Let's cover the break at end option and learn why there is no lesson about it to students.
- 17 Apr 2017
Explanation of the setting
The last setting is "Break at end". The default is True and it means that the controller will try its best to keep the motor at place.
The controller is sending current to the motor in order to keep it at place. The controller is applying electrical break to the motor.
Even if we apply enough power to turn the motor by hand, it will return to its initial position.
When set to false, no such behavior is present - the motor can freely rotate and the robot slowly coasts to a resting position.
There is no lesson about this for students
With small, lightweight robots, the effects of "break at end false" are barely visible. So we just share that knowledge with you as a teacher.
When the time is right, you can demonstrate it to your students.
Let us know about that moment in the comments section of either this video in comments of the video that you needed to add "break at end" explanation.
A note for the teacher for the Brake at the end option. And on every motor block that you have in the EV3 software there is an option in the end that's called 'Brake at the end'. It might be true or false. In this teacher note I'd like just to stop briefly on this option and tell you how to use it.
The option is right here at the end of the block. Brake at end. And it could be true of false. And by default it's true. What I'd like to do is to implement a simple program where I'll just move for one rotation and brake at the end then I'll wait for like
3 seconds and then I'll move again
this time with brake set to false. And I hope I could show you the difference of how the robot behaves.
There is a really really small barely visible difference between using the brake at end and brake at end: false. Again, I'll start the program. First, it will brake at the end then I'll just move it and you see that at the end it just continues moving forward. The reason is that when you have brake at the end the motor is exerting some force on the wheel and this force makes the whole wheel stop. So, there is some current flowing in the motor that makes the wheel stop. This is if you have the brake at end: true. If you have the brake at end: false, what happens is that the brick just cuts the power of the motor, stops the current from the motor and the wheel will continue forward with the inertia that the robot has gained. We've thought about different ways to explain this to the students but the whole challenge with this is that at this stage with these small robots it is very difficult to develop a real visible example where students could see this difference and they could see it at a large magnitude. So, not just a few millimeters as a difference. That's why we are honest with you. We don't have an example for brake at the end and for coast for the students and we can't show them the inertia that the robot can have because the robots are quite small. That's we are telling it just to you. Again, I'll develop another program that will help you understand it further how the brake at end and how the brake at end: true and how the brake at end: false work.
Using the previous program for the wait block I'll just set a value of 5 or even 10.
And I'll download and run the program.
The robot is currently waiting and if I try to move the wheel with a hand you can see that it's difficult to move it with a hand. Because there is some force from the motor to the wheel that prevents the whole wheel from moving. Again. If the option is brake at end: true, the motor will try to brake and it will try not to move forward. You can't move forward. If you are using the brake at end: false, then at the end of the block you'll be able to just freely move the wheel like this.
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