Ethernet Shield2 with PoE - Max current issues.


I’ve developed a small controller using a Mega2560 that gets rotary encoder input from 3 HEDS-9040 units, and sends the data out using an official Ethernet Shield2.

I have it running absolutely fine when plugged into my computer using a USB cable, or powered from a 5V adapter via USB.

But when trying to use the PoE module on the ethernet shield2, it appears to continually reboot the device (I don’t have the USB cable connected at this point). I have almost 50 of these units to install, and really want to use PoE to minimise the cabling that is required!

I suspect its down to power drawn by the combination of ethernet shield and sensors, when running via USB I have a small current monitor that shows that about 320mA are being drawn, each sensor uses about 50mA.
When using the PoE I have found I can stop it rebooting the unit if I only plug one sensor in, so I suspect that the current that the shield can supply is causing the issue.

I know that the PoE board is a separate device from Silvertel and the spec sheet for it shows its capable of supplying 6W @ 12V, which I’m assuming is a max 500mA load, given that the voltage is getting converted to 5V in the arduino, I’d assumed that it would still be capable of supplying enough current to keep my full circuit powered, even after power loss due to the voltage regulators.

Anyone have any ideas or more information on exactly how much current a PoE powered shield is able to supply?

The AG9210-S module that usually drives the PoE of an Ethernet Shield supplies up to 12W (1A) of power to the Arduino. This should be more than enough to power your setup, your PC doesn't allow that high current (there's a fuse on the board to ensure that). There's still the possibility that the power source is the problem: Have you checked the other side? What provides the PoE? If your switch or PoE injector does not deliver 15W to the device it might show exactly these problems.