We will demonstrate an alternative way to make the robot move backward
- 04 Feb 2017
- LEGO MINDSTORMS
- EV3, Classes with students, Motors
- K.Mitov, A.Pavlov, M.Grozev, С.Матинян, D.Staykov, М.Кирилов
The power option
The second option in the Move Steering block regulates the power of the motor. It is measured in percent and could be from -100% to +100%. A hundred percent means to use the maximum power that the motor is able to provide. Zero power means that the motor does not move at all. Negative power means a backward movement.
Default positive direction of a motor
It is important to know what the default turning direction of a motor is when constructing a robot and when planning the usage of a construction.
It is easy to remember - do you see the small appendix to the motor next to the rotating end? Use it as a starting point and make a circle in the air around the motor. This is your positive direction of a large motor.
You can make the robot move backward by using minus rotations. But there are also other ways to make the robot move backward. And this also sets the question what is forward and backward from the motor perspective.
In the EV3 software I'll just zoom this block so that you can see it on the screen
we can change the number of the rotations to minus 1 and this will make the robot move backward and we can also change the power. This option here is the power of the motor. And you can think of the power as a value between 0 which means the robot stops, to 100 which means 100% of the power that the motor could output. So, that's the maximum power of the motor. And it's generally a good idea to use 50 because it is round and it won't drain the battery that fast. But if you set -50 like this you can use the slider for setting or you can use the keyboard -50. This will also make the motors move backward. Download and run.
As you can see the whole robot moves backward. And this is the program with the modification for minus power. The next question is what is the default positive power for rotating of the motors. If you take a motor and this motor could be placed on the robot in many different ways. You can place it like this or like this, or like this, or like this. So, in an unlimited amount of configurations. So, you should be able to directly find the positive direction of the motor just by looking at it. And a simple trick for this is if you take the motor and if you place your finger right here at this side of the motor. You can distinguish this side from the other side because they're different. And then what you try to do is move from this side to the bottom with the finger. And this is the positive way of rotating of the motor. You see that you cannot do it in reverse because you'll have to cross the motor but just place your finger here. And this is the positive side. So, even if the motor is placed like this below, you know that when you're programming to move forward it'll rotate like this - from here to here. And you can then customize, modify your program.
Courses and lessons with this Tutorial
This Tutorial is used in the following courses and lessons