Optical Encoder from HP Printer

Forum 2005-2010 (read only) Hardware Interfacing
1

Simple project but very newbie to electronics. Trying to use an optical encoder and its mating 200 LPI, 1800 ct / rev wheel. Its a 4 wire guy with a 10,000 pF cap between power and ground.

Its most likely an Agilent 09863-58 but can't find exact specs on it, seems most follow wiring specs for HEDS-9711 (Google it I can't post links yet)

I'm putting ground wire to ground on arduino, Vcc to arduino 5V out, Channel A to Digital Pin 2, and Channel B to Digital Pin 3.

Is this all there is to wiring or am i missing part of the circuit? I see things about pull up resistors is that for mechanical detent encoders only?

With that said, will this code work (from bottom of Arduino Tutorials):

//PIN's definition
#define encoder0PinA 2
#define encoder0PinB 3

volatile int encoder0Pos = 0;
volatile boolean PastA = 0;
volatile boolean PastB = 0;

void setup()
{

pinMode(encoder0PinA, INPUT);
//turn on pullup resistor
//digitalWrite(encoder0PinA, HIGH); //ONLY FOR SOME ENCODER(MAGNETIC)!!!!
pinMode(encoder0PinB, INPUT);
//turn on pullup resistor
//digitalWrite(encoder0PinB, HIGH); //ONLY FOR SOME ENCODER(MAGNETIC)!!!!
PastA = (boolean)digitalRead(encoder0PinA); //initial value of channel A;
PastB = (boolean)digitalRead(encoder0PinB); //and channel B

//To speed up even more, you may define manually the ISRs
// encoder A channel on interrupt 0 (arduino's pin 2)
attachInterrupt(0, doEncoderA, RISING);
// encoder B channel pin on interrupt 1 (arduino's pin 3)
attachInterrupt(1, doEncoderB, CHANGE);

}

void loop()
{
//your staff....ENJOY! :smiley:
}

//you may easily modify the code get quadrature..
//..but be sure this whouldn't let Arduino back!
void doEncoderA()
{
PastB ? encoder0Pos--: encoder0Pos++;
}

void doEncoderB()
{
PastB = !PastB;
}

2

Got the encoder working without any circuitry at all. I simply had to remove the pull up resistor code in the encoder examples page for "Tighten up ISRs" example.

The encoder datasheet i mentioned above is the wrong unit, its basically a HEDS-9700.

It provides a 0 Volt Low, 5 Volt High square wave ouptut, so simply putting channel A to Digital I/O 2 and B to 3 works awesome.

With this setup I am getting a resolution of 0.05°!!!!!

Code as follows:

enum PinAssignments {
encoderPinA = 2,
encoderPinB = 3,
clearButton = 8
};

volatile unsigned int encoderPos = 0;
unsigned int lastReportedPos = 1;

boolean A_set = false;
boolean B_set = false;

void setup() {

pinMode(encoderPinA, INPUT);
pinMode(encoderPinB, INPUT);
pinMode(clearButton, INPUT);
digitalWrite(clearButton, HIGH);

// encoder pin on interrupt 0 (pin 2)
attachInterrupt(0, doEncoderA, CHANGE);
// encoder pin on interrupt 1 (pin 3)
attachInterrupt(1, doEncoderB, CHANGE);

Serial.begin(9600);
}

void loop(){
if (lastReportedPos != encoderPos) {
Serial.print("Index:");
Serial.print(encoderPos, DEC);
Serial.println();
lastReportedPos = encoderPos;
}
if (digitalRead(clearButton) == LOW) {
encoderPos = 0;
}
}

// Interrupt on A changing state
void doEncoderA(){
// Test transition
A_set = digitalRead(encoderPinA) == HIGH;
// and adjust counter + if A leads B
encoderPos += (A_set != B_set) ? +1 : -1;
}

// Interrupt on B changing state
void doEncoderB(){
// Test transition
B_set = digitalRead(encoderPinB) == HIGH;
// and adjust counter + if B follows A
encoderPos += (A_set == B_set) ? +1 : -1;
}

3

Thank you for the code!!!