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Rajesh Panicker (Unlicensed)

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544 – 1500 – 2400 us

  0°  –   90° – 180°

Continuous Rotation Servos

  • Continuous rotation servos are normal servos modified to perform open loop speed control (instead of closed loop position control)
  • Rotation speed and direction are controlled through PWM signals (pulse width) for continuous rotation servos, just like how position is controlled for standard servos
  • Effectively, continuous servos are DC motors with integrated motor drivers and reduction gears in a compact, inexpensive package
  • FS90R continuous rotation operating speed: 110RPM (4.8V); 130RPM (6V)
  • Can continuous rotation servos be used to achieve accurate positioning without any additional hardware?

Servo Library

  • This library allows an Arduino board to control servo motors.
  • Standard servos allow the shaft to be positioned at various angles, usually between 0° and 180°. Continuous rotation servos allow the rotation of the shaft to be set to various speeds
  • Any digital pin on UNO can be used, not necessarily those supporting PWM. However, note that using Servo library disables analogWrite() functionality on pins 9 and 10
  • attach(int) - attach a servo to an I/O pin, e.g., servo.attach(pin), servo.attach(pin, min, max)
    • servo: a variable of type Servo, pin: pin number, default values: min = 544 us, max = 2400 us
  • write(int) - write a value to the servo to control its shaft accordingly
  •   Standard servo - set the angle of the shaft
    •   Continuous rotation servo - set the speed of the servo(0: full speed in a direction, 180: full speed in the other, and around 90: no movement)
  • e.g., servo.write(angle),  angle = 0 to 180 
  • detach() - stop an attached Servo from pulsing its I/O pin

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C++Blocks
Code Block
languagecpp
themeConfluence
#include <Servo.h>
 
Servo servo_7;
 
void setup()
{
  servo_7.attach(7);
}
 
void loop()
{
  servo_7.write(45);
  // a variable can also be used instead of the constant (45)
  delay(10); 
}
/* servo connected to pin 7 will maintain an angle of 45 degree */

]] ></ac:plain-text-body></ac:structured-macro></div></td><td><div class="content-wrapper"><p><ac:image ac:thumbnail="true" ac:width="300"><ri:attachment ri:filename="image2020-1-20_17-58-31.png" /></ac:image></p></div></td></tr></tbody></table><p><br /></p><p><br /></p><p><br /></p><p><ac:image ac:height="250"><ri:attachment ri:filename="image2019-12-28_18-47-48.png" /></ac:image></p><p>Caution : Do not overload the servo. The servo and your battery / power source could be damaged if servo is overloaded.</p><p>Do not power the servo from a 9V battery. Most servos can&rsquo;t take &gt; 6V.</p><h3>Continuous Rotation Servos</h3><ul><li>Continuous rotation servos are standard servos modified to perform <em>open loop speed control </em>(instead of <em>closed loop position control</em>)</li><li>Rotation speed and direction are controlled through PWM signals (pulse width) for continuous rotation servos, just like how the position is controlled for standard servos</li><li>Effectively, continuous servos are DC motors with integrated motor drivers and reduction gears in a compact, inexpensive package, rather than true 'servo' motors</li><li>Continuous rotation servos allow the rotation of the shaft to be set to various speeds<ul><li>Electrical connections are identical to that of a standard servo.</li><li>The original servo library can be used; e.g., <em>servo</em><span>.write(angle),&nbsp; angle = 0 to 180&nbsp; &rarr;&nbsp;</span>0: full speed in one direction, 180: full speed in the other, and around 90: no movement</li></ul></li><li>FS90R (SG90 360<sup>o</sup> continuous rotation) operating speed: 110RPM (4.8V); 130RPM (6V)</li></ul><p>Can continuous rotation servos be used to achieve accurate positioning without any additional hardware?</p><h3>Screencast</h3><p><ac:structured-macro ac:name="widget" ac:schema-version="1" ac:macro-id="130a4cd8-f2f3-4273-9603-263a3a40dc78"><ac:parameter ac:name="url"><ri:url ri:value="http://youtube.com/watch?v=ZbdlY9k7Am4" /></ac:parameter></ac:structured-macro></p><p><br /></p>