USB power troubleshooting question

Hi all,

Think this is the right place to post. My device is behaving differently under AC-DC USB adaptor vs PC USB.

Setup is: MegaADK Ethernet shield Colour TFT Ethernet 433 router via crossover

The console is displayed with both power supplies but the ethernet connection (data stream for console log) is only active when connected to PC USB.

I assumed my 2A PC USB was more meaty than my mains adaptor but have now tried 2A, 2.5A, 4.2A even. So I no longer think it is insufficient current to run all the components.

Please point me in the right direction if you have something to try, I must be missing something. Thanks.


Problems likes this usually are the result on not having everything grounded (Arduino, sheilds, external sensors, etc. all need to share a common ground)

Without some sort of schematic, no further help is possible.

here's a thing:

American 2 amp power supplys are a meaty fistful. you would rather not drop one on your foot. Asian 2 amp power supplys are ice cubes with human hair sized cables. Red Wing 10 1/2 shoes are good for 12 hours working. Asian 10 1/2 shoes feel like they are chewing your feet within minutes. An American 1 HP motor off a Craftsman table saw needs to be carried by a beefy guy. Asian 1 HP motors look in every way like an American 1/3 hp motor

it is "call it what it is" versus "call it what people are asking for"

I measured the power on my USB connector yesterday. 4.15 volts.

believe nothing until you have measured with a reliable and consistent meter. I keep piles of these around. they are helpful for troubleshooting. the ammeter will show current draw from one tiny little CCD video camera

Just to be sure, are you powering the Mega ADK through the USB jack in all cases?

@hackysack, do not cross-post. Threads merged.

Thanks for replies!

Sorry for the cross-thread, slow connection looked like it gave up but mustv'e posted first time as well. Will take care in future.

All parts are powered by their USB port.

There is continuity between grounds on all boards, all beeping.

I have now tried the trusty Maplin bench supply and tested meter against my scope.

The fault isn't intermittent so seems unlikely but will try increasing the gauge of the connecting wires and add extra grounds.

The boards are arranged by

MegaADK > Ethernet shield on top > TFT shield on top of that.

The 433 router is connected by crossover cable to Ethernet shield and by USB to the same power crimps as MegaADK USB.

We need a picture - showing all components - of both the working and non-working configurations.

Something is clearly wrong in your description, but we cannot figure out what it is since you have given very few actual details. A properly taken picture (in outside daylight unless you have a genuine photo studio) should give the clue,