Teensy 4.1 Ethernet Kit w/POE Module

B

bLackburst

Active member
Hi
I'm wondering about the feasibility and hookup method for using a POE module such as this https://www.adafruit.com/product/3848 with the Teensy 4.1 and ethernet kit to power up the teensy.
The module's pins are meant to be connected to ethernet pins 4,5,7 and 8 but I can see the PJRC ethernet kit's capacitor is tied between 2,5 and 8. Would it still be needed?
I would actually prefer to use a panel mount ethercon connector anyway. Can someone please advise me on the best way to hook this up?
TIA
 
PaulStoffregen said:
It can not work with the Cetus J1B1211CCD Magjack we use on the Ethernet Kit.

A different Magjack meant for PoE is needed. Most of them are incompatible with PoE because they include the 75 ohm common mode termination resistors without capacitors in series, and without access to those other pins to extract the power. Here is one which looks promising...

https://www.digikey.com/product-detail/en/abracon-llc/ARJM11C7-114-BA-EW2/535-14168-ND
Click to expand...

Hmm, Ok. Other than the pin access it's over my head. Can you recommend an ethercon-style of panel mount connector that would be appropriate? Or at least what specs to look for? And would it need other components in the way the J1B1211CCD does?
If there is a better way to PoE the teensy 4.1 please let me know.
 
MarkT said:
Or just use a separate PoE extractor - something like this https://www.amazon.co.uk/Ethernet-Injector-Extractor-extractor-included/dp/B0044LFO70
(not that I know if that particular one is any good or not, the reviews are rather mixed, but its inexpensive)
Click to expand...

Thanks MarkT, but that's not a panel-mount connector. I find it difficult to build sleek, enclosed devices out of already enclosed devices. I would rather use compact daughter-boards, MCU's etc and achieve a tidy result for the customer. I think I just need a PoE compatible panel connector(d-style or ethercon style) that complies with the teensy. The capacitor in the kit throws me off on what to look for.
 
bLackburst said:
If there is a better way to PoE the teensy 4.1 please let me know.
Click to expand...

This really depends on what you consider "better". The easiest way would be to use a PoE splitter that's designed to extract the power and pass the signal on to a regular non-PoE ethernet port, and give you the power safely converted. While these are bulky and add extra cables, they're cheap and readily available.

But if "better" means all integrated onto a small PCB rather than another product with extra cabling, then I'm afraid quite a bit of design work is needed.


Or at least what specs to look for?
Click to expand...

Generally a magjack that is designed for PoE.

But even then, that can have many different forms. The main thing all PoE compatible magjacks have in common is access to either RJ45 pins 4+5 and 7+8 (the unused pins), or the center taps of pins 1+2 and 3+6 (the pins used for 10/100 speed), or both. The Cetus J1B1211CCD part we use now does not bring any of the RJ45 signals out.

PoE magjacks also must not have a DC path through 75 ohm resistors. Some add 22nF capacitors in series with those 75 ohm resistors. Others omit the resistors completely, and it's up to you to add them if you want the better signal quality that common mode termination brings. Still others seem to have 2 or the 4 resistors.

Once you get DC coupled access to 2 or all 4 twisted pairs, you also need diodes to couple the DC to the input of that switching power supply. Some PoE magjacks have diodes built in, others have a minimalist design where you need to provide the diodes.


And would it need other components in the way the J1B1211CCD does?
Click to expand...

Yes. I've not seen any magjacks that have absolutely all the needed parts built in.

The reality is this gets into designing your own PoE splitter, which means a pretty deep dive into lots of PoE circuitry details.
 
I am not a hardware guy (and these days how much of a software guy I still am is open to question) but it occurred to me that the olimex POE board is open source, and might provide a good source of inspiration for someone who wanted to design a POE solution for the teensy 4.1. I would like see such a creature, for a project I am working on. The information is here:
https://github.com/OLIMEX/ESP32-POE/tree/master/HARDWARE

Note that the boards are available on Digikey for $22.70 in single quantities, so the parts are probably not pricey. It is even claimed to have 3000V galvanic insulation.
 
I just wanted to update my reply because I made a mistake. The board I indicted does NOT have galvanic isolation. I misunderstood a press release. If you want the 3000V galvanic isolation, you must get the ESP32-POE-ISO board, which is a bit more expensive than the one I have. So I had to buy a USB isolator gadget .. which has yet to arrive.
 
PaulStoffregen said:
It can not work with the Cetus J1B1211CCD Magjack we use on the Ethernet Kit.

A different Magjack meant for PoE is needed. ...

https://www.digikey.com/product-detail/en/abracon-llc/ARJM11C7-114-BA-EW2/535-14168-ND
Click to expand...

Hi!

Just a clarification for those not requiring power but wondering if you can connect the Teensy to a PoE switch.

The Cetus J1B1211CCD Magjack can be used with active PoE switches because active switches do send a signal to detect if the devices requires power or not. In this case, it would detect a non-PoE device and the switch would not send power over Ethernet.

However, if the switch is passive and non-IEEE compliant, it will send power regardless and it can burn a non-PoE device. Then a different Magjack or adaptor is needed.

"In summary, the PoE switch is not totally different from the non-PoE one, it can be connected to either the non-PoE switch or non-PoE devices. You just have to make sure that your PoE switch is rated to be IEEE 802.3af, IEEE 802.3at or IEEE 802.3bt compliant." Otherwise, be wary and try a PoW Magjack.

Cheers
 
Slightly different solution

bLackburst said:
Hi
I'm wondering about the feasibility and hookup method for using a POE module such as this https://www.adafruit.com/product/3848 with the Teensy 4.1 and ethernet kit to power up the teensy.
The module's pins are meant to be connected to ethernet pins 4,5,7 and 8 but I can see the PJRC ethernet kit's capacitor is tied between 2,5 and 8. Would it still be needed?
I would actually prefer to use a panel mount ethercon connector anyway. Can someone please advise me on the best way to hook this up?
TIA
Click to expand...

While not a direct solution to your answer, Sparkfun now markets the Teensy MicroMod combined with the Wiz5500 module embedded IPv4 processor and a 3.3V 1A 802.11.3af. It's 3 PCB's that screw together, along with IIC and a microSD card socket. It's not the cheapest solution, but it's good enough to start writing application code and evaluate the POE solution they used. The schematics I believe are open sourced. The selection of function boards is limited for the moment, and I wish they exposed SPI pins. There is talk that you can expose the second ethernet interface from the MicroMod CPU with a custom board solution.

Teensy MicroMod CPU
MicroMod Single Slot Main Board
Wiz5500 POE Function Board
 
Bumping this thread up in case things have changed in a year. I too am wanting to integrate PoE in my project, and am wondering if there are now any viable options for Teensy 4.1?

Robert
 
I have used these in a few projects and use the output do supply a buck converter that supplies 5V to my board including the Teensy 4.1


One could design a small board with a built in 5V buck converter and then 5V output terminal to run the Teensy off.

There are equivalents available from sources in China where the price per part cost comes down to under U$1 ea but you need to order 100.
 
I've been using the PoE Featherwing plus the RP2040 shim made by Silicognition to make the light switches in my home wired ioT devices. While the RP2040 is plenty for tracking switch presses, Teensy is actually my favorite MCU. I looked over the schematics ans see no reason why the Teensy Featherwing adapter + PoE featherwing + Teensy would not work as long as I do two things:

1) Cut the jumper on the featherwing adapter to isolate the PROG pin on the teensy
2) Cut the VBUS - VUSB jumper on Teensy so that the USB programming port can be used while the PoE Featherwing is connected to a PoE switch. I've soldered a shottky diode across those pads in the past to make it safe to use USB or VBUS power on the teensy. I've also used AfaFruit's Ethernet Featherwing with Teensy 3.2 with good results.

The PoE Featherwing has a WiZ5500 on it so I plan to use that instead of the built-in one (if I'm using the Teensy 4.1) the Teensy 4.1. Or, maybe just have two ethernet ports:)

I could conceive of a variant to the ethernet dongle for the 4.1 that used a rectifying magjack and a silvertel PoE buck supply to deliver 5V for teensy over a Dupont wire or some press fit gizmo + a higher power output for the higher power stuff to be controlled.

The PoE featherwing is limited to 4W, so it can't drive many lights. I've been looking at PoE based LED drivers that essentially replace the DMX inputs with a PoE RJ45 but still drive several LED channels. There's a bunch of stuff out there for commercial building (with prices to match). A product called the Moodifier shows up in searches that looks like a good fit, but I can't get pricing on it.

So I'm angling towards a DIY using a Magjack capable of 90W 802.11bt (Type 4, I think), a small 5V regulator for teensy, and then using MeanWell CC LED driver modules running off the rectified PoE voltage to drive an LED channel. You can get thee from Mouser or Digikey for $5-6 per channel and easily have teensy receive Artnet or MQTT, baybe even ESPHome emulation and drive PWM to the modules. These should be smaller than the usual DMX In > LED out decoders out there. And, no power supply hassles. Probably less than 10 parts for a five channel Artnet PoE -> LED driver.
 
Be careful of any pins acting as inputs on the Teensy that might be driven by the featherwing adapter. The T3.2 was 5VDC tolerant, whereas the T4.x devices are not (with the exception of the power input, 3.3VDC inputs only).

Mark J Culross
KD5RXT
 
Good point. This PoE Featherwing, when used with the adapter, drives +5V to the VBUS pin on the Teensy. It uses the 3.3V output from Teensy to power the Wiz5500, which is a 3V part. What I haven't checked is if the 5500 draws more than 250ma, but I'd be surprised if it did.

If I make smoke, I'll let folks know.

Perry
 
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