Can Arduino (UNO) "pass thru" external power to my project?

Official Hardware UNO Family UNO R3
1

Hello,
I am using an UNO to power my light display which uses external 2A USB (wall wart) power. I know that I can power my display directly with 2A USB, share ground with the UNO, and also power the UNO by tying my external USB power to the 5V pin on the UNO.

BUT, it would be simpler if I could do this:

Power my UNO directly via the 2A USB wall wart, then tap off power from the UNO to my project (5v and ground). In effect, I want the UNO to be powered off the wall wart and then be able to tap off power from the UNO to my project (presumably from the 5v pin). Is this possible?

Thanks!

2

Please don't !

The board is only able to supply a very limited amount of current.
Circuits and devices that may use more than the board can handle are often the culprits in damaging a board.

A schematic of your requirements would also help a great deal.
Take a wander through the links below please.

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Thanks to all those who helped and added to this list.
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3

Thank you. I figured this was a limitation, and thanks for confirming it!

Best wishes,
Greg

4

Actually, another solution would be to always power my UNO externally, then use a modified "data only" cable when programming. I think that would solve my problem.

Greg

5

A good question at the right place in a project. You have gotten several answers which probably will save you from purchasing more Arduinos although the sales people would love to sell them. A simple rule I follow is "The Arduino a Power Supply it is NOT!". You can tap power off the UNO for your project but it can only supply a small amount, do not go to the max. With the 5V wall wart you can connect to that without going through the Arduino great. I like to use 7-12V input via Vin, this gives me a more stable system especially when using the A/D because of the extra filtering and load surges do not appear on the power lines to the micro because hardware is powered externally from the Arduino.

6

Thanks for the suggestions. My goal is to minimize the effort to go back and forth from "standalone" operation to "programming and development" mode. After thinking about it some more, I believe powering everything off of the external supply, including the Arduino, is my best bet. (Note that since I am using a 2A USB wall wart, power TO the Arduino would be through the 5v pin). Then when bouncing back to programming mode, I'll plan to use a dedicated (hacked) "signal only" usb cable to the Arduino. That way, I don't have to deal with any re-wiring hassles.

Greg