[Resolved] Unable to Power Arduino and Shield Together from Barrel Plug

Hello, I am having a problem powering an Arduino and Ethernet shield together using the Arduino's barrel connector. The duo runs fine, and the sketch executes as intended, when powering them from the USB connector. I even had it running by way of an iPhone 5v wall charger as the source into the USB jack with success.

When connected via the barrel jack, using anything from a stable 5v benchtop PSU to a 12v power brick, only the red power LED on the ethernet shield glows dimly if I use my Duemilanove board as the host. And, the onboard pin 13 LED of the shield glows, along with the power light, if I use an Uno board on the bottom. I do not see any of the ethernet activity lights using either Arduino board and the barrel plug.

I have also uploaded the blink sketch to both Ardunio boards by themselves (without shield attached) and was successful in powering each of them using the barrel connector from all source voltage supplies mentioned. So, both Arduino boards, and their onboard regulators, seem to function just fine.

The last test I performed was running the blink sketch while having the ethernet shield connected. With this configuration, again using the USB connector, both onboard LEDs blink, power lights appear bright and (most important) the ethernet activity lights are, well, active. However, trying to power even this configuration using the barrel connector still fails as mentioned above. (EDIT: the shield's onboard pin 13 LED does in fact blink when running blink sketch along with using the barrel plug, just no ethernet lights work)

Am I to assume the ethernet board is causing this failure of the power circuit? Is there some configuration (jumper, etc) that I'm missing while having both boards connected together? Any suggestions on cause and possible workarounds are greatly appreciated.



Both boards work off USB, right?

If so, your problem could be one of two things:

  1. The arduino
  2. The Wall wart

I am thinking that it is not #1 because you wouldn't have the problem on two boards. So it is probably the plug. Do you have another wall wart?

Also, you can try something else. Plug one arduino into USB, and connect 5V on that arduino to 5V pin on the other. Connect GNDs, too. Now flip boards (plug the other one into USB, and switch ethernet shield). If this works(it should) your problem is not with the arduino or ethernet shield. On the wall wart, is there a label or something on it? Could you take a picture/type up what it says on it? My though is that you are exceeding the wall wart's current maximum, since it works with only the arduinos.

Odd, though.


Do you have another wall wart?

Welp, first, I can't believe I spent this long and went through all that troubleshooting [failure] when I should have just done this simple, but effective, suggestion FIRST.

I must say using a computer PSU 5v/20a supply, and a 12v/1.2a wall wart both of which I've used many times before powering things would both fail to run this thing still baffles me. I just tried a 20 year old POS multi-select wall wart. It's on 4.5v range selector and outputting a spot-on 8v on idle draw as the meter shows things. And, the original Duem/shield combo is now powering up and I got many blinking things.

Double cheers for the reply!