[ Science Tutorial #1 ] - The World's Smallest Line Follower Robot!

If you are interested in robotics, you certainly hear the robots following the line. As you can do your own design, you can find dozens of projects on the internet. Unfortunately, this robot does not guarantee to be the first in the competition, but it is a great choice for entertainment.

This robot can be the smallest line follower you can see. It's quite easy to do, but you have to be careful. This robot follows the black line on the white background.

The cost is about 10 US$

Components:

Circuit Diagram:

The circuit diagram is quite simple. The area with the red LED is the transmitter sensor. The green framed area is the receiving part. In the purple frame we have our motor drivers and motors.

At the same time, you need to connect the part that writes V +, the positive pole of the battery and the part that writes the ground to the negative pole of the battery. If you want, you can add a small switch to the circuit.

Here is the completed state of the robot:

Finally, the robot codes:
/* Robot version 2 Simpler. ATtiny85, 2 motors, LED, two sensors

Sensor stuff: both white : no prior : random walk : prior : turn in direction of last black


one white    :    ideal situation, move straight
both black    :    no prior    :    random walk

:    prior        :    turn in direction of last white

Sorry if that was hard to understand

*/
#include "Arduino.h"
// the pin definitions


#define lmotorpin 1 // PB1 pin 6


#define rmotorpin 0 // PB0 pin 5


#define lsensepin 3 //ADC3 pin 2


#define rsensepin 1 //ADC1 pin 7


#define ledpin 4 //PB4 pin 3
// numbers for random walk and memory


#define steplength 300


#define smallturn 200


#define bigturn 500


#define memtime 1000
uint8_t lspd, rspd;

uint16_t lsenseval, rsenseval, lwhiteval, rwhiteval;
// functions

void testSensors();

void followEdge();

void moveTime(uint8_t lspeed, uint8_t rspeed, uint16_t time);

void move(uint8_t lspeed, uint8_t rspeed);

void stop();

void senseInit();

void flashLED(uint8_t flashes);
// just for convenience and simplicity (HIGH is off)


#define ledoff PORTB |= 0b00010000


#define ledon PORTB &= 0b11101111
void setup(){

pinMode(lmotorpin, OUTPUT);

pinMode(rmotorpin, OUTPUT);

pinMode(2, INPUT);

pinMode(3, INPUT);

ledoff;

pinMode(ledpin, OUTPUT);

analogWrite(lmotorpin, 0);

analogWrite(rmotorpin, 0);
lspd = 17;

rspd = 17;
// give a 6 second pause to set the thing on a white surface

lsenseval = 6;

while(lsenseval){

lsenseval--;

flashLED(1);

delay(989);

}

flashLED(4);

delay(500);

senseInit();

}
void loop(){

followEdge();

}
void followEdge(){

// now look for edge

uint8_t lastMove = 1; //0=straight, 1=left, 2=right

unsigned long moveEndTime = 0; // the millis at which to stop

unsigned long randomBits = micros();
unsigned long prior = 0; // after edge encounter set to millis + memtime

uint8_t priorDir = 0; //0=left, 1=right, 2=both

uint8_t lastSense = 1; //0=edge, 1=both white, 2=both black

uint8_t i = 0; // iterator
while(true){

// only update about once every 20ms

delay(18);

// read the value 4 times and average

ledon;

delay(2);

lsenseval = 0;

rsenseval = 0;

for(i=0; i<4; i++){

lsenseval += analogRead(lsensepin);

rsenseval += analogRead(rsensepin);

}

// don't divide by 4 because it is used below

ledoff;
if(randomBits == 0){ randomBits = micros(); }
if((lsenseval > lwhiteval3) && (rsenseval > rwhiteval3)){

// both white - if prior turn to black, else random walk

if(lastSense == 2 || millis() < prior){

// turn toward last black or left

if(priorDir == 0){

moveEndTime = millis()+smallturn;

move(0, rspd); // turn left

lastMove = 1;

}else if(priorDir == 1){

moveEndTime = millis()+smallturn;

move(lspd, 0); // turn right

lastMove = 2;

}else{

moveEndTime = millis()+bigturn;

move(0, rspd); // turn left a lot

lastMove = 1;

}

}else{

// random walk

if(millis() < moveEndTime){

// just continue moving

}else{

if(lastMove){

moveEndTime = millis()+steplength;

move(lspd, rspd); // go straight

lastMove = 0;

}else{

if(randomBits & 1){

moveEndTime = millis()+smallturn;

move(0, rspd); // turn left

lastMove = 1;

}else{

moveEndTime = millis()+smallturn;

move(lspd, 0); // turn right

lastMove = 2;

}

randomBits >>= 1;

}

}

}

lastSense = 1;
}else if((lsenseval > lwhiteval3) || (rsenseval > rwhiteval3)){

// one white - this is the edge

// just go straight

moveEndTime = millis()+steplength;

move(lspd, rspd); // go straight

lastMove = 0;

lastSense = 0;

prior = millis()+memtime;

if(lsenseval > lwhiteval*3){

// the right one is black

priorDir = 1;

}else{

// the left one is black

priorDir = 0;

}
}else{

// both black - if prior turn to white, else random walk

if(lastSense == 1 || millis() < prior){

// turn toward last white or left

if(priorDir == 0){

moveEndTime = millis()+smallturn;

move(lspd, 0); // turn right

lastMove = 2;

}else if(priorDir == 1){

moveEndTime = millis()+smallturn;

move(0, rspd); // turn left

lastMove = 1;

}else{

moveEndTime = millis()+bigturn;

move(lspd, 0); // turn right a lot

lastMove = 2;

}

}else{

// random walk

if(millis() < moveEndTime){

// just continue moving

}else{

if(lastMove){

moveEndTime = millis()+steplength;

move(lspd, rspd); // go straight

lastMove = 0;

}else{

if(randomBits & 1){

moveEndTime = millis()+smallturn;

move(0, rspd); // turn left

lastMove = 1;

}else{

moveEndTime = millis()+smallturn;

move(lspd, 0); // turn right

lastMove = 2;

}

randomBits >>= 1;

}

}

}

lastSense = 2;

}

}

}
void moveTime(uint8_t lspeed, uint8_t rspeed, uint16_t time){

analogWrite(lmotorpin, lspeed);

analogWrite(rmotorpin, rspeed);

delay(time);

analogWrite(lmotorpin, 0);

analogWrite(rmotorpin, 0);

}
void move(uint8_t lspeed, uint8_t rspeed){

analogWrite(lmotorpin, lspeed);

analogWrite(rmotorpin, rspeed);

}
void stop(){

analogWrite(lmotorpin, 0);

analogWrite(rmotorpin, 0);

}
// stores the average of 16 readings as a white value

void senseInit(){

lwhiteval = 0;

rwhiteval = 0;

ledon;

delay(2);

for(uint8_t i=0; i<16; i++){

lwhiteval += analogRead(lsensepin);

delay(1);

rwhiteval += analogRead(rsensepin);

delay(9);

}

lwhiteval >>= 4;

rwhiteval >>= 4;

ledoff;

}
void flashLED(uint8_t flashes){

while(flashes){

flashes--;

ledon;

delay(200);

ledoff;

if(flashes){ delay(500); }

}

}