Neo Motor brake force?

[Amitgm3316]

Has anyone tested the braking force a Neo motor is capable of producing?

I know they can be used for climbing and staying airborne, but I was wondering the pure numbers just to be sure.

[MrForbes]

Do you mean “braking” force? As in, stopping something from rotating? As in, applying a brake?

The word “breaking” means to break something, to damage it so it no longer works.

Spelling matters, sometimes.

[Amitgm3316]

oh,sorry , autocorrect

[Weldingrod1]

I wondered that too, and did some testing…

Neo braking mode information

I didn’t see anyone else had posted this data… I just checked the winding resistance on a room temperature NEO motor: 4.99 Amps produced 0.75 Volts. 0.15 Ohms from X to Y. This means that each coil is 0.225 Ohms. Just FYI, when I plug X into Y, I get quite a bit of drag torque and some cogging. With 5 Amps going from X to Y the motor holds position quite strongly; more torque than I was able to casually put on the shaft with my fingers. Running the model, it looks like you might get 1.4 Nm…

[Amitgm3316]

Great!!!
Thanks so much, ill check it right now

[Will_Toth]

Just remember that when no current is applied by the controller (i.e. when you either command 0 volts, or when the robot is disabled, say at the end of a match) there is no braking force when the motor is not spinning. See this post in particular Neo braking mode information - #16 by Richard_Wallace

[Amitgm3316]

But setting it so that it brakes at the end of a match is possible, if i’m not wrong.

[Amitgm3316]

I want to use it instead of a ratchet and just keep the robot in the air for enough time.

Can the jvn calculator check if a 9:1 is a viable ratio? (For motor brake)

[MazeOfEncryption]

I would not recommend trying this. Intentionally stalling motors usually isn’t a good idea. A rachet or a friction brake are much more reliable solutions.

[Alex_Y]

There definitely is some current running at the end of the match. Last season, our climb would drop only when the main breaker was manually powered off.

[Will_Toth]

You can set it to brake mode, but this does not apply any current to the motor, but it will cause any back emf generated by the motor to be converted to current (torque). This is what Richard means by ‘viscous brake’ in that post.

To calculate torque in brake mode, you can use the speed of the motor. To get a rough idea, you can look at the motor curve specifically the torque vs RPM plot. Invert the plot (i.e. set 0 torque at 0 RPM and max torque at the max shown RPM), and that is the lookup table.

Very simply: in brake mode, the motor brakes the faster you manually spin it.

@MazeOfEncryption

Intentionally stalling motors usually isn’t a good idea

You can stall the motor, just make sure to set a current limit, and set it lower than you think you need. This testing can guide you NEO Brushless Motor - Locked-rotor Testing and remember that this current turns off the moment the match ends.

@Alex_Y

There definitely is some current running at the end of the match. Last season, our climb would drop only when the main breaker was manually powered off.

There would only be current running in the motor if the motor was spinning. Brake mode will help brake the motor if it is moving and prevent it from moving fast since the brake force increases with speed. However if the motor is not moving, the holding force is not based on current in the motor.

[Weldingrod1]

Just confirming some of the items above, based on my testing:

• If you set the SparkMax to “brake” mode, it will provide a large braking drag even when the robot is disabled at the end of the match.
• The brake torque at zero speed is very close to zero. You need a non-zero speed to get significant torque. You need to design/model for a slow lowering after the match using the NEO braking torque.
• When you turn off the breaker the braking torque will go to zero and your robot will drop if its not touching the ground already. Safety tip