Use a POE switch to power ESP32 wired

You can buy POE splitters on Amazon that convert the "standard" ~50V to 5V. I've used them to power a raspberry Pi. Just be aware that there are POE devices that use 24V instead of 50V, mostly wifi "bridges" from China in my experience so far, but its something to look out for.

For a single device POE inserters are available:

For more devices, POE switches are available in 4-port, 8-port, or more, where on cable to your router "fans out" to 4 or more POE ports at the switch. I have a pair with "industrial" temperature ratings in my attic, no issues thru two very hot summers.

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But why do all this ?? Why not just bite the bullet and order the Olimex ESP32 with POE - job done and it can feed your sensors from on the board

It seems like - "i have bought this bloody Wt32 board and by hook or by crook i am going to make it work !!"

WHy not put it to the side for another project (i am sure you have one on the go somewhere !!) and just get the Olimex board for this particular project ?


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Hey Craig,
In theory you are 100% right. But here is the practical situation: I have those wt32 boards in my basements for already quite some time. Last week I finally managed to reserve a few spare hours to figure out how to flash them, install EspEasy firmware and connect them to Node-RED. It was pure magic that those tiny devices suddenly started sending ultrasonic distance measurements via mqtt over a cat cable to Node-RED running on my Raspberry. So now I just want to finalize this setup. Otherwise it would be a majure personal failure :woozy_face:

And moreover I will never find free time for a next project, so then they would end up again in my basement until ethernity :wink:

But by the time you place ordered with Ali express etc the Olimex stuff would arrive. Now that you understand how to flash some of the precompiled firmwares you will see it is a doddle and they are all much of a muchness


Yes true, but then I would never be able to use my wt32 boards. Because if I ever would like to use them, I would need the POE splitter/converters anyway :wink:

No not true - i thought in this case you were going POE because it was in the garden with no other power options - this sounds like confirmational bias to me !!

Save these boards for an inside job where you can power them relatively easily and remove the complications of the splitters etc etc


I would be very wary of this. I initially thought the 48V of the POE standard (802.3af from memory) was odd, considering we were connecting 12V IP cameras and 5V WAPs ... then I remembered that power = volts x amps ... and at 48V the amperage is probably low enough to minimize interference with signals on the other wires of the ethernet cable.

However I am no expert, and YMMV depending on the power transmitted and the length of ethernet cable.

From memory, the 802.11af POE standard uses the ground wires in the cable pairs to send power - but since Gigabit ethernet uses all the wires to get the faster speed, they are (or used to be) mutually exclusive. I note the switch referenced also supports a newer standard (802.3at) which I am not familiar with - but it might be a case of POE or Gigabit on a per channel basis.
Even so, 100Mbps on a downstream link to a camera or any single device to the switch should be plenty ... it's the upstream (combining data from all the connected devices) where a user might need the faster speed.

802.3at is the higher power standard - af capped the output at (top of my head) 1 amp per circuit - at extends that.

Gigabit only uses 4 pairs and POE uses the grounds cables so they can coexist and you do not blow up non POE devices when you plug them in (as long as your switch follows the standard)

What is Gigabit Ethernet? How is It Used with PoE?.


Thanks for that link Craig, bit of a refresher. I was wrong about 802.3af using ground wires - it didn't sound right when I wrote it - 10/100Mbps Ethernet uses only 2 of the 4 pairs for data; allowing POE to use the 2 unused pairs for data.
Gigabit Ethernet uses all 4 pairs for data - which at the time meant they were mutually exclusive on any individual cable.

As implied, it has been several years since I was doing tech support, and obviously things have evolved. Curiously the link provided goes into magical black box territory explaining how gigabit Ethernet manages to send power AND data down ALL 4 pairs - but what's important is that it works with hardware all supporting the same standards. And, as you point out, they manage to push more power down the cable.

This won't help with the existing PoE-less ESP32's but just for sake of the completeness, I didn't see this one mentioned: LILYGOĀ® TTGO T Internet POE ESP32 WROOM LAN8720A Chip Ethernet Adapter And Downloader Expansion Board Programmable Hardware|Circuits| - AliExpress.

Surprisingly it seems that the Olimex board might actually be cheaper at the moment (didn't check shipping cost). This one looks pretty cool though (I've got one)! and it has an sdcard slot as well if someone finds such useful.


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