What is a PoE camera? The advantages of carrying power and video over a single cable

How does PoE work?

A normal network cable contains four pairs of thin copper wires. PoE sends low-voltage direct current over these wires along with the data. The device that supplies the power is called a PSE; this is usually a PoE switch or an NVR with PoE ports. The device that receives the power is the camera.

PoE is a safe system. Before the switch sends power to the cable, it checks whether the device at the other end supports PoE. Even if you plug a computer that does not support PoE into the same port, no electricity is sent to the computer. This check applies to standard PoE; passive PoE, found on some cheap devices, does not do this check and can cause damage if plugged into the wrong device.

What does it save in cabling and electrical work?

With an analog or non-PoE camera, two lines are needed at every point: a video cable and power. For power, either an outlet is run next to the camera or a separate power cable is brought from a central point. Because there are no outlets on an outer wall, a pole or a ceiling, this work often needs an electrician.

With PoE, a single Cat6 cable goes to each camera. Since there is no adapter next to the camera, there is also no outlet or transformer box that needs protection from rain and dust. On a sun-exposed wall in Şanlıurfa's summer heat, adapters placed next to the camera can overheat and fail; PoE removes that part.

Maintenance also gets easier. When a camera freezes, instead of climbing a ladder to reach it, you can restart the camera by turning the power of that port off and on from the switch's management screen. This feature is found on managed switches.

PoE standards and power budget

PoE has several standards, and each provides a different amount of power per port. The camera's technical datasheet states how much power it draws and which standard it requires:

• 802.3af (PoE): up to 15.4 W per port. Enough for most fixed dome and bullet cameras.
• 802.3at (PoE+): up to 30 W per port. Needed by models with strong infrared or white light and some cameras with motorized lenses.
• 802.3bt (PoE++): higher power. For outdoor cameras with heaters and large PTZ cameras.
• Total PoE budget: the highest power the switch can supply to all its ports at the same time.

Expert note: Look at the switch's total PoE budget, not its number of ports. If the total budget of an eight-port switch is not enough, the last cameras you plug in will not work, or they will start restarting when the night infrared turns on.

The 100-meter limit and distant points

A single run of copper network cable can be at most 100 meters according to the standard. This distance applies to both data and PoE. On longer runs the connection can drop, the image can stall or the camera may not get enough power.

There are several solutions for points farther than 100 meters. A PoE extender can be used along the route; this small device passes the signal and power on to the next segment. For points that are farther away or have several cameras, a PoE switch is placed there and connected to the main system with a fiber cable. Fiber both goes much farther and is not affected by lightning or electrical interference.

Cable quality also affects distance. Cheap cables with copper-clad aluminum (CCA) conductors instead of copper have more resistance and lose PoE power along the way. Using pure copper Cat6 cable for camera cabling prevents most of the problems seen over long distances.

Switch or NVR with PoE ports?

In a small system, connecting the cameras directly to the PoE ports on the back of the NVR is the simplest solution. No separate switch is needed, and installation is plug and play. However, every camera's cable must reach the room where the NVR is.

If the cameras are spread over different floors or distant parts of the building, a PoE switch is placed in each area and the switches are connected to the NVR. This keeps cables short and the 100-meter limit is not exceeded. This setup is preferred in large buildings such as schools, factories and housing estates.

As the number of cameras grows, the benefit of managed switches grows. Seeing power consumption per port, restarting a camera remotely and separating the camera network from the computer network are possible with these switches.

Is PoE infrastructure only for cameras?

The same infrastructure can also power other devices in the building. Ceiling-mounted Wi-Fi access points, IP phones, some models of video intercoms and card access readers can run on PoE. No outlet needs to be run next to these devices either.

That is why it makes sense to plan the network and camera infrastructure together in a new building or a major renovation. The cables pass through the same conduits, come together in the same cabinet in the server room and are backed up with the same UPS. However, keeping the camera network in a separate network segment (VLAN) from the office network gives a tidier structure in terms of both security and traffic.

At the planning stage, the power need of each device is added up, and switches are chosen with a PoE budget above this total. Leaving a margin for devices to be added later reduces the need to replace the switch a few years on.

PoE's advantage during a power outage

In a PoE system, since all cameras get their power from the switch, backup is easy. Connecting the switch and the NVR to a single UPS keeps all the cameras running when the power goes out. In a system with adapters, each camera's adapter would have to be backed up separately; this is rarely done in practice.

When choosing a UPS, also take into account the total consumption of the switch and the NVR, and the extra camera consumption when the night infrared turns on. How many minutes the UPS will last depends on this total load and the battery capacity.

Lightning and surges should also be considered. Long outdoor cables can damage switch ports when lightning strikes nearby. Using a network surge protector on outdoor lines reduces this risk.

In camera projects, Desa Bilişim calculates the switch and UPS according to the total power of the cameras and shows this calculation separately in the quote.

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