturally cannot be that high, so 48V is a compromise.
Composition of the POE system
A complete POE system includes two parts: the power supply end device and the power receiving end device. The PSE device is a device that supplies power to Ethernet client devices and is also the manager of the entire POE Ethernet power supply process. The PD device is a PSE load that receives power, that is, the client device of the POE system, such as IP phones, network security cameras, APs, and many other Ethernet devices such as PDAs or mobile phone chargers. Based on the IEEE802.3af standard, the two establish information connections about the connection status, device type, power consumption level, etc. of the powered device PD, and based on this, the PSE supplies power to the PD through Ethernet.
The main power supply characteristic parameters of the POE standard power supply system are:
The voltage is between 44 and 57V, with a typical value of 48V.
The maximum allowed current is 550mA, and the maximum starting current is 500mA.
The typical operating current is 10~350mA, and the overload detection current is 350~500mA.
Under no-load conditions, the maximum required current is 5mA.
Provides three levels of electrical power requests for PD equipment: 3.84~12.95W, with a maximum of no more than 13W. (Note that PD classes 0 and 4 are not shown and should not be used.)
Power supply method
The PoE standard is for use with Ethernet Two methods are defined for transmitting DC power to POE-compatible devices through transmission cables:
1. Mid-Span method (Mid-Span)
Use unused idle pairs in the Ethernet cable To transmit DC power, it is used between ordinary switches and network terminal equipment. It can supply power to network terminal equipment through network cables. Midspan PSE (mid-span power supply equipment) is a specialized power management device that is usually placed together with the switch. It has two RJ45 jacks corresponding to each port, one is connected to the switch with a short wire, and the other is connected to the remote device.
2. End-Span method
is to transmit DC power simultaneously on the core wire used to transmit data. Its power transmission adopts the same method as Ethernet. network data signals at different frequencies. The corresponding Endpoint PSE (end power supply equipment) includes Ethernet switches, routers, hubs or other network switching equipment that support POE function. It is foreseeable that End-Span will be popularized rapidly. This is because Ethernet data and power transmission use common line pairs, thus eliminating the need to set up dedicated lines for independent power transmission. This is especially true for cables with only 8 cores and matching standard RJ- The 45 socket is particularly significant.
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