Jaguars failing
 

So, does anybody know if the jaguars were improved or are we going to have the same extremly high failure rate this year?
Bruce

Re: Jaguars failing
 

Bruce, there are a number of posts discussing the failure rate of the jaguar.

For instance, here:
http://www.chiefdelphi.com/forums/sh...fai lure+rate

In that post they discuss a total of 88 jags to date. When you consider that close to 4000 jags were shipped to teams just in the kit of parts, I'd wager the failure rate including all jags sold is well below 1%. I think I would argue with your "extremely high" statement.

There will be a new black jaguar that has been discussed repeatedly both on this forum and the usfirst.org official beta forums that has some modifications to improve the durability further.

Re: Jaguars failing
 

hey

this from the first team of Australia
we would like to know anything vaubleable info on the Jaguar motor





thank you


3132 :D

Re: Jaguars failing
 

Interesting note on the failure rate. We lost 3 ourselves and everybody I talked to at the Milwaukee regional lost at least one.
Bruce

Re: Jaguars failing
 

Considering that the vast majority of teams don't post on CD, I'm certain that far more than 88 Jaguars have failed, and consequently that the number easily exceeds 1%. Definitions of "extremely high" may vary, but I don't recall a single report of a Victor failing for any reason other than negligence, so in comparison this seems very troubling.

Re: Jaguars failing
 

Not us.

I think the reason people think the failure rate is higher is because failed Jags came bunched together in the same kits. My team got the "good batch" last year.

Re: Jaguars failing
 

Tom,
Can you give us a good way to know if the Jaguars have the latest software updates? The KOP box says rev A on it, does that imply a certain level of software or hardware revision?

Re: Jaguars failing
 

The way to tell is by plugging it into CAN. If using a black jag as a bridge, you can use the bdc-comm utility to query the version. If you intend to use the Servo PWM interface, then you don't need to upgrade the firmware.

As for hardware revisions, they are either black or gray plastics. All gray jags are the same hardware inside.

Re: Jaguars failing
 

The 88 figure came directly from TI, I believe. Meaning that's how many they had returned by teams. That has nothing to do with CD.

And speaking of negligence, in the top two causes of failure, one was negligence... and that was removing the screws from the jaguar power terminals which leaves metal shavings inside the case. The new black jag does not use retaining screws since people are going to remove them even if it will cause a failure.

Re: Jaguars failing
 

Mea culpa. Thanks for the info.

Re: Jaguars failing
 

That figure of 88, EVEN if its accurate as to the number of units that LM/TI received back still doesnt really tell us anything.

There are LOTS of teams, i'm sure, who just had one blow up and never thought to contact LM/TI.

I know 1075 used 6 jags on our 2009 bot, and we had no fewer than 2 jags fail on us. Both in the same way, a plume of smoke and upon closer inspection, toasted FETs. We're very careful about filings getting into speed controllers, over the years we toasted a few Victors... including an entire robot's worth of electronics when the ground clip fell off the robot during welding. Ever since then welding is done without electronics on the bot.

My count says 2/8, thats a 25% failure rate. There seems to be no shortage of the well known names around here with similar numbers. That sort of leads me to believe that the numbers are bigger than it would seem from what LM/TI tells us.

Re: Jaguars failing
 

FACT: The number of failed Jaguars is higher than what TI has reported. This is not attributable to malice; they simply are not psychic. I am at a loss as to why any team would choose to not tell LM/TI of a failure; why not get a free replacement?

FACT: The grey Jaguar has/had(?) a failure mode that silently disables one direction of motor control.

Jaguar failures that include emitting smoke are user induced.

Please note that clustered failures are much more likely to be indicative of the user than of the design. I did a lot of tech support last season, and almost all of the cases of multiple failures were user error. Most of these cases also featured the fabled line of "I've been doing FIRST for X years, of course I didn't read the documentation!" Actual Example:
Edit : The quote came from someone who plugged the battery in backwards.

Re: Jaguars failing
 

oh. I forgot to mention that when I opened the case to look at the damage to the jags we toasted, there was NO noticable chunks, flecks, or specks, of metal shavings inside.

I'm very reluctant to just accept that all magic-smoke-emitting failure modes are user-error-induced.

I think its rather likely that either (and this does sort of qualify as user error i suppose) a loose or otherwise high resistance connection is causing the jags to enter some weird failure mode. Alternately, it has been suggested that the loads induced by running a motor full forward and jamming it to full reverse very quickly can reach huge numbers. I expect that some of the toasted FET failure modes could be caused by this happening in a fashion that the fault-detect circuit couldn't detect fast enough.

I can't say carte-blanche that it wasn't our fault they blew, but IMO they blew for other reasons. I know the precautions we take.

Re: Jaguars failing
 

Perhaps the team had no intention of using Jags after the incident? In which case requesting a replacement would be extra work for no benefit. Perhaps they already had a spare and didn't bother or forgot to send in the broken one? Or maybe they came to CD and saw some of the many posts here that suggest that a failed Jag is the teams' fault and figured they must have done something wrong and didn't bother to request a replacement because they didn't want to be embarrassed. There's a lot of posts here, including yours that I just quoted, that like to point out dumb things that people have done to destroy electronics. Maybe people are becoming afraid of being cited as an example of "user error" and made to look foolish and figure it's easier to just keep their mouth shut and pony up the extra $70 on their own.
Joe's post above indicated that at least some failures were because of shavings when someone fully backed out the terminal screws. Ultimately this may be considered user-induced, but given that the black Jag was redesigned to eliminate this problem I'd say that it is at least partially due to a misunderstood requirement or design defect. If enough people are doing something that they thought was logical that ends up ruining the product, I usually consider that a design shortcoming.


Ultimately, there's at least some teams who had issues with the Jags and are not comfortable with them. Citing the data (which may or may not be an accurate reflection of reality) over and over is not doing much to help the perception problem. I keep seeing threads like this where teams say they had issues (sometimes multiple), and the response is always the same: someone cites the data that claims to show a "low" failure rate, then suggests that the team must have screwed up. I understand that that is what most people at NI and TI must be thinking, but I don't think it's helping the perception problem.

Re: Jaguars failing
 

Not exactly. High continuous current would cause the current sense resistor to unsolder itself and/or self destruct. Sustained near stall current on a CIM is 16 times the power dissipation of the resistor.

Re: Jaguars failing
 

This was actually considered a design enhancement originally. The idea was if the screws are painted a color code, then it will be LESS likely that teams will accidentally wire them up backward and set fire to them. But what if a team fully removes the screws and replaces them in the wrong place... then the color code is misleading. Ok... make the screws retained so that they won't be easily removed all the way, thus helping to ensure the color code stays correct.

After a year of teams overpowering the retention, TI must have decided that if teams are going to take them out anyway, the may as well not have metal shavings inside on top of the possible bad color coding.

Essentially, what was intended to help teams, only hurt them more since they didn't follow instructions.

Re: Jaguars failing
 

Perhaps the problem is that it isn't in the instructions (even now).

Re: Jaguars failing
 

I wouldn't have considered this a design enhancement. I've always considered ring connectors to be much safer than fork connectors. A loose terminal screw will not result in a stray wire loose in a robot frame.

Also, weren't ring terminals given in the KOP? How do you get a ring terminal onto a screw without backing the screw completely out? We had zero burned out Jaguars last year and we backed out all of our screws to use ring terminals. I suspect the issue is something else.

Reverse polarity on the line side is the quickest way to smoke a speed controller, so why not place color coding on the case so that when careless people remove the screws they get back in the correct positions? Also, while the case on the Jaguars is much more user friendly at preventing metal filings getting where they shouldn't, it's not fool-proof. Many teams claim they're careful about metal filings, but I can't count the number of times I've witness teams drilling, filing, grinding, or cutting (Dremel cutoff wheels are a big one) over vital electronics with no cover to catch flying chips and dust. They don't see any metal chips or filings, but there is conductive dust from the cutoff wheels everywhere.

Re: Jaguars failing
 

We always use wire cutters to snip a little slot out of the ring right by the wire connection resulting is a hook. Much easier to wire and similar protection against loose connections.

Shavings inside aren't a guarantee of failure, it just makes it likely. If I were you, I would open up all of them and clean them out thoroughly. I'm not sure what the most appropriate way is... perhaps an air duster. You can probably get advice from TI. I wouldn't use them until they were cleaned though.

Re: Jaguars failing
 

Oops. Perhaps someone should let TI know about this.

Re: Jaguars failing
 

Joe,
If a Jag was opened and metallic dust found inside, I think a vacuum is more appropriate. Compressed air will force some of the dust between or under the pins of surface mount components and under the shroud that surrounds the FETs. Many teams do not realize how much metallic dust is actually generated right on their robot. Open gears and sprocket/chain interfaces for instance throw a lot of fine metal dust while they wear. The big offenders are rotating or moving parts that rub against robot frames. i.e. arm attachments, shafts with no bearings, etc.

Re: Jaguars failing
 

Thanks Joe! Unfotunately I'm working afternoons and midnights right now. Getting home at 4am is killin' me, and putting a crimp on responding to chief delphi questions in a quick manner is a bit tough.

Re: Jaguars failing
 

It has started again. We have already toasted two Jags from last year. We purchased a number for last year's bot and removed them all from the robot after toasting 4. We just built a prototype drive base and in two days have smoked 2 of the "replacements" we got last year. Same symptom, it only loses one direction after issuing the magic smoke. I really wanted to move to CAN, but I CAN'T if I CAN'T rely on the Jags. Has anyone smoked a Black Jag yet???

PGR
:( :( :( :( :(

Re: Jaguars failing
 

Peter, are you covering the open connectors on the jags with tape, a plastic jumper, or something else? It's been shown that direct static to the open jag connectors can cause issues.

Have you tested your frame to see if you're running electricity through it?

Are you mounting your electronics on a conductive or a non-conductive surface?

Re: Jaguars failing
 

Tom,
The direction failures are attributable to one of the power FET gate drivers shorting. I don't remember if the cause of the failures was ever found or reported.

Re: Jaguars failing
 

We smoked our first Jag today. I was a bit surprise how it decided to go up in smoke.

We did not have any failures last year. This was a brand new one just out of the box. It was not under any stress, and decided to smoke. It's less than two days old. That's too bad because I am sure Luminary probably doesn't replace them because they assume you abused them. I hope we don't have any more that die like this one. It was almost in "coast mode" and poof...

Re: Jaguars failing
 

That seems like quite an unfortunate assumption to make considering that Luminary Micro's Failure Analysis Report states that Luminary Micro promptly replaced every failed Jaguar last year.

Re: Jaguars failing
 

Thanks for this report.

Looks like ours is a U6/U7 failure.

Re: Jaguars failing
 

Team 1279 worked on the Black Jag Beta program and we did manage to blow up two with static discharge, one by accident, and one on purpose (under TIs direction). Last years robots were very static prone, and the encoder and potentiometer inputs are fairly exposed. I would recommend covering the inputs with empty connectors when not using them to prevent that type of failure.

I would note that we also blew up our Kwik Byte driver station's ethernet connectors when running tethered at a fundraiser, so the Jaguars are not the only static sensitive devices. Use due care with all your sensors, etc..

TI was very good to work with about the failures, and they seem committed to improving their product. I would say that any team who has a failure should contact TI, document the conditions, and return the blown part. The Jags have many cool features and I would very much like to see them become a reliable component.

Re: Jaguars failing
 

Al,

I stated that because there was some discussion previously regarding the static. I wasn't sure if it had been on the beta test boards or not, but the summarization was that static charge directly applied to the exposed terminals could create issues in the jags. I couldn't remember who said it (fortunately someone spoke up here).

We'll be using Jag's again this year on our practice robot. I'm interested in seeing how they behave. We used them last year on our sparring-partner in the drive train and never experienced any issues with, though I know that anecdotal evidence is really of no help in determining their reliability.

Tom

Re: Jaguars failing
 

Oh you silly Northerners! There is a simple fix to your whole static discharge problem...MOVE TO FLORIDA!:D Sure, the education system isn't as good and there's a constant threat of hurricanes, but it's not very often my car shocks me!;)

Re: Jaguars failing
 

We didn't send our failed and now failing Jags back to TI because we couldn't determine if they were user error or production error. For instance, we have one which has been slowly failing for about 6 months. Was it from being outside at outreach events? Humidity? I don't know. I think our original failed Jag was probably due to user error and I did talk with the TI rep at GSR. So there was some feedback.

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