Servo motor sweeps beyond 180

Question

I'm trying to get my servo motor to sweep from 0 to 180 degrees then back to 0 degrees for infinite amount of times. I using the following code but my motor keeps resetting when it get backs to 0 degrees (meaning it goes 0-->180-->0 then completes a 360 and starts over). Also the 0-180 degree sweep appears to be more of a 0-270 degree sweep. Anyone running into these problems?

int angle = 0;

void setup() {
  myservo.attach(9);
  myservo.write(angle);
}

void loop()
{
  for (angle = 0; angle < 180; angle += 1)
  {
    myservo.write(angle);
    delay (50);
  }

  for (angle = 180; angle > 0; angle -= 1)
  {
    myservo.write(angle);    
    delay(50);
  }   
}

Answer 1

Are you trying to have the servo sweep at a particular speed? Why not just use:

void loop()
{
  angle=180;
  myservo.write(angle);

  delay(500); //Allow 0.5 seconds for servo to complete it's move; adjust as necessary depending on servo's rotation speed.

  angle=0;
  myservo.write(angle);

  delay(500); //Allow 0.5 seconds for servo to complete it's move; adjust as necessary depending on servo's rotation speed.
}

Answer 2

Is your servo the modified 360 degree type with no position feedback (meaning the internal feedback potentiometer has been disabled)?

Answer 3

I had a bunch of SG90 mini servos so I tried your code. My servos turn 0 -> 180 -> 0 -> 180 -> 0 -> 180, over and over. No 360 spins at all.

• Maybe your servo is defect? (can you check with another servo?)
• Maybe it is not getting enough power? (how are you powering it?) It needs at least 4.8V and at least 220mA
• Maybe it doesn't get a strong clean PWM signal? (You'll probably need an oscilloscope to check this)