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Servo wobble?

I used the circuit from this website http://www.hvlabs.com/555servo.html to control dc servo motor. 

However, i changed R1 to 1k, potentiometer to 10k, R2 to 68k and C3 to 470nF so that the servo able to turn to about 180 degree.

From this formula F = 1.44 / (R1+R2)(C3), i calculated the output frequency is about 44.4Hz.

When i turned the dc servo to the positon desired using potentiometer but the dc servo would not stay still and it will wobble for a while before it became stationary. So, what causes the dc servo to wobble?

Sorry, im kinda new to servo andd 555 timer.

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Are you sure that your servo is capable to make 180° turns?. Most servos can only move 90°. There is a hardware stop inside the servo. Maybe you can modify the servo like shown here.

The servo able to turn to 180 degree without modifying but it will wobble for a while before becoming stationary at any angle i turned to.

Thank you.

If this were me, I would build the circuit as described and get it working as is. When it does, I would modify from there. I count 4 variables that you describe that could be the cause. I have this issue when writing code sometimes. When it happens to me, I reduce the problem to as simple as I can get it and add from there.

Actually I built the exact circuit before, but it only rotate up to 90 degree and i want the dc servo to rotate to 180 degree.

Do you know any reason that causes a dc servo to wobble?

Thanks