Servo jitter with Arduino We're complete beginners with Arduino and we're working on a project that moves a pointer based on a color sensor reading.

We used two servo motors each: one performs a specific task, the small servo works pretty fine. The problem is with the larger one.

We used this servo motor model: (towardpro MG996R), Arduino Uno and a color sensor. Because the motor is large we connect it to a 9 V power supply. 

But when we run the code it just vibrates in place and the arm won't move :(

Is there anything else we need to add to the circuit like a resistor or some thing?

#include &lt;Servo.h&gt;
Servo largeServo;

void setup() {
  largeServo.attach(6);
  largeServo.write(0); 
}

void loop() {
  largeServo.write(0);
  delay (2000);
  largeServo.write(30);
  delay (2000);
  largeServo.write(60);
  delay (2000);
  largeServo.write(90);
  delay (2000);
}
According to (MG996R)'s datasheet
You must connect a 6 volts - 2.5 amps power supply for it's best performance (max. Torque)
Maximum voltage of this servomotor is 6 volts
And be careful, exceeding that voltage can be cause of some damage to it's control board
Try 6 volts 2.5 amps power supply and if doesn't work maybe your servomotor's control-board is damaged by over-voltage.