HI there I am trying to find out if I can use my Ubiquiti EdgeSwitch 8XP to power my HA Yellow (POE version). The ports on the switch can be set to 24v or 48V passive POE. Are these suitable or will they fry my HA Yellow?
Odd that they do PoE at 24V instead of the standard of 48V (it came about due to IP Phones and 48V is a voltage that came over from the old PSTN phones). Anyway, though I do not have a HA Yellow, and am using a Raspberry Pi 4B (HA Yellow is based on a Raspberry PI 4), I can tell you from my experience with those, Pi 3s, Phillps Hue, and Tempest Wetherflow, there is such a thing as a PoE splitter that you can use for this kind of operation.
Typically, you are going to be limited to 15.4-Watts, which has been fine for these devices.
It works as a RJ-45 that goes toward the switch and then another that goes out to the device, so it goes inline with your network connection. Then, it has a wire outside of it to provide power to the device. You can pick them up all day long on Amazon with a USB-C power plug to plug into your HA Yellow. In fact, you can buy the Yellows with the PoE Splitter.
So, I think if you set the output on your switch port to 48V and get one of those splitters, you should be fine.
The key word here is “passive”. Ubiquiti used to use 24V or 48V basically connected to the 4x unused 100bT pins on a RJ45. This is power over Ethernet, but not Power over Ethernet compliant with the 802.3af standard (which requires a lot more power control logic to negotiate power draw).
I’d not connect a PoE Yellow to passive power injection. Passive is not “proper PoE”.
I have a mix of older and new Unifi cameras and the older ones worked with a cheap dumb passive injector, but with a “proper” 802.3af switch, Unifi sells a 802.3af to 24V passive adapter (INS-3AF-O-G). I’ve never seen the reverse - a passive to 802.3af converter, but they do sell PoE injector PSU in many variants depending on power needs (U-POE-at, etc).
Unifi also sell 802.3af to USB and others offer PoE to barrel jack power supplies to run other kit from PoE, which might run a Yellow (2A might be a stretch) but you’ve got a passive switch…
If this helps, 
this post!
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I’ve checked with Ubiquiti and they said
“All the passive injectors in all switches sense their current draw and will disconnect power if it exceeds a certain value, so they don’t burn up an improperly connected cable or device.”
They go on to say “802.3af and 803.3at POE+ compliant devices can be powered with passive power - I do this all the time. Including bt (PoE ++) units from the passive 50V injectors. They work just fine.”
My understanding is Ubiquiti’s passive POE ports are mode B and use pins 4,5 7 and 8 whether 24v or 48V and are powered constantly when switched on through their GUI. In contrast, active POE or POE+ ports autosense using the industry standard methods to decide when and if to provide PoE or not.
They finally say “No 802.3af/at/bt PDs I am familiar with are incapable of working with a UBNT passive PoE source - they all just work. And they will be modeB unless it’s one of the oddball 4 pair units, which look like 802.3bt power (unless they are 24V, obviously).”
Based on this I think its safe to use 48v passive POE power on my HA Yellow. Only one way to find out!
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