Core Electronics Forum

PoE to Run RPi and LEDs

Hi all,

Would like to quickly ask please: what things do I need to calculate or consider if I’m looking at running an RPi and a length or 2 of LED strip lights over PoE? How would I go about working out if there’s enough power etc.? I have it all currently (successfully) running from a 5V power adapter for the LEDs and the standard RPi power adapter for the RPi, but hoping to get rid of both of these and run it all over PoE if possible.

Cheers.

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Hi Kirk,

Excellent question, you should be able to do that. How long are the strips, and how much current do they draw per metre?

As seen above, you’ll want to check the standard for which type and cable should do the job after this is determined. As for the actual setup itself, active PoE injection with splitters is probably the easiest way to go. Core Electronics has a few parts that you may be able to get away with using for this such as that which I’ve linked below. Although, the current ratings tend to be a little low, particularly given how power hungry strips tend to be. If you’re running a Pi 4 they can draw a fair bit too.

If you determine all of the ratings for the Pi and your strips when operating at full brightness with that resource I linked earlier, you should be able to work out the most appropriate standard to use in your setup, and what parts would be most appropriate. I hope that helps! :slightly_smiling_face:

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This is wonderful feedback @BryceT. Thank you. Very comprehensive.

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Just a further question on this please: if I have BOTH an RPi and separate LED strip light length to power over PoE, is there sort of a ‘double adaptor’ that would split the power from the PoE Splitter to both the RPi and lights?

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Definitely possible, but I don’t know if there’s a single off the shelf product. Something like this with a PoE splitter will probably work though:

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That’s wonderful @Oliver33, thank you.

FWIW there are quite high standards for the amount of power you can send through an Ethernet cable, right up to 71w available at your device at the moment, so assuming you had a supporting Device you could power quite a few devices from an Ethernet cable…

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Thanks @Michael140458.

So it would be fair to say then, that the power won’t be an issue to power both an RPi 3 B+ and some LED strip lights via PoE, but I’d need a PoE splitter and a 2-way DC Barrel Jack Splitter to then split out the power for each device. Connected to the Barrel Jack Splitter then would be what - some form of transformer for the RPi and lights?

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Sorta yes Sorta no

to get the full power out the other end of the cable you’d need the right Switch, the right cable and the right PoE extractor/converter (to correctly communicate with the switch and enable the switch to send the 70w down the cable)

from there you’d need to figure out your Pi max power draw and LED’s cumulative max power draw

in theory the LED’s can do around 60ma each (0.03w), the Pi up to 7w… so in theory you have a good 60w left over with the right equipment… so something like 2000 LED’s in a perfect world (feel free to check my maths :slight_smile:

now keep in mind that the right switch will also have a power budget, so if you were to try and get 71w out of each port in a 48 port switch from every port at the same time you’d need something with an appropreate budget.

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I say Sorta No, as I’ve never seen a 71w PoE power extractor… (or whatever the term is)

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Hi Michael,

I did some digging, and found a chip that can extract up to 70W from a PoE connection:
https://www.digikey.com.au/en/products/detail/analog-devices-inc/LT4294IMS-PBF/7321595

And I figured this would lead to a product that could do this, lo and behold:

Seems these pricey devices get used in industrial settings to get big power out of PoE.

-James

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Mad Respect for finding this!

$200 USD you’d wanna be desperate for it!

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