Make stun gun with Arduino as oscillator
I suppose in your "schematics" the npn base is the middle pin? In that case you'll indeed fry the arduino (or transistor, or diode, or...) because there is nothing limiting the current.From arduino pin to ground there is the equivalent of two forward biased diodes, which at reasonnable current levels would drop about 1.5v. Forcing 3.3 or 5v across that means unacceptably high current.