I’m powering some home automation controllers remotely using PoE from the server cabinet.
Option 1 is using active PoE (802.3af) directly from a switch and some electronics at the arduino end to negotiate power according to that standard. This is technically the best option, as 48v over long cable runs means minimal power loss. However this is a brain-ache for various reasons:
- PoE switches are very noisy, not nice anywhere in the home
- PoE electronics on the arduino end adds a good £15 to the total project cost for each unit (expensive for 20 units)
Option 2 is using passive PoE. I’ve seen these nice injectors that take a single power supply (I get to decide the voltage) and then I can split the cable at the arduino end and simply hook the power lines up, making use of the arduino’s regulator. This is cheaper, quieter, and more simple.
On to my question.
To achieve minimal power loss, I want to put the highest voltage over the line as I can. I know Arduino is spec’d at 20V limit (as per here) but
Q1. How hot will the arduino get if that regulator is working at 20V? Too hot to include project into a wall back box? Or is heat related more to current draw? I am not at the stage I can test this yet.
The regulator on my nano clone is labelled AMS1117 5.0 H424TE. Data sheet from that chip suggests maximum voltage is not 20V but 15V.
Is this a different regulator to the nano original?
Q2. Any other quick win to get my voltage stepped down, cheaper and more simple than using proper 802.3af? Maybe add a secondary regulator to my board?
Q3. Any other thoughts to share on this subject?