I have just disassembled a RC car (a BBR 1:18 Scale Ferrari Enzo from 2005). Attached to the stepper motor that controls the steering of the car was a small circuit board with a cog wheel attached to it. I am trying to figure out what this circuit does. My idea is that it is responsible of keeping track of the wheels position but I am not certain. Here is a picture of it:

Photo of Sensor - 1

Photo of Sensor - 2

As you can see there are 5 wires coming out of it and I know that the green one is GND. Does anyone have an idea of what its function might be?

  • 1
    $\begingroup$ Can you edit and update your question with the make and model of your RC car? The more information you provide, the more certain the answer will be... $\endgroup$ Jan 10, 2016 at 2:06
  • $\begingroup$ Is there a part number on it? I would guess it's a position encoder, but just a guess. $\endgroup$
    – Chuck
    Jan 10, 2016 at 14:09

1 Answer 1


At a guess this is either a Hall Effect, or Optical, speed and direction measurement device. The five wires will be GND, and outputs of Sensor1 and Sensor 2, and the other two would be the power supply to the Hall Effect/Optical Sensor (with there being a separate Vcc or GND for the power).

This is a basic schematic for a Hall Effect based device

Hall Effect speed and direction measurement device

This is a basic schematic for an optical device:

Optical speed and direction measurement device

Two sensors are required, as using only one sensor will provide just speed data; adding a second offset sensor will also provide the direction.

I could be wrong though.


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