Mark cable connections after opening the RC car. Find the + and the - of each element Pro Preview

TL. DR.

Use small sticky markers. Stick one marker to each cable. Write down on the marker what is this cable connected to and if it is Ground or Voltage.

Marking cables

It does not matter if we work on the car here or if we work on a professional network server. There are always cables. 

Initially, the car looks like the first picture, at the end should be like the second picture. (these are pictures of different cars. The first is with cables that are not marked and the second is with cables that are marked)

When marking the cables stick a marker at about 2-3 centimeters/1inch from the end of the cable. Write down on the marker if this cable is connecting a motor, a led diode, a switch.

For the front motor write down FM+, FM-. This means Front Motor + and Front Motor -

For the back motor write down BM+, BM-

For the leds write down FL+, FL-. This means front light + and front light -.

For the Switch write down S+, S-. This means Switch + and Switch -.

Now you know all the cables. 

Can you find the antenna?

We use the following markers but others are also possible.

Ground or Voltage

Each electronic component has two cables connected to it. If you want to have current flowing through the system the current must "enter" the element from one of the cables and must "exit" the element from the other cable. This is truly an over-simplistic view of the system but is good enough for now.

Each cable could be connected to the source of power or to the ground. The current flows from the source of power to the ground. The source of power is where we have voltage. Generally, it is a pin marked as +, or 5V or V.

The real part of the Reverse-engineering process is to understand the controller of the car and whether a cable is connected to the Voltage (which we would refer to as the + "plus") or to the Ground (which we would refer to as the - "minus"). We would prepare separate resources for different cars. Here is a general principle.

The cables are connected to the controller. On the controller, there is a small sign of + or - which says if the cable is connected to the plus or to the minus. On the picture look at the yellow rectangles that highlight where is the + and where is the -. From then on you can continue knowing the red cables for this particular car are the +(plus) and white cables for this particular car are the - (minus).

What about the antenna?

There is a cable that is connected to the controller and to the antenna? Because remember, the car was initially a remote control car :). In the picture, this is the black cable on the left.