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Questions tagged [poe]

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

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PoE power extractions using RT9400

I want to get power using RT9400. The thing is I have schematics for RT9400 connections diagram in which they used magnetic transformer. My question is can I directly use RT9400 with PoE connector to ...
Ali Hamza Malik's user avatar
2 votes
1 answer
102 views

Telecom Lines Conducted emissions noise travel

I am seeking an explanation of how conducted emissions on telecom lines are measured. The frequencies of interest are at 150kHz to roughly 850kHz. The size of the unit is 30cm by 30cm by 15cm. The ...
DRF's user avatar
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9 votes
2 answers
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Is there a way to non-destructively test whether an Ethernet cable is pure copper or copper-clad aluminum (CCA)?

I got an Ethernet cable on Amazon for what was, in hindsight, a suspiciously good price. The description says it's copper but one of the one-star reviews claims it's actually copper-clad aluminum (CCA)...
hbraunDSP's user avatar
2 votes
0 answers
32 views

Telecom Lines Conducted emissions [closed]

We have rented a Telecom line ISN to conduct some in-house pre-compliance testing. The test setup closely follows the CISPR32 standard. We encountered issues with conducted emissions in the lab, which ...
DRF's user avatar
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7 votes
3 answers
261 views

ESD knocking out PHY on device with unisolated POE

I inherited this design, one problem I am having is ESD on the chassis knocks out the PHY, sometimes it can't even be reset via software. I am curious if anyone can spot any glaring errors with the ...
Voltage Spike's user avatar
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5 votes
1 answer
161 views

Is this heat from the PoE module normal?

I have added the Silvertel Ag9205S 5 V PoE module to my design in order to provide 5 V power to the system using Ethernet. I also have USB power that can provide 5 V as well. I have a diode on the USB'...
Sean's user avatar
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1 vote
0 answers
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Conducted Emissions from a PoE powered equipment according to En55032/CISPR32

I'm seeking clarification on Conducted Emissions measurements for a PoE powered device. I've reviewed both the CISPR32 and CISPR 16-2-3 standards, yet I couldn't find specific guidance on the setup ...
DRF's user avatar
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1 vote
1 answer
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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 ...
Red Dragon's user avatar
7 votes
2 answers
2k views

Is using the shield in a CAT cable for return current a bad idea?

Consider a PoE solution that uses shielded CAT cables and where the shield is connected to signal ground on both the PSE and the PD side. In this case, the shield is most probably presenting a lower ...
FreddaH's user avatar
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1 vote
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Selecting Optoisolator CTR for MPS MP8009 SSR Forward Topology

Do the optoisolator Current Transfer Ratio (CTR) Min and Max matter for this design, and if so, what is the benefit of selecting each ratio? Here is the MPS MP8009-GV PoE controller datasheet, inside ...
Wes Ellgass's user avatar
3 votes
1 answer
192 views

Raspberry Pi 4B POE Rectifier Circuit recommendation

Am I doing the signal rectification properly for the POE application using the Diodes on the RPI 4B 4 pin header? I have attached images of my design, as I am trying to use a Raspberry PI 4B with POE (...
Wes Ellgass's user avatar
0 votes
0 answers
33 views

Signal Ground near Earth POE

I have Earth Ground 48V poured around the components before our diode array. I have three seperate ground planes, one for Earth, one for our POE components before the transformer, and our signal 5V ...
Wes Ellgass's user avatar
0 votes
0 answers
56 views

Transformer Schematic Explanation

Why does this design use two winding secondary outputs? I do not understand what is happening here. I know that the device converts for POE 5V 4.8W, but that secondary winding setup, how could I ...
Wes Ellgass's user avatar
0 votes
0 answers
72 views

Help troubleshooting a PoE circuit

After much ado I've designed a simple PoE addon board for a custom ESP32. However, when plugged in, the PoE light on the switch goes on for about half a second, and then goes back off. Seems like its ...
Maciej Swic's user avatar
2 votes
1 answer
66 views

Conducted emissions testing for POE 802.3 device?

For IoT devices with a Powered Device (PD) for Power Over Ethernet (POE) and not plugged into AC mains; What, if any, standards would a device potentially be subject to at an Nationally Recognized ...
Voltage Spike's user avatar
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2 votes
1 answer
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PoE: PSE isolation requirements

On the robot I'm currently designing, there will be several connectors with PoE ethernet and supply voltage (0 V, 24 V) and some other signals (referenced to 0 V). I'm unsure if I need isolation for ...
Sandro's user avatar
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1 vote
1 answer
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Can I run PoE++ on DisplayPort/HDMI over Cat6?

I'm working on a project for an industrial application where I need to run a monitor with a single cable carrying both data and power. 7" LCD with a few Watts backlight, 1024x600@30fps or so, ...
Mitcham Tuell's user avatar
0 votes
1 answer
58 views

Power limitations for Ethernet cabling

I have a 60 watt constant current Meanwell driver that has the following output options: .9 amps @ 67 volts or 57 volts @ 1.05 amps. I want to know what specific ethernet cable is required. Can I ...
Tim's user avatar
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1 vote
1 answer
62 views

POE circuit with small transformer and small volume footprint

I would like to make an isolated POE802.3af controller that can convert POE ~48V to 5V 2A, but the main problem is most designs use a standard POE transformer that has multiple coils. The problem with ...
Voltage Spike's user avatar
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1 vote
1 answer
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Connecting Ethernet to PIC18F97J60

I am currently working on my diploma thesis and since circuit construction is not the main topic, I am unfortunately not making any progress. I would like to connect the PIC18F97J60-IPT with PoE. I ...
simox357's user avatar
0 votes
1 answer
81 views

Magjack to TPS2378 connection

I'm designing a PoE shield for an ESP32, but am having some trouble figuring out the CT connections for the TPS2378. In their schematic, they have some rectifiers connected to the CT pin of each ...
Maciej Swic's user avatar
1 vote
1 answer
152 views

LAN8720A - PoE Protection

I will go straight to my question. I have currently a PoE PD using LAN8720A PHY, i follow almost all manufacturer recommendations on PCB layout and schematics, anyways i have dead LAN8720A straight ...
Radu G.'s user avatar
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2 votes
1 answer
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Earth for custom POE+ board design

after getting the center tap pins for poe, I have an example schematic to design an EARTH ground. I have the understanding that that would be our Earth in AC over cabinet. That would remove our value ...
Wes Ellgass's user avatar
2 votes
1 answer
155 views

Problem with PoE implementation and newer switches

I am using Power over Ethernet (MP8007 as Powered Device) and it works perfectly with old PoE switches and PoE injectors. In this application PoE is used as a secondary power source so when the main ...
Gusto's user avatar
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1 vote
1 answer
144 views

PoE circuit can not connect when using injector

I am designing a PoE powered development board with an ESP32 microcontroller module. I am using the following circuit for the PoE power supply: This is a direct copy of the PoE power circuit used by ...
Oliver Norin's user avatar
2 votes
2 answers
280 views

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: ...
personal_cloud's user avatar
6 votes
1 answer
642 views

What is 3 wire I2C?

This is first time I'm seeing 3 wire I2C and have no idea how it works. How can I implement it in STM32 in Cube IDE using its GUI? I'm using TI TPS23881 (PSE controller) in one of my projects and I ...
Muhammad Ali Jayyad's user avatar
1 vote
1 answer
46 views

Useing a PoE RJ45 ICM Magnetics but not using it for PoE?

I plan on using the Bel G27-122T-015 (PoE ICM RJ45) but I don't need it for PoE. Can I just leave these pins unconnected? The ICM already has an internal Bob Smith termination.
miggyEE's user avatar
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Feedback for ESP32-POE board

just working on an ESP32 board featuring a WROOM32-UE and POE functionality. One of my first PCBs, so I'd appreciate some overall feedback on layout and routing. Note that not everything is done yet. ...
239843u1fjw's user avatar
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1 answer
101 views

Does PoE require impedance matching

I'm currently designing a PCB that's powered through Power-over Ethernet. It's my first time working with ethernet on a PCB. I've based the schematic on a Development board by Espressif (Link : https:/...
Samuel Mathieu's user avatar
-1 votes
1 answer
165 views

Hot-plugging current - TVS and ethernet

My question is based on this question over here In one of the comments, it is mentioned, "TVS on the media side would seem to invite short-circuit currents on hot-plugging. Putting it behind the ...
Freshman's user avatar
-1 votes
1 answer
43 views

Ethernet questions - SPE

I have a question regarding Single Pair Ethernet, is it possible to carry power with two wires? For example, controlling and powering a motor 12V 0.5/1A
Freshman's user avatar
0 votes
0 answers
97 views

Not working IEEE 802.3af PoE-PD Interface Controller (NCP1091)

For a hobby project, I am developing a PoE-powered PCB. At the moment, I have the following schematic and pcb layout designed. When testing the PCB, I just can't get the PoE to work. My Switch (...
NeDor's user avatar
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0 votes
1 answer
101 views

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 ...
Voltage Spike's user avatar
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0 votes
0 answers
56 views

Ethernet transformer RX Centre tap connection to ground

I was going through some schematics that would have a PoE application and stumbled upon the below portion of a PoE camera application schematic. In the above schematic, we can see the R66 resistor is ...
user avatar
0 votes
0 answers
137 views

PoE supply : what isolation is garanteed?

I'm currently designing a PCB that will be powered by PoE (or external supply). I have some doubts about what isolation the PoE supply (PSE, typically a PoE switch) is guaranteed to provide : are the ...
Sandro's user avatar
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0 votes
3 answers
286 views

What are the rated voltage and current of a single wire within an ethernet cable?

I haven't been able to find a clear cut answer to this question. I've found online somewhere that the entire cable can carry a max of 57V. Each pair can carry a max of 960mA. Is there any validity to ...
rrowhe4d's user avatar
0 votes
1 answer
263 views

Convert On-Q Legrand intercom to powered doorbell

My home came with a c.2007 On-Q Legrand Inquire 1000 intercom system. All stations only issue a gravely hiss. The Talk and Door buttons do not work. Mute works. Volume adjust works. All units use Cat ...
Jim Simpson's user avatar
0 votes
3 answers
115 views

Can I run a dedicated power source through along with Ethernet?

Instead of utilizing POE, what if I used a seperate power supply for power and Ethernet for data using 2-pair shielded Cat5. Has anybody ever tried this, or thought of it? Are there any theoretical ...
Erric DiFilippo's user avatar
0 votes
1 answer
174 views

Using resistors to create a virtual center tap in PoE applications

I am designing an application where existing PoE infrastructure should be used to power a device instead of supplying each device with its own power supply. In this application, no data needs to be ...
joelsa's user avatar
  • 33
0 votes
3 answers
131 views

ANDing isolated power supplies

Is there any specific challenge to ANDing two isolated power supplies, assuming that ideal diodes are used on their outputs? I'm interested in making a particularly compact PoE supply capable of ...
foxtrot's user avatar
  • 167
6 votes
3 answers
2k views

What's the connector on this PSU for a PoE switch?

I bought this switching power supply (PAC-500WA-BE) that I plan to use to power a PoE switch. The documentation is very poor and I would like to know the name of the connector on the back, where the ...
leopicchio's user avatar
0 votes
2 answers
180 views

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's user avatar
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2 votes
1 answer
538 views

How do you measure power consumed by a PoE-powered device?

For a weekend project I would like to make a Power Over Ethernet (PoE) power meter. There have been five situations where this could have come in handy during fault-finding in my projects. I finally ...
Jake quin's user avatar
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0 votes
0 answers
169 views

Does an outdoor PoE Access Point need seperate grounding?

I've searched high and low for an definitive answer on this, including speaking with electricians, but still get conflicting opinions on this. The goal: Install an outdoor wifi access point (AP), ...
cottonBallPaws's user avatar
5 votes
5 answers
5k views

What to connect to center-taps of Ethernet magnetics?

I'm designing a couple of PCBs to send data and be powered over Ethernet, however, I am not entirely sure what to connect to the center taps. I've heard different suggestions, from connecting it to 3....
Cole Weber's user avatar
1 vote
2 answers
284 views

Whole-house DC using PoE cheaper than multiple 5/12 V wall warts?

I have seen plenty of questions asked and answered about setting up whole-house low-voltage DC via something like PoE (passive over standard Cat5e cable, run through plasterboard walls). With the cost ...
Marl's user avatar
  • 21
1 vote
0 answers
53 views

EMI Filter compatible to both IEEE 802.3at and MIL-461F standards

I'm designing an EMI filter for a PoE DC-DC converter. It's a typical filter: However, IEEE 802.3at standard requires input bypass capacitor (from VDD to VSS) of 0.05 μF to 0.12 μF only. Per my ...
Ariel Narboada's user avatar
0 votes
1 answer
308 views

ESP32 with onboard ethernet interface [closed]

I'd like to know which is the best and chapest way to add an ethernet port (possibly POE enabled) to an ESP32 board. Alternatively I'm looking for a cheap ESP32 with onboard LAN. Any idea?
M4Biz's user avatar
  • 359
0 votes
1 answer
179 views

Ground reference for POE 48V

We have POE 802.3af in our design. We are facing some issues with it as elaborated below. We have connected an LED load to the connector end with a POE splitter. A splitter is used to convert 48V to ...
Chitharanjan's user avatar