Twitchy Motors

[hwu24110]

So we have another problem with the roborio (the connection issue is fixed). I noticed that the motors twitch, regardless if it is a Talon SR or VIctor SP. We have tried another schools Talon SRs and PWMs, it still twitches, so I think it may be an issue with the wiring or the physical roborio. It is not a shortage since the electronics board is mounted on a wooden board and the only wires touching the metal frame are the motor wires and the battery cables, which I am fairly sure is not causing the issue.

[pribusin]

What programming language?

Is it possible you're addressing motors from more than one area in your program? It's a favorite mistake I find with my students. They forget that somewhere else in the program a motor is set to 0 and in another part they're trying to run it at some speed. Causes motor twitch.

[hwu24110]

I am using Java. There are only four lines of codes that tell the motors to do something.

LF.set(-stickL.getRawAxis(1));
LR.set(-stickL.getRawAxis(1));
RF.set(stickR.getRawAxis(1));
RR.set(stickR.getRawAxis(1));

I can determine these are the only lines of code that make the motors move by commenting them out. When I do that, the talons blink orange.

[Lireal]

It sounds like it is something wrong with the joystick. What joystick are you using? You should be able to recalibrate your joystick to fix it.

[nighterfighter]

Put the robot up on some blocks of wood, and change your teleop code to this:

LF.set(-1.0);
LR.set(-1.0);
RF.set(1.0);
RR.set(1.0);

That will rule out the joysticks being a problem. I'd also double check all your code, just to be sure.

[Dan Waxman]

Check the battery voltage. Sometimes with brownout protection the wheels will be a bit twitchy.

[Tom Line]

We've seen the same behavior from victor sp's in past years. Our best guess is that they can be sensitive to noise on the PWM wire. Are your PWM wires running along side power wires?

[evanperryg]

Originally Posted by Tom Line

We've seen the same behavior from victor sp's in past years. Our best guess is that they can be sensitive to noise on the PWM wire. Are your PWM wires running along side power wires?

Interesting, with a digital line like PWM, noise shouldn't be a big deal unless it's really, REALLY bad. Hopefully OP comes back with a response soon cause I'm genuinely curious. The only thing that hasn't been mentioned is the faint possibility that both motor controllers are incorrectly calibrated, but it is still feasible.

[Mark McLeod]

Need more description of the symptoms.
For all we know the drive motors are wired into 30amp breakers, rather than 40a breakers.

[hwu24110]

I have tried setting each motor to a value of 0 and it still twitches.

I do not have the robot in front of me to confirm the breakers.

We've calibrated the victors and talons multiple times. I don't think we're calibrating it incorrectly.

[scca229]

Originally Posted by hwu24110

I have tried setting each motor to a value of 0 and it still twitches.

I do not have the robot in front of me to confirm the breakers.

We've calibrated the victors and talons multiple times. I don't think we're calibrating it incorrectly.

Since you mention different types of motor controllers, are the correct motor controller types being initialized for each of them in the code?

[hwu24110]

Yes, I had made sure of that.

[Mark McLeod]

Perhaps photos of your wiring setup would help identify additional potential problems/solutions.

P.S.
I do have a rookie team describing motor controller twitching, too, but they always have the robot apart when I've been visiting so I haven't been able to diagnose it yet.

[nighterfighter]

You could also post all of your code, that will help us make sure something isn't inadvertently happening.

[Omer Huly]

Originally Posted by hwu24110

so I think it may be an issue with the wiring or the physical roborio.

We had a twitching talon SR... we managed to solve this by connecting the talon to another PWM port.
Since we are getting a strange error in the driver station about PWM (something like PWM 0FRC in some WPIlib).