Never Do This, and Other Good Ideas Gone Bad

[boomergeek]

Originally Posted by JackS

Here is a list of 2791's don'ts with some explanations beneath it.

...
2. No Jags
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2. Jaguars. In '09 we blew at least 4 Jaguars, maybe even more if you count off-season work. Until we are convinced Jags are as tough as Vics, we won't put another one on our bot.

No Jags... without using the CAN interface to limit the rate of voltage change allowed.

http://www.chiefdelphi.com/forums/sh...k#post9 47848


Team 241 had 3 Jaguars short out in 2010 and one in 2009:
All resulted in the circuit breaker on the associated Jaguar breaker trip continuously that made the rest of the robot uncontrollable- (caused variable lag time of one to three seconds on all other functions on the robot).
We guessed that the failure mode was caused by voltage spikes caused by attempts at wide voltage swings too quickly.

One failure occurred at BAE unveiling event ; (less than 5 minutes total use prior to failure)
One at the Granite State Regional ; (less than 10 total minutes use)
One at the Connecticut Regional ; (less than 40 minutes total use)

The first two were on our drivetrain (CIMs).

The last on was on our ball magnet roller (Fisher-Price).

At Manchester, we added a CAN control to limit the rate of voltage change so that the Jaguar would not be swung from +12V to -12V too quickly (and vice versa).
Since we make that change, no more the Jaguars blew on the drive train- Because we had 2 blow out of 40 minutes total use (10 minutes times 4 CIMs) and we have not had any more blow after 240 minutes total use- we think the workaround helped.

But due to an oversight, our CAN workaround to baby the Jaguars did not get put on the Jaguar driving the fisher-price until after we blew another Jaguar.
After we put the CAN workaround on the roller, we have not had another Jaguar blow. (16 minutes use without a failure).

---update---

In over 8 hours of off-season use, not a single Jaguar has blown since we put in the CAN workaround.