In the previous chapter we agreed that the best, professional Wi-Fi solution is to place Access Points (APs) in the center of the ceiling. The same goes for security cameras, which go high up on the walls under the eaves.
Here comes the practical problem of installation: How are you going to power these devices? Installing a classic 230V power outlet on the ceiling of the living room next to the Access Point, or externally next to each camera, is aesthetically unacceptable, expensive for the electrician and often dangerous.
The solution to this impasse is PoE (Power over Ethernet) technology. It is one of the most intelligent and life-saving inventions of networks. Let's see how exactly a simple internet cable manages to become a power cable, and what "traps" you should avoid in order not to burn your equipment.
The acronym PoE means exactly what it describes: Power over Ethernet. This technology allows the classic network cable (e.g. Cat6 or Cat6a) to carry both digital data (internet) and electrical energy (current) to the terminal device at the same time.
The cable itself, of course, has no current. A machine at the other end (in the Rack or main panel) must "throw" power to it. There are two ways:
Instead of buying a simple Switch to share the internet, you buy a PoE Switch. This Switch has a large power supply built in. When you connect the camera or antenna to it, the Switch itself understands that the device needs power and sends it to it. It is ideal when you have multiple devices (eg 4 cameras and 3 Wi-Fi antennas).
If you have an old Switch (that doesn't output power) and you only want to put in one Wi-Fi antenna, you don't need to change the whole Switch. You are using a PoE Injector. It's a small "brick" (like a laptop power supply) that plugs into the outlet. It has two ports: One port ("Data In") connects to your old Switch to get internet. The other port ("PoE Out") outputs the same internet but it has been "injected" (injected) and current! From there starts the cable that goes to the ceiling.
Not all devices "burn" the same current. A simple camera consumes very little, while an Access Point with built-in speakers and lights needs a lot of power. Thus, 3 generations of standards were created:
Tip: When purchasing a PoE Switch, check the Total PoE Budget (the total power of its power supply). If the Switch has a Budget of 60W and you put 4 antennas on top that ask for 20W each (80W total), the last antenna will just never turn on.
This is where beginners make the biggest mistake, literally "baking" their equipment. There are two power supply philosophies:
Rule of thumb: Always buy equipment that says "802.3af/at/bt" standards. Avoid the anonymous "Passive PoE Injectors" unless you know exactly what you're doing. Also, for this reason we are forbidden to use aluminum cables (CCA): PoE+ current melts aluminum due to overheating. Only pure copper (Bare Copper)!
It's the standards we mentioned above (802.3af/at/bt). They are completely safe. When you connect a device to the Switch, the Switch first sends a minimal control current (Handshake). The machine "asks": "Are you a PoE device? How much power do you want?". If the device (eg your laptop) says "No, I'm just a computer", the Switch does NOT send power, protecting your port.
It's a cheap, old method (usually at 24V). Injector or Switch doesn't ask anything. It sends current (24 Volts) non-stop down the wire, no matter what you plug into the other end. If you accidentally connect your computer's network card or TV to a Passive PoE port, the current will instantly "fry" its motherboard.
PoE dramatically simplifies the installation of the Smart Home. It eliminates the need for expensive electrical work, cuts the number of cables in half and allows you to place cameras and Access Points in the most inaccessible places. By investing in a good PoE+ Switch, you create a central "heart" that will feed life to your digital ecosystem for many years.
Next Step: We talked about powering the antennas. But which antennas should we choose today, when technology changes every two years?
We continue to the next analysis: Wi-Fi 7 and Wi-Fi 6E: What infrastructure is required in the walls (Multi-Gigabit Ethernet) to support the new, super-fast standards.
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