Modify a switch

[IgorM]

Considering that PoE switches are considerably more expansive than regular ones, can you mod a normal switch and turn it into PoE?

[Mr Technician]

Definitely not.

[Bitter]

Welll.....probably. POE runs at 48 volts, right? So you need a buck converter to turn that 48 volt down to the needed voltage for the non POE switch and solder the buck converter output to the switch board or solder the power plug socket onto the buck converter. You'd have to match the amperage capacity of the buck to the needs of the switch, so say your switch uses a 7.5 volt 3 amp power supply, you need a buck converter that can take 48 volt input and output 7.5 volt at 3 amp. You'll likely need to get an adjustable buck converter and set it up yourself with a multimeter.

[Lurick]

7 hours ago, Bitter said:

Welll.....probably. POE runs at 48 volts, right? So you need a buck converter to turn that 48 volt down to the needed voltage for the non POE switch and solder the buck converter output to the switch board or solder the power plug socket onto the buck converter. You'd have to match the amperage capacity of the buck to the needs of the switch, so say your switch uses a 7.5 volt 3 amp power supply, you need a buck converter that can take 48 volt input and output 7.5 volt at 3 amp. You'll likely need to get an adjustable buck converter and set it up yourself with a multimeter.

You forgot that you'll also need to write code and find a way to implement everything with the switch so that it can properly negotiate the different PoE levels

[Bitter]

Doesn't it default to a 12.9W power level if there's no signature sent back after it senses the 25k ohm resistor? 12.9W would be enough for a small switch, possibly. http://www.veracityglobal.com/resources/articles-and-white-papers/poe-explained-part-2.aspx

I did forget about the resistor, that's my bad, but power will be sent without software. Of course if an older POE injector that's pre standardization was used then you'd just get what you get out the other end and buck it down to needed voltage, probably.

 

Or you could do your own "dumb POE" injector to just buzz down the power needed for the switch, just as long as you never plug anything else into that line except the switch. Just like this instructable, except you'd connect a power supply and account for voltage drop across the span when selecting the needed power supply. https://www.instructables.com/id/DIY-10100M-Ethernet-PoE-Injector/

[GuruOfNothing]

All things considered...(the chances of nuking anything you were trying to power because it wasn't able to deal with the power you were ramming down it's throat) a true POE router is cheap. I bought a 4 port for $50US on Amazon and it works great. I run camera's off it. By the time you jack around with creating new hardware to inject power, you could just buy external injectors and do the exact same thing. But still at a cost that is negligible compared to just spending a few extra bills and buying proper equipment. Now if you are costing out Gigabit POE gear, I feel for you but let's get realistic... Unless you are running a crap ton of powered gear, you don't need gigabit speeds for it. Having non-POE gear plugged into a POE router is a serious waste of money when non-POE gear is so stupid cheap. If you are worried about flooding your network because you are limited to 10/100 speeds, keep your computers off the routers that are doing the POE heavy lifting and buy cheap gigabit routers for the file transfers and media serving needs.