IPVMU Certified | 08/12/13 04:48pm
Also, be wary of this:
If the switch is fully burdened with PoE powered devices, it will not issue the full 15.4W (or 30W on 1-4) per port. Most cameras work fine at 9W, but some types (especially outdoor models) will not.
Yeah, really difficult to say for sure without knowing exactly what cameras you're using and what their specific power requirements are...
IPVMU Certified | 08/12/13 05:02pm
Hmmm it claims <4W power consumption, but that's GOT to be without the IRs. I'd expect that to at least double when the IR turns on... you MIGHT be okay, but it would be pushing the switch to its limit.
Kind of worrisome that they don't provide power ratings both with and without IRs on.
We have used many times and works well. Remember good quality cables and cable lenghts, max. 150ft. Full loaded switch can not handle very long cables (100m, 300ft) for all cameras. Camera power consuption max. 10W.
I struggled with this when I worked for an Integrator and spec'd systems. In the end I decided it was far easier to standardize on switches that were able to provide full PoE out each port. It's easier for the installers to not have to worry about it and fail safe if you add cameras in the future and fill the switch up.
I am with Jason about this, especially since insufficient PoE power manifests itself in very bizarre patterns, like cameras randomly going offline, initially making people feel the cameras are 'broken', rather than simply that there's not enough power.
IPVMU Certified | 08/12/13 05:17pm
What if i only use 16 cameras instead of 24?
I will be using Dlink Cat 6 (NCB-C6UGRYR-305)
There are about 4 cameras which are about maximum of 70m each and the remaining are all below 50m each.
IPVMU Certified | 08/12/13 05:31pm
i'm with john on his statement... an underpowered camera will be intermittent at best in its performance... it will work long enough to install but it will guarantee a call back... troubleshooting will potentially lead you to mistakenly identify the camera as being the issue when it is truly the switch... i am with jason in standardization of equipment... makes bidding more efficient, technicians more efficient and increases customer satisfaction...
Inaxsys Security Systems
@ Matt: this could be a 4W with IR on for the camera. Take a look at the spec for an ACTi D54 - they specify the power with IR on and they say 4.26W :
IPVMU Certified | 08/12/13 05:51pm
"Remember good quality cables and cable lenghts, max. 150ft. Full loaded switch can not handle very long cables (100m, 300ft) for all cameras."
If a switch cannot provide full rated power at 100 meters, that is a shortcoming of the switch. PoE specification is supposed to cover maximum Ethernet cable distance limits.
I think you should really involve your sales or manufacturers rep to confirm specifications meet your requirements. Get the name, numer and date/time that you talked to them. If the system doesn't work and meet the needs after they said it would, it's on them to make it right or at least offer full RMA. There may be intelligent people here on IPVM happy to help, but their reputation and liability is not on the line as yours is. I'm not saying it hurts to ask, but forums should not be the end all authority when you need confirmation on performance specifications.
No disrepect to my collegues here, I'm just always concerned when someone seems to ask beyond simple advice or opinions out of a forum when specific performance criteria is concerned that should be confirmed by the manufacturer themselves.
IPVMU Certified | 08/12/13 06:02pm
^^^ or do both: confirm with the rep AND collaborate. Then you can compare answers!
In some cases, its like putting two scorpions in a jar and shaking it.
(Luis offers sage advice.)
IPVMU Certified | 08/12/13 06:31pm
Any manufacturer of a PoE device should have datasheets with device wattage and PoE type requirements. If you're unsure on anything, you should clarify it with the device manufacturer. I've find rule of thumb is be wary of any manufacturer that buries or makes this information hard to find.
Testing PoE power draw is easy and can be done with a small device (we use Byte Brother Power Panel). We have tested dozens of IP cameras and the low end is 3 to 4 watts - that's a simple mini-dome like the Dahua but with no IR on. Contrary to this spec of 4.26 watts, I do not believe this is with IR on. As Matt said earlier, it's like with them off.
Of course, you can and should do the test yourself. Actually, I think we have that (or a similar Dahua unit). Derek/Ethan, please run that test.
We just tested a Dahua IPC-HDW2100, and it's about 2.3W with IR off, and 3.5 with IR on.
The bullet uses 4.5W with IR on and 2.3 with it off. But it's also got bigger LEDs.
RJ, as far as figuring overhead, when I was dabbling in electronics design many snows ago, it was common practice to de-rate listed specs by at least 10%... so if you needed, say, a capacitor for a 12V circuit, you'd select one rated for MINIMUM 13.2V (next step up is usually 16V, but you get the idea).
10% is probably a good place to start... if a switch claims it will provide "X" watts to PDs, assume it will actually only give you X * 0.9 (or 90% of X). Some may not even be that generous, and some may actually be de-rated already in their own specs from their actual capacity (ie. it's capable of 110% of what it says)... but again, it's a good place to start. You'll never go wrong de-rating equipment yourself.
[IPVM Editor's Note: Poster is from D-Link]
The DES-1210-28P WebSmart switch has a PoE power budget of 193W, which can be allocated across the 24 PoE ports in any manner necessary.
Because this is a smart switch, there is a graphical user interface that provides useful tools related to the PoE functionality. For instance, the UI displays the actual power consumption of each device (camera), the total amount of power used, and the total amount of power remaining in the budget.
Additionally, each switch port can be assigned a priority. If additional cameras are turned up and the switch would otherwise exceed its power budget limit, the switch can be configured to either “deny next port” or “deny low priority port.” This prevents any particular port from being underpowered and “manifesting bizarre patterns”, which is mentioned by another contributor previously in this thread.
Since the cameras are Class 2, the switch would allocate 7W per camera or 168W for 24 cameras, well within the 193W power budget.
I continue to see many PoE Siwtch power questions and fully agree with Jason and John that specifying a switch with full power capability per port is essential. Now that swicthes support AF and AT PoE, the math gets complicated again and you can expect further issues in this regard.