We're a bit stuck on the following problem :
We've connected a bunch (18 to be precise) of Arduino NANOs on the same +12V supply and they all share the same PWM output from another device (which goes into an input of each Arduino) and also a boolean signal in the form of a +5V (12V going through a voltage divider).
Problem is: On the bench with two units, it works perfectly fine. But when we put all of the 18 units in parallel in the system, the Arduinos start to fry one after the other (about 8 so far and usually 2 or 3 at a time).
The µC gets real hot and lets out the magic smoke. The regulator itself is completely OK and doesn't heat up significantly.
We don't see where we might be wrong. I completely agree that inputs should be buffered, protected and whatnot, but for a prototype we really thought that'd work... But that's not the case!
Thanks for your help!