I'm trying to set up a weather display that runs on a 24V DC adapter with a max output of 24 watts, although the display itself is only rated for 10 watts. The adapter that came with it has a barrel plug, and the instructions indicate I can use 12 gauge speaker wire for a direct connection. Since I already have Ethernet cable run to the mounting location, I'm wondering if it's safe to use a POE injector (limited to 24V) to power the device since there's no data being sent. I can't rewire anything easily because the cable is stapled in the wall. I've monitored the power with a kilowatt meter and it hasn't gone above 2 watts so far. Any advice or tips would be appreciated!
4 Answers
If I were in your shoes, I'd just split the pairs and use two pairs for the + and the other two for ground. That’s probably the simplest method, but I always like to play it safe and stay within the rules.
If you already own a POE switch, I recommend using a standard 24V active POE adapter. This keeps everything within standard Ethernet norms and helps prevent any mishaps with miswired connections. Plus, the switch will automatically limit the current to what the wiring can support without any risk.
When using wires, it’s crucial to keep voltage and current in mind. The voltage isn't a problem here since Ethernet cables can handle that, but the current might be an issue. POE is generally limited to 350mA per pair, while your device drawing 24V at 10W would require around 416mA. I suggest using at least two pairs of wires for the power connection. Since you're not sending data, you could safely use all four pairs instead. Alternatively, consider injecting 44V and then stepping it down to 24V at the device end. By the way, the 2 watts reading you got is likely on the AC side, so you'll need a good ammeter to measure the DC power draw accurately.
You might want to check out some POE injectors and splitters online. For example, there’s a splitter that will work perfectly for your needs. Just plug the injector on one end and the splitter on the other side. This will simplify your setup and ensure safety. And just a heads up: the rated power on the supply is just a limit, not a strict requirement. Cat5 can absolutely handle 10 watts without a hitch.