Code doesnt do what it should do

Using Arduino Programming Questions
1

hi guys,
so i just made obstacle avoiding robot using one ultrasonic sensor and two H bridges(l289n), and two dc motors and the arduino uno.But the program i wrote wouldn't do what i want.I want to turn when it sees a object ten cm way, however, what it does do is that only the right dc motor turn and when there is something infront of it both turn. help please!

#define echoPin 6
#define trigPin 7

int maximumRange = 200;
long duration, distance;
void setup() {

Serial.begin (9600);
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);
pinMode(8, OUTPUT);
pinMode(9, OUTPUT);
pinMode(11, OUTPUT);
pinMode(12, OUTPUT);

}

void loop() {

digitalWrite(trigPin, LOW);
delayMicroseconds(2);

digitalWrite(trigPin, HIGH);
delayMicroseconds(10);

digitalWrite(trigPin, LOW);
duration = pulseIn(echoPin, HIGH);

distance = duration/58.2;

Serial.println(distance);
if(distance>=10)
{
digitalWrite(8, HIGH);
digitalWrite(9, LOW);
digitalWrite(11, LOW);
digitalWrite(12, LOW);
}
else
{
digitalWrite(9, HIGH);
digitalWrite(8, LOW);
digitalWrite(11, HIGH);
digitalWrite(12, LOW);
}
}

this is my code. help !!

2

Without knowing what is connected and how, it is impossible to help. It would help a little if the pins had names instead of numbers.

I notice that pin 12 always gets written LOW and never HIGH. Is this intentional?

I also noticed that the turning (when it happens) will only happen until the distance is greater than or equal to 10 cm. Is that intentional?

Darned if I know why duration and distance are declared as long. duration should be unsigned long. Because distance is declared as long, it can NEVER have a fraction. A distance of 12.9 cm will be shown as 12 cm.

What does your Serial.println(...) tell you? More Serial.println(...) inside the if/else might help as well.

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Good Luck!

3

His code is slightly modified from the Article "Arduino HC-SR04 (Ultrasonic sensor)" at -

http://blog.whatgeek.com.pt/arduino/arduino-hc-sr04-ultrasonic-sensor/

… except, as you noted, he's attempting to to do something on the unnamed pins 8, 9, 11 and 12.

4

Nice find!

I see that the original code had a delay(100) in it. In general, I hate delay(...) and prefer to use millis() and an FSM, but I hope that the sensor can operate without it.

I also see that the original code converted time to distance using a divisor of 58, while the code from the OP uses a divisor of 58.2

In any case, I hope that the OP understands the differences between integer arithmetic and floating point arithmetic, but it doesn't affect the current question.