Chief Delphi - EP4 Encoder and Arduino

Quote:

Originally Posted by samirext (Post 1233187)

Hello there!;) , I'm having a little problems programming this encoder with arduino, i'm doing it manually (without a library) but it is not the best way to get the data.
I want to know if anyone of you have used it with Arduino or if you know how to get accurate data from the device, i need to obtain speed from a shaft. Your help is welcome ! Thanks!!
Best regards from Chile!

There are several approaches you may consider, below is one I have used.

Using one channel of the encoder attached to one of the external interrupts and the other to a digital input. Use the interrupt service routine to determine the direction.
Each tick of the encoder will also represent a distance of travel or amount of rotation of a shaft. With those values known, you can calculate RPM and/or distance.

As mentioned by tr6scott, the Arduino may be somewhat limited on the maximum rate it can manage, so keep that in mind. How fast your Arduino can process interrupts will be directly related to how tightly you code your ISR.

Here is a piece of code I used to control the motor's rate. The motor directly drove the encoder. I use the Servo library to drive the motor because the signal generated is the same as the speed controller uses.

Code:

/**********************************************************

* Quadrature Encoder code using Interupt 0 (Dig pin 2) to *

* trigger ISR and accumulate count in variable "Accum"    *

*controlling servo(motor) on D9.                          *

**********************************************************/

#include <Servo.h>



Servo myservo;  // create servo object to control a servo 

                // a maximum of eight servo objects can be created 

                

const int COUNTPERREV = 128; // Encoder count per revolution

const int LOOPDELAY = 100;  //ms to delay the loop ie. 100 is 100ms

const int TARGETRPM = 1; // for testing, this establishes the RPM target RPM

long lastAccum =0;  // Holds the Accum count from the previous sample

int B = 5;  // Phase B pin connection

int pos = 90;    // variable to store the servo position

int desiredcount = (COUNTPERREV/TARGETRPM)/(1000/LOOPDELAY); // sets desired loop count

int errorAccum = 0; //this is added to neutral to position(drive) the servo(motor)

volatile long Accum = 0;  // Accumulator for total count

int rate = 0;  //measured # of counts per sample period



void setup(void)

{

  myservo.attach(9);  // attaches the servo on pin 9 to the servo object 

  pinMode (B, INPUT);  // Phase B pin type

  attachInterrupt (0, ISR0, RISING);  // Interupt 0 calls "ISR0"

   Serial.begin(115200); // connect to the serial port

}

   

  void loop (void)

  {

    GetRate();

    errorAccum += (desiredcount - rate);  // adds difference between the desired count and the actual,

                                          // , the rate error, to be used to correct the motor speed

   myservo.writeMicroseconds(1500 + errorAccum);  // send servo(motor) control pulse 

    Serial.print (" errorAccum is ");

    Serial.println (errorAccum);   

    delay(LOOPDELAY);                       // waits the number of ms defined by LOOPDELAY 

  }

  

  void ISR0(void)

  {

    if (digitalRead(B) == HIGH)

   

    {

      Accum ++ ;   

    }

    else

    {

      Accum -- ;

    }

  }

  

  void GetRate (void)

  {

    long samplediff;

    samplediff = (Accum - lastAccum);  // Creates the counts since last sample

    lastAccum = Accum;  // Saves the count for the next loop

    rate = (int) samplediff;  // Cast the sample to an int and sets rate

  }