Terminology Series: Power Over Ethernet (PoE)

Moved to www.NetworkCameraCritic.com

Power over Ethernet or PoE technology describes a way to power a camera using the very same Ethernet cable used to connect the camera to the network. The big advantage is that you do not need a seperate power supply and 110VAC to power a camera.

The standard for PoE is 802.3af and provides up to 15.4 W of DC power (minimum 44 V DC and 350 m to each camera.

Your home router does not have this feature built in. You either have to get a switch that has the PoE feature or what is called a PoE injector.

A PoE injector plugs into your AC near your router, a cable goes from the injector to your router and the Ethernet cable from your camera plugs in the other connector. This powers only one camera per injector. Prices vary from $10-100 depending on brand name, but they all pretty much do the same thing.

Typical Injector

A PoE switch makes more sense if you are running low on open ports on your router and you plan on having more than one camera. A typical home/small business PoE switch looks like any other switch, but will have designated ports for connecting PoE devices, usually half will be PoE, half will be standard ports. Switches just plug into an open port on your router and are sort of like an intelligent extension cord. If you are looking for an inexpensive PoE switch, a Trendnet TPE-S44 can be found for about $50, has 8 ports, 4 of which are PoE.

PoE Switch

Inexpensive consumer cameras in many cases are WiFi and this does not apply. The negatives on WiFi are that you have to have an A/C outlet to plug the camera into. Indoors this may not be a problem, but outdoors, finding a convenient outlet is difficult, and running low voltage ethernet may be easier than setting up a 110VAC GFI circuit outdoors, not to mention having a transformer plugged into it to power the camera. Also, while cameras may connect to WiFi, it may not get a strong enough signal to achieve the frame rates advertised, especially when mounted outdoors.


6 Responses to “Terminology Series: Power Over Ethernet (PoE)”

  1. 1 josh
    March 1, 2011 at 10:18 pm

    I setup a Foscam b/g wifi ip camera it was straight forward after reading the instructions on your web sight. The only problem I have is each time I reboot the camera it sets up with a new IP address. Is there a way to change the ip address on the camera? I contacted the Foscam support and haven’t gotten any respond.
    Thank you

  2. May 19, 2011 at 10:43 pm

    There are two types of PoE, to two different standards but you don’t mention this.

    • May 19, 2011 at 11:14 pm

      There are some cameras, typically PTZ speed domes that use a different standard PoE or even their own propriatory PoE scheme, but in general, most PoE based cameras and PoE switches comform to the IEE 802.3af type 1 spec from 2003 which provides a maximum of 15.4W of power for a connection.If you buy a switch that supports the higher wattage of type 2, that will still work with cameras that are type 1, but I’ve never run into a camera requiring type 2.

  3. December 15, 2011 at 1:57 pm

    There is a cheap alternative available to send Power over Ethernet to non-POE cameras. It’s a simple converter that sends the power of the stock wall transformer to over the 4 usused wires of an Ethernet cable, with a break-out cable at the camera end. It uses the stock camera transformer, which usually operates at 5 or 12 volts, not at the 48 volts used by true POE. This lower voltage means there is less max power capability and more voltage drop as cable length increases. So, for wiring runs longer than about 50 feet, it may require a different transformer or may not work at all. At a price of only $6, it’s worth a try. But given the option, a real POE solution using the IEE 802.3af type 1 spec is recommended.

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