Power Over Ethernet May Be The Way to Go
Power over Ethernet (PoE) is a technology that powers a
remote Ethernet device by transferring electrical power over the same standard
twisted-pair Ethernet cable that used to also send Ethernet data communication.
Here are some benefits to using PoE:Simple – A single cable can supply power and network connection
Space – Only one set of wires to deal with saves space and simplifies installation
Maintenance – Easier to deal with low voltage issues
Easy –Very easy install cameras and extend your network
Reach – Supports longer camera runs with Ethernet cable (ft.)
Savings – Cost savings on many levels (installs, labor, etc)
Look into Power over Ethernet injectors or switches to assist you in transmitting electrical power, along with data, to remote devices over your network. The benefits could be endless!
There are two main types of PoE, active and passive.
- Active PoE is standardized
by the IEEE 802.3af (PoE) and 802.3at (PoE+ which provides more power).
Active PoE requires negotiation between the device and the power source.
Double check if this matters, but I am pretty sure this is supported to
the supported length of cable for ethernet of the particular type (100Mbps
or gigabit). Active PoE is mostly the domain of enterprise stuff. It's not
generally inexpensive. In general[1] you can plug a non 802.3af/at PoE
device in to network port that has power being provided to on that
standard and all will be fine.
- Passive PoE is simplistic and simply uses a pair of the 8 wires in an ethernet cable for running power. How much power this can provide and how far the device can be from the power source varies wildly. There are some "standards" but they are by convention rather than formalized. It's generally bad (tm) to plug a device that is not expecting passive PoE in to a port that is powered as such. If you have a well designed network device, it might not fry the device, but it really shouldn't work.
Typical Application |
In standard cat-5 cabling for 10Mbit or 100Mbit Ethernet
only 4 of the 8 wires are actually used.
Power over Ethernet is a technique to use the unused pairs:
(4,5 and 8,7) to carry DC power to the device.
Some devices contain the circuitry to actually be powered
directly; in other cases you need to split the power off the Ethernet cabling
and feed it into the equipment the normal way.
Intel, Ayaya, Orinoco, Wavelan, 3Com and Symbol use 4,5 =
ground and 7,8 is positive
Cisco aironet use 7,8 = ground, 4,5 = positive.
RJ45 Pin #
|
Wire Color
|
10Base-T Signal
|
PoE
|
(T568A)
|
100Base-TX Signal
|
||
1
|
White/Green
|
Transmit
(+)
|
Mode A +
|
2
|
Green
|
Transmit
(-)
|
Mode A +
|
3
|
White/
|
Receive
(+)
|
Mode A -
|
4
|
Blue
|
Unused
|
Mode B +
|
5
|
White/
Blue
|
Unused
|
Mode B +
|
6
|
Receive
(-)
|
Mode A -
|
|
7
|
White/
Brown
|
Unused
|
Mode B -
|
8
|
Brown
|
Unused
|
Mode B -
|
Power over Ethernet
Pinout
|
|||
Same As The
Straight-Through Cable Pinout for T568A
|
It eliminates the need for power outlets at the camera locations
and enables easier application of uninterruptible power supplies (UPS) to
ensure 24 hours a day, 7 days a week operation.
PoE technology is regulated in a standard called IEEE
802.3af and is designed in a way that does not degrade the network data
communication performance or decrease the network reach. The power delivered
over the LAN infrastructure is automatically activated when a compatible
terminal is identified, and blocked to legacy devices that are not compatible.
This feature allows users to freely and safely mix legacy and PoE-compatible
devices, on their network.
The standard provides power up to 15.4W on the switch or
midspan side, which translates to a maximum power consumption of 12.9W on the
device/camera side - making it suitable for indoor cameras. Outdoor cameras as
well as PTZ and dome cameras have a power consumption that normally exceeds
this, making PoE functionality less suitable. Some manufacturers also offer
non-standard proprietary products providing suitable power for these
applications as well,but it should be noted that since these are non-standard
products, no interoperability between different brands is possible. The 802.3af
standard also provides support for so-called power classification, which allows
for a negotiation of power consumption between the PoE unit and the devices.
This means an intelligent switch can reserve sufficient, and not superfluous,
power for the device (camera) - with the possible result that the switch could
enable more PoE outputs.