Build your own Power Over Ethernet (PoE) Injector
by stugs on Feb.05, 2009, under Uncategorized
I have been working on an embedded wireless application and the development board only supports power over ethernet (PoE). The manufacture hasn’t released their official PoE injector so I started looking for an economical alternative online. For such a simple device I was amazed at how expensive a basic 802.3 PoE injector can be.
After looking at what was required to build one, I decided I would give it a try.
What you’ll need
- Two keystone jacks
- Dual port surface mount jack
- A short length of cat5 cable
- Power supply of your required voltage :: My SBC supports 12-36V DC so I used an old 12V (1.2A) power supply from a Netgear broadband router
- Multi-meter, wire stripper, and a punch tool
First comes the standard data connections. If you’ve ever made an Ethernet cable then these are pretty familiar.
- PIN1 -> PIN1
- PIN2 -> PIN2
- PIN3 -> PIN3
- PIN6 -> PIN6
On the power side, we will need to supply positive (+) and negative (-) power to a total of four pins. To do this, you’ll need to loop two of the PINs for positive (+) and two for negative (-) as shown above.
The power connections are:
- PIN4 :: positive (+)
- PIN5 :: positive (+)
- PIN7 :: negative (-)
- PIN8 :: negative (-)
Once you have your power connections looped, install the power supply cable. I had a bunch of CAT6 jacks “laying around” the office and decided to use those as they have a ziptie connector at the back of the jack. This is useful for securing the power supply cable.
After you assemble the surface mount box label the two ports and verify the power pins with a multi-meter.
This cost me nothing as I stole all of the parts from our telephone supply closet. If I had purchased all the required parts at retail it would have been about $25. This is the same price as the cheapest PoE injector I found w/out shipping.
If you want to remotely power a device that isn’t PoE, build another for the other end but replace the power supply with the approporiate connector for your device.
6 Comments for this entry
Leave a Reply
-
Welcome to HR Geeks!
We're a group of (mostly) Hampton Roads based technology enthuisiasts. Our members take part of many different groups, from 757 Labs to TWUUG to sitting at home watching TV.
Our goal with HRGeeks.com is to be a sort of 'clearing house' of all technology related goings-on in Hampton Roads, as well as a home for collaboration and discussion between area geeks.
Check out our our Friends for a full listing of available technology groups in Hampton Roads.
-
Email / iCal Subscriptions
Stay updated on meetings and activities via email or iCal!
February 8th, 2009 on 8:28 pm
Neat hack!
Doesn’t this *always* supply the juice over those pins though?
PoE dynamically is off on the pins until the protocol on the line says ‘gimme juice’.
If you accidentally plugged this into something that wasn’t expecting or needing power, wouldn’t it cause problems? I guess this would work for anything that needs an injector, rather than regular from-the-switch PoE?
October 31st, 2009 on 10:07 am
Non-PoE compliant devices won’t have the powered pins connected. These pins are normally unused for typical 10/100 data transmissions per IEEE 802.3af specification
October 31st, 2009 on 10:32 am
Ethan: Nobody uses 10/100 data transmission anymore. Every RJ45 plug I have is fully connected – we live in the 21st century and use Gigabit
November 27th, 2009 on 1:52 pm
This may be the 21st century, but if you want PoE, you’ve gotta know how to use it. This is used for security cams and distance locations. Not the private sector in a kids basement.
August 8th, 2010 on 4:59 am
Thanks for the DIY. I really appreciate it.
January 10th, 2011 on 1:33 pm
You rock. I dropped in a fuse and a little red LED for kicks. Thank you.