Arduino Powering


First of all sorry for my bad english.

I am here for a question about powering my arduino uno. I am working on a project where i am powering a lot of logical devices and they all are driven by an LM7805 witch gives me an output voltage of 5V.

Now the print layout is allready done and now i noticed that i need to power the arduino on the Vin Pin with more then 7 volts, wich would destroy my current project pretty much because its all done allready and i put in a lot of work.

However, after looking at the shematic, if i have an allready regulated 5V, could i just attach it to the 5V output pin? Shouldnt it work because the 5v pin is set directly after the arduino uno onboard regulator?

I would be very thankfull for an answer.


Yes, u can power with a 5V regulated supply direct the 5V and GND pins.

Hi Topi,

Welcome; I’ve lived in several countries where I did not understand much of the Chinese/French/Arabic etc :slight_smile:

See more information HERE:

See the UNO schematic Diagram HERE:

And Power Considerations HERE:

You should be OK with 5V regulated to the “5V” UNO pin.

Great. I read about the voltage drop if you attach 5V to the Vin. With that I would have my other devices not recognizing the logical high signal from the I/O-Pins because it would be lower.

That caused me a lot of trouble.

Thank you for the help, I will attach the GND and Vout from my LM7805 directly to 5V and GND pins.

One last question: the GND Pins are connected right? so i dont need to connect the "LM7805-GND" to both arduino gnd pins? One of the three aviable should be enough right?

Thank you guys very much.

Yes, u need only connect to one GND pin - they are all common.