←back to thread

Power over Ethernet (PoE) basics and beyond

(www.edn.com)
257 points voxadam | 1 comments | 16 Oct 25 14:09 UTC | HN request time: 0.208s | source
Show context
skopje ◴[22 Oct 25 00:53 UTC] No.45663732[source]▶
PoE is awesome. My custom home security system is all CCTV PoE with a gstreamer backend running on four-core fanless linux box. Way to go. Complete control. No batteries, no wares spying on me, no personal data getting scraped by big guys. (Cloud connectivity sucks because I have segmented mp4s and jogging through them hurts but I only care for events after they happen, not while they happen.)
replies(6): >>45663770 #>>45664711 #>>45664915 #>>45665099 #>>45665193 #>>45667449 #
dheera ◴[22 Oct 25 05:11 UTC] No.45665099[source]▶
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.

replies(7): >>45665150 #>>45665155 #>>45665251 #>>45665484 #>>45665487 #>>45670739 #>>45673430 #
buccal ◴[22 Oct 25 05:23 UTC] No.45665155[source]▶
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.
replies(1): >>45669791 #
1. dheera ◴[22 Oct 25 14:37 UTC] No.45669791[source]▶
> 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.