Jaguars always providing voltage
 

Hello!
I've been testing chassis with CIMs and Jaguar motor conterollers for the past few weeks now, and I've encountered a problem with a Jaguar.

It's always on.

To elaborate:
When testing the robot, they apparently had one motor go forwards immediately, without warning, the second the robot was turned on, it apparently started going. I've brought it back to my area and started testing on a simple electrical board we have set up. With or without a PWM wire connected to it, the Jaguar provides the same amount volts that the battery the system connects to provides. Additionally, I'm always getting connectivity across the V+ and M+ terminals.

I'd like to be able to fix this if I can, and I'm wondering if there IS a way to fix it so that it returns to it's previous functionality.


Thanks!

Re: Jaguars always providing voltage
 

We have fried a few Jaqs and and the "always on" effect is the result.

Re: Jaguars always providing voltage
 

I've seen this once before when the Jag was hooked up backwards - power was provided to the motor inputs, and the motor was hooked up to the power inputs.

Re: Jaguars always providing voltage
 

It sounds like one or more of the FETs in the Jaguar's H-Bridge have shorted. There's nothing you can do yourself to make that Jaguar FRC legal again, as the rules prohibit modifying speed controllers. If it's a 2012 Jag, then you could RMA it. If you wanted to repair it for testing purposes, you'd need to crack it open and identify which FETs are shorted and replace them.

If you don't know what FETs are, how to identify shorted ones, and how to replace a surface-mount part, then I'd advise you to cut your losses and give it up for dead.

Re: Jaguars always providing voltage
 

How did you "fry" it? We've had nothing but normal operation of this component over the past few weeks, and this is the first issue we've had. The other Jags in the system were operating fine, while this one malfunctioned.

Re: Jaguars always providing voltage
 

We have a Jag in our shop that is "always on". I opened it and it is obvious which FET is cooked. The plastic housing around the base of it is a melted pile.

I didn't notice which FETs are being used and don't have access to it right now. Does anyone know what replacement part could be used? Yes, it will not be legal for FIRST use, but it might still be recoverable for testing and learning.

Re: Jaguars always providing voltage
 

Normal operation followed by "inexplicable" malfunction can often be attributed to metal shavings in your Jaguar.

If this is a gray Jaguar, some of those had a known failure mode cause by sudden rapid speed reversals under heavy load. (ie. Throwing a CIM drivetrain from full forward immediately into full reverse.) This kind of failure usually resulted in the Jag not working in one direction, however.

Re: Jaguars always providing voltage
 

It is very easy to get metal shavings/dust into the jag, that happened a lot last year. We got some of them working again by opening them up and blowing the gunk out with a pneumatic hose, but if the shavings have become too ingrained in the circuitry, it becomes nearly impossible to fix :(

Re: Jaguars always providing voltage
 

This sounds like a symptom of the following:

I encourage all teams to inspect their wiring often and regularly! I even mess up sometimes when hooking up lots of Jaguars... Always double check!

Metal shaving can also be the culprit, like others have stated. Never drill, cut, file, or modify metal while the electronics are on the robot or unprotected. Be sure to clean the robot before driving it because metal shavings like to release themselves into electronics as soon as the robot starts moving.

-David

Re: Jaguars always providing voltage
 

Actually according to R58 this year, repairs are legal in 2012 as long as they function identically to the original.