Introduction

This is the DFRobot Micro DC geared motor with encoder. It is a motor with a 120:1 gearbox and an integrated quadrature encoder that provides a resolution of 16 pulse single per round giving a maximum output of 1920 within one round. With an Arduino controller and motor driver, applications for this might include a closed-loop PID control or PWM motor speed control. This motor is an ideal option for mobile robot projects. The copper output shaft, embedded thread and reinforced connector greatly extends the motor's service life.

Specification

Pin Description

<File:FIT0450.png>

Grade Name Functional Description
1 Motor power supply pin + 3-7.5V,Rated voltage6V
2 Motor power supply pin -
3 Encoder A phase output Changes square wave with the output frequency of Motor speed
4 Encoder B phase output Changes square wave with the output frequency of Motor speed(interrupt port)
5 Encoder supply GND
6 Encoder supply + 4.5-7.5V

Tutorial

Requirements

Connection Diagram

FIT0450+UNO.png

This tutorial is about Encoder usage. We are using D2&D3 as driving pins, you can select other ones, but it requires at least 1 interrupt pin. (We selected D2, Interrupt 0 in this tutorial).

Interrupt Port with Different Board

Notice: attachInterrupt() interrupt.png

If using an Arduino UNO and you want to use interrupt port 0 (Int.0), you need to connect digital pin D2 on the board. The following code is only used in UNO and Mega2560. If you want to use Arduino Leonardo, you should change digital pin D3 instead of digital pin D2.

See the link for details http://arduino.cc/en/Reference/AttachInterrupt

Sample Code 1

//The sample code for driving one way motor encoder
const byte encoder0pinA = 2;//A pin -> the interrupt pin 0
const byte encoder0pinB = 3;//B pin -> the digital pin 3
byte encoder0PinALast;
int duration;//the number of the pulses
boolean Direction;//the rotation direction


void setup()
{
  Serial.begin(57600);//Initialize the serial port
  EncoderInit();//Initialize the module
}

void loop()
{
  Serial.print("Pulse:");
  Serial.println(duration);
  duration = 0;
  delay(100);
}

void EncoderInit()
{
  Direction = true;//default -> Forward
  pinMode(encoder0pinB,INPUT);
  attachInterrupt(0, wheelSpeed, CHANGE);
}

void wheelSpeed()
{
  int Lstate = digitalRead(encoder0pinA);
  if((encoder0PinALast == LOW) && Lstate==HIGH)
  {
    int val = digitalRead(encoder0pinB);
    if(val == LOW && Direction)
    {
      Direction = false; //Reverse
    }
    else if(val == HIGH && !Direction)
    {
      Direction = true;  //Forward
    }
  }
  encoder0PinALast = Lstate;

  if(!Direction)  duration++;
  else  duration--;
}

Code 1 phenomenon:

Explanation: Serial data, when the motor forward, the output value> 0, when the motor reverse rotation, digital output <0. The faster the motor speed, the greater the absolute value of number.

FIT0450_data_out.png

Sample Code 2

PID control: PID algorithm to control the motor speed by L298P DC motor driver board

  1. Motor power port is connected to the L298 drive motor M1 port
  2. Download and install Arduino PID
//The sample code for driving one way motor encoder
#include <PID_v1.h>
const byte encoder0pinA = 2;//A pin -> the interrupt pin 0
const byte encoder0pinB = 3;//B pin -> the digital pin 3
int E_left =5; //The enabling of L298PDC motor driver board connection to the digital interface port 5
int M_left =4; //The enabling of L298PDC motor driver board connection to the digital interface port 4
byte encoder0PinALast;
double duration,abs_duration;//the number of the pulses
boolean Direction;//the rotation direction
boolean result;

double val_output;//Power supplied to the motor PWM value.
double Setpoint;
double Kp=0.6, Ki=5, Kd=0;
PID myPID(&abs_duration, &val_output, &Setpoint, Kp, Ki, Kd, DIRECT);

void setup()
{
  Serial.begin(9600);//Initialize the serial port
   pinMode(M_left, OUTPUT);   //L298P Control port settings DC motor driver board for the output mode
   pinMode(E_left, OUTPUT);
   Setpoint =80;  //Set the output value of the PID
   myPID.SetMode(AUTOMATIC);//PID is set to automatic mode
   myPID.SetSampleTime(100);//Set PID sampling frequency is 100ms
  EncoderInit();//Initialize the module
}

void loop()
{
      advance();//Motor Forward
      abs_duration=abs(duration);
      result=myPID.Compute();//PID conversion is complete and returns 1
      if(result)
      {
        Serial.print("Pluse: ");
        Serial.println(duration);
        duration = 0; //Count clear, wait for the next count
      }


}

void EncoderInit()
{
  Direction = true;//default -> Forward
  pinMode(encoder0pinB,INPUT);
  attachInterrupt(0, wheelSpeed, CHANGE);
}

void wheelSpeed()
{
  int Lstate = digitalRead(encoder0pinA);
  if((encoder0PinALast == LOW) && Lstate==HIGH)
  {
    int val = digitalRead(encoder0pinB);
    if(val == LOW && Direction)
    {
      Direction = false; //Reverse
    }
    else if(val == HIGH && !Direction)
    {
      Direction = true;  //Forward
    }
  }
  encoder0PinALast = Lstate;

  if(!Direction)  duration++;
  else  duration--;

}
void advance()//Motor Forward
{
     digitalWrite(M_left,LOW);
     analogWrite(E_left,val_output);
}
void back()//Motor reverse
{
     digitalWrite(M_left,HIGH);
     analogWrite(E_left,val_output);
}

void Stop()//Motor stops
{
     digitalWrite(E_left, LOW);
}

Code 2 phenomenon:

The code PID value has been set as 80, so the motor will stabilize at about 80 rpm. If outside forces such as changes in motor drive voltage, the motor's resistance, etc affect the speed, the program will adjust the PWM value to stabilize the rotational speed at 80.

FAQ

Q&A Some general Arduino Problems/FAQ/Tips
A For any questions, advice or cool ideas to share, please visit the DFRobot Forum.

More Documents

DFshopping_car1.png Get TT Motor with Encoder (6V 160RPM 120:1) from DFRobot Store or DFRobot Distributor.

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