Ken
I'm not sure what the demo board really is that comes with the PICKIT2. If it has to be soldered, you may want to consider getting a proto or bread board to do your prototyping. This is a board with holes into which you can place jumper wires (which you can buy a box of different lengths already cut and bent) and make connections without soldering Typically, I need to mess around with the circuit to make it work or optimize it. Soldering and unsoldering really impacts my ability to try different things and make progress. I save soldering once the circuit has been fully debugged. Also, I would typically put a voltage regulator IC such as the 7805 to provide clean regulated power to the PIC on the proto board. I also use In Circuit Serial Programming (ICSP) using a 6 pin header that the PICKIT2 plugs right into to program the PIC. I don't want to have to pull the chip out every time to program it.
I usually break my project up into logical units and test individually. If you are going to control the throttle with the PIC, you could build a circuit to do this and the PWM code to control it. Same for steering, test out servo control with the kinds of inputs you expect. You may find that the PIC cannot actually drive a steering servo with its own power supply. You may have to provide the control signal from the PIC, but provide a separate power supply for the servo.
Same is true for the light seeking hardware and control software (which will be a bit challenging I think) and your manual/auto relay switching.
Only when all the pieces work, do I attempt to integrate. Even then, one at a time. Thus you can see the benefit of a proto board without soldering (at least for me).
You are also quite right to isolate the power for the motor from the electronic control supply. There are big spikes on it and would be very hard to clean up.
I found an oscilloscope extremely useful in debugging the PWM control circuit and hardware. You can learn a lot about the hardware and software if you can look at the signals.
You may know all this, and can just wire it up, program it and it will all work. If my approach is different than what you want to do, just say so and I will back away from the keyboard
Hope this helps
John
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