Power over ethernet

[finncapt]

I want to put an IP camera on the rear of my garage to record passing wildlife - lynx in particular.

There are many cameras on the market and, since my garage is hardwired for ethernet, I thought a PoE/Nvr solution would be the most practical and minimise cabling.

I can then view through my Lan.

PoE cameras seem to come with a variety of required voltages.

I can find the wattage available for various PoE switches but am unable to find at what voltage those watts are delivered - maybe the PoE sorts itself out.

Perhaps someone knows the answer.

[tb10er]

poe

Your PoE switch specification sheet will give you the max milliamps allowed at any one time over all of the available ports.

As you will only use 1 port, calculate the max wattage by:

220v x (milli)amps. = wattage

As long as the output wattage is less than the required wattage, then you are fine

[Bushfiva]

220V

That should be nominally 48V, but eqpt must work from 37V to 57V because the cabling is quite lossy (cat 5 standard is 24AWG)

[finncapt]

I understand the wattage problem.

Most of the cameras I've seen seem to run on 12v or 15v so, if PoE works at around 48v, how do we go from that to, say, 12v or am I missing something.

Suppose, for instance, I get a Dlink DGS-1008P/E switch, do I just plug in my ethernet cable to it and the other end into the ethernet port of a Dlink DCS-7513 camera (which is 12v) or do I need some additional equipment in between (I am not suggesting I will go with Dlink but it should give an idea)?

I've been using a battery stealth camera with a storage card until now - haven't got a picture of a lynx but have heard it and seen the tracks (in the snow) - but I am looking for some better and continuous video solution.

Having reread the notes on the camera, it seems it must take care of the PoE volts by itself and the 12v power is if you wish to use a wall socket and adapter, seems quite clever.

[Bushfiva]

You use a PoE splitter to get typically 5, 9 or 12V. There are lots on the market. It seems your camera is 802.3af-compliant, so it connects directly to the cable and the splitter is effectively built in.

[finncapt]

Thanks for that, I will now start to see what is available.

I may try with a PoE box, decent camera and using a linux computer with something like Zoneminder before investing in a standalone system.

Have to do something to keep my retired mind active!!!!

[jimjim1]

DCS-7513 Outdoor Full HD WDR PoE Day/Night Fixed Bullet Network Camera | D-Link UK
The DCS-7513 has a built-in 802.3af compliant PoE module

External Device Interface
10/100 BASE-TX Ethernet port with PoE

As long as the switch is 802.3af you will be good. 802.3at MAY or may not be backwards compatible. Should be easy enough to check.

You need nothing other than the switch, camera and a cat5/6 cable.

The PoE voltage is higher to deliver the required power while minimising losses in the fairly flimsy cable.

[Avtrician]

The power uses the un-used portion of the 8 wire cable, here is a simple explanation.

Power over Ethernet (POE) Explained - Understanding and using POE

[mixture]

The power uses the un-used potion of the 8 wire cable, here is a simple explanation.

Ahem cough splutter, is that the sound of someone asking to be corrected ?

Only FE uses two pairs.... GE requires all four !

Your understanding of the theory is wrong ... PoE is more comparable to ADSL which magically allows you to use broadband and make phone calls at the same time, not forgetting of course the fact the phone company is also sending voltage down your line too !

It is unfortunately a widespread misunderstanding, which indeed renders many cheap PoE injectors INCOMPATIBLE with Gigabit ! So caveat emptor if you're running Gigabit and are thinking about being stingy on PoE injectors !

PoE uses a phantom power technique. Similar in concept to what you find in lav mics.

IEEE 802.3 if you need bed-time reading.