Hello everyone,
I have a project with an arduino uno connected to a smartphone as a display to output data.
My question is if it's safe to connect a external battery to arduino's jack input to avoid drawing the smartphone battery? Is it safe to have 2 sources of power?
Thank you!
Yes, 7V - 12 V on the jack of an Uno will block the power coming from the USB. Be aware that you can draw a limited amount of power from the onboard regulator (that converts the barrel voltage to 5V) so if your display is a big consumer, it might not work. The closer to the 7V the better from that perspective.
Your your topic has been moved to a more suitable location on the forum. Installation and Troubleshooting is not for problems with your project 
See About the Installation & Troubleshooting category.
Safe, but not entirely sensible. 
This topic was automatically closed 120 days after the last reply. New replies are no longer allowed.