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Topic: Encoders changing and serial crashing on servo (Read 531 times) previous topic - next topic


I am developing a servo drive for a cnc machine and have run into a problem.

When the motor power is of the encoders and step interrupts work as expected (using the serial port display)

If I turn on motor power (50 vdc), then the encoders trigger and add up real fast.

I am using PWM pins 9 and 10 with a modified frequency and resoultion.

I use INT0 for channelA encoder and INT1 for the step count

Any ideas on why my PWM channels are counting?

Also, if I turn on the power with the Arduino plugged in the usb serial connection locks up.

Here is my code, any help would be appreciated

Code: [Select]
volatile long EncoderCount = 0;
volatile long StepCount = 0;

const int EncoderA=2;
const int Step=3;
const int EncoderB=4;
const int Direction=5;
const int PulseA=9;
const int PulseB=10;
const double MaxSumOfError=256;

long Error=0;
long SumOfError=0;
double P=0;
double I=0;
double D=0;
double PID=0;

double Kp=0;
double Ki=0;
double Kd=0;
double IMax=1000;
long PreviousEncoderCount=0;

 if (PIND &_BV(4) )
 if (PIND &_BV(5) )

void setup()

 pinMode (EncoderA,INPUT);
 pinMode (EncoderB,INPUT);
 pinMode (Step,INPUT);
 pinMode (Direction,INPUT);
 pinMode (PulseA,OUTPUT);
 pinMode (PulseB,OUTPUT);
 EICRA = 15;
EIMSK = 3;
TCCR1B = TCCR1B & 0b11111000 |0x01; // change frequency
// Set pwm resolution  to mode 7 (10 bit)

TCCR1B &= ~(1 << WGM13);    // Timer B clear bit 4
TCCR1B |=  (1 << WGM12);    // set bit 3

TCCR1A |= (1 << WGM11);    //  Timer A set bit 1
TCCR1A |= (1 << WGM10);    //  set bit 0





void loop()
// Error is the difference in stepper counter and encoder count interrupts
Error = StepCount - EncoderCount;

// proportional
P =Kp * Error;

// Integral
SumOfError += Error;  // Add up the error
IMax =  MaxSumOfError /Ki;    //Make Sure that the sum of the error does not get too large

 if (SumOfError >IMax)
   SumOfError= IMax;
 else if (SumOfError < -IMax)
   SumOfError = -IMax;

I = Ki * SumOfError;
 D = (Kd * (StepCount - PreviousEncoderCount));
 PreviousEncoderCount= EncoderCount;
PID=(P + I - D)+512;

if (PID>1000) PID=1000;
if (PID<24) PID=24;


Serial.print(", ");
Serial.print(", ");


void invertAnalogWrite(int pin, int value)
   analogWrite(pin, value);
  TCCR1A = TCCR1A & ~B00110000; //switch off output B
  TCCR1A |= B00110000;  //switch on the B output with inverted output


Any ideas on why my PWM channels are counting?

Also, if I turn on the power with the Arduino plugged in the usb serial connection locks up.

Since both of the anomalies occur when the external power source is used, I don't suspect that it's a software issue. We'd need to know more about the external power, the servos and encoders, and how they are wired up.


Jul 25, 2010, 07:05 pm Last Edit: Jul 25, 2010, 07:15 pm by rlwoodjr Reason: 1
I would add a schematic image, but I dont seem to have a button to do so.  :-[

I am sending the output of pins 9 and 10 of the arduino to a pair of FAN73832's.

I added my schematic here:

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