Questions tagged [poe]

Power Over Ethernet.

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31 views

PoE Design for Camera Interface Isolation Question

We are designing a PoE design to power our camera. The block diagram below is the basic design we are planning to implement. I want to get some advice to make sure we will not be damaging our camera ...
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1answer
40 views

What happens if PD tries to consume more than allowed PSE power provided? [on hold]

What happens if a Powered Device (PD) tries to consume more than allowed (Power Sourcing Equipment) PSE power provided, even though it has requested a set amount of power? http://www.ti.com/lit/df/...
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32 views

POE design to support both Mode A and B

I am working on a POE design for the first time that supports 100Mbps. I plan on using the mEZS84801A evaluation board that uses MP8007 as a reference design to do all the signature detection, ...
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53 views

Two POE devices on One Ethernet Cable via a Y splitter

Is it possible to run two PoE devices at the same time off of 1 ethernet cable from a PSE? Assuming that the ethernet cable is run through some sort of custom splitter connector to both PoE Devices.
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26 views

PIC32MX795F512H + DP83822I Transmit Error Signal

I am using PIC32MX795F512H with DP83822I as the Ethernet PHY transceiver. On the PIC32MX there is a pin for Transmit Error (ETXERR) but no Transmit Error pin on DP83822I. What should I do with the ...
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2answers
153 views

What does Ethernet 100BASE-T signal look like?

Hey guys what does the signal look like on the right of the transformer (T1) on the data lines {TXD_P, RXD_P}? Just trying to understand what it might look like...Is it a square wave? sine wave? Vmax? ...
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1answer
32 views

PIC32MX795F512H Ethernet signals

Hey guys I am designing a PoE circuit board and the microcontroller that I want to use (PIC32MX795F512H) seems to be missing some pins to connect my data lines or it's not clear to me where the lines ...
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1answer
44 views

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?
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2answers
50 views

Do PoE network switches have low output impedance and high input impedance?

I am just curious, and wanted to know if a Network Switches that have PoE ports have low output impedance, and high input impedance?
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30 views

PoE Transformer

I am using a transformer (7490220122) for signal isolation on a PoE controller design. If I am using 2 pair of the ethernet cable for data and 4 pair to provide the necessary power to the PoE device. ...
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2answers
59 views

isolated vs. non-isolated DC/DC converter in PoE

I am looking at powering a PoE circuit that drives a 24V motor at 2A. I am considering the LT4275/LT4276 LTPoE++™ Controller. I noticed on the datasheet for the controller LT4275 they recommend an "...
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51 views

PoE Design Question

I am working on a PoE project that calls for a power to be supplied to a application circuit. The application circuit requires ~41W (24V, 1.7A). I am exploring using PD70201 as the PD controller. The ...
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1answer
19 views

Why is the ground of the component, SP1050-04BTG, connected to the Power Supply of POE?

The SP1050-04BTG is a surge protector.
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42 views

What is the maximum voltage and current for Data Signal in RJ45?

I am using a POE switch 1000Mbs to power a Blackfly camera. I know that each Ethernet port sends 48V to camera. What is the max voltage and current through the data cable. Or would the data signal (...
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2answers
80 views

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 ...
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0answers
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
27 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
177 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
91 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
140 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
59 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
159 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
193 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
170 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
95 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
90 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
64 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
236 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
251 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
801 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
254 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
2k 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
233 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
118 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
364 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
558 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
92 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
73 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
171 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
193 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
96 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
369 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
192 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
163 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
946 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
106 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
30k 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 ...