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Power over Ethernet (PoE) basics and beyond

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257 points voxadam | 7 comments | 16 Oct 25 14:09 UTC | HN request time: 0s | source | bottom
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stego-tech ◴[22 Oct 25 01:41 UTC] No.45664020[source]▶
PoE is a godsend that should really be in more consumer devices and households, alongside structured wiring. An AppleTV, Chromecast, or NVIDIA Shield can easily fit within the envelope of PoE+, as can many enterprise-grade switches and WAPs (see UniFi as an example). Converting AC to DC once at the switch is more efficient (in resources and often, but not always, power) than including bulky PSUs for every device, while simplifying the ease of setup for end users (in theory).

Whenever possible, I opt for PoE. It’s a damn shame it’s limited to a niche userbase given its myriad advantages.

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morshu9001 ◴[22 Oct 25 02:17 UTC] No.45664212[source]▶
Might be because it's scary. User plugs passive poe into something not expecting it, magic smoke
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1. ianburrell ◴[22 Oct 25 02:25 UTC] No.45664260[source]▶
Passive PoE is evil, standard PoE is safe since does negotiation.
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2. morshu9001 ◴[22 Oct 25 02:27 UTC] No.45664271[source]▶
Step 1 is to eradicate passive poe then
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3. ocdtrekkie ◴[22 Oct 25 02:30 UTC] No.45664286[source]▶
Passive PoE is already extremely rare today. Early Ubiquiti stuff probably is the most passive PoE stuff likely still in service.
4. ianburrell ◴[22 Oct 25 02:33 UTC] No.45664304[source]▶
Ubiquiti has stopped selling anything with passive 24V PoE, and has lots of standard PoE. The risk is low since I think only worked with injector so no switches providing power to everything.
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5. wolrah ◴[22 Oct 25 04:36 UTC] No.45664922{3}[source]▶
> Ubiquiti has stopped selling anything with passive 24V PoE

In their consumer "UniFi" product line. Pull up their store and switch over to the "UISP" product line. Most of the smaller wireless devices and consumer-tier CPE are 24v passive, most of the larger wireless devices, 60GHz bridges, etc. are 48v passive, a few devices in the middle support both, and standard "active" PoE is almost nowhere to be found. Even on product lines that weren't even dreamed up when modern standard PoE was ubiquitous.

They say it's because the WISP crowd loves passive PoE as it can easily be wired to batteries on towers, and I get that, but that's no excuse for not also supporting standard-based PoE on the device end. There's no good reason for a product designed in the 2020s to force the installation of passive PoE where there was none prior.

They demonstrated they can do both with most of the transition-era UniFi products. Support and encourage the use of standards, allow the use of non-standard but common alternatives where they make sense.

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6. morshu9001 ◴[22 Oct 25 05:18 UTC] No.45665134{4}[source]▶
Also my UniFi AP has passive poe cause it's just that old. Without researching, idk when that got fixed because nothing on the boxes tells you. Consumer tier means people will plug whatever fits.
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7. wolrah ◴[22 Oct 25 16:09 UTC] No.45671292{5}[source]▶
> Without researching, idk when that got fixed because nothing on the boxes tells you.

In fact it did, in the transitional models that were sold both with and without 802.3af support there was a sticker added to the box on the ones that had it.

The switch was early in the life of the UAP-AC series of access points. IIRC the "Pro" and in-wall models always supported 802.3af but the "Lite" and "LR" models initially were 24v passive only. I vaguely recall there also being transitional models of their cameras but we were not deploying those at the time.

> Consumer tier means people will plug whatever fits.

And this is why I hate passive PoE with a passion. Standards-based PoE ports are safe, you can plug devices not supporting PoE (or requiring passive PoE) in to them with no risk of damage. Passive PoE ports are dangerous, they can and will destroy things that are not expecting to receive power on those ports.

They're even dangerous to devices designed for it in some cases, Ubiquiti actually famously had problems with UAPs on the end of long cables being damaged when fed by passive PoE from the source and eventually recommended that those installs add their "Instant 802.3af" adapters which took standard 802.3af over the wire and converted it to passive right at the device end. I had one site that lost three UAP-LRs before that was revealed.