Rotary encoder troubleshooting

Other Hardware Sensors
1

Hello everybody, I am trying to use a rotary encoder with my arduino uno.

Unfortunately I am having many troubles that seems to have no reason to be.

This is the setup:

Arduino with connected a rotary encoder, encoder's pin C to 5V, encoder's pin A and B respectively to PIN 2 and 3 (interrupt). I have added two pulldown resistors (10K?) that connects pins 2 and 3 to ground.

I have just written this simple sketch:

int encoderA = 2;
int encoderB = 3;

void setup() {
  pinMode(encoderA, INPUT);
  pinMode(encoderB, INPUT);
  attachInterrupt(0, doEncoderA, RISING);
  attachInterrupt(1, doEncoderB, RISING);
  Serial.begin(9600);
  Serial.println("Test:");
}

void loop() {
 
}

void doEncoderB(){
  int A = digitalRead(encoderA);
  detachInterrupt(1);
  if(A == LOW){
    Serial.println(0);
  }else{
    Serial.println(1);
  }
  attachInterrupt(1,doEncoderBFall,FALLING);
}
void doEncoderBFall(){
  int A = digitalRead(encoderA);
  detachInterrupt(1);
  if(A == HIGH){
    Serial.println(2);
  }else{
    Serial.println(3);
  }
  attachInterrupt(1,doEncoderB,RISING);
}
void doEncoderA(){
}

What this code should do is to print a pair of numbers, 02 if going clockwise and 13 if going counterclockwise.
And it does, but not always, sometimes I get a 02 03 02 03 12 when turning clockwise and something like 13 12 03 when turning counterclockwise.

This is driving me crazy because it don't make sense at all!!

I was shouting to my arduino and my code when I decided to hook up my oscilloscope to the two signals and what I get is the image attached, each and every single pulse is perfectly identical to the one in the picture, no strange behaviour. So I came up that the problem is in the code.

But it is extremely simple, it's almost bulletproof, what am I doing wrong??

pic_6_2.bmp (1.1 MB)

2

The scope trace and your description of the circuit don't make sense to me. The usual connection with 3-pin encoders is to have C grounded, with pullups on A and B and normally capacitors would be used to prevent contact bounce from interfering with the pulse detection.

Your code is far from clean and simple -- for one, you should never print from within an interrupt.

Here are two links that might help.

3

The actual scheme is like in the picture attached, now with this sketch it seems to be working, but with only one interrupt.

int encoderA = 2;
int encoderB = 3;
int encoderPos = 0;
void setup() {
  pinMode(encoderA, INPUT);
  pinMode(encoderB, INPUT);
  pinMode(13, OUTPUT);
  pinMode(11, OUTPUT);
  attachInterrupt(1, doEncoderB, RISING);
  Serial.begin(9600);
  Serial.println("Test:");
}

void loop() {
}

void doEncoderB(){
  int A = digitalRead(encoderA);
  detachInterrupt(1);
   detachInterrupt(0);
   encoderPos = 0;
  if(A == LOW){
    digitalWrite(13,HIGH);
  }else{
    analogWrite(11,255);
  }
    //Serial.print("0: ");
    //Serial.println(A);
  attachInterrupt(1,doEncoderBFall,FALLING);
}
void doEncoderBFall(){
  detachInterrupt(1);
  digitalWrite(13,LOW);
  analogWrite(11,0);
    //Serial.println(2);
    encoderPos = 2;
  attachInterrupt(1, doEncoderB, RISING);
  
}

It blik a led when turning CW and another when turning CCW.

Is there any chance to detect the speed to change the ratio of the increment?

Schermata 2014-08-13 alle 18.44.35.png

4

no one?

5

Sure, capture micros() and do a little math,
elapsedTime = laterTime - earlierTime; // time elements are unsigned long
will tell you the between events.

6

kevinpirola:
no one?

Sure. Bet you are using an inexpensive mechanical encoder switch rather then a more expensive optical or magnetic encoder? If so the dreaded "switch contact bounce" is causing your problem of random intermittent multiple steps.

7

retrolefty:

kevinpirola:
no one?

Sure. Bet you are using an inexpensive mechanical encoder switch rather then a more expensive optical or magnetic encoder? If so the dreaded "switch contact bounce" is causing your problem of random intermittent multiple steps.

I'm using indeed a mechanical one, but it seems that with a capacitor 100nF I can solve the problem. Maybe I will focus on magnetic or optical for the final project if they are better, I didn't know they existed.

Thanks