So I'm happily working away on a bit of code and I see some wisps of white-ish smoke waft by.
So I shut down the power supply and think to myself... what is causing this. I'm using a buck converter (switching power regulator) for the first time and I've so far been happy with the setup. The AVR (mega8) is warm but not hot.
So I turn it on again, wait a second, and smoke again. It looks like it's coming from a jumper wire. Sure enough, the insulation on it is melting. On my breadboard I have a power rail that has a separation in the middle, essentially two separate sets of rails that I just jumper over in order to have power and gnd available the entire length of the board.
Interestingly enough, I have the gnd from my bench supply plugged in about 12 holes from this jumper wire that is smoking. I moved the gnd connection from that rail to the connection row for the gnd on the buck converter. Now I don't have a hot wire and I don't have the smoke.
Why did this happen? I'm only pulling about 60mA off the bench supply which is outputting 7V.