Rotate DC servo motor with ARDUINO

Question

I have this servo motor (http://robokits.co.in/motors/high-torque-encoder-dc-servo-motor-60rpm-with-uart-i2c-ppm-drive?gclid=CLHf9_fCqNQCFVAeaAodhM0Ddg&). Generally, I have seen servo motor with three wires only but this servo motor have 6 wires. I want to rotate this using PPM signal and accordingly I made connection as described in motor manual. Arduino Code to rotate motor is:

// Include the Servo library 
#include <Servo.h> 
// Declare the Servo pin 
int servoPin = 10; 
// Create a servo object 
Servo Servo1; 
void setup() { 
   // We need to attach the servo to the used pin number 
   Servo1.attach(servoPin); 
}
void loop(){ 
   // Make servo go to 0 degrees 
   Servo1.write(0); 
   delay(1000); 
   // Make servo go to 90 degrees 
   Servo1.write(90); 
   delay(1000); 
   // Make servo go to 180 degrees 
   Servo1.write(180); 
   delay(1000); 
}

But what the motor does is it continuously turning. How to control motor position using PPM. Thanks.

Answer 1

Read this : http://www.robokits.co.in/documentation/RMCS220x_DCServo_Driver.pdf This is not exactly a servo. But it is a brushed DC motor coupled with an encoder and an inbuilt microcontroller to control the position from encoder feedback. The datasheet clearly says you can use PPM signal for speed control (RPM control) and not position control. Hence it does not work as a servo with PPM signal.

You need to use UART or I2C using Arduino to communicate with the motor, which is simple. You can check this tutorial on serial with Arduino : https://www.arduino.cc/en/reference/serial

Out of the six wires, only 4 will be used in case of controlling via UART:

• V+ = 12V
• UART RXD = Arduino TXD
• UART TXD = Arduino RXD
• GND = Arduino GND and power source ground

Now either you can program Arduino to send UART commands or use Arduino's Serial Terminal directly in the way the mentioned in Page 4. Make sure the baud rate is 9600 For a servo action you will mostly be using the commands :

• GXXX
• RXXX where XXX can be replaced with suitable encoder value. By using encoder specification from Page 3 : \begin{equation} XXX = \frac{Angle (in\hspace{5pt}degrees)}{0.2} \end{equation}