Object Avoiding Car

Using Arduino Programming Questions
1

I'm trying to create a car that can detect an object in front of it and move around it. I've been taking this project in steps, and as of now, I'm just trying to make the car back up when it detects an object. In this project, I am using an Arduino Uno, an HC-SR04 Ping Sensor, an L298 Dual H-Bridge, and 2 DC Motors. When I upload the code onto the Arduino, the car moves forward for a few seconds, then moves backward without stopping, without any object ever going in front of it. When i pick it up and move my hand in front of the sensor, it continues moving backward, so I believe it's not the polarity of the motors. I also put the sensor in a test circuit and it is still detecting objects. I'm also convinced it's not the wiring because when I isolate either part (the motors or the sensor), it works fine. This is the code I created by fusing my ping sensor code with my motor code:

#define trigPin 13
#define echoPin 12

void setup() {
Serial.begin (9600);//ping
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);

pinMode(3, OUTPUT);
pinMode(4, OUTPUT);
pinMode(2, OUTPUT);

pinMode(5, OUTPUT);
pinMode(6, OUTPUT);
pinMode(7, OUTPUT);
}

void loop() {
long duration, distance;
digitalWrite(echoPin, LOW);
delayMicroseconds(2);
digitalWrite(trigPin, HIGH);

delayMicroseconds(10);
duration = pulseIn(echoPin, HIGH);
distance = (duration/2) / 29.1;
if (distance < 4) {
digitalWrite(2, HIGH);
digitalWrite(4, LOW);
analogWrite(3, 160);

digitalWrite(7, HIGH);
digitalWrite(6, LOW);
analogWrite(5, 160);
}
else {
digitalWrite(2, LOW);
digitalWrite(4, HIGH);
analogWrite(3, 160);

digitalWrite(7, LOW);
digitalWrite(6, HIGH);
analogWrite(5, 160);
}
if (distance >= 200 || distance <= 0){
Serial.println("Out of range");
}
else {
Serial.print(distance);
Serial.println(" cm");
}
delay(500);
}

I believe the problem is in the code, but I am not confident in my Arduino coding abilities to see what it is (I've been staring at this code and making small alterations for about a week). If someone could help me with this, that would be great! Thanks!

2 
 if (distance < 4) {

Four cm is less than two inches. Are you sure your car can reverse in time, especially since you only check the distance twice per second?

Note that you check for <4 before you check for =0 (out of range). That means your car is going to switch to reverse whenever there is nothing in range.

3

Okay so i changed the distance to 10cm and i switched the order that the sensor checks in, and i got the same result. no matter what was in front of the sensor, it moved backwards. I may have interpreted what you said wrong? Thanks for the help!

4

Your code would be much easier to understand if you gave names to the motor control pins.
What are pins 2 to 7 connected to on the H-bridge ?

5

Does the car drive forward if you load this sketch?

void setup() {
   pinMode(2, OUTPUT);
   pinMode(3, OUTPUT);
   pinMode(4, OUTPUT);
   pinMode(5, OUTPUT);
   pinMode(6, OUTPUT);
   pinMode(7, OUTPUT);


  digitalWrite(2, LOW);
  digitalWrite(4, HIGH);
  analogWrite(3, 160);

  digitalWrite(7, LOW);
  digitalWrite(6, HIGH);
  analogWrite(5, 160);
}

void loop() {}

Does the car drive backward if you load this sketch?

void setup() {
   pinMode(2, OUTPUT);
   pinMode(3, OUTPUT);
   pinMode(4, OUTPUT);
   pinMode(5, OUTPUT);
   pinMode(6, OUTPUT);
   pinMode(7, OUTPUT);

  digitalWrite(2, HIGH);
  digitalWrite(4, LOW);
  analogWrite(3, 160);

  digitalWrite(7, HIGH);
  digitalWrite(6, LOW);
  analogWrite(5, 160);
}

void loop() {}
6

UKHeliBob, The H-bridge i am using requires three pins per motor to use. 3 and 5 determine speed, then 2 and 3 determine direction for one motor, and 6 and 7 determine direction for the next motor.
Johnwasser, Yes to both questions, the first sketch makes it go forward and the second makes it go backwards.

7

The H-bridge i am using requires three pins per motor to use.

However many pins it uses and whatever they are used for your code would be much easier to understand if you gave names to them

8

UKHeliBob:
However many pins it uses and whatever they are used for your code would be much easier to understand if you gave names to them

It would also be helpful if your description of which pins are used for what made any sense. How can pin 3 determine speed and direction for one motor?

9

Is this good? i defined each pin, so hopefully it looks more understandable...
This H-bridge uses 3 pins per motor. 1 PWM pin controls the speed. The other 2 digital pins alternate HIGH an LOW (if one is high, the other is low and vice versa). Depending on which pin is HIGH changes the direction of the motor. I'm not great at explaining, but hopefully I said that right.

commented_Ping_motor.ino (1.18 KB)