10. Line Follower

It's time to start moving on to larger and more challenging projects. We're going to use the Light Sensor we used earlier to control the motors and get your robot to follow a line on the ground. From now on, I'm only going to give you the new parts of the code. You will have to use previous knowledge to fill in the missing pieces.

The basic idea behind the Line Follower is that you will place the robot on the line so the light sensor is next to the edge of the line. When you turn it on, it will drive one motor forward until it sees the line. Then it will turn that motor off and the other one on until it no longer sees the line. This process will repeat with the robot following the edge of the line. It's important to remember that no motor should ever go in reverse on this program.

Start by running your Light Sensor code with the sensor pointed at the ground next to the line. Write down the value you get. Let's say it's 200. Then place the sensor above the black line and record that value. Let's assume it's 300. Now we need to determine the threshold value (we'll use this later) by finding a middle number between these two. For our example, we'll use a threshold value of 250, but you'll need to test your robot because you will have a different threshold value.

For this program, the new blocks we need are if/else from Control and "<" from Test. The if/else tells the Arduino to test whether the light sensor gets a value higher or lower than the threshold value we got before. If the light value is lower then, we know we're on the line. Turn the right motor on and set the left motor to 90 (or whatever your stopped value is). Else, we know we're off the line and need to switch motor is on. Here we'll drive the left motor forward and stop the right motor. Below is an example of the code, but you'll need to replace the bright green code in the then and else sections with the correct code for the motors

Here's the code with the same parts that you'll need to complete. You can see how the if/else statement is done in code.

void setup()

{

}

void loop()

{

 if ( ( analogRead(0) ) < ( 250 ) )

 {

   //Right motor forward

   //Left motor stopped

 }

 else

 {

   //Right motor stopped

   //Left motor forward

 }

}

Hint: You'll need to bring in the code from Drive and combine it with the code above.