2012 FRC Team 1717 Uncut

[dcarr]

One more thing...the swerve modules seem to rotate a lot as you stop and prepare to shoot. Is this part of re-zeroing the gyro for each shot, or some other reason?

[jakemochas]

Hi everyone! Our answer to the gear cutting question has been approved and can be seen above at post #65. The post is above because it was posted on the 18th, but it didn’t show up until today. We are working hard to post all of our other answers as well! Thank you for your patience.

Originally Posted by dcarr

I had a few questions regarding encoders:

We're working on our drivetrain over the summer. The past two years we have used CAN with our Jaguars, connected to a 2Can, but it has been riddled with problems. So we are switching to PWM which I know you guys use and plugging the encoders into the sidecar. Since each encoder can take 2 I/O ports, how did you manage that-did you fill one up? (if so, did you use more than one sidecar?) How did your sensor arrangement work, did you use many others besides the encoders and the gyro?

Thanks for taking the time to answer these questions, it is greatly appreciated!

In order to PWM our 14 motor controllers and have enough I/O for the encoders, we did use two digital sidecars. As a result of the new motor allowance this year, it was the first time we used two digital sidecars.

We had many sensors on our robot that were wired to the analog and digital slots of the cRIO. For our swerve drive, we used two types of sensors: we used magnetic encoders on the analog board for wheel orientation and optical encoders for the wheel drive. Also, the gyro was attached to an analog port.

For the shooter, we used a magnetic encoder attached to the analog breakout to detect the platform position. For the hood angle, we used a multi-turn potentiometer on the analog breakout. To detect flywheel speed, we read from a light sensor that was attached to the digital sidecar I/O.

Originally Posted by dcarr

One more thing...the swerve modules seem to rotate a lot as you stop and prepare to shoot. Is this part of re-zeroing the gyro for each shot, or some other reason?

The rotation of the wheels when we prepare to shoot is mostly from re-zeroing, but some of the turning is from fine adjustments the driver makes while lining up for the shot.

[JamesTerm]

Originally Posted by jakemochas

To detect flywheel speed, we read from a light sensor that was attached to the digital sidecar I/O.

When you say light sensor do you mean optical encoder?

[Jared Russell]

Originally Posted by JamesTerm

When you say light sensor do you mean optical encoder?

He may just mean a light sensor (like a Banner sensor, or a 2011 KOP line sensor) being used as a digital tachometer with a piece of reflective tape or a photogate. Nothing to "encode" (in a quadrature sense), since your wheel generally isn't changing the direction that it rotates.

[JamesTerm]

Originally Posted by Jared341

He may just mean a light sensor (like a Banner sensor, or a 2011 KOP line sensor) being used as a digital tachometer with a piece of reflective tape or a photogate. Nothing to "encode" (in a quadrature sense), since your wheel generally isn't changing the direction that it rotates.

Thanks Jared, that is what I was thinking as well... I'd love to see how well this compares against an encoder (either kind)... as of now, I am still frustrated with encoders with these high of speeds.