Servo question



  • I am trying to add a servo to my cartesian machine , which will drive a small purge bucket. It is suggested to add a 220µF capacitor between ground and +5V to help absorb the voltage generated by the servo . The voltage rating of the capacitor needs to be 5V or higher? Might be a stupid question but my knowledge regarding electric circuits is very basic.



  • @Ntrack you are talking about RC servo? 220-470µF 12V or 16V 105C. I also like to add a diode (simple 1n4001 will do) across that elco.



  • @smece said in Servo question:

    @Ntrack you are talking about R

    Yes, a micro servo. I have some 10V 220uF capacitors. Do I need bigger capacitance or voltage rating ?


  • administrators

    @Ntrack said in Servo question:

    @smece said in Servo question:

    @Ntrack you are talking about R
    

    Yes, a micro servo. I have some 10V 220uF capacitors. Do I need bigger capacitance or voltage rating ?

    How micro? My suggestion of 220uF was for a MG996R, which isn't exactly micro.



  • Yes, a micro servo. I have some 10V 220uF capacitors. Do I need bigger capacitance or voltage rating ?

    That will work fine.



  • Mine is a 7g 1.6kg/cm micro servo.


  • administrators

    @Ntrack said in Servo question:

    Mine is a 7g 1.6kg/cm micro servo.

    That should be OK with no capacitor.



  • @Ntrack no need for higher rating than 10V (the rule of thumb is 2x the voltage you are going to be normally using, so as you use 5V 10V rating is enough and will last long time, higher voltage rating won't be a problem but will not bring anything to the table) 220uF is enough for few watt motor, so if you are running some micro RC you can probbly go without it but I kinda like to go with 220 or 470uF (those two values I always have tone of) + diode any time I connect a motor, especially if that's some PRC motor... the RC servo should have diode and block cap over the motor directly and the input voltage should not be affected (there is supposed to be a cap on the input already on the servo board), but I seen boards that do not populate those so adding a few cents on the input worth of parts is always safer 😄



  • @smece I might have some diodes as I was planning to add a air pump some time ago. If end up using a bigger servo I'll add one, thanks for the tip.



  • @Ntrack note just that it should not be required, I just like to overdo everything 😄 and it's cheap so why not 😄



  • For some reason is not working properly. I added M950 S1 C"duex.pwm4" to my config.g and created some macros to move the motor using M280 P1 Sxx (xx 0...60 , being a 60 degrees motor) . If I move it to 30 (M280 P1 S30) all is fine, but if I try to move it to 0 or 60 it will move then will vibrate for some seconds and, after that , the paneldue screen goes blank(that's when I soil my underwear and quickly cut the power) . It happened every time I moved the motor to its minimum or maximum position.If I move it to 30 while is vibrating all is fine .
    I also inverted the pin name in M950 with the same results.



  • Some more weird stuff from these servos. I can command it to move to 90 degrees (M280 P1 S90) and it moves without issue even if it is supposed to be a 60 servo.everything below 30 makes it vibrate and weird stuff can happen to the paneldue. So it's a 60 degrees stepper that can work between 30 - 90 degrees :).


  • administrators

    @Ntrack said in Servo question:

    Some more weird stuff from these servos. I can command it to move to 90 degrees (M280 P1 S90) and it moves without issue even if it is supposed to be a 60 servo.everything below 30 makes it vibrate and weird stuff can happen to the paneldue. So it's a 60 degrees stepper that can work between 30 - 90 degrees :).

    It sounds like the pulse timings it uses are set up for a range of 30 to 90 degrees, rather than 0 to 60 degrees as you expected.

    When a servo vibrates, it normally means you are trying to drive it beyond its travel range.



  • @dc42 said in Servo question:

    @Ntrack said in Servo question:

    @smece said in Servo question:

    @Ntrack you are talking about R
    

    Yes, a micro servo. I have some 10V 220uF capacitors. Do I need bigger capacitance or voltage rating ?

    How micro? My suggestion of 220uF was for a MG996R, which isn't exactly micro.

    Hey,

    would I need that capacitor for a MG996 on a Duet 3? Better safe than sorry?
    Thanks.


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