Can't drive servo

Question

I purchased a 20KG Digital Servo, DS3218MG with a Control Angle of 270° .

I am trying to get it to rotate with the following code:

#include <Servo.h>

Servo myservo;  // create servo object to control a servo

void setup() {
  myservo.attach(9);  // attaches the servo on pin 9 to the servo object
}

int restingVal = 0;
int keyDown = 80;

void loop() {
  int minutesDelay = 1;
  Serial.print("Value");
  Serial.println(restingVal);

  delay(10000/2);  

  myservo.write(keyDown);
  delay(500);
  myservo.write(restingVal);

}

It makes a small "clicking" noise, but it never moves. I have tried:

• powering it from the arduino using a USB cable
• powering it using a power cord plugged into an electrical outlet
• powering it with 4 AA batteries in a battery pack (power from the battery pack to the servo with it's ground to the Arduino's ground and the arduino plugged into an outlet)
• using a 470uF capacitor and then tried a 680uF capacitor.

What am I doing wrong? Is there something else I could look at?

update: changed code to:

#include <Servo.h>

Servo myservo;  // create servo object to control a servo

void setup() {
  myservo.attach(9);  // attaches the servo on pin 9 to the servo object
  myservo.write(60);
  delay(2000);
  myservo.write(120);
}

int restingVal = 0;
int keyDown = 80;

void loop() {

}

I get the same problem.

The power cord I'm using to connect the arduino is 12V DC 1A.

Here is a photo of the wiring in one configuration (with the battery pack and the wall outlet):

Orange wire goes to GND on arduino, the long green goes to ~9, yellow goes to VCC on battery pack.

Answer 1

The DS3218MG servo motor is a strong servo motor and it requires more current than normal servo motors.

With a normal servo motor the peak current can be 500 mA or even 1 A. This DS3218MG is specified somewhere at 1.8 A stall current (only 80 to 100 mA during normal operation). However this YouTube video measures a stall current of 2.3 A.

During normal operation, the average current will not even be near the stall current. The peak current on the other hand can be close to the stall current. The peak current occurs at the moment that the servo motors starts to move.

You need a 5 V 2.5 A power supply for that servo motor, together with wires and connectors that are suitable for that current.
You could cheat a little by adding a capacitor. I suggest 2200 µF or 4700 µF.

It is a common mistake to underestimate the current of a servo motor. A power supply is often more expensive than the servo motor.
If a lot of torque is required, perhaps a geared motor is easier to use.

Answer 2

My guess is that the servo is drawing too much current from the Arduino 5v pin which can provide up to ~450mA when powered from USB and ~650mA from power jack.

Try providing 5v from an other source to the servo while keeping the GND of that power source and the Arduino common.