Are you ready for POE lighting?

[texie]

And just where, pray tell, does the PoE -supplying switch get its power? Still gotta plug that switch into an AC receptacle...



SceneryDriver

True, plus it will also have to be stepped down an additional time from 480 to 120 volt to feed the POE supply.

 

[Adamjamma]

And just where, pray tell, does the PoE -supplying switch get its power? Still gotta plug that switch into an AC receptacle...



It depends upon the actual applications and voltages but there are more and more converters for the poe applications to feed in the power. They make rack mounted, din rail mounted and wall mounted power transformers that can be hoooked up to supply quite a few different wattages... you also have transformers that make 24 volt center tapped so you in effect have the 24/12 volt options and they are starting to use an AC option for up to 36 volts.. so you have 24 and 36 vAC rather than volt DC... UL and BS registered along with EC registered..
seen a bunch of the options in my latest Rexel UK catalogue
SceneryDriver

 

[tom baker]

And just where, pray tell, does the PoE -supplying switch get its power? Still gotta plug that switch into an AC receptacle...



SceneryDriver

I have POE switches that are DC powered. My telemetry cabinets are all DC devices. A AC DC 24 v power supply goes to a DC UPS, it charges a 12 VDC battery, in a power outage the DC ups converts 12 into 24 volts. I use a european battey that is rated at 10 years. I ran the telemetry panel on an 500 VA UPS - 3 hours on the DC ups it went 3 days

 

[n1ist]

There are multiple POE standards.

Ad-hoc or poor-man's uses the two unused pairs in 100baseT; voltage varies based on the power supply. Note that gigabit Ethernet uses all 4 pairs for data so this won't work.

True POE passes the power between two data pairs with the power fed to the center tap of the data isolation transformer on one end and picked up from the transformer on the other end. Voltage is 48v nominal though it can drop down to 37v at the far end. Current standards allow up to 50w depending on the standard; it looks like there's a new standard in the works for 100w

/mike

 

[IMFOTP]

Whats the life span of a POE switch? And aren't they expensive?