Arduino Uno usb 5v and external power supply 12v overheating

Question

I have a issue with my Arduino Uno r3.

I am sorry for my English and explanation of my problem I am not great with explaining.

I'm not sure why is that happening but I have 5V 18A power supply to power my LEDs. I connected 5v from arduino to 5v from external power supply and I plugged this combined cabble to my LEDs. I did the same with GND. On data pin 6 I used 220 Ohm resistor. Also I am using 12V power supply to power my arduino.

In the same time the usb was plugged.

In and between usb and power some chip is getting HOT I got quickly scared and un plugged whole arduino I am not sure how I should plug this in. It worked fine until I plugged in external power supply and I was using few LEDs at the time.

This is how it looked like in more understandable way.

Just point to me what I did wrong. I will be gratefull for any kind of help.

Answer 1

I suggest you do not use the 12V external power when you are already supplying it with an externally regulated 5V source.

The sole purpose of the 12V input is to provide a 5V regulated supply voltage for the microcontroller. The PCB outputs this on the 5V header. The problem is that you are feeding your external 5V into that pin.

You can either continue powering the Arduino from the 12V supply and disconnect the external 5V from the Arduino (keep the GND from the external 5V conected). Or you can just remove the 12V power source.

It could end up that you have damaged the chip that overheated. If the Arduino still works after doing one of the solutions above, then you may be lucky and not damaged anything.

As a precaution, please measure your external 5V source with a multimeter to make sure it is within specs that Arduino allows.