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Topic: Suppling power to the Arduino UNO R3.. (Read 384 times) previous topic - next topic


Which power source wins?
Can I plug a 9V power supply AND the USB cable in at the same time?

I have a project that I am working on that uses multiple analog inputs.. I need to calibrate the inputs in the code. The easiest way to do this is to leave the Arduino hooked up to the USB cable and use the serial monitor to read the outputs (uploading changes as they are made).

However the USB power is too inconsistent to use, my values are all over the place and I can't trust them.
With a regulated 9V power supply I get stable values but it is a pain to be constantly connecting and disconnecting the Arduino.

Is it possible to plug both in and have power supplied ONLY by the regulated power supply yet still keep the serial monitor (and ability to upload changes) working?


Sep 23, 2016, 04:46 pm Last Edit: Sep 23, 2016, 04:48 pm by Budvar10
Yes, it is possible to plug both. 9V "wins".

There is on-board automatic switch.
Arduino clone with ATmega1284P   http://forum.arduino.cc/index.php?topic=277260.0

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