Falcon 500 Bring Up Loud High Pitch Sound

Hey CD, this year we were going to experiment with moving to brushless motors for our drivetrain, we’ve been using a 4-cim setup with Talon motor controllers for a long time now.

So, we were trying to follow the user guide for the Falcon and the Bring Up procedures at: https://phoenix-documentation.readthedocs.io/en/latest/ch08_BringUpCAN.html

and we end up with a really odd result. After updating the firmware and loading the factory default configs in the phoenix tuner when we go to the control tab with an enabled robot and set the Percent Output mode to any non-zero number (can be as small as .05) the LEDs properly blink (red for +, green for -) and the Falcon emits this very high pitched sound and the shaft never spins.

When they aren’t connected to power or anything they spin freely, in that the motors aren’t bound or anything.

These are attached to a plywood test harness not actually driving any load or anything so I was expecting to see the shaft spin.

The falcons are basically taken straight out of the box, wired to the Roborio CAN bus (as stated in step 2 of the user guide).

The roborio has an empty Command Robot template as the robot code on there.

Phoenix Tuner can see the device on the can bus, and interact with it successfully.

Am I missing something here? I couldn’t find any documentation that suggests that the high pitch squeal we hear is an error condition, or normal. Seems bad though. There weren’t any other steps I could find in CTRE documentation that we have missed. Any ideas?

Is there any chance the motors are stalling here? In the initial release thread of the Falcon 500, there was discussion of a built in “feature” where the falcon would emit a high-ish frequency whine when it detected stall (stall like?) conditions.

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This video has a great example of the stall squeal from the Falcon 500. Is this the sound you hear, or is your sound different?

I’m not sure how stalling could occur if the motor shaft is not connected to anything. There is a known issue where mounting screws can be too long and lock the motor internals, but if the shaft spins easily when unpowered while the motor is mounted to the test rig, it doesn’t seem like this could be a source of stalling either.


Hmm, that is indeed the exact sound we’re hearing.

So, I guess we’ll do some experimentation with the mounting screws to see if that’s locking it up.

Thanks all for the replies.

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I believe there was also an issue with some motors’ shaft retention screws that used to stall the motors

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That’s good to know we need to watch that more carefully. We took our two motors we were testing yesterday, wired them inline on the CAN bus with a couple Talons (a more representative setup), and today they worked as expected with the tuner (shafts turning, etc).

Excited to dig in more to the integrated encoder, and next exploring getting our setup using path following etc with the trajectory tutorials.

You don’t want to use a Talon with a Falcon 500. The Falcon 500 includes a built-in motor controller, so this isn’t a good idea (and may not be legal for competition). I imagine you have the Talons doing something else, but just in case…

I appreciate the heads up, and yes your supposition was correct. In this case, the Talons would be powering cims or 775s on other subsystems.

However, if anyone else checks this thread that’s an important distinction.


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