Questions tagged [poe]

Power Over Ethernet.

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7 views

How to use the earthing connectors on an NVR-Switch-PoE Camera system? What power outlet to use?

Location: West Bengal, India. Electrical Supply: 220v AC. I am setting up a network camera system for home surveillance. All installations will be done by trained electricians and integrators. I ...
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1answer
24 views

GbE Phy(88E1543) with POE+ PSE(LTC4266) design (POE+ magnetics? RJ45 with Integrated magnetics?)

I'm trying to understand how i can inject power to a 4 bank RJ45. I want to use these parts : - LTC 4266 4 ports PSE (802.3 at compliant for GbE, in type1 class3 for 13W at each port) - Marvell ...
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3answers
166 views

DC-DC Buck Converter Failure Mystery

I'm a software engineer, so please excuse my gross ignorance of this topic. We are trying to figure out why our DC-DC converters sometimes fail and stop outputting power after a month or so of runtime....
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2answers
70 views

Can I run DC voltage through RJ45 Connector with Magnetics?

I am designing a PoE (Power over Ethernet) application. My question is can I run 48V DC Voltage through a standard RJ45 Jack WITH Magnetics? or do I need one WITHOUT magnetics? I am planning to use ...
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2answers
106 views

Develop PoE with Si3402

I am currently designing a PoE device with IC Si3402B Isolated refer and circuit my design: I use an RJ45 port with an internal diode bridge: I bought the RJ45 but not yet. I tested the external ...
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1answer
57 views

External Wall Adapter Detection in MP8007?

I am reading the datasheet of MP8007. I found ambiguity in section Wall Power Adaptor Detection and Operation on Page 16. After reading the section, i am not able ...
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1answer
132 views

Cable Side and Physical Side of a PoE Magnetics

I am reading the datasheet of PoE Magnetics. I am not able to understand which side belongs to cable side and which belongs to ...
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1answer
147 views

MagJack for PoE Powered Device

I am adding Power over Ethernet functionality in my Toradex's System-on-module (Colibri iMX6ULL) based carrier-board design. I ...
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1answer
141 views

PoE and Adapter Power Supply Design

I am designing a power supply cicruit. The circuit will get it power from PoE (preferably) and external adapter (7 - 12V). For ...
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1answer
82 views

Parallel PoE injector from pc psu?

So I was wondering if I could power my 8 or at least 4 ip cameras from my old pc psu. I have: *500 W psu, where 12 V can use up to 360 W *GV-EBL1100 ip cameras which require 12 VDC / (IEEE 802.3af), ...
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0answers
81 views

PoE+ Forward Converter Issues

I want to implement a 12v PoE+ PD power supply, and have settled on the LTC4269 for use in this application. Unfortunately I'm having problems getting my head around everything that is going on. A ...
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1answer
58 views

Why does PoE use duplicate wires for power

When a PoE cable is used to transmit power, it uses two wires for DC+ and two wires for DC-. In contrast, a simple light bulb powered by a battery circuit uses just one DC+ wire and one DC- wire. Why ...
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2answers
183 views

Measuring wattage to PoE device - how to hook up a multimeter inline?

I'd like to measure the amount of power drawn by a PoE client device (PD) and would like to hook up a multimeter inline to do so. However, power is supplied to the PoE device over two pairs of wires (...
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1answer
212 views

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 ...
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1answer
670 views

PoE 802.3af injector circuit

I am wondering if this little guy will work or if it will fry my router. Router is a UniFi AC Pro requiring 802.3af Gigabit PoE. I don't have one laying around so I came up with this. Its a voltage ...
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1answer
206 views

How can I make a PoE circuit that is compatible with 24V passive PoE and 802.3at active PoE?

I'm designing a PoE circuit that should be compatible with both active (802.3af/at) PoE and also 24V passive PoE. How can I do this? Can I just use a PD chip that doesn't include a DC-DC converter? ...
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2answers
1k views

Determining how much current I can actually run through my Cat6 24AWG Cables in my confirguration?

I want to use a CAT6 (24AWG) RJ45 cable to carry a total of 2A at 48V. As per the AWG Chart, I see that the Maximum amps for power transmission is 0.577A but the <...
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1answer
215 views

How to get Power into a Power over Ethernet cable?

I need to feed 12 volts into an Ethernet cable. The vendors datasheet states: Power Method: Passive Power over Ethernet (pairs 4, 5+; 7, 8 return) Does that mean I connect both the 4 and the 5 to ...
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2answers
89 views

Power over Ethernet: AC?

All commercial POE products I have seen feature DC current to power endpoint devices. What are the reason(s) why AC is not used for POE products?
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2answers
339 views

Pushing 50W over PoE?

I'm wondering if it's possible to drive 50W via PoE (cat 6e or cat 7) single cable? I want to power up a quite hungry ARM board, which has power rating of 5V 3A (15W) and a camera, which needs 12V 2....
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2answers
502 views

Powering a 2amp micro-usb device over cat5

There was once a phone in my bathroom, so now there is an LV box with a Cat5 cable in it at the end of a 30ft run. Can I hack something together to power a Google Home Mini with that cable?
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1answer
88 views

Power over ethernet design

I've been reading the data sheet for a power over Ethernet module, the si3402-B. There is an application schematic which shows how the system is typically designed. However, it says it's a ...
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1answer
70 views

Power supply using POE PD

I am designing an embedded system that involves a PIC18F66J65 MCU and a RN677 bluetooth module and passive elements. The main power source will be module called TPD as POE(power over ethernet) PD (...
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1answer
142 views

Why doesn't PSE circuit maintain power to PD?

I am trying to make a PoE 802.3af solution. This are my schematics: The problem is that the power does not maintain. It only provides 48V for about 300ms, then it drops. Also, the above statement is ...
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1answer
178 views

POE power will not interfering on Data travelling on Ethernet , Whats the logic

I was design POE+ circuit , so I read lot of articles on POE(power over Ethernet) IEEE802.af 15.4W on PSE side , For 10/100 base T can use Alternative A method where it use to deliverer power on data ...
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1answer
95 views

Power over Ethernet identification error?

I have a custom board which is powered by Ethernet and I am using the LT4275B from Linear using the recommended schematic. When I am using a cable with only the data pairs [1-2]&[3-6] ([4-5]&[...
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1answer
335 views

Battery Power Management PCB Design [closed]

I am working on an old PCB that uses a lot of the TI IC's for performing its functions. It's essentially a power management board that takes a DC input and charges 12 batteries connected to the ...
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3answers
186 views

How can I use power over ethernet to transmit data and power to the OpenMV Cam M7?

I'm trying to make the OpenMV Cam M7 PoE enabled. See the link below for the camera: https://openmv.io/collections/cams/products/openmv-cam-m7 It has USB interface, SPI, UART and CAN buses. My ...
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1answer
47 views

IEEE802.3af, 802.3at @ 2 x 30 Watt. But now @ 2 x 75 Watts [closed]

I have built large networks with IEEE802.3af & IEEE802.3at in PoE midspan and endspan style. I favor 48VDC, because it is the only standard used world-wide. AC can be anything depending the ...
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2answers
152 views

Why is it necessary to isolate MCU from the PoE part of the board?

MCU is usually connected to a PoE controller via I2C interface. Most of the relevant documents show that I2C should be optically isolated in this application. What are the reasons to have such ...
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2answers
2k views

Ethernet Trace Layout with PoE & Integrated Magnetics

I'm a hobbiest & I've put together a simple PoE board using a LinkIt Smart Duo, the AG9050-2BR and a Bel Fuse 0813-1X1T-57-F. The power circuit works but the Ethernet signal wont work. The ...
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2answers
1k views

Why are Ethernet jack center taps connected to VCC?

Taking this schematic as an example: EtherTen Can someone explain to me why the center taps of the transformers (TXCT, RXCT) are connected to VCC? I've seen this connection in many (although not all)...
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1answer
891 views

How to implement PoE with WIZnet W5500?

I want to implement a PoE solution and I started to design the board based on WIZnet's W5500 reference designs. I am using the design with the external transformer. My questions are: How to adapt ...
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1answer
103 views

Does 802.3af compliance require support for both Alternative A and Alternative B?

I am looking to purchase some PoE cameras. The camera description specifically states that they require power to be delivered on the data pairs (1,2,3,6), which indicates PoE standard 802.3af ...
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9answers
29k views

How safe is 48V DC?

In many Power over Ethernet (POE) setups the transmission voltage is 48V or slightly more. While higher voltage has obvious efficiency advantages, how safe it is? Is there any risk of electrocution ...
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1answer
4k views

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 ...
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1answer
455 views

Ethernet PoE Magnetics Pin swap

I have the following circuit right now Is it possible to connect PHY_TRXP0 on TD1- and PHY_TRXN0 on TD1+ and taking ETH_MX1_P from MX1- and ETH_MX1_N on MX1+ respectively? Signals on RJ45 will go as ...
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1answer
492 views

Modified BoB smith termination for PoE— Will it work?

I am using DP83620SQ/NOPB PHY for our 10/100Mbps Copper Media Ethernet Interface. We had connected through the Magnetics part 749013011A which is not PoE supported. But we need to use this for ...
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1answer
88 views

In PoE: is alternative A compatible to all PDs?

I am currently designing a PoE plus device. I'm using 1G speed and currently following alternative A configuration (data pairs 1/2 and 3/6). Question is: Can all Powered Devices (PD) support ...
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2answers
1k views

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 (...
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1answer
112 views

802.3at PoE power splitter design - how to pass the actual Ethernet signal along

I'm researching the design of a PoE splitter. I understand the actual 802.3at portion of things, and have some confidence in being able to get the 48 VDC out (TPS2378). The question I have is... I've ...
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1answer
157 views

Requirements on dielectric strength and isolation between the conductors in an Ethernet transmission line with PoE

I am trying to find out what the requirements are on dielectric strength and isolation between the conductors in a Gigabit Ethernet transmission line. A first place to look would of course be the TIA-...
2
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1answer
2k views

DC Resistance of Cat5e Cable and Type 2 PoE

I see that the PoE Type 2 standard assumes a maximum loop resistance of 12.5 Ω/100 m, but cat 5e is specified to have maximum loop resistance of 18.8/100 m Ω. Does this mean that PoE type 2 is not ...
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1answer
906 views

RS-485 bus with PoE bus

I'm working on a home automation/security system (Only in my head at this point) and stumbled upon RS-485 transceivers. using RS-485 with PoE seems to be like a great idea to keep cords to a minimum. ...
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1answer
284 views

Understanding the second transformer in PoE designs

I'm trying to understand the PoE reference designs contained in the datasheet and the evaluation board user's guide for the TI TPS23756. The major difference between the "typical application" and the ...
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1answer
135 views

Differential POE 1000base-t signaling through analog multiplexer

I want to make a test device which can route network inputs to one output. For example it could sit between two computers and a network switch. The TS3L301 looks promising, but I am unclear about the ...
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2answers
1k views

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). ...
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3answers
2k views

Termination of unused PoE pairs

How important are the specific termination values used for PoE pairs (pins 4&5, 7&8)? Below is the recommended Ethernet front end for Micrel’s KSZ8841/42. http://www.micrel.com/_PDF/...
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2answers
681 views

Powering multiple devices from a single supply with 48V

First of all I asked this question in DIY.stackexchange.com, because of the cabling in the house. Here I would like to ask about the electronics (or electrical) part of it. And there is a very ...
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2answers
2k views

Passive POE: Need 5V @ 2A at the destination

Having a bit of trouble finding the right information on google, and I'm worried I might fry some cables so I thought it best to ask some far more knowledgable than myself. I want to connect 2 or ...