Arduino uno -Usb connected and external power  ?

Arduino uno -Usb connected and external power ? Can i have the arduino uno connected to the computer usb to communicate and at the same time feed an external power trough the jack ?

will it automatic switch from usb power to external power and reverse ? or it will burn something ?=


This will be fine, it will use the external power if available else it will use the USB power.

Make sure your external power isn't too high a voltage else the Arduino's regulator could get quite hot. Definitely not more than 15V else the on-board 3.3V regulator could be damaged.

-- The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, light sensor, potentiometers, pushbuttons

hi i will have voltage between 12v and 13.8v, i was thinking on having a 7805 on front and like that having only 5v to arduino... but if this 13.8v will be good for arduino better one less component on the solution, Will the 13.8v get the vr too hot ? will worth to have the 7805 ? thanks for your help..

Much depends on the current draw of the Arduino plus whatever other shields or connections you have. If it’s just the Arduino then count on about ~35mA of current draw. The power dissipated by the Arduino’s regulator will be about (13.8-5)*0.035=0.3W which is not too bad. It will be warm but it’s not a problem. Now if you stack a power-hungry shield on top…it’s a different story. Then it’s best to use a voltage closer to 7V for the external input.

You should not use an external 7805 because the external voltage input on the Arduino expects at least 7V or so to get 5V internally.

The Quick Shield: breakout all 28 pins to quick-connect terminals

i will have voltage between 12v and 13.8v

Are you going to be using this in a car? If so, you might want to consider using some good filtering.

Its not car will be a clean ac-DC power unit and with failback to a 12v battery.

My main concern is if the 13.8v will not get the arduino VR too hot... Regards.

It depends on how much extra current you draw with sensors, switches and lights. For a discussion see:-

James C4S, what do you suggest I use for filtering? I’m thinking of doing an automotive application on a vintage car where the voltage is all over the place.

For the vintage car, I would suggest a DC-DC converter, do a search, someone found one that would be good just recently.