You just picked up some new Power over Ethernet devices – a few of
the hottest new IP cameras. However, after opening the box you run into a
series of unexpected problems. No its a really powerful decision.
First: Each camera comes equipped with its
PoE injector capable of supplying the appropriate level of power.
However, prior to even mocking up your panel it becomes clear – four PoE
injectors and a standard Ethernet switch will not fit.
Second:
You are able to find a small label
printed on the bottom near the Ethernet port of the camera – something that
specifies how this camera can be powered. Now you have some numbers to
shoot for, but what exactly do they mean?
While listed on the label in the above order, Power over
Ethernet is best addressed in this order:-
1.
Is
this a Power over Ethernet device?
A.
Will the device accept
Power and data through the Ethernet port? Has the device been designed to make
use of Power over Ethernet.
2.
Is
this device IEEE 802.3af or IEEE 802.3at compliant?
A.
How much power will
the device draw? Both IEEE 802.3af and 802.3at are based off +48VDC voltage but
differ in wattage.
B.
IEEE 802.3af =
“Standard PoE” = devices consuming up to 12.95W of PoE power IEEE 802.3at =
“PoE Plus, High-Power PoE” = devices consuming up to 25.50W of PoE power
3.
Which
class of Powered Devices (PD) is the device a member of?
A.
PoE capability and
power level compliance – the class level of Powered Devices further specifies
how much power the device will draw
Class 1 = 0.44 – 3.84W
“Very low power”
Class 2 = 3.84 – 6.49W “Low power”
Class 3 = 6.49 – 12.95W “Mid power”
Class 4 = 12.95 – 25.5W “High power, suitable only for IEEE 802.3at PoE”
Class 2 = 3.84 – 6.49W “Low power”
Class 3 = 6.49 – 12.95W “Mid power”
Class 4 = 12.95 – 25.5W “High power, suitable only for IEEE 802.3at PoE”
Translating the above power label again we find:
1.
Is this a Power over
Ethernet device? Yes, this camera can accept PoE
2.
Is this device IEEE
802.3af or IEEE 802.3at compliant? IEEE 802.3af – the maximum it
will draw is 12.95W at 48VDC
3.
Which class of Powered
Devices (PD) is the device a member of? Class 2 – this device will draw
between 3.84 and 6.49W – it is a “low power” device
After finding a Power over Ethernet switch that
will provide suitable power conditions on a per-port basis, there is one final
element to consider – power budget.
Will the switch you choose provide enough power
per port for each camera? You bought four cameras to use four cameras, not to
use just one or two. Your choice in a Power over Ethernet switch needs to
reflect this… Will the switch provide suitable power to all ports at all times?
Finally, after considering space in your panel,
power demands of one camera, power ability of a switch for one port, and
powering ability of a switch across all ports, you are prepared to make a
decision!
