Servos
Standard servos are used to maintain a certain angle, not meant for full rotation
Uses closed-loop feedback control
Servos are used in applications requiring high torque, accurate rotation within a limited angle such as Robotic arms, valve control, rudder control etc.
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Courtesy : https://howtomechatronics.com/how-it-works/how-servo-motors-work-how-to-control-servos-using-arduino/
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SG90 Micro Servo
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SG90 is a servo motor which operates based on PWM control signals
The servo maintains a certain angle (position) based on the width of the pulse fed in through a signal input
Some technical specifications
Weight: 9 g
Dimension: 22.2 x 11.8 x 31 mm approx.
Stall torque: 1.8 kgf·cm
Operating speed: 0.1 s/60 degree
Operating voltage: 4.8 V (~5V)
PWM frequency = 50Hz
Pin configuration: Yellow / Light Orange / White (Signal), Red / Dark Orange (+5V), Brown/Black (Ground)
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Note : The pulse width in the image does not correspond to SG90, for illustration of the concept only.
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0° – 90° – 180°
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°
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)
write(int) - write a value to the servo to control its shaft accordingly
detach() - stop an attached Servo from pulsing its I/O pin
http://arduino.cc/en/Reference/Servo
| theme | Confluence | #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’t take > 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), angle = 0 to 180 → </span>0: full speed in one direction, 180: full speed in the other, and around 90: no movement</li></ul></li><li>FS90R (also known as SG90 continuous / 360<sup style="letter-spacing: 0.0px;">o</sup>/ full 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> |
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