Power the UNO and the Breadboard


I am fairly new to the Arduino and now I am collecting all the stuff I need for basic trying and experimenting.

Just a basic question arises now: To program and operate the UNO, I need to connect the device via USB to my Notebook.
I’ll use a breadboard for the experiments with the parts and this needs to be powered too.

I got one of those breadboards mounted on a plasticplate with 2 terminals ( blue and red ) for 4mm banana jacks. Here I would like to connect a 9V or 12V stabilized DC power supply to provide power to the circuit.

Are there any concerns programming the UNO through the USB and having on the other side the circuit powered with 9 Volts.

Then I need to unplug from USB and provide 12V to the circuit on the breadboard …

This all sounds not right to me, so I would like to ask you guys with lots of experience.

thank you


You cannot apply more voltage than the microcontroller pin can withstand. But you can use different voltages on the breadboard as long as the unsupported voltage circuit is isolated (Using additional circuits such as transistors, relays, optocouplers etc.).

But if you are concerned about leaving the Arduino UNO powered from an external source while programming via the USB port, be aware that this is not a problem as long as the source conforms to the supported standard for the Arduino board, including correct polarity.

There is no issue with the way you want to do it.

Just remember to have a COMMON GROUND between whatever is on the breadboard and the ground on the UNO.
If you don't do that you might find some things do not work.

When you have finished with the USB and want to power your UNO independently Then I put a small flying lead with the power jack plug on it.