4 ms·

Except when it isn't awesome. There are multiple PoE standards. Passive PoE, active PoE, PoE+, PoE++, PoE+++, 802.11af, 802.11at, 802.foo, blah blah. If they h

by dheera 1y ago

Except when it isn't awesome. There are multiple PoE standards. Passive PoE, active PoE, PoE+, PoE++, PoE+++, 802.11af, 802.11at, 802.foo, blah blah. If they had just stuck with 12VDC and buildings had 12VDC wall sockets everywhere, everything would have been fantastic. I also had a PoE HAT for a RPi that smoked it. Never doing PoE again. 48V and 3.3V electronics probably don't belong within 10cm of each other.

buccal 1y ago
240V AC and 5V DC manage to live close in a charger without problems. Problems with quality does not depend on voltage. I love the concept of PoE with one exception that it requires constant 1W or similar load to work even if it is not needed for low power device.
- dheera 1y ago
  > 240V AC and 5V DC manage to live close in a charger without problems. I mean, yes and no. My laptop case is at 78VAC to ground right now. It gives the tingles. I don't use my laptop much while plugged in. They all skimp on making proper 3-pronged chargers these days. My desktop has a grounded case and doesn't have this issue. My phone, when plugged into wall AC, the touch screen stops working because the whole phone is at an elevated potential and it messes up the capacitive sensing.
varenc 1y ago
I use a PoE "extractor" to power my RPi over PoE and it works great. The extractor does the negotiation and safely gets the normal 48V PoE power, then converts that to 5V outputted on a USB-C cable that powers the RPi. Extractor also has an Ethernet[1] passthrough port that goes into the RPi as well. A bit basic, but seems relatively error proof. [1] https://x.com/varenc/status/1961587127931867466 https://x.com/varenc/status/1961587127931867466
skopje 1y ago
I never had to know the difference. I have four cctv cams on ~100ft of cat5 each. didn't have to think about it, just plugged them in and they worked.
ssl-3 1y ago
> If they had just stuck with 12VDC and buildings had 12VDC wall sockets everywhere, everything would have been fantastic. Huh? We used to have low-voltage AC and DC powered cameras in the world (and we still do, too). Those are awful in implementation because buildings, whether or old or new, don't have 12VDC sockets everywhere -- or at all, really. Nor should they have 12VDC sockets for cameras; they're unnecessary. I've run my share of siamese coax for low-voltage-fed analog cameras, and also separate power for low-voltage Ethernet-connected cameras, and I'm completely over those concepts. With proper-fucking IEEE POE, we have standards and it only takes one cable to make it work properly instead of more than one. If a switch isn't up to the power demands of a particular camera, then: No big deal. I can upgrade or supplement that switch without rewiring even more of the building than was already necessary to get Ethernet going. (Structured cabling for the win. Passive POE: Not even once.)
- eqvinox 1y ago
  > Passive POE: Not even once. Amen.
eqvinox 1y ago
> There are multiple PoE standards. No, there aren't, not in the way you imply. There is the IEEE 802 PoE standards, which are all compatible (save for not enough power), and designed to carefully negotiate and especially never break non-PoE devices. And there is bullshit (sorry) like "Passive PoE" that is ironically an active violation of the IEEE specs, can break pretty much anything, and you shouldn't buy so the likes of Ubiquiti and Mikrotik finally get the wallet vote and stop f*cking doing. Unfortunately, the proper PoE PD logic is a few dollars of extra expense. Yes, there is a slightly higher risk of killing devices due to faults in the PoE supply logic. I have the official PoE HAT for a RPi 4. I have to say it is somewhat poorly designed due to space constraints; the isolation between 48V and 3.3V should be better. I'm not even sure the RPi PoE HAT is spec compliant. But I don't think you can/should blame this on PoE.
- yread 1y ago
  I have a ubiquiti 30w poe+ injector that somehow doesnt provide enough power for 20W aruba AP. When I plug it in a 120W switch it works unless the cable gets too twisted or something. I vote not awesome
  - eqvinox 1y ago
    Don't buy Ubiquiti. Personally speaking, anyone doing passive PoE (even if only on other device series you're not looking at) is automatically on my shitlist. I'm not surprised they can f* up a basic PoE injector. The reason for doing passive PoE is saving a few bucks, on the back of safety and compatibility. Of course they would try to pinch hard on the PoE injector too. Oh and I'd say they (together with Mikrotik) are responsible for 90% of the bad rep PoE gets. The IEEE 802 stuff really just works. And I say that having been part of rolling out 15000 people conference deployments with several hundred wifi APs in the span of a few days. The only real problem is broken cables, but the Ethernet link commonly fails before PoE is impacted.
    - deviantintegral 1y ago
      Ubiquity only did passive PoE in the very early days. Everything has been 802.11 variants for a long while wow. The injectors that shipped a decade ago with my APs were all 802.11af.
numpad0 1y ago
The (negative)48VDC voltage comes from regular telephones. So did the RJ45(8P8C) plug. It's not an invented thing.
throw0101c 1y ago
> Except when it isn't awesome. There are multiple PoE standards. There are three: IEEE 802.11af, at, and bt. af can deliver up to 12W at the powered device (PD), at delivers up to 25 W, and bt either 51W (Type 3) or 71W (Type 4): * https://en.wikipedia.org/wiki/Power_over_Ethernet#Standard_implementation https://en.wikipedia.org/wiki/Power_over_Ethernet#Standard_i... Any device you purchase should list the IEEE standard it supports and how much power it may draw.

by dheera 1y ago

buccal 1y ago

240V AC and 5V DC manage to live close in a charger without problems. Problems with quality does not depend on voltage. I love the concept of PoE with one exception that it requires constant 1W or similar load to work even if it is not needed for low power device.

dheera 1y ago
> 240V AC and 5V DC manage to live close in a charger without problems. I mean, yes and no. My laptop case is at 78VAC to ground right now. It gives the tingles. I don't use my laptop much while plugged in. They all skimp on making proper 3-pronged chargers these days. My desktop has a grounded case and doesn't have this issue. My phone, when plugged into wall AC, the touch screen stops working because the whole phone is at an elevated potential and it messes up the capacitive sensing.

varenc 1y ago

I use a PoE "extractor" to power my RPi over PoE and it works great. The extractor does the negotiation and safely gets the normal 48V PoE power, then converts that to 5V outputted on a USB-C cable that powers the RPi. Extractor also has an Ethernet[1] passthrough port that goes into the RPi as well. A bit basic, but seems relatively error proof. [1] https://x.com/varenc/status/1961587127931867466 https://x.com/varenc/status/1961587127931867466

skopje 1y ago

I never had to know the difference. I have four cctv cams on ~100ft of cat5 each. didn't have to think about it, just plugged them in and they worked.

ssl-3 1y ago

> If they had just stuck with 12VDC and buildings had 12VDC wall sockets everywhere, everything would have been fantastic. Huh? We used to have low-voltage AC and DC powered cameras in the world (and we still do, too). Those are awful in implementation because buildings, whether or old or new, don't have 12VDC sockets everywhere -- or at all, really. Nor should they have 12VDC sockets for cameras; they're unnecessary. I've run my share of siamese coax for low-voltage-fed analog cameras, and also separate power for low-voltage Ethernet-connected cameras, and I'm completely over those concepts. With proper-fucking IEEE POE, we have standards and it only takes one cable to make it work properly instead of more than one. If a switch isn't up to the power demands of a particular camera, then: No big deal. I can upgrade or supplement that switch without rewiring even more of the building than was already necessary to get Ethernet going. (Structured cabling for the win. Passive POE: Not even once.)

eqvinox 1y ago
> Passive POE: Not even once. Amen.

eqvinox 1y ago

> There are multiple PoE standards. No, there aren't, not in the way you imply. There is the IEEE 802 PoE standards, which are all compatible (save for not enough power), and designed to carefully negotiate and especially never break non-PoE devices. And there is bullshit (sorry) like "Passive PoE" that is ironically an active violation of the IEEE specs, can break pretty much anything, and you shouldn't buy so the likes of Ubiquiti and Mikrotik finally get the wallet vote and stop f*cking doing. Unfortunately, the proper PoE PD logic is a few dollars of extra expense. Yes, there is a slightly higher risk of killing devices due to faults in the PoE supply logic. I have the official PoE HAT for a RPi 4. I have to say it is somewhat poorly designed due to space constraints; the isolation between 48V and 3.3V should be better. I'm not even sure the RPi PoE HAT is spec compliant. But I don't think you can/should blame this on PoE.

yread 1y ago
I have a ubiquiti 30w poe+ injector that somehow doesnt provide enough power for 20W aruba AP. When I plug it in a 120W switch it works unless the cable gets too twisted or something. I vote not awesome
- eqvinox 1y ago
  Don't buy Ubiquiti. Personally speaking, anyone doing passive PoE (even if only on other device series you're not looking at) is automatically on my shitlist. I'm not surprised they can f* up a basic PoE injector. The reason for doing passive PoE is saving a few bucks, on the back of safety and compatibility. Of course they would try to pinch hard on the PoE injector too. Oh and I'd say they (together with Mikrotik) are responsible for 90% of the bad rep PoE gets. The IEEE 802 stuff really just works. And I say that having been part of rolling out 15000 people conference deployments with several hundred wifi APs in the span of a few days. The only real problem is broken cables, but the Ethernet link commonly fails before PoE is impacted.
  - deviantintegral 1y ago
    Ubiquity only did passive PoE in the very early days. Everything has been 802.11 variants for a long while wow. The injectors that shipped a decade ago with my APs were all 802.11af.

numpad0 1y ago

The (negative)48VDC voltage comes from regular telephones. So did the RJ45(8P8C) plug. It's not an invented thing.

throw0101c 1y ago

> Except when it isn't awesome. There are multiple PoE standards. There are three: IEEE 802.11af, at, and bt. af can deliver up to 12W at the powered device (PD), at delivers up to 25 W, and bt either 51W (Type 3) or 71W (Type 4): * https://en.wikipedia.org/wiki/Power_over_Ethernet#Standard_implementation https://en.wikipedia.org/wiki/Power_over_Ethernet#Standard_i... Any device you purchase should list the IEEE standard it supports and how much power it may draw.