(Non) humming servo

Posted on pon 28 maj 2018 in micropython

While I'm IoT, my servo is humming in almost every position. I hear annoying noise every time it's not moving.

After asking Dr. Google, I know that: servo is bad and I need to use another one, or is set to position which it unable to achieve and need to find another position [2], or sigal transmitter makes inaccurate signal and servo set different possition each time and I need to add capacitor to average it [3], or it's connected to two different sources of DC [4] or grounds are not connected.

None of suggestions above worked. All my servos jitters, I tried various combinations about DC sources, ground is common and I tried all available servo position. It makes noise all the time. Louder or more silent, but almost all the time. `

So, I decided to just ... turn off servo, once it reach the target.

I asumed that 1 second is enough for servo to turn from min to max position (may vary in different servos), the code is here:

from random import random
import machine
import time

class Servo:
        def __init__(self, pin_num):
                self.pin = machine.Pin(pin_num, machine.Pin.OUT)
                self.pwm = machine.PWM(self.pin)
                self.pwm.freq(50)
                self.pwm.duty(0)
                self.pos = None

        def set(self, pos):
                ftime = 1.0
                if self.pos is None:
                        sleeptime = ftime
                else:
                        sleeptime = ftime * abs(pos - self.pos)
                self.pos = pos

                duty = int(40 + (115-40)*pos)
                self.pwm.duty(duty)

                print("sleeptime", sleeptime)

                time.sleep(sleeptime)
                self.pwm.duty(0)