Falcon 500 poping circuit breakers

Our team has been using 4x Falcon 500’s on our 8 wheel drop center tank drive. So far it has been nothing but problems for us. At week zero we were able to drive properly for 3 matches. In the middle of our fourth match, we were got pushed back by another bot. Right after that we started to pop breakers and were unable to properly control our robot. We thought this could be solved by current limiting, but at our first district, we were unable to turn at all. The breakers would pop as soon as we tried to turn(even with current limiting). We think this is due to a bug in the falcon firmware and this has been confirmed by CTRE. I am wondering if any teams have encountered this issue and to what extent were the motors damaged.

We need more details about your drive train. Is it the KOP? If so, is anything custom (not KOP) about the drive train? If not, we need a lot more details about the design.

Are you sure that you put Loctite on the internal bolts/etc, as recommended by vexpro’s site (and sent in an email to their customers)?

It is a custom drive train with a custom 10.24:1 ratio gearbox. 190 has the exact same gear ratio and they were not able to find any problems with our setup. We also put loctite on the screws. I don’t think it is a issue with the motor mounting shaft. The motor turns smoothly. It is a 8 wheel tank drive with a 1/4in drop with andymark 6in pneumatic wheels. Weights around 117 lbs. The main drive rails are VERSA 2x1 tubes. Gearbox is mounted in the back. Nothing changed when the Falcons suddenly stopped working.

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What is your current draw when you run the robot in the air.

What tire pressure do you run the tires at?

I don’t recall the exact number but if i remember it correctly it was anywhere from ~15-30 amps total at 100% (before it was run at week 0). I can give you an “post-damage” number when i get back in

Your drive train should not be drawing anywhere near that if the wheels are in the air spinning.

we don’t run them at a set pressure, we just pump them up until they are hard and they don’t really give when we pinch them. We did take one set off and replace them with omni wheels to try and completely removed another set to try and reduce wheel scrub

Maybe your breakers are weak. Try replacing them. Sounds simple, but it’s worth a try.

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What is the bug in the Falcon (Talon FX) firmware that you are referencing in the CTRE release notes?

We have had success with the Talon FX current-limiting feature for our drivetrain. Prior to making use of the current-limiting features of the Talon FX, we were having trouble with the Falcon 500s tripping breakers on our drivetrain.

We replaced all the 40 amp breakers and that had no effect.

Phoenix Framework 5.18.2 Installer (Feb 19 2020):
Talon FX Firmware (20.3.0.2): Fixes issue where Talon FX can be damaged when being backdriven at high speed and power cycled.

To clarify we think this issue could have damaged our Falcons when we (team 246) were back driven at week zero quarter finals 4 match 1 in Nashua. 20.3.0.2 was not yet released when week 0 started.

We have the same drivetrain as you guys? very cool.

My guess is you somehow weren’t writing values to one of two of your falcons, and fried it. Coincidentally, we almost did the same thing. One time I opened up the Phoenix Tuner and one of our falcons said the firmware version was “255.255.255.255” which didn’t make any sense, and the falcon didn’t work until I reflashed… who knows.

Hope you can get a new one/fix it!

Hmm. I’m not sure, but I don’t think the referenced issue would come up in a “pushing match” with another team, as I don’t think the motor RPMs would be high enough unless you were getting pushed really fast. I had the impression that the referenced issue would really only happen in circumstances like that of a high-speed shooter wheel that suddenly had the power cut when near full speed (such as tripping a breaker on an at-speed flywheel shooter).