Low Res Optical Encoders for Speed Control

[KrazyCarl92]

Originally Posted by Ether

Use only one channel of the encoder and use the Counter class to trigger on rising edge only.

Our team uses Java. I'm not much of a programmer as it relates to the robot, but I have a bit of experience.

I notice that all of the constructors for Encoder objects require both an A channel and B channel as arguments, whereas the Counter constructors allow you to specify a single channel. Is this why we would use the Counter class to only count the rising edges? The Counter class doesn't have a getRate method, but would the getPeriod method return values that are useful for what we're trying to do?

And I noticed that 1x, 2x, and 4x counting are mentioned in the descriptions of many of the methods in the Encoder class. Is this something we need to consider when using the Counter class as well?

[Ether]

You could use the getperiod method which returns the elapsed time between the two most recent edges, or you could read raw counts and divide the change in counts by the actual elapsed time since the counts were last read.

Each method has its pros and cons, and teams have been successful with both methods.

One or the other might be more appropriate depending on your encoder speed and the control algorithm you plan to use.

[jspatz1]

We also had trouble with the 360 res quad. US Digital trying to control up to 1500 rpm with pwm. We switched to 100 res single channel, at it worked great.

[Ekcrbe]

I'm not the one to go to for technical answers, but this year, we actually put our encoder on a gear reduction from the shooter so it wasn't running as fast as the shooter, and then compensated accordingly in the calculations.

My 2 hillbilly pennies.

[R.C.]

We are using a 360 count s4 encoder from US Digital, we basically use the same PID loop with feed forward that 341 does.

We were getting our shooter +- 25 rpms pretty easily.

-RC