Hey guys If i want to hook up an external power supply to my existing circuit, say to run a motor, and it needs 12V - once i have it hooked up can I lead the negative of the 12V supply into the Arduino's ground? Or will this "force" current in and blow something?

A common GND

system November 1, 2010, 7:39pm 3

Thanks. I'll go read those articles.

At the moment I'm going to use a relay.