Possible Jaguar bug

[Salmonfishyfish]

We succesfully built a running tank drive and it was working well for the first few test runs but now two jaguars wired to 1 pwm will only move forward when the joystick is tilted forward but wont move in reverse when the joystick is tilted to the back. Does anyone know what the reason for this is and how to troubleshoot it?

[Jon Stratis]

Check the limit switch jumpers in the Jag, and look at the LED on the Jags - they flash status messages when something is wrong.

It sounds like the "reverse" limit switch jumper came out, which will prevent the Jag from going in reverse.

[tsaksa]

Originally Posted by Jon Stratis

Check the limit switch jumpers in the Jag, and look at the LED on the Jags - they flash status messages when something is wrong.

It sounds like the "reverse" limit switch jumper came out, which will prevent the Jag from going in reverse.

Good ideas. I also like to use a servo in situations like this to test that the PWM signals are doing what you expect. There could be a problem with the driver station, controls, or code, and you are not really generating any reverse signals. Our team has put together a servo that is self powered so it can plug directly in place of a Jag or Victor to quickly test the signals without the need for a jumper.

In the future you may also want to consider building or buying one of the small boards that generate PWM signals if you don't have one. Between having a servo to test the signal out, and a small box that generates a reliable PWM signal you can quickly isolate almost any problem like this.

[Kevin Sevcik]

Check what the previous two posters have suggested, if that doesn't work...

640 is a pretty veteran team number. Are these Gray Jaguars or Black Jaguars that you're using? The Gray Jaguars have a known failure mode with these symptoms. Rapid command reversals under high load could blow out one of the FETs, rendering the Jag non-functional in one direction. If you were using Gray Jags, swap them out with some new Black Jags and see if things work again.

[Salmonfishyfish]

We are using grey jaguars. Other than that one-direction bug could there be anything else wrong with it? all jumpers seem to be in place. Is there a way to reset the grey jaguars?

[Alan Anderson]

If you don't have 12 volt power connected properly to the Digital Sidecar, the PWM signals have a tendency to drop out when they call for reverse. Do the Jaguars show a steady light or a blinking yellow one when the problem occors?