Questions tagged [poe]

Power Over Ethernet.

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37 views

POE power pass through

Is it possible to connect the center taps of two Ethernet magnetics to each other back-to-back to pass the power from one port to another. Does it make sense? Is anything special required?
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27 views

Classification on PoE

I am working with a PoE device and it has a PD controller which allows for the user to set the power class requested by setting the class resistors (CLSA,CLSB). My question is if the PD class ...
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19 views

Multi-Voltage PoE Splitter

I researching a pet project for an electric door strike controlled by a networked microcontroller. I would like to use PoE to power all of the components (strike, microcontroller, RFID reader) using a ...
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2answers
37 views

Can I use pre-regulated PoE power safely/within specifications?

I'm attempting to design a PoE PD for fairly high-power applications; chiefly, powering/driving stepper motors. Currently, both motors and drivers run at 24V and will consume about 30W per PD. At that ...
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1answer
117 views

Ethernet with transformer

I have a schematic of Ethernet Transformer that supports POE, and 2.5GBT. I plan on using Ethernet with transformer on my PCB to connect to Network Switch. Are pin VC12 13, VC36 14, VC45 15, VC78 16 ...
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68 views

UL certification requirements

I'm designing a circuit board for a large industrial product which is intended to be UL certified, so the boss wants as many individual submodules to be UL certified as possible, including mine. The ...
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4PPoE PD cost reduction

My current project is designing a PD circuit for use with 4PPoE/802.3bt (up to 60W), powering 24V stepper motors/drivers. I've found a couple of different chip combinations - I quite like this diode ...
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2answers
51 views

Single-package DC/DC converters for PoE — good idea?

I'm planning a design where we'll use PoE to power a data acquisition board (essentially, an ADC + microcontroller + ethernet PHY and interface). I look at DC/DC isolated converters to get the 5V or ...
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63 views

Two Gas Discharge Tube in parallel; a fast acting gas acting tube and a gas discharge tube

I want to know what happens if we put two gas discharge tube (fast acting GDT and a GDT in parallel), and a tvs diode in parallel. Would there be an issue in putting GDT in parallel? Datasheet of ...
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91 views

What are these resistors for?

I am looking at implementing a MOSFET Bridge Rectifier circuit. I am trying understand why there is a difference in the basic application circuit and layout from the app note. The layout image below ...
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22 views

FDMQ8203 vs. FDMQ8205/A

From the appnote FDMQ8205/A is almost identical to FDMQ8203 except the externa circuitry is no longer required. I am curious if anyone knows why in the FDMQ8205/A design VOUTN is NOT connected to ...
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35 views

How do you determine what amount of capacitance is bad for data lines?

I am currently deciding on putting a TVS diode from line to ground on POE ethernet. The issue is that I don't know how the capacitance of TVS diode will play role on the data signal. Is 1000pf bad or ...
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39 views

Ethernet POE voltage measurement to determine Voltage clamping between line ot Ground

I am planning on using a tvs diode to clamp power peak to protect network switch; the Port is POE. The issue is that when I measure the voltage of ethernet line to ground, I get around 0.6V. When I ...
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47 views

HR911105A or similar integrated magnetics for POE

Is it ok to use this RJ-45 socket for low power POE application (just to power the uC)? The only available datasheet : https://www.google.com/url?sa=t&source=web&rct=j&url=http://www....
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56 views

What to do with unused Ethernet magnetic center taps on POE?

I'm using a MAGJACK GIG PDJACK 1X1 CLASS 4 (Molex # 0857914020 - Link: https://www.digikey.com/products/en?keywords=WM9656-ND) to run POE on a 100MBit network connection. I thought this was a nice ...
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1answer
80 views

Practical considerations using Ethernet bus for a large number of sensors?

I understand that an Ethernet bus design with hubs has largely been superseded by star topologies with switches and that is largely due to the issues of collisions. However, I am interested in ...
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1answer
41 views

Measured Drain to Source Peak Voltage seems very high on PoE circuit

I am looking at TI's PMP20878 test results found on their website. Based on the schematic I am very confused how the Drain to Source peak voltage can be much greater than the typical PoE input of 48V. ...
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35 views

Are the topology of these flyback transformer for PoE the same?

I am looking for a transformer with the topology like 750310059 as shown below unfortunately the winding ratio and L value will not work with the PoE controller (MP8007) I am using for my design since ...
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1answer
44 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
41 views

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

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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1answer
59 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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2answers
65 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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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
301 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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38 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
65 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
67 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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69 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
249 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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64 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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23 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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97 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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9 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
57 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
219 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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163 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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263 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
66 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
228 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
347 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
264 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
145 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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98 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
169 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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515 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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403 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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1k 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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344 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
4k 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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275 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 ...