Analog Encoder Troubles

We’re trying to use an analog encoder (http://www.usdigital.com/products/mae3) to measure rotations off of a motor shaft. I’m trying to use the Counter class for this, but the measurements are very erratic. It’ll halt measuring at all for a few seconds, then the number will increment by 4 or 5, and then it will start regularly updating but by increments of 2 for a while, then normally by increments of 1, etc etc. The motor shaft is turning at a constant speed.

Right now in the subsystem that’s executing the counter code I have


private static AnalogTrigger horRotEncoder = new AnalogTrigger(RobotMap.horRotEncoderPos);
private static Counter horRotCounter = new Counter(horRotEncoder, true, true);

to declare the Encoder and the Counter.

Then I have


protected void initDefaultCommand() {
    horRotCounter.setUpSource(horRotEncoder, AnalogTriggerOutput.Type.kRisingPulse);
    horRotCounter.setUpSourceEdge(true,false);
    horRotCounter.reset();
    horRotCounter.start();
}

public double getHorRotations(){
      
    return horRotCounter.get();
}

What I’ve tried to do with that is make it only count when it increments up, just for testing. And I’m printing the output of getHorRotations() to see what the values are.

We have an oscilloscope hooked up to the encoder, so we can see it’s getting the right values, so I suspect the problem is in the Counter class.

I thought the Counter class was for counting pulses. The device you linked to provides only analog or PWM output of absolute angular position.

from the datasheet:

*Analog output provides an analog voltage that is proportional to the absolute
shaft position. Analog output is only available in 10-bit resolution.

PWM output provides a pulse width duty cycle that is proportional to the absolute
shaft position.*

We were trying to use Counter with an analog input created from the Encoder. I thought the analog output of the encoder might be acceptable to it, and it seems to work, just very sporadically.

EDIT: To be more clear, horRotEncoder is an AnalogTrigger, which takes the AnalogInput from the encoder, and should essentially convert that to a digital signal triggered by the analog input’s shifts from 5v to 0v and vice versa.

We did this a few years ago in LabVIEW. Here’s how we opened everything. Maybe it will help getting it working in Java.

ContPotOpen.png


ContPotOpen.png

Clever !