Robotics RC Car hack help

Question

I need help with a robotisation project, please.

I am new to robotics and have the Maverick RC car pictured below:

My project is to add Arduino and Raspberry Pi boards to control the speed and direction of the car. So, the hand held control was thrown out.

I started by hooking up my Arduino to the front servo marked 9 in the diagram and I can successfully move the wheels to specific angles by using the examples like servo.write(180);.

My problem is the drive wheels. I have no idea how to power the wheels from the LiPo battery and use the Arduino to control the speed.

I'm open to and would welcome any help, please.

UPDATE:

After further consultation of the RC cars' specifications, the rear drive is controlled by a MM-25 brushed motor.

My problem is how do I interface with the MM-25 using my Arduino as it's wired into the RC car?

So far, I have connected my Arduino to the brushless motor by the same connection it uses to connect to the Transmitter/Receiver. I'm running the same servo code which worked for turning the servo(front) wheels but I get no response from the rear wheels. My code is below:

#include <Servo.h>

const int servo_pin = 9;
Servo servo;

void setup()
{
  Serial.begin(9600);
  servo.attach(servo_pin);
}

void loop()
{
  servo.write(180);
  delay(1000);

  servo.write(-180);
  delay(1000);

  /*servo.write(-180);
  delay(1000);*/

  /*servo.write(180);
  delay(1000);*/

  /*for(int pos=0; pos <= 180; pos+=25){
    servo.write(pos);
    Serial.print("Moving to: ");
    Serial.println(pos);
    delay(1000);
  }*/
}

Answer 1

I'm fairly certain you can't control a DC motor solely by plugging it into pins on the Arduino. You could use a diode and a transistor to power the motor, however you cannot control the speed. To control the speed you will need an ESC(electronic speed controller). This can be connected to the Arduino like a servo. Hope this helps!

Answer 2

Check out this great opensource project called DonkeyCar, which sounds pretty close to what you are trying to achieve. You can fork the project on GitHub and add your own modifications as required. They have a very active Slack group as well. They are available most of the time, and are an enthusiastic bunch as well. Check them out here.

Answer 3

If you are using the motors that came with the car, the car's circuit should include a motor driver, which takes an RC signal and decodes it to control the motor. I believe that the existing controller would have different circuits for controlling the steering motor and the drive motor.

Brushless DC Motors (BLDCM) require a different motor controller board that the normal Brushed DC Motors (DCM). You can search online for controllers. The only one I know a bit about is the ODrive. This is almost certainly too large and expensive for your project.

The RobotShop has a full section of BLDCM controllers.

The big thing to know is the power that the motor uses during startup and at stall (when something prevents the motor from running and yet you're still applying power).

Sounds like an interesting project.

I did build a robot out of an RC tank, many years ago. I used the original circuit for the controller, and faked the RC signals. But it used two DC brushed motors