Wireless is convenient, but wire is dependable. A cable does not drop out in a storm, does not fight for airspace, and can carry both the data and the power a device needs on the same run. For anything permanent, a wired backbone with a few access points hanging off it is the most reliable network a farm can have, and often the cheapest over time.
Why wire it.
Radio is at the mercy of distance, weather, and interference; a wire is not. An Ethernet run carries a solid, fast link up to about a hundred meters, and a switch at the end fans that one cable out to many devices. For a barn full of gear, or an access point out at the greenhouse, a wired backbone is what everything else hangs off. It is more work to install than dropping in a wireless gadget, and it pays that back in nights you do not spend chasing a dropout.
Power over Ethernet.
This is the part worth getting excited about. Power over Ethernet sends electricity down the same cable as the data, so a camera, an access point, or a sensor node out at the end of a run needs no separate power supply at all: one cable does both jobs. A PoE switch or a small injector puts the power on; the device (or a splitter) takes it off. For anything mounted somewhere awkward, where running mains would be a project of its own, PoE is the tidy answer. Boards like the Olimex ESP32-POE put it within reach of a homemade sensor too.
The wired pieces.
These compose rather than compete; a real setup uses several together. The prose under the table says how they fit.
| Piece | Ethernet switch | Power over Ethernet | Fiber + converters | ESP32 + Ethernet |
|---|---|---|---|---|
| What it does | Splits one drop into many | Power and data on one cable | Long, lightning-immune link | A wired sensor node |
| Range | ~100 m per run | ~100 m per run | Hundreds of m and up | ~100 m per run |
| Carries power | No | Yes | No | With a PoE board |
| Best for | Wiring up a building | Cameras, access points, far nodes | Between buildings, long runs | A node where Wi-Fi is flaky |
Use good cable (Cat5e or Cat6) and keep each run under about a hundred meters. A plain unmanaged switch is fine for most farms; a managed one adds features like VLANs if you want to separate networks. For a homemade wired sensor, an ESP32 with an Ethernet board (or an ESP32-POE) skips Wi-Fi entirely. To power a far device down that same cable, see the PoE splitter.
Between buildings, use fiber.
This is the tip that saves equipment, and most people learn it the hard way. A copper Ethernet cable run between two separate buildings is an invitation to trouble: the buildings sit at slightly different electrical grounds, and a nearby lightning strike can push a surge down that copper and fry the gear at both ends. Fiber-optic cable carries light, not electricity, so it is immune to that. For any run between buildings, use fiber with a small media converter at each end, or at the very least proper surge protection on the copper. It costs a little more and it is the difference between a network that survives a storm and one that does not.
Where it fits, and where it doesn’t.
Where it fits
- A permanent, reliable backbone for a building.
- Powering cameras, access points, and far nodes over one cable.
- Long or between-building runs (with fiber).
- A sensor node where Wi-Fi is unreliable.
Where it doesn’t
Resources.
These open in a new tab:
Olimex ESP32-POE Ubiquiti (switches & PoE) TP-Link (switches & fiber) Wi-Fi for the far building
Frequently asked questions.
What is Power over Ethernet (PoE)?
PoE sends power and data down the same Ethernet cable, so a device at the far end needs no separate power supply. A PoE switch or injector adds the power; the device or a splitter takes it off. It is ideal for cameras, access points, and sensor nodes mounted where running mains would be hard.
How far can an Ethernet cable run?
About 100 meters per run for copper Ethernet (Cat5e or Cat6). Beyond that, or between separate buildings, switch to fiber with media converters, which carries much farther and is immune to electrical surges.
Should I run Ethernet between two buildings?
Use fiber, not bare copper. Separate buildings sit at different electrical grounds, and a nearby lightning strike can send a surge down a copper cable and destroy gear at both ends. Fiber carries light, not electricity, so it is immune. If you must use copper, add proper surge protection.
Do I need a managed switch?
Usually not. A plain unmanaged switch fans one cable out to many devices and is all most farms need. A managed switch adds features like VLANs to separate networks, which is worth it only if you specifically want that control.
Can an ESP32 use a wired Ethernet connection?
Yes. With an Ethernet board, or a ready-made board like the Olimex ESP32-POE, an ESP32 can skip Wi-Fi and connect by cable, which is more reliable for a fixed node. A PoE version also takes its power from the same cable.