POE Camera's / General POE Question

[Waketech]

I am starting to look at POE camera's and have a few questions.....

 

1) I assume you will need a POE switch ?

2) Can non POE devices still be connected to a POE switch w/o damage ?

 

Thanks

[Teken]

I am starting to look at POE camera's and have a few questions.....

 

1) I assume you will need a POE switch ?

2) Can non POE devices still be connected to a POE switch w/o damage ?

 

Thanks

 

Power Over Ethernet is a very large area that you really need to study and learn about. There are many standards with POE and various DC supported voltages in the market.

 

POE is classed as either 802.3af / 802.3at, the former supports up to 15.4 watts, where as the other supports 25.5 watts, up to 51 watts running on a four pairs of wire.

 

There are various POE devices which run on 5, 12, 18, 24, volts etc.

 

Those devices which are true and meet the above POE class have chips inside to talk to either a POE switch, hub, expander that it is indeed a POE device and will energize that cable. While dumb POE devices will energize the line at all times.

 

So long as your wire pairs follow the standard nothing needs to be worried about other than the simple fact there is DC power on the line at all times and you must ensure safety measures are in place.

 

You must also ensure you use only pure copper CAT5e or CAT6 cable.

 

Using CCA (Copper Clad Aluminium) is not allowed per the CEC / NEC or safety rated and is a fire hazard. There are many POE switches / routers that can provide switched voltages to provide more flexibility. None of them provide 5, 12, 18, volts support. 

 

I haven't even covered EEE (Energy Efficient Ethernet) or the simple fact many of the consumer grade products do not output enough power either in 15.4, 25, 51 watts per channel.

 

Some more robust units know when to go to sleep where as others can also manage the (regulate) the voltage to ensure consistent operations of the end device. Keep in mind if any camera is mounted out doors lightning protection must be addressed as you essentially have a very large antenna that is scattered throughout your building.

 

Induction is always possible when lightning is present and you really need to ensure protection against life and property is paramount when deploying your systems. 

[Bob P.]

Waketech, I got a 16 channel POE injector that sits on top of my switch (PowerDSine). Short jumpers go to the POE unit, and out to the cameras. Anything not POE goes straight from the switch. Every POE device that I've plugged in has worked fine.

 

I see there are lots of cheap POE switches on ebay, and if you go that route, many of them seem to have configurable POE/Non-POE ports.

 

Here's some text from an injector unit on ebay:

 

"The 7012G is also safe to use on non-PoE devices, because the injector first tests the line to make sure it is safe to send power. If the device indicates it is PoE compliant, then the injector supplies 55 VDC on pins 4&5 (+) and 7&8 (-) on the CATx cable."

 

I was kind of surprised at the 55 volts, since most of these cameras and other devices run on 5VDC, 24VDC, or other, but that seems to be a standard. I guess the devices handle dongle power and POE power differently.

[Brian H]

Many of the better POE Injectors use around 48 volts DC.

The camera or device has a voltage regulator in it to output the proper voltage the device needs.

That way the voltage loss in the cable between the injector and device doesn't effect it operation.

 

I have seen passive unregulated ones used by X10's cameras. All they did was use the power supply for the camera at the one end and a power splitter at the other end. It was not uncommon to see the 12 volts at the injector end. Much lower at  the cameras end. Sometimes the camera would work but if you tried to pan or tilt. The added current would pull the voltage so low. The camera would reboot or just get lost.

[larryllix]

Thanks guys! I am getting to that same point and looking at IP cameras.

 

I see pass-through devices to add PoE to regular Ethernet circuits. I wonder if it is that simple. It sounds like they want to get the voltage high so that cable resistance won't be such a factor for a camera that could absorb 10-15 watts. At a 12vdc line the 1-1.5 amperes required would get lost in those cat5-6 cables and pinprick connectors.