Talon SRX magnetic encoder issues

[cjl2625]

Originally Posted by Ether

More detailed info would be helpful.

What exactly are you measuring with this encoder? It sounds like it might be steering angle of a swerve wheel? But that's just a guess.

What is the max angular speed the encoder will see in this application?

In normal operation, does the encoder cross the 360/0 discontinuity?

And just to be perfectly clear, the encoder is wired directly to the SRX, right?

1. It's a rotating cage that holds the ball. Video for reference
2. Rotates fairly slowly, it should take several seconds to go one rotation.
3. No, I've made sure that it doesn't cross
4. Yes

[Ether]

Originally Posted by cjl2625

1. It's a rotating cage that holds the ball.
2. Rotates fairly slowly, it should take several seconds to go one rotation.

So to be clear, the encoder is mounted to the cage?

[cjl2625]

Originally Posted by Ether

So to be clear, the encoder is mounted to the cage?

The encoder is integrated right into the versaplanetary gearbox that rotates the cage.

RyanShoff: that could be a good idea, I'll try that if I can't figure out how to fix it directly.

[Ether]

Originally Posted by cjl2625

The encoder is integrated right into the versaplanetary gearbox that rotates the cage.

Does the encoder rotate at the same speed as the cage?

If not, what is the max angular speed the encoder will see in this application?

[cjl2625]

Yes, it should be rotating at the same speed.

[ozrien]

It sounds like you have a cabling issue between the magencoder and Talon.

You can confirm this by grabbing the self-test before and after reproducing the problem and observing that the absolute position (pulse width) and relative position (quadrature) disagree. That's one of the benefits of the CTRE magnetic encoder; you have two references that rely on different physical wires.

Most likely the ribbon cable needs to be replaced, or if you are using a breakout inspect the solder contacts/wiring.

Are you close or exceeding the peak rated RPM for CTREMagEnc_Absolute? If so then select CTREMagEnc_Relative and setposition() to what the absolute reading reports. See github examples/Talon SRX Software Reference manual for more info and peak RPM specs.

[cjl2625]

Originally Posted by ozrien

It sounds like you have a cabling issue between the magencoder and Talon.

You can confirm this by grabbing the self-test before and after reproducing the problem and observing that the absolute position (pulse width) and relative position (quadrature) disagree. That's one of the benefits of the CTRE magnetic encoder; you have two references that rely on different physical wires.

Most likely the ribbon cable needs to be replaced, or if you are using a breakout inspect the solder contacts/wiring.

Are you close or exceeding the peak rated RPM for CTREMagEnc_Absolute? If so then select CTREMagEnc_Relative and setposition() to what the absolute reading reports. See github examples/Talon SRX Software Reference manual for more info and peak RPM specs.

The rotation is quite slow, so I don't think exceeding RPM is an issue.

At some point, I switched to relative mode and the problem stopped. So perhaps you are correct.
But we have two components robot using a mag encoder, and I've seen the same issue in both of them, so I figure it would be unlikely for them both to have the same cabling issue.

[Ether]

Originally Posted by cjl2625

The rotation is quite slow, so I don't think exceeding RPM is an issue.

At some point, I switched to relative mode and the problem stopped. So perhaps you are correct.

Are you sure the encoder is spinning at the same (slow) rate as the cage itself? Or is there a gear ratio between them?