Arduino Micro 5v and gnd shorted


I bought a new Arduino micro in december and it worked fine. I made a PCB for it on which i can plug in the micro (like a shield)

Now, I was using the board and it worked fine for about 2 weeks. Suddenly yesterday, I noticed that it refused to connect to Serial monitor and refused to upload.

I took out everything and found out that the 5V and GND on the micro were shorted (had 34 ohm resistance between them). I was powering the micro with 5V from a LM7805 with an input of 12V. The output was fairly stable (within errors of 7805) 4.7-4.9V. The whole board in general was working fine.

I was wondering if there was something wrong that I was doing or is this some random coincidence where maybe on of my wires shorted with something.... I have another Micro, but am hesistant to put it on and start, as I think it may burn also.

Is it possible that the voltage regulator on the micro has become bad ? If so, how do i test it out ? Any suggestions as to what might have happened ?

I was running a L298 (a motor and a relay with it) and also had multiple switches attached to it. And an IR sensor, (was using it for robotics purposes.)

Thanks !


I read your post the first time. The voltage regulators are protected against overheating and shortcuts. So it should not be a problem. However, you mention a L298 and a motor and a relay. If you have 12V around the Arduino Micro, you could easily blow it when something is not well wired.

If the Arduino Micro is working okay at 5V, and it was only a shortcut as you wrote, the board is as good as new.