Powering non-PoE devices from a PoE switch

A brief note explaining how to use a standard Power Over Ethernet (PoE) switch to power non-PoE equipment.

Introduction
These days Power over Ethernet (PoE) switches are standard in larger organisations as they are typically used to connect desk phones on users desks using one cat-5 or cat-6 data cable.  This one cable provides both the data and power connections that the phone needs and saves time, effort and power (and therefore costs) in the modern office.

Increasingly you will find PoE is being used in homes and smaller business to power WiFi access points or small security / CCTV cameras where the savings are even more noticeable.  For example, if you decide to install a security camera outside your house you can easily see that only having to run one cable to the camera greatly simplifies the installation and saves on installation costs as no separate power socket or adapter is needed.

The only drawback to this approach is that you have to already have a PoE switch and you would normally need to buy a PoE-compatible camera. At least - you did need to buy a PoE-compatible camera.  This note explains how you can use a normal 12V / Ethernet camera and a nice piece of technology from TP-Link - the TP-LINK TL-POE10R PoE Splitter.

What is Power over Ethernet?
Power over Ethernet or PoE is a general term that is used to describe systems that pass power alongside data on twisted-pair (Cat-5 or Cat-6) Ethernet cables.  There are several common techniques used to transmit this power but in this note I'll stick to the IEEE 802.3 standard which defines the power supplied to be typically 15.4W or 25.5W for PoE+.

Anyone wanting to learn more about other alternative PoE systems are encouraged to look at the PoE entry on Wikipedia.


What is a PoE Switch?
A PoE Switch is just like any other Ethernet switch - except it is designed to provide 15.4W of power, on demand, down the Ethernet cable to the end device along with the Ethernet data signals.  Similarly, a PoE+ switch can provide upto 25.5W.  In my network I use a 24-port PoE+ Gigabit Ethernet switch similar to this TP-Link T1600G-28PS JetStream 24-Port Gigabit Smart PoE+ Switch.  You should consider one of these - or maybe a smaller 4 or 8 Port Gigabit PoE Switch to power your IP cameras if you are looking to do the same in your home or small business.

What is a PoE Splitter?
A PoE Splitter is a small device that passes the Ethernet data signals from input to output and at the same time draws power from the incoming PoE signal and provides a stable output power feed suitable for small devices such as a camera or WiFi access point as this diagram from TP-Link's user guide shows:

You can see from the diagram that this little device supplies power AND data to the end device but only has one cable connecting it to the switch.  To illustrate this the image below shows that I have powered a small 5-port Cisco switch from the unit.  The purple wire on the left connects to my PoE switch; the grey wire passes the Ethernet signal from the splitter to the Cisco switch and the black wire supplies power from the splitter to the switch.

In my next project I will be using this splitter to power a Raspberry Pi together with a Camera Module and LED light source as I construct a wildlife camera to watch the wildlife using the small pond in my garden.

I hope this note has been of use to you. I'll refer to it when I write up the Raspberry Pi outdoor wildlife camera project.