as per attached photo,
i got this simple schematic sketch.
i got GPS and Wireless module connected to arduino,
and i got another circuit for on-off latching switching,
this circuit out put feeds into the base of NPN transistor to turn the whole system,
the problem is when hc12 starts, it draws 200mA of current which causes short drop in voltage, this drop restart arduino each time !
i used 2n2222 npn transistor,
i tried changing it to Mosfet IRFZ34N and worked fine.
can somebody explain why NPN didnt work for me ?!