One thing that has puzzled me for a while is the legality of replacing the motor controller in the Falcon 500. I have always had good luck with CTRE motor controllers, but our mentors value the ability to replace a broken motor controller independent of the motor*. Today one of my teammates was tearing down a broken Falcon and found how seemingly easy it is to replace the motor controller in a Falcon 500. The rule we thought may prevent this is R502:
Rule R502: Don’t modify motors (mostly)
The rule has a few exceptions, notably exception J says repairs are allowed as long as it doesn’t change specifications or performance.
I think this would count under repairs and doesn’t modify performance. Is there a definitive answer to this? If not, what are y’all’s experiences with this?
While I may be wrong, I believe to take out the motor controller you have to take out the encoder as well. Taking out the encoder would cause the motor to lose track of it’s absolute position, rendering it unable to properly time the internal magnets. As far as I’m aware, the only way to recalibrate a falcon is to send it back to vex, and they may not take back a modified falcon.
For the controller this rule applies similarly to the motor rules
R710 *Only specified modifications to control system devices permitted. … motor controllers
M. Devices may be repaired, provided the performance and specifications of the device after
the repair are identical to those before the repair.
Taking it apart was easy; back together is harder especially since I didn’t get the stainless bolts. I have repaired (for the most part - it shakes a little) a now practice Falcon 500 and have a big soldering iron that might do the job if I succumb to temptation but I think I’ll wait until someone knows for sure that it does not need recalibration after rebuilding it.
We do like the integrated packaging of the controller and motor but must admit that the motor part we tore up and the controller part we smoked are expensive wear and tear if we can’t repair them from other dead, salvaged Falon 500/Talon FX.
The magnet stays in its absolute position to the motor but you undoubtedly “calibrate” your swerve turn encoder to the magnet; likely making sure your wheels are pointed straight for the wheel’s reference to the encoder and the robot.
You had to save the magnet’s offset angle with the wheels straight somewhere. Somehow we’d have to determine and save that angle for the changed TalonFX. I don’t see a way to do either.
It’s unlikely that every magnetic sensor is exactly the same and mounted in the TalonFX exactly the same so I’d think calibration is necessary. But I notice the motor twitches a tiny bit when it’s started so maybe it’s self-calibrating.
Warning
DO NOT remove the screws from the controller end cap. This can result in a loss of
calibration between the motor and motor controller and will void the warranty. A loss in
calibration will result in decreased performance or permanently damage your Falcon 500.
Once the end cap is removed the Falcon 500 can no longer be put back into its original state
due to the loss of calibration.
Given that it’s stated that it voids the warranty and decreases performance or causes damage, it seems like it wouldn’t count as a repair under R710.
I replaced a bent shaft with one from a burned out TalonFX. Not perfectly smooth but works well enough for prototypes and programmers. Mark the casing as such - NOT for competitions.
I strongly suspect that without the ability to reprogram the Hall Effect encoder IC or the microcontroller on the new motor controller PCB, your franken-Falcon would not work well.
Thanks to you and @Joe_Ross for reminding me of that chapter in the manual I had forgotten.
I assumed the excess vibration was from slight damage to the bulk of the motor that wasn’t replaced. Apparently that damage isn’t expected with a slightly bent output shaft. I’ll have to verify that by testing a new Falcon 500 to see how smooth it is. I had also replaced the bearing but I don’t see that as being an available repair part.
I had noticed the vibration when trying to help another on CD tune their flywheel. Testing with my repaired Falcon 500 I have multiple frequency oscillations in my velocity PIDF that I could change or control only by squeezing the case by different amounts.
For anyone tempted to remove the long screws from an older Falcon 500 I suggest getting the stainless screws if your motor doesn’t have them or you’ll need patience and dexterity for about 10 minutes.
Considering we still don’t have the advertised FOC, I’m not holding my breath for Vex following through and supporting their products with appropriate diagnostic and repair tools.
Field Oriented Control (Vector Control), it’s a different type of control for a brushless motor that gives you better efficiency, higher top speed among other things.
Edit: It’s a firmware update that was in the initial marketing for the Falcon as coming later
