Duet 2 Ethernet questions

RCarlyle

@dc42 surge protectors and UPSs are definitely a problem; I do put some of my printers on a UPS so I won't put the powerline adapter inside the enclosure for those. I don't know whether an IEC power cord and a foot of chassis wiring will be an issue. It does work (with some acceptable speed loss) between different breakers in a house, meaning in the US it could be going from a 14ga 15A 120v circuit, across a bunch of outlets, back to the load center, through a GFCI breaker, hop the bus bar to the other 120v leg in the 240v supply, through an AFCI breaker, then go down 12ga 20A 120v wiring through another bunch of outlets. There will be a ton of pigtails and wiring nuts and such in that sequence.

(For UK/EU people who may not know, US domestic wiring splits 240v hot-hot service from the power company into two separate 120v hot-neutral services where neutral is tied to ground at the load center.)

Come to think about it, I have no idea HOW it works on separate 120v legs, since all they share is a grounded neutral at one point, but it does work...

What I'm finding is that powerline ethernet has improved a ton over the last few years. I had a lot of problems back, oh, 2013 or so when I first tried it, but it has been great for me recently.

The age of your house can also make a big difference. I'm in recent construction now, and powerline has worked great. A previous place I lived in New Orleans (built 1851) probably wouldn't handle powerline well; it had a mix of knob-and-tube wiring from around 1920, ungrounded BX from the 1960s, and NM Romex from the 1990s. There were only three or four grounded electrical outlets in the entire house. Frickin' nightmare for electrical equipment.

RCarlyle

Ok, I have confirmed that neither a normal ethernet nor crossover ethernet cable allow the Duet Ethernet to talk to the Comtrend PG-9172. Unclear why. I suppose I'll put a switch between them.

On the Power Over Ethernet note, I can confirm that the Duet works fine hooked up to a POE switch.

T3P3Tony

@rcarlyle is it trying to force some other mode such as 10base T or half duplex?

RCarlyle

@t3p3tony no idea. The powerline adapter doesn’t have all that much documentation. It’s not the sort of thing I care enough about to keep troubleshooting. If it doesn’t work through a switch (powerline-switch-Duet) then I’ll look at it some more. New switch delivering later today.

RCarlyle

Works fine via switch.

vmario89

Hi. I bought a Duet 2 Ethernet and a Shanqiu FX5-24 USV for a project(https://fablabchemnitz.de/y/shanqiu-fx5-24). I thought about powering Duet by using the POE feature of that USV. It has a switch to put out 15V or 24V over POE. But i did not test because i am afraid to damage the Duet. I was not able to find any details in the specs about what would happen. I nearly fried a non-POE device at the USV already. Has anyone tested Duet with POE successfully? I know there is also POE with 48 Volts outside.

the only good sounding message was "On the Power Over Ethernet note, I can confirm that the Duet works fine hooked up to a POE switch." from RCarlyle, but he did mention the device he uses/used.

regards, Mario

Danal

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Danal

This post is deleted!

A Former User

If using proper 802.3at or 802.3af PoE you will not damage non PoE equipment by plugging it into a PoE supply.

Problems can occur when using non compliant or passive PoE.

I couldn't find any reference to what this decide using but having 24v as an option is usually a sign that it is non compliant.

There are a range of external PoE splitters that can split PoE into separate network and power circuits, which would allow you to supply f.ex. 24v to the Duet without risking damage. These also come in 802.3at/af or passive varieties and has to be matched to the source (output voltage is usually fixed, but 5, 12, and 24v versions are common)

dc42

Please note, the Ethernet socket with magnetics used on the Duet Maestro and Duet Ethernet is not PoE compatible.

Danal

@dc42 said in Duet 2 Ethernet questions:

Please note, the Ethernet socket with magnetics used on the Duet Maestro and Duet Ethernet is not PoE compatible.

Interesting... I will edit or delete my post above.

dc42

My understanding is that PoE works by applying 48V between the two data pairs in the cable. Duets use the Hanrun HR911105A socket, whose schematic is here http://www.kosmodrom.com.ua/pdf/HR911105A.pdf. If this is connected to a powered PoE cable, the results would be 48V applied across two of the internal 75 ohm resistors in series. I think this would probably burn them out.

A Former User

@dc42 said in Duet 2 Ethernet questions:

My understanding is that PoE works by applying 48V between the two data pairs in the cable.

802.3af/at PoE only applies a voltage after handshaking as part of establishing the link (handshake will also control which pairs and what power limit to use). So using a standards compliant switch is safe even with non PoE devices, they'll just get a non PoE link.

Passive PoE has a constant voltage, usually on the unused pairs. This causes issues with devices not made for passive PoE. Which will make thinks a bit toasty indeed.

(Standards compliant PoE is limited to 15/30W so not suited for anything but stand by supply really)

dc42

@bearer said in Duet 2 Ethernet questions:

@dc42 said in Duet 2 Ethernet questions:

My understanding is that PoE works by applying 48V between the two data pairs in the cable.

802.3af/at PoE only applies a voltage after handshaking as part of establishing the link (handshake will also control which pairs and what power limit to use). So using a standards compliant switch is safe even with non PoE devices, they'll just get a non PoE link.

If the device is powered by PoE, how can it do a handshake if power is not provided until after the handshake? Does the switch supply a small current until after the handshake, enough to provide power for the handshake but not enough to destroy a non-PoE device?

Passive PoE has a constant voltage, usually on the unused pairs. This causes issues with devices not made for passive PoE. Which will make thinks a bit toasty indeed.

From what have read, for 100baseT Ethernet (as supported by Duets), the PoE standard defined two modes: mode A and mode B. Mode A uses the same two pairs of wires that carry the data, which would likely damage a Duet. Mode B uses the unused pairs, so it should be safe.

A Former User

@dc42 said in Duet 2 Ethernet questions:

Does the switch supply a small current until after the handshake, enough to provide power for the handshake but not enough to destroy a non-PoE device?

pretty much, it does a few pulses (not 48v) to detect a the impedance of a poe compliant device, it will not damage non-poe stuff.

you're right about the modes, pretty much all passive poe solutions will use mode B, compliant will negotiate, but still not damage a duet as it wouldn't get past the detection phase. a third mode is defined for 1000BaseT which basically has data and power on all pairs iirc.

dc42

@bearer, thanks for the clarification.

A Former User

Just to be very clear, the passive PoE solutions will not attempt to detect a supported device, they just supply a constant voltage. But there are few switches of this type, more common with inline power injectors.

(Also people using passive PoE in their products ought be taken out back and, uhm, be dealt with)

((compliant devices will also have just the PoE PD circuitry powered until handshaking is complete and the host device receives power))