Looking for a high power efficiency POE Switch. Do they exist?

Endgame

Gawd
Joined
Jan 10, 2007
Messages
728
I'm looking for a high power efficiency PoE switch, which is something the switch manufacturers don't seem to emphasize in their marketing. I'm thinking something along the lines of a 90+ Titanium Power supply efficiency - ~95% efficient at 50% load. I'd be looking at something around a 12 port switch with 8w / port.

The reason I'm looking for something high power efficiency is that I'm running distributed computing on a stack of raspberry pis. See below for the thread on the topic:
https://hardforum.com/threads/distributed-computing-on-raspberry-pi.1997998/

Generally speaking, the cell phone power supplies suck when it comes to power efficiency and are anywhere from 65% to 80% efficient. Raspberry Pis have the possibility to be the most efficient way to run these projects on a per watt basis, but realistically its going to require higher efficiency power supplies than what you can buy from cell phone chargers. I'm thinking a PoE switch may be the way to go, if someone makes a high efficiency one, AND it isn't so expensive that I might as well go buy another 5950 and put it in eco mode.

Thoughts and suggestions?
 

Smoblikat

Limp Gawd
Joined
May 28, 2020
Messages
343
I dont know the efficiency of this unit, and its only 8 ports (the 2930 has a 12 port option for 15X the cost, id rather buy 2 of these) but I do have a few of them and they work pretty well, and have a full CLI if you ever intend to do any config with them.

https://www.ebay.com/itm/363248389169?epid=2254373460&hash=item54934a8c31:g:7-cAAOSwHPNf9dlu

I believe the PSU is HP P/N: 5066-2164

Heres a pic of its label, not sure if you can find the effeciency info you want from there:
HTB1QrJYKkOWBuNjSsppq6xPgpXat.jpg
 

longblock454

2[H]4U
Joined
Nov 28, 2004
Messages
2,055
If you want ultra high efficiency ditch the POE and buy the best 5v supply you can find. Places like Digikey allow you to sort power supplies by efficiency, if you need help picking one out let me know.

The POE hats really suck when it comes of efficiency.
 

michalrz

2[H]4U
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Jun 4, 2012
Messages
3,092
I'll preface by saying I haven't had the opportunity to use POE.
However I was going to make a 5V/12V supply out of a PC PSU for my cameras and other misc little devices.
For now this is on hold, because I'm slowly moving those devices to solar (luckily there aren't many).
I'm almost done getting the numbers for speccing solar for the Pie.
So yeah I've been meaning to ask - why not use a high quality unobtanium rated PSU?
That said I don't want to be 'that guy', just curious.
 

Endgame

Gawd
Joined
Jan 10, 2007
Messages
728
I'll preface by saying I haven't had the opportunity to use POE.
However I was going to make a 5V/12V supply out of a PC PSU for my cameras and other misc little devices.
For now this is on hold, because I'm slowly moving those devices to solar (luckily there aren't many).
I'm almost done getting the numbers for speccing solar for the Pie.
So yeah I've been meaning to ask - why not use a high quality unobtanium rated PSU?
That said I don't want to be 'that guy', just curious.
I would love to use a titanium level 5v PSU - do any exist that don’t require me to break out the soldering iron?
I’ll figure out how to use basically any power supply I can get my hands on in the 93%+ efficiency range, be it PoE (convenient for single wire per pi), cell chargers, 5v supplies, etc, but my novice soldering skills are not suited to building my own wires / connectors.
 

michalrz

2[H]4U
Joined
Jun 4, 2012
Messages
3,092
I would love to use a titanium level 5v PSU - do any exist that don’t require me to break out the soldering iron?
I’ll figure out how to use basically any power supply I can get my hands on in the 93%+ efficiency range, be it PoE (convenient for single wire per pi), cell chargers, 5v supplies, etc, but my novice soldering skills are not suited to building my own wires / connectors.
Sadly I don't have answers for the PoE part of your question. I don't even know what one would need to buck 12V to 5V on the Pi's NIC side.
The cheap Chieftec (the rating is probably 80+ Rusted Iron) unit I was going to sacrifice has 18 A on the 5V rail, 22 A on the 3.3V (great for little IoT boards).
This isn't even that great - systems somewhere in the K7/K8 days went from using 5V to 12V and before that the 5V rails were beefy. Now, not so much.
After snipping the connectors I'm left with 7x 5V wires w/corresponding grounds.
Having that, the easiest hook-up (if you don't want to solder USB-C connectors) would be through the GPIO block.
One of the downsides I can think of is that apparently (I haven't tested this yet) the PSU might behave weird without a dummy load on all rails, which would be wasteful.
That's all I've got ATM, will probably test this idea soon, but need a killawatt or something to determine the PSUs efficiency at such weird circumstances.
 

Nobu

Supreme [H]ardness
Joined
Jun 7, 2007
Messages
6,422
Problem with poe is you lose a lot of power over the wires, being a DC transmission technology. You probably lose more over the lines than you could make up with a more efficient switch.

If you want better efficiency, you're better off with a good DC supply as close to the switch as possible (unless your PoE components are close together).
 

Endgame

Gawd
Joined
Jan 10, 2007
Messages
728
Problem with poe is you lose a lot of power over the wires, being a DC transmission technology. You probably lose more over the lines than you could make up with a more efficient switch.

If you want better efficiency, you're better off with a good DC supply as close to the switch as possible (unless your PoE components are close together).
My switch is right next to my literal stack of Pis. I’m currently using 6” cables for most of the pis.
 

Nobu

Supreme [H]ardness
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My switch is right next to my literal stack of Pis. I’m currently using 6” cables for most of the pis.
Oh, the switch is powering the Pis? Here:
https://www.mouser.com/Power/Power-...s/_/N-brvy9?P=1yxt7euZ1yxt794Z1yxt79wZ1yxt6xm

Filter the results and pick your efficiency. They have up to 88% efficient units, which isn't bad. Some put out quite a lot of power, so you could probably power a few Pis from one unit with a splitter.

Screenshot_20210628-182335.png


Or you can get a larger bench-top supply with multiple outputs and hook up some barrel cables to that. Will likely be more efficient, but more expensive and more work.
 

Nobu

Supreme [H]ardness
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Messages
6,422
Might be able to find a switch that's more efficient, but you'll have to dig through specs, whitepapers, etc to find them.
 
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