This my very first post and cry for help. I got an arduino starter kit containing cables, buttons, lcd screen and an adruino, of course.
I had a read and noticed that 7-12v is recommended and 6-20v is the limits.
When I started testing I read an article saying that e.g. to measure temperature, an external power supply is recommended (rather than using USB). I used a 9v block battery for that, it worked fine.
Then I attempted to measure am adjustable 0-90 Ohm resistor but i couldn't measure anything. Because this resistor is powered by 12v (in my car), I assumed 5v is not sufficient. I connected a block consisting of 10x1,2v batteries. The same block I saw included in another starter kit offered on eBay.
When I connected it without USB connected in paralell, after just a few seconds I recognized a smell that made me think "hey this is nooo good". The Arduino board is no longer connecting go my computer or running the program previously uploaded. All digital pins are now on 5v.
*** Broken ***
Question is, how come??? It was 12v and even it it was a little above, 20v is the limit. What went wrong?