servo Write

Tell a servo to rotate to some angle or turn at a certain speed.

pins.A1.servoWrite(90)

Servos turn a shaft in one of two of directions by an amount of angle in degrees. With a servo, you are using just 180 degrees to position an arm, gear, or wheel that is connected to the shaft. The position at 90 degrees is the base, or neutral position. To turn the servo shaft left (counter-clockwise) you write to it a number of degrees to the between 0 and 90. The 0 degree spot is all the way left and any other number up to 90 is somewhere between left and the neutral position. The same thing works for going all the way to the right (clockwise). All the way to the right is 180 degrees.

Continuous rotation

Now, there is another type of servo called a continuous rotation servo that might look the same as a regular servo. It’s different because the shaft doesn’t stop at a particular position in degrees. In this case, the number you write to the servo is not degrees but a speed number. The shaft keeps rotating if you write a number other than 90 to the servo. Instead of being an angle of degrees, the number is a speed rating in one of the directions. The number 0 is full speed rotating to the left and 180 is full speed rotating to the right. The number 90 is no rotation in any direction.

Parameters

• value: a number for shaft angle or servo speed, depends on your servo type:

  • regular servo: the number of degrees of angle to turn the shaft.

• 90 is the neutral, or center, position.
• 90 to 0, the shaft turns to a position towards the left.
• 0 is all the way turned to the left.
• 90 to 180, the shaft to a position towards the right.
• 180 is all the way turned to the right.

• continuous rotation: the speed to turn the shaft in one direction or the other.

  • 0 full speed rotating to the left.
  • 90 to 0, the shaft spins faster rotating to the left as the number goes to 0.
  • 90 no speed, shaft doesn’t turn.
  • 90 to 180, the shaft spins faster rotating to the right as the number reaches 180.
  • 180 full speed rotating to the right.

Example

Connect a servo to pin A1. Wag (rotate right and left) the arm on the servo shaft 45 degrees in each direction for 5 times.

for (let i = 1; i <= 5; i++) {
    pins.A1.servoWrite(135)
    pause(500)
    pins.A1.servoWrite(45)
    pause(500)
}

See also

servo set pulse, analog set period

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