Subscriber Discussion

IPVM Track Camera PoE Use Versus Advertised

Steeming from the conversation about Mobitix's PoE wattage usage, I think it would be nice if IPVM started doing PoE measurements in all tests to compare against the manufacturer's stated PoE consumption. It'd be interesting to see if there is a large discrepency against what manufactures claim veruses actual. I think more end users might start becoming more interested as "green initiatives" start becoming more common. If you find a large discrepency in one particular camera you could maybe show what the theroretical dollar cost differnance in energy usage for that one camera might be in a year. Maybe it will be a significant, or maybe not.

At the very least I think integrators would be interested if a camera rated at near 15w (say if it has PoE IR or heater/blower), actually tries to draw more than 15w since most your common PoE switches still usually put out only 15.4w max (advertised).

Yes, we'll start with a roundup of test of some cameras we already have tested to get a baseline.

Luis this is an excellent idea. There are solutions out there for intelligent power management built into a camera housing. For example, Videotec makes a housing using Intelligent Power Management Technology. The IPM system automatically detects all accessories connected to perform an automatic power balance and an appropriate distribution of the same to the connected devices.

Alluding to what luis said about green initiatives they advertise it as a "green friendly" solution. However, this is more for management of power than for lower power applications, but a solution like this will prevent the overdraws you mentioned above.

"but a solution like this will prevent the overdraws you mentioned above."

Michael, well, just to be clear, knowing if a camera rated at 15w actually tries to draw more power isn't out of concern that it will overload the port, which it won't because it can't go byond the limit of what the port can put out. My concern is if the camera tries to draw more power than what it says it's supposed to need and end up not funcitoning properly because it can't get enough. There's a significant price differance between PoE 15w per port switches and PoE+ 30w per port switches, and if I actually need to use a 30w per port switch I wan't to know that ahead of time. Making sure everything stays within maximum stated requirements can be more significant if for example you have a switch with maxinimum 15w per port, but the power budget is limited so it will only put out a max of 7.5w per port if all ports are in use at the same time. (This is a gotcha integrators have to be careful about.)

I apologize in advance if I mis-interpreted your statement.

I just found this. Could IP cameras go in and out ( brown out) if the POE switch will not hold the amount of cameras? I have 15 cameras on a 12 port cisco switch with 3 on POE bricks. The cameras are giving me a hard time.


Fundamentally, yes, although it depends how 'smart' the switch is. The 'power budget' of the switch is fixed at a certain number of Watts, and if the total demand exceeds the output, then problems can result.

Sometimes the switch can manage this situation, and take down ports altogether or even reconfigure how much power each port is getting. If you have more make/model details on the cameras, the PoE 'bricks' (injectors?) and the switch we can pretty quickly focus in or rule out 'power budget' as the problem.

Also: are cameras the only devices plugged into the switch? Any other PoE devices: WAP, VoIP phones, etc?

Undisclosed, what's the maximum PoE power rating of that Cisco switch? Compare that to the number of PoE ports.

For instance, if it's 12 PoE ports and the switch supports 90 watts total, you have a real risk because that's only 7.5 watts per port while IP cameras ('regular' 802.3af) can require up to 15 watts each.