My Sixth Project: Smart Tank Chassis With Ultrasonic Sensor

In the previous projects I tried different ways to control the smart tank manually. But how about if the tank makes its own decision and control itself? It should be quite interesting. Ultrasonic sensor can help to do so by sending sound wave in front of the sensor. It receives the wave once the wave meets obstacles and reflects to the sensor so as to determine the distance. So I've bought an ultrasonic sensor and start another project.

HC-SR04 Ultrasonic Sensor with Servo and Rack

Smart Tank

Arduino Uno

Small Breadboard

Battery Box AA x 4

Battery Box 9-volt

I just add one more sensor on top of the third project actually.

I leave the servo unwired at this stage. For the sensor the wiring is as follow:

GND > Arduino GND

Echo > Pin 6

Trig > Pin 5

VCC > 5V

For the smart tank I listed the wiring again below. That is the same as the previous projects:

IB on the right side > pin 8

IA on the left side > pin 9

IA on the right side > pin 10

IB on the left side > pin 11

VCC on both side > + of the battery box

GND on both side > - of the battery box and Arduino GND

I wanna test if the sensor works, so I google it and find anything can help. Google is our friend and this link can be one of the reference:

http://arthursrobotorial.blogspot.hk/2012_12_01_archive.html

#define trigPin 5
#define echoPin 6
void setup() 
{
  Serial.begin (9600);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
}
int CheckDistance()
{
  long duration, distance;
  digitalWrite(trigPin, LOW);  // Added this line
  delayMicroseconds(2); // Added this line
  digitalWrite(trigPin, HIGH);
//  delayMicroseconds(1000); - Removed this line
  delayMicroseconds(10); // Added this line
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  distance = (duration/2) / 29.1;
  return distance;
}
void loop() 
{
   int testDistance = CheckDistance(); /// get object distance using ping
   /// if object is more than 50 cm away it is out of range
    if (testDistance >= 50 || testDistance <= 0) /// if object is more than 50 cm away it is out of range
    {
    Serial.println("Out of range");
    }
    else /// object is closer than 50cm, print distance
    {
    Serial.print(testDistance);
    Serial.println(" cm");
  delay(500); ///wait half a sec before next ping
}

In Arduino IDE, select Tools > Serial Monitor. It shows the distance if succeeds.

Then I combine the code in the first stage with the code in the third project and revise a little bit: If the distance between the sensor and the object is more than 30cm, it goes forward. Otherwise it turns right.

#define trigPin 5
#define echoPin 6
int motorPin = 8; //right side to IB - forwward
int motorPin2 = 9; //left side to IA - forwward
int motorPin3 = 10; //right side to IA - backward
int motorPin4 = 11; //left side to IB - backward
void setup() 
{
  Serial.begin (9600);
   pinMode(motorPin, OUTPUT);
   pinMode(motorPin2, OUTPUT);
   pinMode(motorPin3, OUTPUT);
   pinMode(motorPin4, OUTPUT);
   pinMode(trigPin, OUTPUT);
   pinMode(echoPin, INPUT);
}
void
forward(){
   digitalWrite(motorPin, HIGH);
   digitalWrite(motorPin2, HIGH);
   digitalWrite(motorPin3, LOW);
   digitalWrite(motorPin4, LOW);
 }
 void backward() {
   digitalWrite(motorPin, LOW);
   digitalWrite(motorPin2, LOW);
   digitalWrite(motorPin3, HIGH);
   digitalWrite(motorPin4, HIGH);
 } 
 void turnLeft() {
   digitalWrite(motorPin, HIGH);
   digitalWrite(motorPin2, LOW);
   digitalWrite(motorPin3, LOW);
   digitalWrite(motorPin4, HIGH);
 } 
 void turnRight() {
   digitalWrite(motorPin, LOW);
   digitalWrite(motorPin2, HIGH);
   digitalWrite(motorPin3, HIGH);
   digitalWrite(motorPin4, LOW);
 }
int CheckDistance()
{
  long duration, distance;
  digitalWrite(trigPin, LOW);  // Added this line
  delayMicroseconds(2); // Added this line
  digitalWrite(trigPin, HIGH);
//  delayMicroseconds(1000); - Removed this line
  delayMicroseconds(10); // Added this line
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  distance = (duration/2) / 29.1;
  return distance;
}
void loop() 
{
   int testDistance = CheckDistance(); /// get object distance using ping
    if (testDistance >= 30 || testDistance
<= 0) /// if object is more than 30 cm away it goes forward
    {
    forward();
    }
    else /// object is closer than 30cm, turns right
    {
    turnRight();
    }
  delay(500); ///wait half a sec before next ping
}

The result seems ok.

The servo included with this sensor can move 180 degree. Because I want the smart tank to avoid anything in the front, it would be too sensitive if it avoids obstacles in 180 degree. I want the servo moves in certain degree in front of the tank, not in the full degree of the servo. The servo has to be calibrate and make sure 90 degree is pointing to the front. You can turn the servo anticlockwise until it gets stuck. Then plug the sensor out and on again pointing at 9. After that turn the servo 90 degree clockwise until it points to the front.

For the wiring of the servo, brown one to Arduino GND, red to 5V and yellow to pin 7.

There is an example in Arduino library for our reference: Examples > Servo > sweep. As I said before, I don't want the servo keeps turning 180 degree, so I adjust the angle so as to fit the need. Here I use 0 to 100 degree. I have also adjust the servo to ensure it moves pointing to the front. I think the response of the servo is quite slow if keep using the example, so I delete the second part of the loop.

#include <Servo.h>
#define trigPin 5
#define echoPin 6
Servo myservo;  // create servo object to control a servo 
                // a maximum of eight servo objects can be created 
int pos = 0;    // variable to store the servo position 
int servoDirection = 100;
int servoDelay = 20;
int motorPin = 8; //right side to IB - forward
int motorPin2 = 9; //left side to IA - forward
int motorPin3 = 10; //right side to IA - backward
int motorPin4 = 11; //left side to IB - backward
void setup() 
{
  Serial.begin (9600);
   myservo.attach(7);  // attaches the servo on pin 7 to the servo object 
   myservo.write(pos);
   pinMode(motorPin, OUTPUT);
   pinMode(motorPin2, OUTPUT);
   pinMode(motorPin3, OUTPUT);
   pinMode(motorPin4, OUTPUT);
   pinMode(trigPin, OUTPUT);
   pinMode(echoPin, INPUT);
}
void forward(){
   digitalWrite(motorPin, HIGH);
   digitalWrite(motorPin2, HIGH);
   digitalWrite(motorPin3, LOW);
   digitalWrite(motorPin4, LOW);
 }
 void backward() {
   digitalWrite(motorPin, LOW);
   digitalWrite(motorPin2, LOW);
   digitalWrite(motorPin3, HIGH);
   digitalWrite(motorPin4, HIGH);
 } 
 void turnLeft() {
   digitalWrite(motorPin, HIGH);
   digitalWrite(motorPin2, LOW);
   digitalWrite(motorPin3, LOW);
   digitalWrite(motorPin4, HIGH);
 } 
 void turnRight() {
   digitalWrite(motorPin, LOW);
   digitalWrite(motorPin2, HIGH);
   digitalWrite(motorPin3, HIGH);
   digitalWrite(motorPin4, LOW);
 }
int CheckDistance()
{
  long duration, distance;
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2); 
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10); 
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  distance = (duration/2) / 29.1;
  return distance;
}
void sweepServo()
{
        for(pos = 0; pos < 100; pos += 1)  // goes from 0 degrees to 100 degrees
        {                                  // in steps of 1 degree 
        myservo.write(pos);              // tell servo to go to position in variable   'pos' 
        delay(10);
        }
}
void loop() 
{
  sweepServo();
   int testDistance = CheckDistance(); /// get object distance using ping
   /// if object is more than 30 cm away it is out of range
    if (testDistance >= 30 || testDistance <= 0) /// if object is more than 30 cm away it is out of range and goes forward
    {
    Serial.println("out of range");
    forward();
    }
    else /// object is closer than 30cm, turn right and print distance
    {
    turnRight();
    Serial.print(testDistance);
    Serial.println("cm");
    }
}

One problem arises: it has to run the loop completely before another loop starts. The sensor detect one time only when the servo move from 0 degree to 100 degree. I want the sensor detecting the distance without waiting the servo moves. In other word, I want the sensor detects several times in one servo rotation. How to do that?

Google tells me I can use the function "millis" or "interrupt" to do so, but I still don't understand after reading several articles...... : ( The most common example is called Blink Without Delay. I still don't know how to use it in my situation...... So.... I try another way that is very cumbersome and the code is as follow:

#include  <Servo.h>
#define trigPin 5
#define echoPin 6
Servo myservo;  // create servo object to control a servo 
int pos = 0;    // variable to store the servo position 
int servoDirection = 100;
int servoDelay = 20;
int motorPin = 8; //right side to IB - forward
int motorPin2 = 9; //left side to IA - forward
int motorPin3 = 10; //right side to IA - backward
int motorPin4 = 11; //left side to IB - backward
void setup() 
{
Serial.begin (9600);  
myservo.attach(7);  // attaches the servo on pin 7 to the servo object 
myservo.write(pos);
pinMode(motorPin, OUTPUT);
pinMode(motorPin2, OUTPUT);
pinMode(motorPin3, OUTPUT);
pinMode(motorPin4, OUTPUT);
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);
}
void forward(){ 
digitalWrite(motorPin, HIGH);
digitalWrite(motorPin2, HIGH);
digitalWrite(motorPin3, LOW);  
digitalWrite(motorPin4, LOW);
 }
void backward() {  
digitalWrite(motorPin, LOW);  
digitalWrite(motorPin2, LOW);  
digitalWrite(motorPin3, HIGH);  
digitalWrite(motorPin4, HIGH); 
} 
void turnLeft() {  
digitalWrite(motorPin, HIGH);  
digitalWrite(motorPin2, LOW);  
digitalWrite(motorPin3, LOW);  
digitalWrite(motorPin4, HIGH);
 } 
void turnRight() {  
digitalWrite(motorPin, LOW);  
digitalWrite(motorPin2, HIGH);
digitalWrite(motorPin3, HIGH);  
digitalWrite(motorPin4, LOW);
 }
int CheckDistance()
{ 
long duration, distance; 
digitalWrite(trigPin, LOW);  // Added this line 
delayMicroseconds(2); // Added this line 
digitalWrite(trigPin, HIGH); 
delayMicroseconds(10); // Added this line 
digitalWrite(trigPin, LOW); 
duration = pulseIn(echoPin, HIGH); 
distance = (duration/2) / 29.1; 
return distance;
}
void sweepServo1(){   
for(pos = 10; pos < 40; pos += 1)  // goes from 0 degrees to 100 degrees 
  {                                  // in steps of 1 degree    
myservo.write(pos);       // tell servo to go to position in variable 'pos'    
delay(10);
}  
int testDistance = CheckDistance(); /// get object distance using ping     
/// if object is more than 30 cm away it is out of range   
if (testDistance >= 30 || testDistance <= 0) /// if object is more than 30 cm away it is out of range
    {   
forward();
    }   
else /// object is closer than 30cm, prit distance
    {
    turnRight();   
    Serial.print(testDistance);   
    Serial.println("cm");
    }
}
void sweepServo2(){   
for(pos = 40; pos < 80; pos += 1)  // goes from 0 degrees to 100 degrees  
{                                 // in steps of 1 degree    
myservo.write(pos);             // tell servo to go to position in variable 'pos'    
delay(10);
} 
int testDistance = CheckDistance(); // get object distance using ping     
if (testDistance >= 30 || testDistance <= 0) // if object is more than 30 cm away it is out of range
    {   
forward();
    }   
else // object is closer than 30cm, prit distance
    {   
turnRight();   
Serial.print(testDistance);   
Serial.println("cm");
    }
}
void sweepServo3(){   
for(pos = 80; pos < 120; pos += 1)  // goes from 0 degrees to 100 degrees  
{                                 // in steps of 1 degree    
myservo.write(pos);             // tell servo to go to position in variable 'pos'    
delay(10);
}  
int testDistance = CheckDistance(); // get object distance using ping
if (testDistance >= 30 || testDistance <= 0) // if object is more than 30 cm away it is out of range
    {
    forward();
    }   
else // object is closer than 30cm, prit distance
    {   
turnRight();   
Serial.print(testDistance);   
Serial.println("cm");
    }
}
void loop() 
{ 
sweepServo1(); 
sweepServo2(); 
sweepServo3();
}

I separate the servo sweep into three parts (sweepServo1 to 3). Each part controls different angles and all parts are looped together in orders.

It works! After trial and error, I think 30 cm is appropriate and the tank has enough time to respond. But the final code can be made much more simple. Please tell me how to revise if anyone knows how to add the function "millis" or "interrupt". Next time I will try a very different stuff. Thanks for your watching. See you!