Learning C++, Arduino, and robotics for beginners - markers at intersection in RCJ Line.

Line robot Overview Simplified assembly Standard assembly 1 Simplified installation Standard installation Standard Assembly 2 Hardware 1 Hardware 2 Skill Basic programming Line following Distance and color sensors Standard assembly 3 Gripper Program flow Advanced concepts For beginners Buy

Line Robot - Basic lessons - Exercises - Marker at intersection

A very useful exercise for RCJ Rescue Line.

Task: if marker detected, turn.

Follow line. If there is a left marker before the intersection, turn left. The same for right. If none, go straight. As usual, start based on line-following code:

void RobotLine::loop() {
	if (line(5))
		go(10, 80);
	else if (line(3))
		go(80, 10);
	else
		go(60, 60);
}

Solution

void RobotLine::loop() {
	if (setup()){
		illumination(0, 1);
		illumination(1, 1);
	}

	if (line(5))
		go(10, 80);
	else if (line(3))
		go(80, 10);
	else
		go(60, 60);

	if (line(0) && line(8)){
		stop();
		delayMs(50);
		if (patternColors(0) == 2)
			turn(-90);
		else if (patternColors(1) == 2){
			turn(90);
		else{
			go(50, 50);
			delayMs(500);
		}
	}
}

First "if" we know already. Illumination is turned on.
Second "if" follows line.
Third "if" contains new elements. First, we stop the robot after both edge transistors found line.
There is a short delay of 50 ms, to allow the color sensors to read colors well.
We check left color sensor, assuming that it is number 0. If not, swap 0 and 1, so in this step sensor 1 should be read. If green is detected, turn 90° left.
The same for the right sensor.
If no sensor found a green marker, continue straight ahead cross the intersection.

You will have to adjust all the parameters. The ones here are just examples.