What Happens When Metal Gets Into A Jaguar (SMOKE!!!!)

[dwaynetrip3119]

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On our practice day at the Michigan State Championship. Our robot began to smoke during a match. At first I thought that the robot had caught on fire because it was so much smoke coming from it. We then took it off the field and mentors from so many different teams cam to our rescue. Even volunteers for the event came to our pit. It turned out that it was a piece of aluminum shaving that fell into the Jag which shut down the fan and caused it to overheat. I really appreciate the help that came from the teams and volunteers( especially team 1718 for the new Jag).

Has any teams had any similar problems???

[engunneer]

One of the things i like about the new Jaguars is that it's harder to get pieces of metal in there. One of the things I don't like it that it's harder to check and get metal out!

I'm glad your robot was up and running again by Friday.

[EricH]

The real question is not whether any teams have had metal in a speed controller, it's whether any teams haven't.

The Victors were really easy to get metal into if you didn't cover them before drilling/cutting. One bit of metal and the same thing happened as you had with a Jaguar. Jaguars are a bit harder to do that with, as you know, but not impossible.

Moral of the story: Cover your electronics when cutting/drilling/producing chips and shavings.

[Kristian Calhoun]

Originally Posted by EricH

Moral of the story: Cover your electronics when cutting/drilling/producing chips and shavings.

And if possible, vacuum out your electronics before turning on the robot.

[Gdeaver]

For years First Teams have assumed that metal cuttings have found their way into victors and caused them to short out and fail. Now the same assumption is being attributed to the Jags. I submit that some of the failures have been from metal but, a far larger number of failures are Fet heat related. Our speed controllers are hard switched and subject to avalanche conditions. That combined with the higher switching frequency and switching losses in my opinion are the reason for many of the failures.

[dwaynetrip3119]

Well actually some of the mentors that helped us out believed that it was caused by a shortage in the power distribution. We really never came to a full conclusion to if it was really the metal or the shortage.

[Uberbots]

Originally Posted by dwaynetrip3119

Well actually some of the mentors that helped us out believed that it was caused by a shortage in the power distribution. We really never came to a full conclusion to if it was really the metal or the shortage.

a shaving causing a short inside the jag or stopping the fan that results in te jag overheaating could have shown similar results, you are right. The fact that a single mosfet is blown leads me to beleive that your shorting idea is the way to look, because overheating would have affected all the fets.

[Lancer Robotics]

Metal is not the only source of smoke and fire in a jaguar. At Wisconsin we had some serious weight loss isues. We covered the electronics (or so we thought) with a shirt before we drilled. Well to make a long story short come Saturday and a quick check of systems on the practice field revealed one side could not reverse, "oh that darn Jag needs replacing". As I walked back to the pit area I turned to say something to the team just in time to see smoke billowing from our robot. It would have made a hollywood director proud.

Then as I rushed to cut power there was flame inside the jag. Not bad, smoke fire and flame. We changed the jaguar and no problems. We kept the scorch marks kind of like a badge of honor. We figured if the White House could why not our robot.

Moral of the story? Smoke happens, if you cannot laugh about it robotics may not be for you.

[dwaynetrip3119]

LoL interesting story. Another situation was at our first regional this year at detroit, a Jag would not reverse also. When we drilled, we covered it up with a T-shirt as well. It didnt flare up or anything because we replaced it right after the match.

[Al Skierkiewicz]

Gary,
I have seen enough failures to recognize a metallic short as a cause in many failures in either Jag or Victor. The good news is both controllers have FETs that are capable of higher currents than we demand. Although there is some good protection of the boards, a metallic fragment or a lot of filing dust causes a nice path between the gate and source. That said, the Jaguar one direction only failure is not one of these that appears to be caused by metal. The gate driver chip is failing without a FET failure. Everyone should remember that the fan blows down against the FETs so any metal on the top gets moved by fan action. In the Jaguars, the fan runs whenever there is an output and for up to 10 seconds after the command ends. The Victors run all the time.

[crake]

While you're at it - please watch out for metal shavings around the other electronics as well. We've seen some cRIO RMA's that had debris inside!

[MrForbes]

Originally Posted by EricH

The real question is not whether any teams have had metal in a speed controller, it's whether any teams haven't.

I'm not aware of any metal in speed controllers on our robots, we've never lost a controller except one that was DOA (inspection showed no metal in it, and it didn't smoke or melt anything).

This year it was extra easy to keep metal out of them, since the electronics box opening points away from the rest of the robot, and besides there's not much metal in the robot, since the chassis, electronics box, shooter, and it's support plate are all made of wood!

[dwaynetrip3119]

Originally Posted by squirrel

I'm not aware of any metal in speed controllers on our robots, we've never lost a controller except one that was DOA (inspection showed no metal in it, and it didn't smoke or melt anything).

This year it was extra easy to keep metal out of them, since the electronics box opening points away from the rest of the robot, and besides there's not much metal in the robot, since the chassis, electronics box, shooter, and it's support plate are all made of wood!

Do you think wood shavings could have any affect on the electronics?

[Al Skierkiewicz]

Dwayne,
In most cases the answer would be no. However, in fans, they tend to bind the rotating parts. The same takes place on motors that have an open frame like the Banebots and Fisher Price. In devices that plug in, they prevent full insertion and that sometimes leads to bent and broken pins. In general, foreign debris of any kind should be avoided, metal in particular.

[keehun]

Out team was spared. Not a singe jag bad, not a single incident with the electronics system during a match. One problem we had was a jag wire coming loose but that's not the jag's fault as we used an easy-to-remove "U" styled connection that gets screwed down instead of an "O" which would've been fine (cost us our quarters elim round!)

Well, what also helped us is our brush mechanism is so large that if you put your hand behind the ball-track the air flow would be so great that it blew all the dust and crap out.