Connecting both USB and 2.1mm center-positive plug

Using Arduino General Electronics
1

Hi,

Would it harm the arduino when I connect both USB and the 2.1mm center-positive plug at the same time? I can imagine that some shorts will occur when connecting it to two power sources.
For my project it will be powered via the 2.1mm center-positive plug, but for easy access to the code I want to have a USB connector build into the chassis and a cable from there to the arduino. This way I do not have to open the chassis to update the code.

2

It is designed to auto-switch from one to the other. (The Uno is, anyway).

3

I do indeed use the arduino Uno.

So this means that I can connect both at the same time without frying it?

4

Yes. From the UNO reference design:

The P-channel MOSFET T1 is used to turn the USB voltage on and off, being controlled by comparator U1A which detects if half of Vin (through divider RN1A/RN1B) is greater than 3.3V (i.e., 6.6V).

switch.png

5

Thanks! That is what I needed to know. It would be a pitty if this couldn`t be done.