I am designing a project where i'm essentially making a really big RC car capable of hauling lodes from a distance. I am mounting a cammera and want to be able to control it from my computer/ or android phone (not sure how i would get video on phone however that is all together a different question.) I am considering using adruino Mega 2560 R3 and using it to control a servo connected to a potentiomiter driving the motor. this seems like a very poop way to do it but even with that my real issue lies with communication. the cammera i am using has a range of 1.5 Km wireless. I would like something capable of controlling the car from the same distance or atleast close.
So what can i add on that will give me the range while also allowing me to control a motor from a different power source and allow me to do variable speed in both directions.
You're going to be controlling a lot of power from the sound of it. You need a proper speed controller, and that will almost certainly be some sort of H-bridge circuit driven by a PWM signal. The only way I'd expect a potentiometer to be involved is if you already have a power system which has a proportional control operated by a lever or pedal. In that case it'd be possible to control that via a mechanical linkage but that doesn't seem like a very smart approach - better to control it electronically, even if that means replacing the speed controller.
The only readily available wireless mechanism I can think of which would give you that sort of range would be a 3G data connection. If you use that, you need to be wary of communication lag and outages - you must make absolutely sure that the system is fail-safe, and be prepared to have delays of potentially several seconds while you wait to see the response to your commands. I think that interactively controlling equipment in real time over that sort of distance would probably be very tedious. I don't know what your remote device is going to need to do, but I'd be very keen to reduce the amount of operator intervention needed and make the machine autonomous as far as possible.