Balun compatible with PoE?

Trashcan · Post by **Trashcan** » Sat Dec 30, 2006 8:25 am

Hi all,

I've recently had some creeps knocking over my trashcan and I really want their faces on tape.

Anyway, I've been designing a system on the cheap and have come across a question that I haven't seen answered here or on the net.

Are balun devices compatible with PoE?

I've got to go about 250 feet with no power at the far end. The cheapest route seems to be:

PIII/600 sitting in the closet
Spare cat5e I plan to cover up with leaves and whatnot
BT878 based 4 channel card and outdoor camera ~$100
Baluns and PoE ~$50?
And Zoneminder, of course!

I seem to be set if baluns will work with PoE. Any other advice or suggestions would be greatly appreciated.

Thanks!

PS: My uncle suggested sitting out all night with a shotgun but I think this works a little better.

Supra Dave · Post by **Supra Dave** » Sat Dec 30, 2006 11:45 am

Well.. Yes..

But you need special baluns with a power connector;

For example.

Do a search on Ebay for balun power and you see what I mean.. There a two little screws on the side for the power (use a water resistant box for outside to be sure).

Succes with your trashcan

Post by **cordel** » Sat Dec 30, 2006 9:47 pm

The only concern would be at 250 ft you would have to use 24VAC. It's to long of a run to use 12VDC.

jameswilson · Post by **jameswilson** » Sun Dec 31, 2006 12:43 am

if your using baluns, make sure you use decent ones like the nvt ones. Cheap baluns have awful losses. But if you use a cat 5 and treble up the supply and use the 1 pair for video then you might have a better chance
250 ft (70 odd meters?) is dfinetly too much for 12v and poss 24 but depends on the draw of the cam. Also dont use a 24v psu on a 12v cam!!!

Supra Dave · Post by **Supra Dave** » Sun Dec 31, 2006 2:27 pm

My camera has a tolerance of 9.5V - 16V according to the manual, so check your manual and check the voltage at the end of the cable with a multimeter.

You can use a 13.8V power supply, used by HAM radio people (like me), they are often properly stabilized and have a high current.

But check your camera voltage tolerance first!

Post by **cordel** » Sun Dec 31, 2006 9:13 pm

But at that length of a run, using a high current supply (Like an astron 7A) and the camera trying to pull more current than the 24 gauge can handle at that distance could cause the wire to heat up and that could be disastrous (not to mention violate building codes). I would suggest using a supply meant for CCTV cams as they all have current limiting so you don't burn things down... like your house

250 feet is to far or a run for 12VDC on 24 gauge wire.
Something to consider is an Axis IP cam with real POE built in, the standard uses 48VAC and would travel that distance.

Trashcan · Post by **Trashcan** » Mon Jan 01, 2007 9:21 pm

I've seen two IP cams with PoE built in, Axis and Toshiba, both of which are too expensive. I was considering this camera:

http://www.gadspot.com/product_info.php?products_id=76

I'd imagine the the IR illuminators would draw a bit of current.

Hmm. Well, if things get too expensive this way I might just drop a full fledged power line out to the road, then I could install a light and go wireless. It's back to the drawingboard...

Thanks a lot for all the input.

Supra Dave · Post by **Supra Dave** » Tue Jan 02, 2007 8:13 am

cordel wrote:using a high current supply (Like an astron 7A) and the camera trying to pull more current than the 24 gauge can handle at that distance could cause the wire to heat up and that could be disastrous

A camera does not pull more current than described in the manual. It does not matter what kind of power supply you are using as long as it's capable of supplying the needed current.

The linked camera above is 12V and 750 mA ... Thats 9 Watt.

The PoE standard allows around 15W maximum.

Post by **cordel** » Tue Jan 02, 2007 9:48 am

Supra Dave wrote:A camera does not pull more current than described in the manual. It does not matter what kind of power supply you are using as long as it's capable of supplying the needed current.

The linked camera above is 12V and 750 mA ... Thats 9 Watt.

The PoE standard allows around 15W maximum.

PoE standard is also 48VAC. At 48VAC 15 watts is only ~300mA (sorry for the head math this should be a generous result). You are correct that the camera will not pull more than what it's speced at but that does not stop the current from exceding the ability of the transfer medium. While there may not be a risk of "Fire", the voltage drop from the impedance from that length on 24 AWG may not reliably power the camera at the end.

jameswilson · Post by **jameswilson** » Tue Jan 02, 2007 1:17 pm

i agree with corey, ake a 2a psu and your cat 5 run it over say 50m and short the brown pairs. YThe fuse wont blow and the cable will get warm. In the uk we have disconnect times and the cable has to be caperble of blowing the protective divice with .5 second. If the volt drop is too high and the current caperbility of the cable too low, it will run without blowing the protective xdevice and eventually the cable will heat up and destroy itself, maybe taking the building with it!!

Flash_ · Post by **Flash_** » Wed Jan 03, 2007 10:31 am

The IP PoE stuff....

Yes, the built in ones are very expensive, but there is another route.

Buffalo do a PoE "In" box for about 20 quid. Adds the power to the Cat5.

D-Link do a cheap (~£15) splitter to provide 5 or 12v OUT at the other end. I've used this with non PoE cameras (the axis 215 / 216s) with no problems, although I had to join the two power leads. Should work for all 5 or 12vdc cameras, given the length from the mains converter isn't /too/ long.