Chris7777:
Thanks for the input Lefty
I see from this datasheet Intelligent Power and Sensing Technologies | onsemi
That the tip122 I was using before I melted the 2n2222a has the SOA
but this datasheet for the MPS2222a I was using does not Motorola MPS2222A datasheet pdf
or is it called something different in this datasheet.I should have worded that question about the wall wart better, since its only rated to output 1000mA should that not be the maximum my multimeter can pull from it through its 10A fuse when testing it?
Your multimeter in 10A current mode uses a very low ohm shunt resistor (maybe .1 ohms?) to measure the voltage drop to calculate the current flowing through the meter. Your wall wart is rated for specific output voltage for up to a specific max current, 1 amp in your case. What isn't specified is how your specific wall result will respond if more then 1 amp is tried to be drawn from it. Some just gradually have their output voltage lower as more and more current is drawn, others may blow open a fuse like link in the primary winding making the wall wart useless. In your case current was still having to pass through the relay coil so that was the current limiting for the circuit and the transistor's failure didn't make that be more then normal flow through the relay coil.
Would the 2n2222 burn out first and not pass any more voltage back to the Arduino's digital out pins? And in fact my Arduino is safe? If so why does it smell like smoke and the 2n doesn't?I'm pretty sure your arduino is OK, but testing the output pin with say a series resistor and led to ground and blinking it should verify it. The failure mode you experience doesn't have to mean the arduino was damaged as there was still the series base resistor to limit current back through the pin. Don't let your nose be your only test equipment, check out the functionality of the output pin so you know one way or another. I wouldn't sweat the problem too much, worst case if you ever do lunch the chip it's just a $6 replacement cost for a new processor chip, and my experience is they are pretty tough chip.
Lefty Thanks
Chris