I want to power Arduino safely from Vin and GND using 9V battery. I cannot also use 2.1 mm power plug or 9V adapter jack since I don’t have the following parts: http://arduino.cc/playground/uploads/Learning/9V_tut_1.jpg. I don’t have time even to buy that.
My concern is that I want to feed the Arduino board(with a wifi shield on it) by using Vin pin with a 9V battery. But I have read in forums here that wiring up Vin and GND in a wrong way is risky and can kill the board even the voltage regulator. Is it possible to prevent this using a diode at the end of the GND pin?