Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [poe]

Power over Ethernet, a set of IEEE standards for transmitting electrical power along with data through an Ethernet cable.

Power over Ethernet, a set of IEEE s for transmitting electrical along with data through an cable.

For other ways of sending both power and data simultaneously through the a single cable, see .

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Passive POE 24V, how can it damage a non POE device

I read that active POE is safe, and that when performing the handshaking it can increase the voltage up to 10.1V. So I infer that generally Ethernet devices can handle 10V no problem. But what about 24V? If one connects 24V passive PoE (pin 1&4 to…
run_the_race
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Requirement of center tap in PoE applications

Why do we connect the power (48 V) and ground (return path for PoE power) on the center taps of transformer for PoE applications? Can't it be directly connected to TD+ & TD- pins of the transformer? If it is legitimate, what is the difference…
Sanjeet
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Minimal PoE handshake to get 12W from an active PoE switch?

What are the minimum handshake elements required to get 12W out of a PoE switch (with 8P8C modular connector) in a compliant way? After some basic but time-consuming research, I found the following: 25 kohm detection resistor do not connect load…
personal_cloud
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Will 802.3af device work on 24v passive poe?

I have seen a lot of questions and answers all over SE about using a passive POE device on an 802.3af network. But can you use an 802.3af device on a passive POE network? In particular, I have this POE injector that outputs 24V @ 0.5A (12 W?), and a…
browly
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Grounding a POE-powered device

I have a small touchscreen hooked up to a Raspberry Pi, powered by (and getting ethernet connectivity from) a 802.11af splitter. Everything basically works. Sometimes when I first walk up to the (capacitive) touchscreen, it behaves oddly - phantom…
Jonathan Rupp
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High Voltage Non-Standard Common Mode POE

What is a quick and dirty circuit for implementing midspan power over ethernet? I would like to operate over two unshielded twisted pairs, at 100 Mbps using common mode injection. Essentially, I want to implement 802.3 mode A PoE that is…
Andrew Wagner
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Power over Ethernet (PoE) power supply requirements clarification, PSE < PD?

IEEE 802.3at-2009 Table 33-7 shows minimum power supply (PSE) levels that seem to be less than the peak power that the powered device (PD) could draw for Class 1 and 2. Can anyone clarify how these are compatible or where I am misinterpretting the…
Red Dragon
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What would happen if I send 220V to my ethernet port?

I found unused cables at home and I connected them: This is obviously made as a joke, but I keep wondering what would happen if I were to actually plug both ends in my computer. Is there some safety where I would only toast my network port? Would…
Guillaume
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Power over Ethernet circuit connection

I'm thinking of making a simple PCB with RJ45 connector delivering both data to the control MCU and power to the whole PCB using the PoE technology. I'd like to use a LM5071 as a power source and i.e. W5100 as a TCP/IP stack. In all of the…
Tomáš 'Guns Blazing' Frček
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PoE design to support both Mode A and B

I am working on a PoE design for the first time that supports 100 Mbps. I plan on using the mEZS84801A evaluation board that uses MP8007 as a reference design to do all the signature detection, classification and DC/DC converter as shown below. I…
k051819
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PoE Circuit Resistor Question

I was looking at a schematic provided by TI for a PoE power supply, and I had questions about certain resistors. What is the purpose of R5,R6,R7, and R8 in this schematic?
be-ee
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PoE without DC/DC converter

I am planning on testing a PoE evaluation board (https://www.analog.com/media/en/dsp-documentation/evaluation-kit-manuals/dc2093af.pdf) with a pwm motor circuit. The PoE evaluation board doc recommends putting it Vout through a dc/dc converter +…
be-ee
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Expected power loss on a PoE (Power over Ethernet) device

I am just starting with PoE (Power over Ethernet), and I would like to use it to power a remote device (Buffalo WHR-HP-G54, manual here) that requires 5 volts and 2 amps DC (so, 10 watts, I assume). If my PoE injector is capable of sending via the…
Sopalajo de Arrierez
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Testing Ethernet POE and surge\transients from other sources like lightning

I've got a POE Powered Device (PD) that I would like to make sure the surge protection is functioning in the event of a surge that it doesn't take down my device. How could I test for surge\transient over POE?
Voltage Spike
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Power over Ethernet voltage

Is all PoE 48 V DC? We are building a PoE power supply at 48 V DC. Do the 12 V loads decrease the 48 V to 12 V?
Roger
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