How to make servo rotate for angle bigger than 180°

Question

Connected servo motor (180°) to Arduino Uno R3.

Currently I am using a servo motor which have rotation angle specified as 180°, but I have a requirement to rotate to certain angles greater that 180°.

So do I need to go for a continuous rotation servo motor (360°), so that I can stop the motor at different angles greater than 180°, was my assumption true, will continuous rotation servo motor satisfy this requirement?

I am referring to Servo - Generic High Torque Continuous Rotation (Standard Size)

Current code, which I am using 180° servo motor.

Servo myservo;
int pos = 0;   
void setup() {
  myservo.attach(9);  
}

void loop() {
   { 
    myservo.write(180);              
    delay(15);                       
  }
}

Answer 1

No. The continuous rotation servo rotates continuously and you can not control where to stop. You can control the rotation direction and the speed at a little.

What you need is either a special 270 degree servo, or you can use some mechanic, e.g. gears to transform the 0..180 rotation to 0..whateverrotation you prefer, depending on the gearbox ratio.

Alternatively, you can use stepper motors, where you can control steps in 1.8 degrees, and at the same time free to move as many turns as you prefer. Note though that steppers have two disadvantages compared to servos:

• steppers require electrical current to hold their current position - for servo, the gearbox works ok for this
• steppers don't know their initial position. So you need an optointerrupter or other means to learn the initial position first, then drive the steps to get to any position.
• steppers require a more serious driving circuit, as well as a good power supply. Not for DIY robot running on batteries.

In industrial solutions, the stepper motor + some gearbox + an absolute rotation encoder is used to compose an industrial servo drive. (Similarly as a DC motor + some gearbox + an inexpensive potentiometer works in a model servo.)