Servo vibration issue

Other Hardware General Electronics
1

Hello!!! ummm? can someone help with this weird servo related issue? So the first two front servos vibrate very much during the "animation", and the two at the back don't have a same issue(they are attached the same with the same screws). Is it a code or servo issue?(if yes I will have to buy new ones[sg90 servos])

code:

#include <Wire.h>
#include <Adafruit_PWMServoDriver.h>
#define SERVO_FREQ 50
//AXLE SETTINGS
#define START_POSITON_AXLE 300
#define AXLE_POSITON_CHANGE 320
#define AXLE_POSITON_CHANGE_a 280
//LEG SETTINGS
#define START_POSITON_LEG 450
Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver();

uint8_t servonum = 0; 

void setup(){
  Serial.begin(9600);
  pwm.begin();
  pwm.setOscillatorFrequency(27000000);
  pwm.setPWMFreq(SERVO_FREQ);
  delay(10);
  startAxle();
  startLegs();
}

void loop(){
  axelMovament_a();
  delay(750);
  axelMovament_b();
  delay(750);
}

void axelMovament_a(){
  for(uint16_t pulselen = START_POSITON_AXLE; pulselen > AXLE_POSITON_CHANGE_a; pulselen--){
    pwm.setPWM(0, 0, pulselen);
    pwm.setPWM(3, 0, pulselen);  
  }
  delay(250);
  for(uint16_t pulselen = AXLE_POSITON_CHANGE_a; pulselen < START_POSITON_AXLE; pulselen++){
    pwm.setPWM(0, 0, pulselen);
    pwm.setPWM(3, 0, pulselen);  
  }
  delay(250);
}

void axelMovament_b(){
  for(uint16_t pulselen = START_POSITON_AXLE; pulselen < AXLE_POSITON_CHANGE; pulselen++){
    pwm.setPWM(1, 0, pulselen);
    pwm.setPWM(2, 0, pulselen);  
  }
  delay(250);
  for(uint16_t pulselen = AXLE_POSITON_CHANGE; pulselen > START_POSITON_AXLE; pulselen--){
    pwm.setPWM(1, 0, pulselen);
    pwm.setPWM(2, 0, pulselen);  
  }
  delay(250); 
}

void startAxle(){
  pwm.setPWM(0, 0, START_POSITON_AXLE);
  pwm.setPWM(1, 0, START_POSITON_AXLE);
  pwm.setPWM(2, 0, START_POSITON_AXLE);
  pwm.setPWM(3, 0, START_POSITON_AXLE); 
}

void setServoPulse(uint8_t n, double pulse) {
  double pulselength;
  
  pulselength = 1000000;   //1,000,000 us per second
  pulselength /= SERVO_FREQ;   //Analog servos run at ~60 Hz updates
  Serial.print(pulselength); Serial.println(" us per period"); 
  pulselength /= 4096;  //12 bits of resolution
  Serial.print(pulselength); Serial.println(" us per bit"); 
  pulse *= 1000000;  //convert input seconds to us
  pulse /= pulselength;
  Serial.println(pulse);
  pwm.setPWM(n, 0, pulse);
}

video: https://drive.google.com/file/d/11L1OhFrI1hX-o10rUGwQUNQFVaVdZ_Kn/view?usp=sharing

2

If you swap them, do the same ones still vibrate?

Yes, some of those SG90 servos are quite bad and vibrate a lot when moving, especially when moving slowly.

3

Hello, so I only have 8 servos, and I'll probably buy 3 new ones and then I'll check. I was just wodering if it is a probelm with code or something.

4

I had one or two servos which vibrated a lot, jumping around on the desk, while others are smooth. That out of a batch of six,

I manually spun the bad ones with the horn back and forth a few times (not recommended unless you are prepared to damage it) and it improved a lot - actually became usable.

1 Like
5

How are you powering these servos?

6

I've found servos vibrate with insufficient power. Also, running the servo power through a breadboard or using the MCU's power can cause servo vibrations.

I, also, dumped using plastic geared servos for projects.

7

Hi,
Can you tell us what/how you are powering your project please?

Can you post a circuit diagram showing power supplies, component names and pin labels?

Thanks.. Tom... :smiley: :+1: :coffee: :australia:

8

I would try putting a tiny delay (5 to 15 milliseconds) in the loops to give the servos more time to react to the position change on each step.

9

post#8 makes a good point.

the time between those 2 commands is not much time for the motor to get to position.

10

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