General > General Technical Chat
Grumpy rant #783
coppice:
--- Quote from: Ranayna on October 15, 2023, 08:34:16 pm ---From what i know this is a real problem for the higher Power over Ethernet modes that also run at 48 volt, but "just" about 2 amps.
You are supposed to turn the power off before you unplug the cable, or the connectors might take arcing damage.
--- End quote ---
If its real standards compliant POE (there are cheap bodgy things loosely called POE) there is only a full 48V after negotiation. The powered device has to be able to start up in a low voltage low power mode to perform the negotiation. So, plugging in is OK. This is similar to USB power delivery. For both ethernet and USB its disconnecting which can lead to arcing. Bad, but at least you don't get huge inrush hits.
SiliconWizard:
Yes, you're never going to get 48V from USB-C before it has been fully negotiated, so it won't happen when plugging. OTOH, it's going to happen when unplugging.
TimFox:
This could all end up as another TikTok challenge, but not as exciting as a 240 V arc.
coppice:
--- Quote from: TimFox on October 15, 2023, 08:57:13 pm ---This could all end up as another TikTok challenge, but not as exciting as a 240 V arc.
--- End quote ---
Could lead to an interesting story arc.
Ranayna:
--- Quote from: coppice on October 15, 2023, 08:53:37 pm ---
--- Quote from: Ranayna on October 15, 2023, 08:34:16 pm ---From what i know this is a real problem for the higher Power over Ethernet modes that also run at 48 volt, but "just" about 2 amps.
You are supposed to turn the power off before you unplug the cable, or the connectors might take arcing damage.
--- End quote ---
If its real standards compliant POE (there are cheap bodgy things loosely called POE) there is only a full 48V after negotiation. The powered device has to be able to start up in a low voltage low power mode to perform the negotiation. So, plugging in is OK. This is similar to USB power delivery. For both ethernet and USB its disconnecting which can lead to arcing. Bad, but at least you don't get huge inrush hits.
--- End quote ---
Ugh, don't get me started on all that crap thats called "PoE"...
Look at the IEEE standards that a product supports. If it lists 802.11af (PoE), at (PoE+) or bt (PoE++), then you can be reasonably sure it's using proper PoE.
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