Preparing the Electrical Components
Every RC car has certain internal electrical components which we will use to interface with the Arduino. The most obvious of these is the large circuit board called the Control Board. This receives the radio signal from the remote and translates it into commands suitable for driving the motors.
The most important electrical components in an RC car are the motors. There are two motors, one used for driving and one for steering. The motor used for driving is the largest, more powerful motor and is almost always a DC motor with 2 wires.
The steering motor is usually smaller as is does not need to provide enough power to move the entire vehicle. In some vehicles this is another DC motor, however in some more expensive models it is a regular servo motor. The servo motor has the advantage of proportional control which means that we will be able to specify how much the car is to turn. If the steering motor is a DC motor the car can turn only fully one way and fully the other.
Disconnecting the motors
We will need to disconnect the motors from the control board. This can sometimes be done by disconnecting a small plug connector, from the circuit board. Other times you might have to cut the wires.
Your RC car will be powered with some sort of battery system, either rechargeable or perhaps AA or AAA batteries. We are going to divert this power to the Arduino so that we do not have to add a second battery box.
If power is coming directly to the control board
In this case for a vehicle such as the Interceptor, the power supply is hardwired directly onto the control board, so we will need to divert this power by soldering onto the correct connections. This will give us the added bonus of being able to use the ON/OFF switch to control the flow of power.
Since we want to connect this either to a breadboard or the Arduino, we should use a jumper wire. Cut one end off and strip about 1/8 inch off the end. Solder to the points specified so that the current will flow only when power is applied.
If power is coming through a wire
If the battery pack routes power through wires, our life is much easier. Simply cut off the wires at the point at which they reach the control board and you now have access to power supplied by the batteries, controlled by the on/off switch.
Preparing loose wires
If you have needed to cut any wires to route to the Arduino, either directly, or indirectly through the breadboard, there is an important step you need to take.
The wire normally used in RC cars is multi-stranded copper wire. This works fine for their application however it is useless for interfacing with a breadboard or Arduino. Therefore, you will need to solder each wire you plan to use to either a wire with a male jumper end or a length of single core wire. Cover the solder with electrical tape.