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Unread 09-02-2011, 14:10
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AKA: Phil Malone
FRC #1629 (GaCo: The Garrett Coalition)
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Possible bad Jaguar.... Thoughts?

Hi

I suspect I have a bad Jaguar, but thought I'd post here just in case.

I'm experiencing a "fault" condition on one Jag that seems to be hapenning too often. By "Fault" I mean that the Jag is shutting down and the LED blinks slow red.

I've got two Jags side/side driving two Swerve drive wheels (in a six wheel setup with the Swerves in the middle and two omni's at each end). Wheels spin freely, robot is only loaded at about 70 lbs, and there is no perceivable different between the two wheels.

While test driving I noticed that when I changed direction sometimes the robot would go into a spin.

I nailed it down to the fact that one Jag is not liking switching from Reverse to Forward suddenly. When the direction changes from R-F the error trips and the wheel shuts down until I stop the robot. The weird thing is that the error NEVER trips when I replicate the action in the opposite direction (rapid Fwd to Rev change.) It also doesn'rt seem to happen when I accelerate from a stop.

I considered battery voltage so I swapped in a new battery with a solid 12.75V No change.

It doesn't always happen, but seems most common when doing the rev-fwd change after a SHORT period of driving.

It's as if one set of FETS (1/4 of H-bridge) are less capable than the others, and are causing an error condition when they engage.

Tonight I'll probaly have the elec. student swap out the Jag, but is there anything else I can try to fix this?

Phil.
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Phil Malone
Garrett Engineering And Robotics Society (GEARS) founder.
http://www.GEARSinc.org

FRC1629 Mentor, FTC2818 Coach, FTC4240 Mentor, FLL NeXTGEN Mentor