Simulating/Mimicking Encoder Output

Using Arduino Sensors
1

Hello!

I am stuck on my first Arduino project and need your help. I have two draw-wire incremental encoders like http://www.micro-epsilon.com/download/products/cat--wireSENSOR--en.pdf. Imagine that I have positioned these encoders on the top left and top right corners of a paper. Now, if I hook the encoder strings to an object moving within the bounds of the paper, I should be able to position the object with respect to the edges of the paper using simple triangulation. Now, I would like to output the position of the moving object with respect to the edges of the paper as if they are from two linear encoders(in quadrature). I am successful :slight_smile: in using interrupts to read both the encoders. I have also calculated the position of the object in Inches. However, I am a little confused on how to generate the output. I have a loop that manually turns output pins on and off to mimic the encoders but, it is too slow. Is there any other way?
Thanks a lot.

P.S. I am using Arduino Uno.

Regards,
Kaar.

2

Show us the code you have.

What does "too slow" mean? How fast is the real object moving?

3

// including libraries for pinchange interrupt
#include <PinChangeInt.h>
#include <PinChangeIntConfig.h>

//assigning pins for encoders

define encoder1PinA 5

define encoder1PinB 6

define encoder2PinA 9

define encoder2PinB 10

// X outputs

define out1PinA 4

define out1PinB 3

// Y outputs

define out2PinA 11

define out2PinB 12

//VARIABLES*****************

volatile long encoder1Pos = 0;//raw encoder count for encoder 1
volatile long encoder2Pos = 0;//raw encoder count for encoder 2

volatile float Apos = 0;//encoder 1 reading in thou
volatile float Bpos = 0;//encoder 2 reading in thou
volatile float Cpos = 14000;//distance between encoders 1&2 in thou

volatile long x = 0;//X position in thou
volatile long y = 0;//Y position in thou
volatile long XposOld = 0;//X position in thou
volatile long YposOld = 0;//Y position in thou
//previous pin positions
volatile long encoder1PinALast = LOW;
volatile long encoder1PinBLast = LOW;
volatile long encoder2PinALast = LOW;
volatile long encoder2PinBLast = LOW;

//temp data holders
volatile long n1 = LOW;
volatile long m1 = LOW;
volatile long n2 = LOW;
volatile long m2 = LOW;
long valNew1 = 0;
long valOld1 = 0;
long valNew2 = 0;
long valOld2 = 0;

long outcount=1;
long outcountY=1;

volatile int Xsmall=0;
volatile int Ysmall=0;

//************************** SET UP **********************************

void setup()
{
pinMode (encoder1PinA,INPUT);
pinMode (encoder1PinB,INPUT);
pinMode (encoder2PinA,INPUT);
pinMode (encoder2PinB,INPUT);
pinMode (out2PinA,OUTPUT);
pinMode (out2PinB,OUTPUT);
pinMode(out1PinA, OUTPUT);
pinMode(out1PinB, OUTPUT);

Serial.begin (9600);
PCintPort::attachInterrupt(encoder1PinA, changeA1,CHANGE);
PCintPort::attachInterrupt(encoder1PinB, changeB1,CHANGE);
PCintPort::attachInterrupt(encoder2PinA, changeA2,CHANGE);
PCintPort::attachInterrupt(encoder2PinB, changeB2,CHANGE);

}

//************************** LOOP **********************************

void loop()
{
encoder1PinALast = n1;
encoder2PinALast = n2;
valNew1 = encoder1Pos;
valNew2 = encoder2Pos;
XposOld = Xsmall;
YposOld = Ysmall;

Apos=(encoder1Pos*-0.984)+4600+2365;//compensating for intial postion of the probe and the extension of the wire cushions
Bpos=(encoder2Pos*1.4925)+6772+475;//compensating for intial postion of the probe and the extension of the wire cushions
Cpos=14000;

if (valNew1 != valOld1 || valNew2 != valOld2)
{

x=( ((sq(Bpos)) + (sq(Cpos)) - (sq(Apos)) ) /(2*Cpos)); //a=Bpos b=Apos
y= sqrt(abs((sq(Bpos))-(sq(x))));

Xsmall=x/10;
Ysmall=y/10;

valOld1 = valNew1;
valOld2 = valNew2;

if (XposOld != Xsmall)
{

switch(outcount)
{
case 1:
{
if (XposOld > Xsmall)
{
digitalWrite(out1PinA,HIGH);
digitalWrite(out1PinB,LOW);
}
else
{
digitalWrite(out1PinA,HIGH);
digitalWrite(out1PinB,LOW);
}
outcount=2;
break;
}
case 2:
{
if (XposOld > Xsmall)
{
digitalWrite(out1PinA,HIGH);
digitalWrite(out1PinB,HIGH);
}
else
{
digitalWrite(out1PinA,LOW);
digitalWrite(out1PinB,LOW);
}
outcount=3;
break;
}
case 3:
{
if (XposOld > Xsmall)
{
digitalWrite(out1PinA,LOW);
digitalWrite(out1PinB,HIGH);
}
else
{
digitalWrite(out1PinA,LOW);
digitalWrite(out1PinB,HIGH);
}
outcount=4;
break;
}
default:
{
if (XposOld > Xsmall)
{
digitalWrite(out1PinA,LOW);
digitalWrite(out1PinB,LOW);
}
else
{
digitalWrite(out1PinA,HIGH);
digitalWrite(out1PinB,HIGH);
}
outcount=1;
break;
}
}
}

if (YposOld != Ysmall)
{

switch(outcountY)
{
case 1:
{
if (YposOld > Ysmall)
{
digitalWrite(out2PinA,HIGH);
digitalWrite(out2PinB,LOW);
}
else
{
digitalWrite(out2PinA,HIGH);
digitalWrite(out2PinB,LOW);
}
outcountY=2;
break;
}
case 2:
{
if (YposOld > Ysmall)
{
digitalWrite(out2PinA,HIGH);
digitalWrite(out2PinB,HIGH);
}
else
{
digitalWrite(out2PinA,LOW);
digitalWrite(out2PinB,LOW);
}
outcountY=3;
break;
}
case 3:
{
if (XposOld > Xsmall)
{
digitalWrite(out2PinA,LOW);
digitalWrite(out2PinB,HIGH);
}
else
{
digitalWrite(out2PinA,LOW);
digitalWrite(out2PinB,HIGH);
}
outcountY=4;
break;
}
default:
{
if (XposOld > Xsmall)
{
digitalWrite(out2PinA,LOW);
digitalWrite(out2PinB,LOW);
}
else
{
digitalWrite(out2PinA,HIGH);
digitalWrite(out2PinB,HIGH);
}
outcountY=1;
break;
}//default
}//switch case
}// if YoldPos!= Ysmall
}//if (valNew1 != valOld1 || valNew2 != valOld2)
}//forever loop

//************************** ENCODER 1 **********************************
void changeA1()
{
n1 = digitalRead(encoder1PinA);
m1 = digitalRead(encoder1PinB);
if (encoder1PinBLast ^ n1 ==1)
{
encoder1Pos--;
//encoder1Pos++;
}
else
{
encoder1Pos++;
}
encoder1PinBLast = m1;
}

void changeB1()
{
m1 = digitalRead(encoder1PinB);
n1 = digitalRead(encoder1PinA);
if (encoder1PinBLast ^ n1 ==1)
{
encoder1Pos--;
//encoder1Pos++;
}
else
{
encoder1Pos++;
}
encoder1PinBLast = m1;
}

//************************** ENCODER 2 **********************************
void changeA2()
{
n2 = digitalRead(encoder2PinA);
m2 = digitalRead(encoder2PinB);
if (encoder2PinBLast ^ n2 ==1)
{
//encoder2Pos++;
encoder2Pos--;
}
else
{
encoder2Pos++;
}

encoder2PinBLast = m2;
}

void changeB2()
{
m2 = digitalRead(encoder2PinB);
n2 = digitalRead(encoder2PinA);
if (encoder2PinBLast ^ n2 ==1)
{
//encoder2Pos++;
encoder2Pos--;
}
else
{
encoder2Pos++;
}
encoder2PinBLast = m2;
}

4

From looking at the code I guess it's not too slow but it's just inaccurate. This is because if you register a change on let's say the x-axis you just go to the next encoder signal and you don't encounter how much the change on the x-axis was.

BTW: change your code to use arrays and it will be much shorter and easier to read. And for posting code please use the code tags and not the quote tags. Thank you.

5