Power supply with interface

Can I plug my Arduino Uno to a 5VDC power supply, and still hook up my laptop to program it?

In other words, can I have my laptop connected to the Arduino, while my external power supply plugged in at the same time.

If I could, It would save me a whole lot of plugging and unplugging. I want to let my Arduino drive my project. However, when the programed routine is complete, I can make changes and upload with little manual frustration.

Can I plug my Arduino Uno to a 5VDC power supply, and still hook up my laptop to program it?

You can.
The problem is that you in effect connect two power supplies together and that will cause the lower voltage one to sink some current which could be bad. In practice though it is one of those things you can "get away with", without any consequences in my experience.

No doubt others will disagree.

Thanks ! :slight_smile:

The UNO has an automatic power selector switch.
An external voltage >= ~7.5volt on the DC socket will switch the USB supply off (sort off..).
USB data still works.
Leo..

Yes but that was in the power jack not the 5V DC the OP asked about.

I understand that the OP wants to connect a 5volt supply to his UNO.
But I did not see in his post where he wants to connect it to.

If he connects it to the 5volt pin, USB power and external will indeed help or fight each other.
If he connects 5volt to the DC jack (or the Vin) the external supply will do nothing.
Leo..

Ok I had no idea that anyone might want to put 5V into a board on any other pin that that which said 5V.
If you do then it won't work correctly.