Servo Library

Hardware Requirements

PWMServo can control up to 3 individual motors, using specific pins.

Both Servo and PWMServo use hardware timers, causing specific PWM pins to become unusable with analogWrite().

PWMServo is much more tolerant of interrupt latency that Servo. Libraries which disable interrupts, like NewSoftSerial, are incompatible with Servo, but can be used with PWMServo.

Most Servo motors require +5 volt power, at considerable current. Usually the black wire connects to ground and the red wire to +5 volts. Please check the specifications for your motors to be sure.

A few very small motors, like the ones above, can run from USB power. Direct connection to a PC or Mac or powered USB hub can provide 500 mA of current. Please be careful not to connect too many motors which could have a combined usage higher than 500 mA.

Larger motors will need a separate power supply. Usually the motor power supply ground much connect to the Teensy/USB ground pin, but the +5 volt lines remain separate, so the motors get their power from the external power supply, not USB.

Basic Usage

Create an instance of the Servo library. You will need to create an instance for each motor, giving each motor a unique name of your choice.

Specify the pin number where the motor's control signal is connected.

Position Control

Move the servo motor to a new angle, between 0 to 180 degrees. Some servo motors are not capable of a full 180 degree travel or have stability problems at the far ends of this range.

Example Program

// Sweep
// by BARRAGAN <http://barraganstudio.com> 

#include <Servo.h> 
 
Servo myservo;  // create servo object to control a servo 
                // a maximum of eight servo objects can be created 
 
int pos = 0;    // variable to store the servo position 
 
void setup() 
{ 
  myservo.attach(20);  // attaches the servo on pin 20 
} 
 
 
void loop() 
{ 
  for(pos = 10; pos < 170; pos += 1)  // goes from 10 degrees to 170 degrees 
  {                                  // in steps of 1 degree 
    myservo.write(pos);              // tell servo to go to position in variable 'pos' 
    delay(15);                       // waits 15ms for the servo to reach the position 
  } 
  for(pos = 180; pos>=1; pos-=1)     // goes from 180 degrees to 0 degrees 
  {                                
    myservo.write(pos);              // tell servo to go to position in variable 'pos' 
    delay(15);                       // waits 15ms for the servo to reach the position 
  } 
} 

Timer Usage

This table can help you avoid using PWM pins which require the timers used by Servo.

Interrupt Latency

Libraries which disable interrupts for long times, likely to cause substantial problems:

• SoftwareSerial
• NewSoftSerial

• OneWire

Arduino Issue #146

However, some libraries directly manipulate pins without disabling interrupts, which is likely to interfere with Servo. Libraries believed to contain issue #146 include:

• CapSense

More Details