Talons start at different times, motors spin at different speeds

[ixchi]

Our team's robot has run into a rather interesting issue resulting in it noticeably and quickly veering off center. Our initial thought was that the wheels weren't perfectly centered or the gearboxes were not correctly installed.

After dismantling and inspecting everything, we noticed that the talons appeared to be starting to receive signal at different times. It was not just that the motor started later, but the indicator light on the talon changed from orange to green or red at a different time. These delays in signal appear to be related to the side that is going forwards or backwards. In order to determine that it was not related to joystick tilt, I modified the code to only allow it to go perfectly straight, eliminating the possibility that the joystick was not perfectly calibrated or we were not pushing it perfectly straight. We also tried switching the PWMs on the talons and which motors they were connected to with no change.

When going forwards, one side starts a little before the other. When going backwards, the opposite side starts first. Assuming that it was some issue with our Java code, I reset everything to the most basic code possible, and still saw the issue occurring.

Additionally, when pushing forwards, so that both sides have just started, the side that started first spins noticeably faster. At full speed we could determine, with the help of a strobe light, that it was still spinning somewhat faster than the other side. When going in reverse, the opposite side was faster.

Is this some kind of intentional effect? Or has something gone awry? All components are running the latest firmware.

[nickbrickmaster]

Do the PWM calibration routine.

Talon User manual: http://ctr-electronics.com/Talon_User_Manual_1_1.pdf

SRX User Manual: http://content.vexrobotics.com/vexpr...e-20150201.pdf

Do you have two (three) motors on each side? If so, try using PWM y-cables, one output for each side.

[ixchi]

Originally Posted by nickbrickmaster

Do the PWM calibration routine.

Will give this a shot!

Originally Posted by nickbrickmaster

Do you have two (three) motors on each side? If so, try using PWM y-cables, one output for each side.

We do have two motors on each side, but the issue is that both controllers on each side are always together, but the different sides start at different times. Will definitely try it though.

[ixchi]

It does appear that calibrating the talons fixed the issue with the signal.
Thank you!