Using the ball angle block

The ‘ball angle’ block (Sensors) is used to get a measurement of angle, between -180 and +180. If the ball is on the left of the robot, the number is negative. If the ball is on the right, the ball is positive.

Rotate to face the ball

Let’s write a program that will rotate the robot to face the ball.

We need an ‘if’ block (Control) - because the robot needs to make a decision.
We also need a ‘comparison’ block (Operators) - because we need to check that the ball distance is greater than 100.

We have three conditions:

If the ball is to the left (ball angle < -20), then the robot should rotate left.
Otherwise, if the ball is to the right (ball angle > 20), then the robot should rotate right.
Otherwise, the robot should stop.

We’re using -20 and 20 degrees because the robot can’t stop instantly.

Let’s start with the if. Here, we drag the if and comparison blocks, and we can also press the + to get the ‘else if’ section.

Now we just need to add the motor movement.

Rotate left means the left wheel needs to go backwards (negative) and the right wheel goes forwards (positive).
The opposite for rotating right.