S1 Check Controller Voltage

For a PC be able to control the remote controller of a RC Car, at least the analog voltage of the potentiometer must be able to be replaced by an external voltage source. I guess what underlying the trigger and the wheel should be some sort of potentiometer, one end for the Vs and the other is GND, with an adjustable R in the middle to get an adjustable ref voltage. Then a chip inside the controller can detect the ref voltage and base on it to output wireless signal to the RC Car.

Fortunately, after open the cover of the remote controller, it was not too difficult to figure out the pins for steering and speed control. And the voltages are measured by the multi-meter:

• For Steering: Left 1.70V - 1.38V (dead zone) 1.30V - 0.96V Right

• For Speed: Backward 1.70V - 1.42V (dead zone) 1.34V - 0.90V Forward

After analyzed the measured data, I found its effective voltage range is very narrow.

Vrange = 1.70 - 1.40 = 0.3V

The external voltage source I picked up is the PWM signal from Arduino 328P. Its PWM signal has 255 levels from 0V to 5.0V. So the minimum resolution is about 0.02V (5.0 / 255 = 0.0196).

So for steering turn left, the voltage under 1.38V means the wheel does not turn at all. Start from 1.38V to 1.70V, it will trun to most left gradully. For Arduino, the best resolution it can do is:

0.32V / 0.02 = 16 levels

For the voltage above 1.70, the wheel can not turn left any more.

Here, the voltages for control have been measured, and the next step will be making a Low Pass Filter for the PWM signal from Arduino.