Program the Crab Bot

Step 1

Briefing videos

These videos go over how to program your Crab Bot. Don’t forget to go through the rest of the lesson!

Step 2

What does it do?

Just like the nocturnal crabs you might have seen at the beach, the Crab Bot is programmed to avoid light! If any of its sensors detect light, the Crab Bot will move away from the light source.

This is the Crab Bot’s pseudocode:

Check the top left, center, and right IR sensors
If the light is shining from the left, move to the right.
Else, if the light is shining from the right, move to the left.
Else, if the light is shining from the center, move back and forth.
Else, stop.

Step 3

Set up the motors

The first thing you need to do is include the Smart Inventor library at the top of your code. Next, in void setup(), include your motors.

#include <SmartInventor.h>

void setup() {
    SmartInventor.DCMotorUse();
}

Step 4

Base level of the sensors

Each sensor corresponds to a pin on the Smart Inventor Board, and those need to be read for anything to happen with your Crab Bot! Underneath the Smart Inventor library and before void setup(), set variables for each sensors’ base values. Use those variables in void setup() so the sensors will know if they’re seeing a value that isn’t normal. Add a buffer of 50 to leave some room for error.

#include <SmartInventor.h>

int leftBaseLevel;
int centerBaseLevel;
int rightBaseLevel;
 
void setup() {
    SmartInventor.DCMotorUse();
    
    leftBaseLevel = analogRead(19) - 50;
    centerBaseLevel = analogRead(20) - 50;
    rightBaseLevel = analogRead(21) - 50;
}

Step 5

Read the sensors

In void loop(), set variables for each sensor so that they get and save the value that is being read from their corresponding pin.

#include <SmartInventor.h> 
int leftBaseLevel;
int centerBaseLevel;
int rightBaseLevel;
 
void setup() {
    SmartInventor.DCMotorUse();

    leftBaseLevel = analogRead(19) - 50;
    centerBaseLevel = analogRead(20) - 50;
    rightBaseLevel = analogRead(21) - 50;
}
 
void loop() {
    int leftSensor = analogRead(19);
    int centerSensor = analogRead(20);
    int rightSensor = analogRead(21);
}

Step 6

Left sensor

Next up: the main section of the code! You’ll need to use an if statement to check if the left sensor has detected any light. This would bring the value of the left sensor lower than the value of its base level. If the left sensor detects light, the left LEDs will light up and the Crab Bot will move to the right.

void loop() {
    int leftSensor = analogRead(19);
    int centerSensor = analogRead(20);
    int rightSensor = analogRead(21);

    if(leftSensor < leftBaseLevel)
    {
        digitalWrite(11, HIGH); // light the left LEDs
        digitalWrite(15, HIGH);
        digitalWrite(12, LOW);
        digitalWrite(17, LOW);
        digitalWrite(13, LOW);
        digitalWrite(18, LOW);

    SmartInventor.DCMotor(M1, CCW, 50); // move right
    }
}

Step 7

Right sensor

You’re going to do the same thing for the right sensor, but you’ll need to use an else if statement instead of an if statement. This means that your code will only check it if the last if statement about the left sensor was false.

void loop() {    
    int leftSensor = analogRead(19);    
    int centerSensor = analogRead(20);    
    int rightSensor = analogRead(21);    

    if(leftSensor < leftBaseLevel)    {        
        digitalWrite(11, HIGH); // light the left LEDs        
        digitalWrite(15, HIGH);        
        digitalWrite(12, LOW);        
        digitalWrite(17, LOW);        
        digitalWrite(13, LOW);        
        digitalWrite(18, LOW);    

        SmartInventor.DCMotor(M1, CCW, 50); // move right 
    }   
    else if(rightSensor < rightBaseLevel)
    {
        digitalWrite(11, LOW); // light the right LEDs
        digitalWrite(15, LOW);
        digitalWrite(12, LOW);
        digitalWrite(17, LOW);
        digitalWrite(13, HIGH);
        digitalWrite(18, HIGH);

    SmartInventor.DCMotor(M1, CW, 50); // move right
    }
}

Step 8

Center sensor

Add another else if statement so that when the center sensor detects light, the Crab Bot will move back and forth.

void loop() {    
    int leftSensor = analogRead(19);    
    int centerSensor = analogRead(20);    
    int rightSensor = analogRead(21);    

    if(leftSensor < leftBaseLevel)    
    {        
        digitalWrite(11, HIGH); // light the left LEDs        
        digitalWrite(15, HIGH);        
        digitalWrite(12, LOW);        
        digitalWrite(17, LOW);        
        digitalWrite(13, LOW);        
        digitalWrite(18, LOW);    

        SmartInventor.DCMotor(M1, CCW, 50); // move right    
    }    
    else if(rightSensor < rightBaseLevel)    
    {        
        digitalWrite(11, LOW); // light the right LEDs        
        digitalWrite(15, LOW);        
        digitalWrite(12, LOW);        
        digitalWrite(17, LOW);        
        digitalWrite(13, HIGH);        
        digitalWrite(18, HIGH);        
    
        SmartInventor.DCMotor(M1, CW, 50); // move right    
    }
    else if(centerSensor < centerBaseLevel)
    {
        digitalWrite(11, LOW); // light the right LEDs
        digitalWrite(15, LOW);
        digitalWrite(12, LOW);
        digitalWrite(17, LOW);
        digitalWrite(13, HIGH);
        digitalWrite(18, HIGH);

        SmartInventor.DCMotor(M1, CW, 50); // move right
        delay(100);
        SmartInventor.DCMotor(M1, CCW, 50); // move left
        delay(100);

        digitalWrite(11, HIGH); // light the left LEDs
        digitalWrite(15, HIGH);
        digitalWrite(12, LOW);
        digitalWrite(17, LOW);
        digitalWrite(13, LOW);
        digitalWrite(18, LOW);

        SmartInventor.DCMotor(M1, CW, 50); // move right
        delay(100);
        SmartInventor.DCMotor(M1, CCW, 50); // move left
        delay(100);    
    }
}

Step 9

Stop the motors

Finally, add an else statement so the Crab Bot stops if the sensors don’t detect any light.

void loop() {
    int leftSensor = analogRead(19);
    int centerSensor = analogRead(20);
    int rightSensor = analogRead(21);

    if(leftSensor < leftBaseLevel)
    {
        digitalWrite(11, HIGH); // light the left LEDs
        digitalWrite(15, HIGH);
        digitalWrite(12, LOW);
        digitalWrite(17, LOW);
        digitalWrite(13, LOW);
        digitalWrite(18, LOW);

    SmartInventor.DCMotor(M1, CCW, 50); // move right
    }    

    else if(rightSensor < rightBaseLevel)
    {
        digitalWrite(11, LOW); // light the right LEDs
        digitalWrite(15, LOW);
        digitalWrite(12, LOW);
        digitalWrite(17, LOW);
        digitalWrite(13, HIGH);
        digitalWrite(18, HIGH);

        SmartInventor.DCMotor(M1, CW, 50); // move right
    }

    else if(centerSensor < centerBaseLevel)
    {
        digitalWrite(11, LOW); // light the right LEDs
        digitalWrite(15, LOW);
        digitalWrite(12, LOW);
        digitalWrite(17, LOW);
        digitalWrite(13, HIGH);
        digitalWrite(18, HIGH);

        SmartInventor.DCMotor(M1, CW, 50); // move right
        delay(100);
        SmartInventor.DCMotor(M1, CCW, 50); // move left
        delay(100);

        digitalWrite(11, HIGH); // light the left LEDs
        digitalWrite(15, HIGH);
        digitalWrite(12, LOW);
        digitalWrite(17, LOW);
        digitalWrite(13, LOW);
        digitalWrite(18, LOW);

        SmartInventor.DCMotor(M1, CW, 50); // move right
        delay(100);
        SmartInventor.DCMotor(M1, CCW, 50); // move left
        delay(100);
    }
    else
    {
        digitalWrite(11, LOW); // light the middle LEDs
        digitalWrite(15, LOW);
        digitalWrite(12, HIGH);
        digitalWrite(17, HIGH);
        digitalWrite(13, LOW);
        digitalWrite(18, LOW);
    
        SmartInventor.DCMotor(M1, LOOSE, 0); // stop
    }
}

Step 10

Final code

Your final code should look something like this:

#include <SmartInventor.h>

int leftBaseLevel;
int centerBaseLevel;
int rightBaseLevel; 

void setup() {    
    SmartInventor.DCMotorUse();        

    leftBaseLevel = analogRead(19) - 50;    
    centerBaseLevel = analogRead(20) - 50;    
    rightBaseLevel = analogRead(21) - 50;
}

void loop() {    
    int leftSensor = analogRead(19);    
    int centerSensor = analogRead(20);    
    int rightSensor = analogRead(21);    

    if(leftSensor < leftBaseLevel)    
    {        
        digitalWrite(11, HIGH); // light the left LEDs        
        digitalWrite(15, HIGH);        
        digitalWrite(12, LOW);        
        digitalWrite(17, LOW);        
        digitalWrite(13, LOW);        
        digitalWrite(18, LOW);        

        SmartInventor.DCMotor(M1, CCW, 50); // move right    
    }        
    else if(rightSensor < rightBaseLevel)    
    {        
        digitalWrite(11, LOW); // light the right LEDs        
        digitalWrite(15, LOW);        
        digitalWrite(12, LOW);        
        digitalWrite(17, LOW);        
        digitalWrite(13, HIGH);        
        digitalWrite(18, HIGH);        

        SmartInventor.DCMotor(M1, CW, 50); // move right    
    }    
    else if(centerSensor < centerBaseLevel)    
    {           
        digitalWrite(11, LOW); // light the right LEDs        
        digitalWrite(15, LOW);           
        digitalWrite(12, LOW);        
        digitalWrite(17, LOW);        
        digitalWrite(13, HIGH);        
        digitalWrite(18, HIGH);        

        SmartInventor.DCMotor(M1, CW, 50); // move right        
        delay(100);        
        SmartInventor.DCMotor(M1, CCW, 50); // move left        
        delay(100);        

        digitalWrite(11, HIGH); // light the left LEDs        
        digitalWrite(15, HIGH);        
        digitalWrite(12, LOW);        
        digitalWrite(17, LOW);        
        digitalWrite(13, LOW);        
        digitalWrite(18, LOW);        

        SmartInventor.DCMotor(M1, CW, 50); // move right        
        delay(100);            
        SmartInventor.DCMotor(M1, CCW, 50); // move left        
        delay(100);    
    }    
    else    
    {        
        digitalWrite(11, LOW); // light the middle LEDs
        digitalWrite(15, LOW);
        digitalWrite(12, HIGH);
        digitalWrite(17, HIGH);
        digitalWrite(13, LOW);
        digitalWrite(18, LOW);            

        SmartInventor.DCMotor(M1, LOOSE, 0); // stop    
    }
}

This lesson uses:

Grade level:

Approx. time required:

CSTA

NGSS

CCSS