Arduino killed by AC then reborn

hi, this is my first post.

Ok, so I made a terrible mistake by accidently connecting my Duemilanove 328 board to a wall supply of 9 AC . Yes, I didnt stop to think id it was ac or dc, and it really damaged my board. All the lights (L, TX, RX) started flashing and I removed the power cord after I realised something was wrong....(lets say 3-5 seconds of damage.)

So after that I reconnected to the Usb port and the pc didnt recognize it.. i couldnt burn anything , he was like dead just flashing his led.

I reenstaled all the drivers etc in vain.

BUT, 15min later it reborn and started working again. My question is, should I give it a rest or so? (sounds silly yes)

Also, this kind of AC disruption damges the atmega328 directly or does it kill other board components ?

is there any Code made to debug and get the arduino living state and its status, like for me to see if everything is ok?

Also, is there a way to use the usb port to send debug info to the pc, like every place i check used the serial Tx Tx pins of arduino...

many thanks,


It sounds like you have blown the input electrolytic capacitor with too much voltage. These heal given time but they are still weakened. Best replace it. All the other components should have been protected from the high voltage by the regulator and series diode.

If it uploads sketches again, then everything is oke.

I as far I know, nothing is damaged, the diode has protected the board for the negative voltage. That why the leds blinks.

ok, thank you for your replies.

Even if it may have damaged some board components, if the chip's functions stay ok, i'm fine with that.

But wait, are those capacitors you mention the two by the side of the Dc power plug? if so, those are very easy to replace.

the caps are fine, 9ac doesn't damage caps when there is a protection diode

9ac doesn't damage caps when there is a protection diode

Yes but if the caps were 16V rating and the PSU gave 12V RMS un loaded then this would have exceeded the 16V DC rating on the caps. Besides what else explains something that was not working but now is apart from the self healing action of an electrolytic capacitor.

the two by the side of the Dc power plug

Yes, it's only the electrolytic one at 100uF I would change.