Servo motor not working with "write"

[diegochen]

Hello all,

I'm a student new to Arduino, and I'm trying to control a servo motor by using write command. However, when I run the code, it just keep rotating clockwise for a small angle at a time, and the time interval does not follow the delay too.

Here is my code:

//Include servo library
#include <Servo.h>
const int servopin = 3;
Servo myservo;

void setup()
{
  myservo.attach(servopin);
}

void loop()
{
  myservo.write(-90);
  delay(500);
  myservo.write(0);
  delay(500);
  myservo.write(90);
  delay(500);
}

I'm using Arduino Nano & servo motor GWS03T. Thanks for any help

(Sorry but English is not my mother tongue, so if there is anything not described clearly, please let me know.)

Here is the video:
https://drive.google.com/file/d/1_4tATJkPVICW7rzEfkdlCIhZ_jj14TqA/view?usp=sharing

[groundFungus]

@diegochen

myservo.write(-90);

Servo write takes only positive numbers. See the Servo write() function reference.

You may need to allow more time for the servo to move. A data sheet that I found has the motion versus time specification. Note that the times are usually unloaded times. A servo with a load will be slower, depending on load.

[diegochen]

I've tried to use the positive parameters, but the problem was still there......

What do you mean to "allow more time?", I don't really understand that part.
Thanks for the reply.

[groundFungus]

It takes time for the servo to start, move to the commanded position and stop. Look at the data sheet under speed:

Speed: 4.8V: 0.33 sec/60° 6.0V: 0.27 sec/60°

with a 4.8V power supply it takes 330ms to move 60° under no load, so to move 90° it would take 495ms (under no load).

How is your servo powered? If it is powered by the Arduino, that can cause problems, too. The Arduino is not a power supply. Power the servo with an external supply like a pack of 4 AA batteries.

[diegochen]

Yes, I powered it only by the Arduino.

So the 5V power supply on the Arduino board is not enough?
Ok, I'll try to give it external power supply.
Thanks a lot!