Servo simulation does not fit 0-180 degrees

[Piero giagnoni]

A simple sketch with a servo, driven by "Servo.h" library, does not fit 0-180 degrees, but about 30-40 instead of 0 and 140-150 instead of 180.
Is there any parameter to trim to adjust right angles?

Ciao,
P.

[Santiago]

Hi Piero.
The only customizable parameter is servo speed.

But it works for me with Arduino Servo library, check Examples/Arduino/servo-sweep , it uses Arduino servo-sweep example and it goes from 0 to 180.

Maybe it would be useful add properties to set pulse timing, but "standard" is 1mS to 2mS as far as i know.

Regards.

[Piero giagnoni]

Hi Santiago.
Thanks for your answer.
I modified servo sweep as follows:

/* Sweep
 by BARRAGAN <http://barraganstudio.com>
 This example code is in the public domain.

 modified 8 Nov 2013
 by Scott Fitzgerald
 http://www.arduino.cc/en/Tutorial/Sweep

 THIS SKETCH HAS BEEN MODIFIED TO SHOW THAT SERVO CONNECTED TO PIN 9
 DOES NOT MOVE FROM 0° POSITION UNTIL ANGLE = 45° AND REACH 180°
 POSITION AT ABOUT 145°
*/

#include <Servo.h>

Servo myservo;  // create servo object to control a servo
// twelve servo objects can be created on most boards

int pos = 0;    // variable to store the servo position

void setup() {
  Serial.begin(9600);               // configure serial port @ 9600 bps
  while (!Serial) { ; }
  myservo.attach(9);  // attaches the servo on pin 9 to the servo object
}

void loop() {
  for (pos = 0; pos <= 180; pos += 1) { // goes from 0 degrees to 180 degrees
    // in steps of 1 degree
    myservo.write(pos);               // tell servo to go to position in variable 'pos'
    Serial.print (pos);               // print position
    Serial.print (" ");
    delay(1000);                       // waits 1s to control the position
  }
  Serial.println ("");
  for (pos = 180; pos >= 0; pos -= 1) { // goes from 180 degrees to 0 degrees
    myservo.write(pos);              // tell servo to go to position in variable 'pos'
    Serial.print (pos);;               // print position
    Serial.print (" ");
    delay(1000);                       // waits 1s to control the position
  }
  Serial.println ("");
}

I verify the sketch and export it in hex form. Then i load firmware in an Arduino Uno with a servo connected at pin 9 as usual.
From the serial monitor I see that servo does not move from o° position until the angle reach about 45° and it reachs 180° position at about 145°.
Maybe there is something wrong in my procedure?

Ciao,
P.

[Santiago]

Yes, you are right.

The example looked like was working, but indeed it wasn't working correctly.
I did a bit of reseach and turned out that Servo.h defaults are 0º= 544 uS, 180º= 2400 uS.
SimulIDE servo is: 0º= 1000 uS, 180º= 2000 uS.

So you should configure it like this ( Servo.h line 37 ):
myservo.attach( 9, 1000, 2000 );

[Piero giagnoni]

I forgot login :-)
"Thank you"

Ciao,
P.

[Santiago]

Thanks to you for reporting.