Hello
I unintentionally smoked a component on my Nano.
It seems to be unaffected when powered through usb, with inputs, outputs and flashing working just fine.
So im just wondering what the smoked component is. Iv marked it on the image.
I had switch wired to a pull up 5v, but i botched the resistor, so when i pressed the button i created a brief short. and magic smoke escaped.
The short was between ground pin #4 and +5V pin #27
Looking at a better photo, and cross referencing with the schematic, my guess is that's D1, an MBR0520 diode.
Any SOD-123 Schottky diode with a suitable current rating (the MBR0520 is rated 0.5A) and voltage rating (the MBR0520 is 20V) will do the job.
If it is a true V3, using the photo from the product page: http://arduino.cc/en/uploads/Main/ArduinoNanoBack_3_lg.jpg and the EAGLE files available there, it does look like the diode majenko identified.
Probably blown by too much current flowing or reverse voltage?
Thanks.
Is it anything i need to worry about replacing? everything seems to work just fine.
Im just using it to sample two voltages, and then output a ppm signal to control a switch.
The diode provides a method to select either the on board 5v regulator or 5v coming from USB. (Well it's more simplified than that. If a voltage is present on both, it prevents the on board 5v from conducting to USB.)
One comment would be, if you don't know what smoked it the first time, it stands to reason you will likely make the same mistake again.
Second comment would be, never hook up an external 5v and USB at the same time, until you replace the diode.
Just out of curiosity, is that conductive foam you have the board sitting on?
If its just to separate usb 5v from the built in 5v, then i doubt ill ever need to replace it.
The only time ill ever connect the usb is if i need to modify the code, and thats doubtful as it does exactly what it should now.
And i know exactly why it smoked, just not what component it was. I shorted a stepup switch, as i had unintentionally bridged the 10kOmh resistor with a bad solder joint on the breadboard.
And no, that is not conductive foam 
. Had it been most of my scratchbuilt model airplanes would have burnt to the ground by now.
Its a variant of depron called ebisol, waterproof and used for floor isolation/scratchbuilding model airplanes.
Xermalk:
Its a variant of depron called ebisol, waterproof and used for floor isolation/scratchbuilding model airplanes.
You should never plug anything static sensitive into something like that, there is a good risk that you destroy the parts. Every time you plug or remove the parts from the plastic foam, hundreds to thounsands of volts develop, destroying stuff.
It's perfectly safe to use components put into the ESD-foam, both the black and red type. The resistance of the foam is very high, so unless you are doing some very very high impedance analog stuff, it won't interfere.
// Per.
Well, some of the black foam does have relatively low resistance. Depending on the type, you can measure in the range of 100s of ohms between test leads. Which could affect digital circuits.
As for depron and static discharge, I concur.
