I had designed my own arduino nano shield for a 2WD line follower robot. In my shield I am using 7805 to regulate Vin to 5v. Connected one diode to avoid reverse current flow before Vin. I am using 11.1v 1800mah Li-ion battery to power my bot. Whenever I try to check the sensor values in the serial monitor using USB my arduino getting very hot and failed I can't able to use the same arduino nano again.
I connected battery to Vin of arduino nano and the 5v from my external 7805 to arduino nano. I already burned 5 Nanos. When I disconnect battery to the Vin of arduino and power it with external 5V then it's working fine.
Why I am facing this problem??? This is happening only when both my BO motors starts running if I not using motors it's working fine