Sensing the world around you!

Our robot is equipped with two types of sensors:

1. 1 x InfraRed (IR) distance sensor.
2. 3 x Line following sensors.

We’ll be using just the first today. I haven’t used the line following sensors yet so there are no functions to use them in the DFRduino library. To measure the distance we can use the readDistanceInCentimeters() function, can you guess what it does…?

Ha… here’s an example:

#include <Servo.h>
#include <DFRduino.h>


DFRduino robot;

void setup() {
  Serial.begin(9600);
}

void loop() {
  // Print the distance sensed by the IR sensor
  Serial.print("Distance: ");
  Serial.print(robot.readDistanceInCentimeters());
  Serial.println("cm");
  delay(500);
}

Pick your robot up and point it’s eyes (the IR sensor) at some stuff, see how far, and how close it measure. Notice what happens when you move your hand too close to the sensor, what happens to the distance read?

The IR sensor works by pulsing a infra red light then waiting to see how long it takes to bounce of a surface and be read by the infra red sensor. Can you explain what happens when you cover up the left hand side of the sensor?

Our goal at the end of the workshop is for you to have built an obstacle avoiding robot. Let’s have a look at how we can move depending on the distance read by the sensor:

#include <Servo.h>
#include <DFRduino.h>


DFRduino robot;

void setup() {
}

void loop() {
  // Providing there are no delays in our code, this loop is being run
  // thousands of times a second. Think about how that might affect the
  // code you write

  if (robot.readDistanceInCentimeters() < 30) {
    // Go back for 1 second
    robot.setDirection('b');
    delay(1000);
    // Turn right by approximately 90 degrees
    robot.setDirection('r');
    delay(350);
  } else {
    // Otherwise we'll just go forward 
    robot.setDirection('f');
    delay(100);
  }
}

Surprisingly, at least in my room this is a relatively effective tactic, in fact, it’s even better than some considerably more complex code I wrote! But we’ll look at the complicated code anyway, so you can show me how I was doing it wrong all along! The method of going back for a second, then turning 90 degrees right is called a heuristic. A heuristic is a way of solving a problem, it will not give you the optimal solution (notice how the robot will not see things below it’s line of sight, like a pen, and will crash into them), but it will give you a reasonable solution none the less. I’m sure you can develop a heuristic that is superior to this demo. Go have a go doing that now…

… or if you’re more interested in making your robot’s head move, then move on to the next section: nodding