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[on:]

hello everyone,
I am trying to make a line following robot. I use continuous rotation servos, the problem is that the servos won't stop turning once started.
This is because the code doesn't check the sensor output after the first time.

Thanks a lot!

I used this sensor: http://dx.com/p/arduino-line-hunting-sensor-module-118057
and these servos: http://www.ebay.com/itm/clear-up-Spring-RC-SM-S4306R-360-Degree-Continuous-Rotation-Robot-Servo-SMS4306R-/350696583715?pt=US_Character_Radio_Control_Toys&hash=item51a7253223

Code:

#include <Servo.h>
  int sensorpin = 3;
  int speed0 = 91;
  int speed1 = 61;
  int speed2 = 111;  
  int speed3 = 71;
 
Servo leftwheel;
Servo rightwheel;

void setup()
{
leftwheel.attach(8);
rightwheel.attach(9);
}

void loop()
{
  while(sensorpin == HIGH){
  leftwheel.write(speed1);
  rightwheel.write(speed2);
}

  while(sensorpin != HIGH){
  leftwheel.write(speed3);
  rightwheel.write(speed3);
  }
}

I already tried: continue, goto, return, break, while, if, if else, swith case

[Reply #1 on:]

The usual advice is to use the writeMicroseconds method on the Servo objects to find the stop point, but it may drift with load or battery state.

[Reply #2 on:]

How would you write that in the code?

And thank you!

[Reply #3 on:]

Where did you get these numbers ?

Code:

  int speed0 = 91;
  int speed1 = 61;
  int speed2 = 111; 
  int speed3 = 71;
 

Your comments say that the servos will be stopped with the speed value set to speed1, speed2 or speed3.  It is very unlikely that they are all true bearing in mind the range of values this implies (61, 111 and 71)

[Reply #4 on:]

http://arduino.cc/en/Reference/ServoWriteMicroseconds

[Reply #5 on:]

Code:

  int sensorpin = 3;
...
  while(sensorpin == HIGH){

sensorpin is the pin number, to get its current value you need to use something like
if ( digitalRead(sensorpin)==HIGH)

http://arduino.cc/en/Reference/digitalRead
http://arduino.cc/en/Tutorial/Button

Cheers,
John

[Reply #6 on:]

 I got these numbers just by trying without the sensor, my mistake(I copy/pasted that and forgot to delete the text)

[Reply #7 on:]

Thanks AWOL and johncc

I got it to work

Code:

#include <Servo.h>
  int sensorpin = 3;
  int speed0 = 91;
  int speed1 = 61;
  int speed2 = 111; 
  int speed3 = 71;
 
Servo leftwheel;
Servo rightwheel;

void setup()
{
    pinMode(3,INPUT);
    leftwheel.attach(8);
rightwheel.attach(9);
leftwheel.writeMicroseconds(50);
rightwheel.writeMicroseconds(50);
}

void loop()
{
  if ( digitalRead(sensorpin)!=HIGH){
  leftwheel.write(speed1);
  rightwheel.write(speed2);
 
 
}

  else if ( digitalRead(sensorpin)==HIGH){
  leftwheel.write(speed3);
  rightwheel.write(speed3);
 
  }
}

[Reply #8 on:]

That's great!  Fiddle and learn!

[Reply #9 on:]

Considering that digitalRead() can only return HIGH or LOW, if the value is not HIGH, is there any possible way that the value can be anything other than LOW?

If you come to the correct conclusion that there is not, then explain why you need to test for HIGH.

The if/else if(/else) construct is used to test multiple conditions when there could be more than two. The if/else construct is preferred when there are only 2 possible conditions (as in the case of digitalRead).

[Reply #10 on:]

hadn't thought about that