So I've got my arduino, arduino BT and my hacked and soldered RC car ready and I've been trying to get it to run by arduino control which I've seen is a fairly common project. I'm running into a problem with the parts I have though. I have 2 NPN power transistors, one H-bridge and 2NPN signal transistors. Aside from that I just have some basic resistors and diodes.
I'm running into 2 problems for controlling the car. 1 is that because the power source controls both motors, if one motor is off the other one will simply run backwards through the circuit and run that one. The other problem is that I'm switching the signal with a transistor and I'm not sure how to isolate the switch from the battery. There needs to be a lead to the base to turn on the current, but at the same time there needs to be one on the emitter back to the controller, so the massive battery current can enter the microcontroller. It works kinda to just put a small resistor (560Ohm) on the base pin and have the emitter run back to the arduino ground, but I'm not sure how safe this is. I'm not sure how to go about solving these two problems, and I'd really appreciate some help.
(Notes: the drive motor can only go forward and backwards until I get another H-Bridge, and the front turning mechanism is just a springloaded DC motor that limits the distance )